Publications from 2013 to 2025
2025
●Solvent-Directed Handedness in a Chirally Twisted Tetrakisporphyrin Macrocycle A chirally twisted tetrakisporphyrin macrocycle was synthesized by incorporating a chiral dioxolane into a tetrakisporphyrin macrocycle. The solvent type influenced the preferred handedness of the twisted conformation. Circular dichroism measurements and computational analyses determined the handedness of the conformers in solvents toluene and dimethylformamide. Kouta Tanabe, Naoyuki Hisano, Takeharu Haino, Asian J. Org. Chem. 2025, Accepted doi.org/10.1002/ajoc.202500251 ●Helical Supramolecular Polymers Formed via Head-to-Tail Host-Guest Complexation of Chiral Bisporphyrin Monomers with Trinitrofluorenone The intermolecular host-guest complexation of head-to-tail monomers consisting of cleft-shaped bisporphyrin and trinitrofluorenone units connected by a chiral binaphthyl linker was employed to construct helically twisted supramolecular polymers. Results from 1H NMR, diffusion-ordered NMR spectroscopy, and viscometry experiments revealed that the supramolecular polymerization of these monomers follows a ring-chain competition mechanism. The introduction of bulky substituents at the linker significantly suppressed the formation of macrocyclic oligomers, whereas smaller alkyl chains facilitated the formation of the cyclic form. The chirally twisted structures of the supramolecular polymers were confirmed using circular dichroism spectroscopy. Atomic force microscopy revealed that the (R)- and (S)-configurations of the binaphthyl linkers induced right- and left-handed helical structures, respectively, in the supramolecular polymer chains. The absence of cooperativity in the supramolecular copolymerization of (R)- and (S)-1a resulted in the formation of stereo-random supramolecular copolymers. Naoyuki Hisano, Tomoki Kodama, Soichiro Koya, Takeharu Haino, Chem. Eur. J., 2025, 31, e202404210.(Very Important Paper) ●Chirality Generation on Carbon Nanosheets by Chemical Modification Chirality is an intriguing property of molecules, and an exciting area of study involves the generation of chirality in nanographene (NGs), also known as graphene quantum dots. Unlike those synthesized through stepwise carbon-carbon bond formation by organic reactions (bottom-up method), NGs are obtained by cutting parent carbons (top-down method) pose challenges in precisely regulating their three-dimensional structures by post-synthesis. This includes the incorporation of non-hexagonal rings and helicene-like structures in carbon frameworks. Currently, edge functionalization is the only method for generating chirality in NGs produced by the top-down method. While various chiral NGs have been synthesized through organic methods, examples of chemical modification remain rare due to limited structural information and the substantial size of NGs. However, these problems can be mitigated by disclosing the structures of NGs, particularly their edge structures. This minireview focuses on recently published papers that address the structural characterization of NGs and their chirality generation by edge modification. Comparing these NGs with those synthesized by organic synthesis will help to develop reasonable strategies for creating sophisticated chiral NGs. We hope this mini-review contributes to the advancement of NG-organic hybrid materials. Ryo Sekiya, Saki Arimura, Haruka Moriguchi, Takeharu Haino, Nanoscale, 2025, 17, 774-787. ●Controlled Helical Organization in Supramolecular Polymers of Pseudo-Macrocyclic Tetrakisporphyrins Tetrakisporphyrin monomers with amino acid side chains at each end form intramolecular antiparallel hydrogen-bonds to adopt chirally twisted pseudo-macrocyclic structures that result in right-handed and left-handed (P)- and (M)-conformations. The pseudo-macrocyclic tetrakisporphyrin monomers self-assembled to form supramolecular helical pseudo-polycatenane polymers via head-to-head complementary dimerization of the bisporphyrin cleft units in an isodesmic manner. The formation of one-handed supramolecular helical pseudo-polycatenane polymers was confirmed by circular dichroism spectroscopy. The methyl and iso-propyl groups at the stereogenic center greatly enhanced the induced circular dichroism (CD) in the Soret bands of the supramolecular helical pseudo-polycatenane polymers. The induced CDs were reduced upon the introduction of large iso-butyl and tert-butyl groups. Atomic force microscopy revealed well-grown and long supramolecular helical pseudo-polycatenane polymer chains with chain lengths in the range of 361 to 13.6 nm. The right-handed helical chains were established by the self-assembly of the right-handed (P)-conformation of the pseudo-macrocyclic monomer. Naoka Fujii, Naoyuki Hisano, Takehiro Hirao, Shin-ichi Kihara, Kouta Tanabe, Masaya Yoshida, Shin-ichi Tate, Takeharu Haino, Angew. Chem. Int. Ed. 2025, 64, e202416770(Hot Paper, Inside Back Cover) ●Temperature-Dependent Left- and Right-Twisted Conformational Changes in 1:1 Host-Guest Systems: Theoretical Modeling and Chiroptical Simulations An efficient strategy for high-performance chiral materials is to design and synthesize host molecules with left- and right- (M- and P-) twisted conformations and to control their twisted conformations. For this, a quantitative analysis is required to describe the chiroptical inversion, chiral transfer, and chiral recognition in the host-guest systems, which is generally performed using circular dichroism (CD) and/or proton nuclear magnetic resonance (1H-NMR) spectroscopies. However, the mass-balance model that considers the M- and P-twisted conformations has not yet been established. In this study, we derived the novel equations based on the mass-balance model for the 1:1 host-guest systems. Then, we further applied them to analyze the 1:1 host-guest systems for the achiral calixarene-based capsule molecule, achiral dimeric zinc porphyrin tweezer molecule, and chiral pillar[5]arene with the chiral and/or achiral guest molecules by using the data obtained from the CD titration, variable temperature CD (VT-CD), and 1H-NMR experiments. The thermodynamic parameters (ΔH and ΔS), equilibrium constants (K), and molar CD (Δε) in the 1:1 host-guest systems could be successfully determined by the theoretical analyses using the derived equations. Nozomu Suzuki, Daisuke Taura, Yusuke Furuta, Yudai Ono, Senri Miyagi, Ryota Kameda, Takeharu Haino, Angew. Chem. Int. Ed. 2025, 64, e202413340. ●Chiral Induction of a Tetrakis(porphyrin) in Various Chiral Solvent Non-covalent interactions offer an alternative way for developing stimulus-responsive materials such as sensors, machines, and drug-delivery systems. We recently reported that a urethane-equipped tetrakis(porphyrin) forms one-handed helical supramolecular polymers in solution in response to chirality of chiral solvents. Conformational changes in helical sense were detected using circular dichroism (CD) spectroscopy, which showed that the tetrakis(porphyrin) can possibly be used as a sensor for determining the enantiomeric excess of a chiral analyte. Hence, we studied the scope and limitations of the chiral-induction behavior of tetrakis(porphyrin) to deepen the understanding of tetrakis(porphyrin)-based chiral sensing systems. Herein, we report the chiral-induction behavior of tetrakis(porphyrin) in various chiral solvents, which was found to be CD-active in many chiral solvents. Notably, the tetrakis(porphyrin) was CD active in a cryptochiral molecular solvent, which is exciting because the chiralities of acyclic saturated hydrocarbons are hard to sense. Consequently, this study highlights the potential advantages of supramolecular chiral sensors capable of targeting a wide range of analytes, including molecules that are absorption-silent in the UV/vis region, ones devoid of anchoring functional groups, and acyclic, saturated hydrocarbons. Takehiro Hirao, Sei Kishino, Masaya Yoshida, Takeharu Haino, Chem. Eur. J., 2024, 30, e20240356. ●Assessment of Edge Modification of Nanographene Carboxy groups on the edges of nanographene (NG) enable functionalization for realizing NG-organic hybrid materials. Therefore, assessment of the edge-functionalization of the electronic structures of NGs is valuable for the rational design of functional carbon materials. In this study, the structures of model NGs comprising 174 carbon atoms with armchair edges and various functional groups at the edges were computed. To achieve the greatest possible similarity between the computed structure and the real one, the carbon framework was designed based on experimental observations. The functional groups can be accessed via suitable chemical reactions. The computations predicted that although the conversion of carboxyl groups with electron-withdrawing/donating groups influences the orbital energies, the HOMO-LUMO (H-L) gap is not significantly affected, except in a few cases. Among the evaluated examples, π-extension had the greatest influence on the H-L gap. Interestingly, for the Pd2+-coordinated NG, the participation of the low-lying LUMO localized on Pd2+ in the surface-to-metal transitions seemingly narrowed the H-L gap, and a surface-to-ligand transition was observed. Ryo Sekiya and Takeharu Haino, ChemPysChem, 2024, 30, e202402922.(Front Cover) ●Latent Porosity of Planar Tris(phenylisoxazolyl)benzene Interest in developing separation systems for chemical entities based on crystalline molecules has provided momentum for the fabrication of synthetic porous materials showing selectivity in molecular encapsulation, such as metal-organic frameworks, covalent organic frameworks, hydrogen-bonded organic frameworks, zeolites, and macrocyclic molecular crystals. Among these, macrocyclic molecular crystals have generated renewed interest for use in separation systems. Selective encapsulation relies on the sizes, shapes, and dimensions of the pores present in the macrocyclic cavities; thus, nonmacrocyclic molecular crystals with high selectivity for molecular encapsulation via porosity-without-pore behaviors have not been studied. Here, we report that planar tris(phenylisoxazolyl)benzene forms porous molecular crystals possessing latent pores exhibiting porosity-without-pore behavior. After exposing the crystals to complementary guest molecules, the latent pores encapsulate cis- and trans-decalin while maintaining the structural rigidity responsible for the high selectivity. The encapsulation via porosity without pores is a kinetic process with remarkable selectivity for cis-decalin over trans-decalin with a cis-/trans-ratio of 96:4, which is confirmed by single-crystal X-ray diffraction and powder X-ray diffraction analyses. Hirshfeld surface analysis and fingerprint plots show that the latent intermolecular pores are rigidified by intermolecular dipole‒dipole and π–π stacking interactions, which determines the remarkable selectivity of molecular recognition. Yudai Ono, Takehiro Hirao, Naomi Kawata, and Takeharu Haino, Nat. Commun., 2024, 15, 8314. DOI:10.1038/s41467-024-52526-9 ●Conformation Regulation of Trisresorcinarene Directed by Cavity Solvation This compound is a synthetic macrocycle comprising three pivaloyl-protected resorcinarene units connected by six pentylene chains. We conducted a conformational study using 1H-NMR, X-ray diffraction (XRD), and computational analyses. The macrocycle adopts two conformers, one open, the other closed. The ratio of the open to closed forms depended on the solvent used. Only the open form existed in [D8]toluene, both forms coexisted in [D6]benzene, and the closed form was the major conformer in [D1]chloroform. The benzene-solvated open form observed in the solid state suggests that cavity solvation by solvent molecules directs the open form. The open form was the major or only conformer in [D10]o- and [D10]m-xylene and [D12]mesitylene, whereas the closed form was the major conformer in [D6]acetone. The open and closed forms were equally populated in [D10]p-xylene, suggesting that the size, shape, and dimensions of the solvent molecules most likely influenced the conformation of the protected trisresocinarene. Daisuke Shimoyama, Ryo Sekiya, Shoichiro Inoue, Naoyuki Hisano, Shin-ichi Tate, and Takeharu Haino, Chem. Eur. J. 2024, 30, e202402922.(Front Cover) ●Spectrally Selective Leakage of Light from Self-Assembled Supramolecular Nanofiber Waveguides Induced by Surface Plasmon Polaritons We report surface plasmon polariton (SPP)-induced spectrally selective leakage of light waveguided in supramolecular nanofibers. The nanofibers are fabricated by self-assembly of tris(phenylisoxazolyl)benzene derivative molecules, and their diameter ranges from nanometers to hundreds of nanometers. Nanofibers with heights of more than 200 nm are shown to function as waveguides for fluorescence excited in one location by a focused 360 nm laser. The fluorescence can transfer the whole length of the nanofibers of tens of micrometers and is outcoupled from the nanofiber ends. The waveguiding phenomenon dramatically changes when the nanofibers are deposited on SPP-generating substrates. The substrates in the form of nanohole arrays are fabricated on a gold film with a pitch of 500 nm, a diameter of 250 nm, and a depth of 40 nm. On the SPP substrates, the nanofiber waveguides exhibit strong leakage of the guided light. The spectrum of the leaked light is consistent with the SPP resonance wavelength, and its polarization corresponds to the TE waveguided mode. We propose mechanisms of the observed phenomena that include either excitation of the SPPs via the waveguide evanescent field or direct enhancement of the leakage by the modified density of states near the plasmonic substrate. Qiwen Tan, Nao Koishihara, Shun Omagari, Takehiro Hirao, Takeharu Haino, Martin Vacha, J. Phys. Chem. C 2024, 128, 10, 4295–4302. ●Selective encapsulation of carboxylic acid dimers within a size-regulable resorcinarene-based hemicarcerand A cavity within a resorcinarene-based hemicarcerand was contracted and expanded through conformational changes induced by the complexation and decomplexation, allowing self-sorting of homo- and heterodimeric carboxylic acid pairs. Kentaro Harada, Yudai Ono, Ryo Sekiya, and Takeharu Haino, Chem. Commun. 2024, 60, 6603(Front Cover) ●Synthesis of Supramolecular Polymers Takehiro Hirao, Masaya Yoshida, and Takeharu Haino, Handbook of Functional Polymers, Chapter 43: Supramoelcule, Y. Chujo Ed., Springer. ●Supramolecular Synthesis of Star Polymers Supramolecular polymers, in which monomers are assembled via intermolecular
interactions, have been extensively studied. The fusion of supramolecular
polymers with conventional polymers has attracted the attention of many
researchers. In this review article, the recent progress in the construction
of supramolecular star polymers, including regular star polymers and miktoarm
star polymers, is discussed. The initial sections briefly provide an overview
of the conventional classification and synthesis methods for star polymers.
Coordination-driven self-assembly was investigated for the supramolecular
synthesis of star polymers. Star polymers with multiple polymer chains
radiating from metal–organic polyhedra (MOPs) have also been described.
Particular focus has been placed on the synthesis of star polymers featuring
supramolecular cores formed through hydrogen-bonding-directed self-assembly.
After describing the synthesis of star polymers based on host–guest complexes,
the construction of miktoarm star polymers based on the molecular recognition
of coordination capsules is detailed. Takeharu Haino and Natsumi Nitta, ChemPlusChem, 2024, 89, e202400014. ●Kinetic Resolution of Secondary Alcohols Catalyzed at the Exterior of
Chiral Coordinated Capsules Abstract: Confined spaces inside molecular hosts can function as reaction vessels.
However, this concept significantly limits the scope of reactants. When
the exterior of molecular hosts is used instead, we can ease the restriction
because reactants are not necessary to be trapped inside molecular hosts,
although studies along this line have not been reported. As a proof-of-concept
of enantioselective reactions at the exterior of chiral molecular hosts,
we utilized host‒guest complexes of enantiomerically enriched Cu-coordinated
capsules and guests possessing a catalytic center to realize the kinetic
resolution of secondary alcohols. Under suitable reaction conditions, a
selectivity factor of 2.6 was realized, demonstrating that the reactions
occur at the exterior of the capsules. A series of experiments indicated
that the substituents on the 2,2’-bipyridyl arms and the alkyl chains on
the lower rim contributed to the enantioselectivity of the reactions. Kentaro Harada, Ryo Sekiya, Takeharu Haino Chem. Eur. J.,2024,30, e202304244 ●Application of Exciton Coupling for Characterization of Nanographene Edge Abstract: The structural characterization of nonstoichiometric nanographenes (NG)-organic
hybrid materials is usually difficult. The number of substituents on the
edge and their arrangements are frequently questioned but are difficult
to answer. Since the number of functional groups is closely related to
the distance between the nearest neighbors (dISD), the extraction of dISD
from spectroscopic data could provide important information on their structural
characterization. We show that exciton coupling, which is a theoretical
prediction of the absolute structures of discrete molecules, is a possible
candidate to address this issue. The comparison of the calculated CD spectra
of the chiral chromophores extracted from the model NG edge with the observed
edge spectra indicated a dISD of ca. 8 Å; this corresponded to substitution
on every other armchair edge. Furthermore, an up-up-down-down alternate
orientation was found to be a possible edge structure. Although the procedure
was limited to NGs carrying chiral substituents, our method could facilitate
the detailed structural characterization of NG-organic hybrid materials. Ryo Sekiya and Takeharu Haino ChemPhysChem,2024,25, e202300740. ●Synthesis and Cooperative Guest Binding of Tetrameric Porphyrin Macrocycle Abstract:A new family of macrocyclic host molecules that possess two bisporphyrin
clefts was synthesized. The tetrameric porphyrin macrocycle provides the
two guest binding sites in which two electron-deficient aromatic molecules
are encapsulated through donor–acceptor and π-π stacking interactions.
The tetrameric porphyrin macrocycle showed positive cooperativity, whereas
the nonmacrocyclic analog did not. The preorganization concept drives positive
cooperativity, which is directed by the entropy benefit to macrocyclization. Kouta Tanabe, Naoyuki Hisano, and Takeharu Haino ChemistrySelect,2024,9, e202305211. ●Intermediate Color Emission via Nanographenes with Organic Fluorophores Abstract:Photoluminescence (PL) color can be tuned by mixing fluorophores emitting
the three primary colors in an appropriate ratio. When color tuning is
achieved on a single substrate, we can simplify device structures. We demonstrated
that nanographenes (NGs), which are graphene fragments with a size of tens
of nanometers, could be utilized as carriers of fluorophores. The addition
of red- and blue-light-emitting fluorophores on the edge successfully reproduced
the purple light. The relative PL intensities of the fluorophores could
be regulated by the excitation wavelength, enabling multicolor emission
between blue and red light. Owing to the triphenylamine units of the fluorophores,
the NGs showed PL enhancement due to aggregation. This characteristic was
valuable for the fabrication of solid polymer materials. Specifically,
the functionalized NGs can be dispersed into polyvinylidene difluoride.
The resultant polymer films emitted red, blue, and purple color. Our study
demonstrated the potential applicability of NGs for fluorophore carriers
capable of reproducing intermediate colors of light. Saki Arimura, Ikuya Matsumoto, Ryo Sekiya, and Takeharu Haino Angew. Chem. Int. Ed.,2024,63, e202315508. ●Supramolecular Polymerization Behavior of a Ditopic Self-folding Biscavitand Abstract:Reported herein is the supramolecular polymerization of a mixture of a
feet-to-feet connected biscavitand and a homoditopic quinuclidinium guest
that is regulated by cooperativity in the host–guest association. The diffusion
ordered NMR spectroscopy (DOSY) was used to evaluate the supramolecular
polymerization in toluene, CHCl3, and THF. Upon concentrating the solutions
of the biscavitand with the quinuclidinium guest in CHCl3 and THF, the
diffusion coefficient (D) values were meaningfully decreased, indicating
that the host-guest complexation facilitated the supramolecular polymerization.
In contrast, the slight change of the D value in toluene suggests that
the supramolecular polymerization was suppressed, although the binding
constant (K) between the cavitand and quinuclidinium guest was reported
to be 105 L mol–1 in toluene. The viscosity measurements showed both the
critical polymerization concentration (CPC) and entangled concentration
(Ce) upon concentrating the CHCl3 solution of the mixture. Neither the
CPC nor Ce was seen in the toluene solution of the mixture. Accordingly,
the strong negative cooperativity in the 1:2 host-guest complexation of
the biscavitand discouraged the supramolecular polymerization in toluene.
These findings are valuable to deepen the understanding of the host–guest
association-driven supramolecular polymerization behaviors regulated by
a combination of cooperativity and K value in solution. Haruna Fujimoto, Takehiro Hirao, and Takeharu Haino Bull. Chem. Soc. Jpn,2024, Accepted. 2023 ●Molecular Recognition Process in Resorcinarene-based Coordination Capsules Cu and Ag capsules can take up various organic molecules. Their molecular
recognition possibly involves partial dissociation and slippage. We investigated
molecular recognition processes in Cu and Ag capsules by CD and 1H NMR
spectroscopy and employed 4,4’-diacetoxy biphenyl carrying two benzothiadiazole
groups as a probe. CD and 1H NMR measurements reveal that the host-guest
complexation proceeds under second-order reactions and that these capsules
undergo partial dissociation to take up the probe in [D1]chloroform and
[D8]THF. Slippage also contributes to host-guest complexation for a Cu
capsule that carries p-methoxyphenyl groups on the 2,2’-bipyridiyl arms.
DFT calculations suggest that π/π stacking interactions between the electron-rich
p-methoxyphenyl group and the electron-poor 2,2’-bipyridyl arm elongate
the capsule, allowing the guest to access the cavity without partial dissociation. Kentaro Harada, Ryo Sekiya, and Takeharu Haino Chem. Eur. J.,2023,29, e202302581. ●A robust heterodimeric bis-Rh(iii)–porphyrin macrocycle for the self-assembly
of a kinetically stable [2]-rotaxane We report the self-assembly of a robust di-nuclear tetralactam macrocyle
based on two symmetric components: a Rh(III) bis-porphyrin and a bis-pyridyl
ligand. We probe the binding properties of the tetralactam macrocycle with
adipamide derivatives using 1H NMR spectroscopy. On the one hand, we show
that the binding of the adipamide having linear alkyl chains that can thread
through the intact macrocycle's cavity produces a weakly bound 1 : 1 complex
stabilized by four intermolecular hydrogen bonds and featuring a preferred
binding geometry of [2]pseudorotaxane topology. On the other hand, we detect
the formation of two different complexes in the binding of an analogous
adipamide possessing bulky stoppers (dumb-bell axle). The initial addition
of the dumb-bell guest induces the formation of a 1 : 1 complex featuring
fast exchange kinetics on the 1H chemical shift timescale and exo-cyclic
(non-threaded) binding geometry. Notably, in the presence of a large excess
of the dumb-bell guest and at suitable concentrations of the macrocycle
(>5 mM) we observe the emergence of a second species displaying
slow exchange kinetics. This observation allows the undisputed assignment
of a [2]rotaxane topology to the second complex. The significant increase
in kinetic stability featured by the di-nuclear Rh(III) [2]rotaxane complex
contrasts with its reduction in thermodynamic stability (more than one
order of magnitude) compared to the previously described di-nuclear Zn(II)
counterpart. Naoyuki Hisano, Virginia Valderrey, Gemma Aragay, Pablo Ballester Dalton Trans.,2023,52, 8344-8352. ●Induction of Chirality on Nanographenes Chirality induction is an important topic in studies of nanographenes (NGs).
We report chirality enhancements of NGs through postsynthetic chemical
modifications of NGs with pyrene and m-terphenyl groups. These substituents
were installed into N-(p-bromophenylethyl)imides on the edges of the NGs
with Pd-catalyzed cross-coupling reactions. Circular dichroism (CD) spectra
demonstrated that these bulky substituents improved the induced CD signal
of the NGs compared to those previously reported and suggested that they
induced the opposite chirality. Density functional theory calculations
indicated possible edge structures for the NGs and indicated that π/π and
CH/π interactions among the neighboring substituents influenced the orientations
of the imides. These imides distorted the edges, and the distorted edges
eventually generated the chiral environments of the NGs. The interactions
among the substituents are, therefore, likely to allow detection of the
CD signals in the visible region and induction of the opposite chirality. Saki Arimura, Ikuya Matsumoto, Shohei Nishitani, Ryo Sekiya, and Takeharu
Haino Chem. Asian J.,2023,18, e202300126. ●Cooperativity in molecular recognition of feet-to-feet-connected biscavitands Octaphosphonate biscavitand and self-folding deep biscavitand show strong
positive and negative cooperativity, respectively. The mechanism of the
cooperativity is discussed in terms of thermodynamic parameters and the
detailed structure of the host-guest complexes. The two cavitand units
of both biscavitands are tightly connected via four butylene linkers; thus,
they are conformationally coupled, with the first guest binding information
transferred to the resting-state cavities. This preorganization modulates
the successive guest binding process in strong positive and negative cooperative
manners, even though they display structural similarity. The first guest
complexation always preorganizes the resting-state cavities where an existing
water cluster and a toluene molecule are enthalpically stabilized. Successive
guest complexation competes with the water cluster or a toluene molecule,
reducing enthalpy gains. However, the desolvation upon successive guest
binding processes liberate the solvents within the resting-state cavities.
The water cluster is composed of 12 water molecules that are released upon
successive guest complexation, resulting in a large entropy benefit. In
contrast, toluene desolvation results in a limited entropy benefit. The
difference in entropy benefits directs the strong positive or negative
cooperativity of the structurally similar biscavitands. Takeharu Haino Pure Appl. Chem.,2023,95, 343-352. ●Negative Homotropic Cooperativity in Guest Binding of a Trisporphyrin
Double Cleft The negative homotropic allostery of a triple-layered trisporphyrin cleft
with two guest binding sites was confirmed. The X-ray crystal structures
of the 1:2 host-guest complexes showed that the trisporphyrin accommodated
two guest molecules within the cleft via π–π stacking and donor-acceptor
interactions. In solution, 1H NMR and Job plots showed 1:2 host-guest complexes.
Isothermal titration calorimetry (ITC) and UV/vis absorption spectroscopy
were employed to evaluate the binding constants and cooperativities. The
guest binding of the trisporphyrin showed negative cooperativity and noncooperativity
depending on the structures of the guest molecules. The correlations between
the interaction parameters (α) and Hill constants were determined. ITC
experiments showed that the host-guest complexation of trisporphyrin with
electron-deficient guests incurred an enthalpy penalty in the successive
guest binding process. DFT calculations revealed that the first guest binding
reduced the electron density of the central porphyrin plane, which led
to an energetic penalty that weakened the successive binding process. Naoyuki Hisano, Tomoki Kodama, and Takeharu Haino Chem. Eur. J.,2023,29, e202300107. ●Effects of Edge Functionalization of Nanographenes with Small Aromatic
Systems Regulation of the physical properties of nanographenes (NGs) by edge functionalization
is an active research area. We conducted a computational study of the effects
of edge functionalization on the physical properties of NGs. The computed
NGs were models of experimentally obtained NGs and composed of a C174 carbon
framework with from one to four 3,5-dimethylnaphthalene units on the edge.
The effects were assessed structurally, magnetically, and electronically
by the least square planarity index, harmonic oscillator model of aromaticity,
nucleus-independent chemical shift, and HOMO-LUMO (H-L) gaps. Density functional
theory calculations indicated that although the structures of the model
NGs were not very sensitive to edge functionalization, the magnetic and
electronic properties were. The installed substituents narrowed the H-L
gap and induced a redshift of the PL band by the π conjugation between
NG and the substituent. These results were consistent with the extension
of the absorption band and the redshift of the PL bands of the experimentally
modified NGs. Furthermore, the calculations confirmed the contribution
of the charge transfer character to the absorption spectra. Shusaku Takahashi, Ryo Sekiya, and Takeharu Haino ChemPhysChem,2023,24, e202300066. ●Nanoarchitectonics of Supramolecular Porphyrins Based on a Bis(porphyrin)
Cleft Molecule This account describes the construction of supramolecular constructs based
on our bis(porphyrin) cleft molecule. The bis(porphyrin) cleft molecule
was originally synthesized as a tweezer-shaped host molecule for planar
guest molecules. A detailed study on the bis(porphyrin) cleft molecule
revealed that the bis(porphyrin) cleft molecule forms two kinds of supramolecular
structures. One structure is a self-complementary dimer obtained through
intermolecular hydrogen bonding, and the other structure is a host-guest
complex, in which the electron-rich cleft cavity accommodates electron-deficient
guests through donor-acceptor interactions. Through the two supramolecular
structures, two distinct supramolecular polymers can be formed through
self-complementary dimerization or donor-acceptor host-guest complexation.
The supramolecular chain structures were modified by judiciously using
two distinct supramolecular structures. In the main text, several results,
including the binding capability of our bis(porphyrin) cleft molecule,
the formation of supramolecular porphyrin complexes, and the supramolecular
polymerization behaviors of the bis(porphyrin) cleft molecule, are reported.
In conclusion, the future direction of the bis(porphyrin) cleft molecule
is provided. Takehiro Hirao and Takeharu Haino J. Porphyr. Phthalocyanines,2023,27, 966-979 ●Substituent-Induced Supramolecular Aggregates of Edge Functionalized Nanographenes Precisely controlled molecular assemblies often display intriguing morphologies
and/or functions arising from their structures. The application of the
concept of the self-assembly for controlling the aggregation of nanographenes
(NGs) is challenging. The title NGs are those carrying both long alkyl
chains and tris(phenylisoxazolyl)benzene (TPIB) on the edge. The former
group secures the affinity of NGs for organic solvents, and the latter
group drives the one-dimensional arrangement of NGs through the interactions
between the TPIB units. The concentration-dependent and temperature variable
1H NMR, UV-vis, and PL spectra demonstrate the aggregation of NGs in 1,2-dichloroethane,
and the aggregation is controllable by the regulation of the solvent polarity.
AFM images give the stacked structures of the NGs, and these aggregates
turn out to be network polymeric structures at a high concentration. These
observations demonstrate that the synergy of the face-to-face interactions
between the surfaces and the interactions between the TPIB units is effective
for controlling the self-assembly of the NGs. Haruka Moriguchi, Ryo Sekiya, and Takeharu Haino Small,2023,19, 2207475. ●Synthesis of Supramolecular A8Bn Miktoarm Star Copolymers by Host–Guest
Complexation We report a brand-new synthetic method to construct supramolecular A8Bn
(n = 1, 2, 4) miktoarm star copolymers via host–guest complexation between
a resorcinarene-based coordination capsule possessing eight polystyrene
chains and 4,4-diacetoxy biphenyl guest molecules keeping one, two and
four polymethyl acrylate chains. The formation of the supramolecular A8Bn
(n = 1, 2, 4) miktoarm star copolymers was confirmed by dynamic light scattering
(DLS), size exclusion chromatography (SEC), and diffusion-ordered NMR spectroscopy
(DOSY). Differential scanning calorimetry (DSC) measurements revealed that
the miktoarm copolymers were phase-separated in bulk. The micro Brownian
motion of the capsule surrounded by polymethyl acrylate arms and polystyrene
arms in the A8B4 structure was markedly enhanced in bulk due to a weak
segregation interaction between the immiscible arms. Natsumi Nitta, Shin-ichi Kihara, and Takeharu Haino Angew. Chem. Int. Ed.,2023,62, e202219001. ●Supramolecular Chiral Sensing by Supramolecular Helical Polymers A tetrakis(porphyrin) with branched side chains self-assembled to form
supramolecular helical polymers both in solution and in the solid state.
The helicity of the supramolecular polymers was determined by the chirality
of solvent molecules, which permitted the polymer chains to be used in
chiral sensing. Takehiro Hirao, Sei Kishino and Takeharu Haino Chem. Comm.,2023,59, 2421-2424. ●Lanthanide and Actinide Ion Complexes Containing Organic Ligands Investigated
by Surface-Enhanced Infrared Absorption Spectroscopy A new technique, surface-enhanced infrared absorption (SEIRA) spectroscopy,
was used for the structural investigation of lanthanide (Ln) and actinide
(An) complexes containing organic ligands. We synthesized thiol derivatives
of organic ligands with coordination sites similar to those of 2-[N-methyl-N-hexanethiol-amino]-2-oxoethoxy-[N′,N′-diethyl]-acetamide
[diglycolamide (DGA)], Cyanex-272, and N,N,N′,N′-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine
(TPEN), which have been used for separating Ln and An through solvent extraction.
These ligands were attached on a gold surface deposited on an Si prism
through S–Au covalent bonds; the gold surface enhanced the IR absorption
intensity of the ligands. Aqueous solutions of Ln (Eu3+, Gd3+, and Tb3+)
and An (Am3+) ions were loaded onto the gold surface to form ion complexes.
The IR spectra of the ion complexes were obtained using Fourier transform
infrared spectroscopy in the attenuated total reflection mode. In this
study, we developed a new sample preparation method for SEIRA spectroscopy
that enabled us to obtain the IR spectra of the complexes with a small
amount of ion solution (5 μL). This is a significant advantage for the
IR measurement of radiotoxic Am3+ complexes. In the IR spectra of DGA,
the band attributed to C=O stretching vibrations at ∼1630 cm–1 shifted
to a lower wavenumber by ∼20 cm–1 upon complexation with Ln and An ions.
Moreover, the amount of the red shift was inversely proportional to the
extraction equilibrium constant reported in previous studies on solvent
extraction. The coordination ability of DGA toward Ln and An ions could
be assessed using the band position of the C=O band. The Cyanex-272- and
TPEN-like ligands synthesized in this report also showed noticeable SEIRA
signals for Ln and An complexes. This study indicates that SEIRA spectroscopy
can be used for the structural investigation of ion complexes and provides
a microscopic understanding of selective extraction of Ln and An. Sakiko Hirata, Ryoji Kusaka, Shogo Meiji, Seita Tamekuni, Kosuke Okudera,
Shoken Hamada, Chihiro Sakamoto, Takumi Honda, Kosuke Matsushita, Satoru
Muramatsu, Takayuki Ebata, Daisuke Kajiya, Ken-ichi Saitow, Toshiaki Ikeda,
Takehiro Hirao, Takeharu Haino, Masayuki Watanabe, and Yoshiya Inokuchi Inorg.Chem.,2023,62, 1, 474–486. DOI:10.1021/acs.inorgchem.2c03618 ●Computational Studies on the Structures of Nanographenes with Various
Edge Functionalities Computational studies have often been carried out on hydrogen-terminated
nanographenes (NGs). These structures are, however, far from those deduced
from experimental observations, which have suggested armchair edges with
two carboxy groups on the edges as dominant. We conducted computational
studies on NGs consisting of C42, C60, C78, C96, C142, and C174 carbon
atoms with hydrogen, carboxy, and N-methyl imide-terminated armchair edges.
DFT calculations inform distorted basal planes and similar HOMO-LUMO gaps,
indicating that the edge oxidation and functionalization do not very influence
the electronic structure. Comparison of observed UV-vis spectra of carboxy-
and N-octadecyl chain terminated NGs with calculated spectra of model NGs
informs the contribution of pi-pi* transitions on the basal plane to the
absorptions in the visible region. A dimeric structure of NG and octadecyl-installed
NG demonstrate that both the distorted basal planes and the steric contacts
among the functional groups widen the surface-to-surface distance thereby
allowing the invasion of solvent molecules between the surfaces. This picture
is consistent with the improved solubility of edge-modified NGs. Shusaku Takahashi, Ryo Sekiya, and Takeharu Haino ChemPhysChem,2023,24, e202200465. ●Macromolecular architectures constructed by biscalix[5]arene-[60]fullerene
host-guest interactions This focus review is designed to summarize the development of macromolecular
architectures formed via biscalix[5]arene–[60]fullerene host–guest interactions.
Biscalix[5]arene–fullerene host–guest complexation leads to various macromolecular
architectures, including block polymers, star-shaped polymers, cross-linked
polymers, and one-handed helical polymers, and host–guest complexation
is not prevented by the long polymer chains owing to the high binding affinity
between biscalix[5]arene and fullerene. These macromolecular architectures
exhibited state-switching natures in response to environmental stimuli.
Notably, one of them displayed behavior concordant with those of corresponding
covalently linked polymers, including solution viscosity and thermal properties,
even though the structures were maintained by relatively weak noncovalent
interactions. These demonstrations indicate that biscalix[5]arene–[60]fullerene
host–guest interactions can be used to create supramolecularly connected
macromolecular architectures that can convert between assembled and disassembled
states because of the dynamic nature of noncovalent interactions. Takehiro Hirao Polym. J.,2023,55, 95–104. DOI: 10.1038/s41428-022-00732-x 2022 ●Development of Supramolecular Polymers with Unique Chain Structures Takehiro Hirao, Takeharu Haino Supramolecular Nanotechnology: Advanced Design of Self-Assembled Functional
Materials, edited by O. Azzaroni and M. Conda-Sheridan, VCH-Wiley, Weinheim
(ISBN-10: 3527349480) ●Improved synthesis of tetrakis(porphyrin) molecular cleft via palladium-mediated
cross-coupling between bis(porphyrin) boronic ester and bis(iodophenyl)butadiyne A tetrakis(porphyrin) was prepared by Suzuki-Miyaura cross coupling between
a bis(porphyrin) boronate ester and 1,4-bis(4-iodophenyl)-1,3-butadiyne.
The overall yield of the tetrakis(porphyrin) was improved to be more than
double the yield preciously reported. The successful preparation of the
tetrakis(porphyrin) was characterized by a combination of NMR and HRMS
techniques. Furthermore, HRMS evidenced the formation of supramolecular
polymeric species driven by bis(porphyrin)-bis(porphyrin) dimerization
in the gas phase. Naoyuki Hisano, Takehiro Hirao, Kouta Tanabe, and Takeharu Haino J. Porphyr. Phthalocyanines,2022,26, 683-689. DOI: 10.1142/S1088424622500523 ●Metal Nanoparticles on Lipophilic Nanographenes Utilization of graphitic domains on nanographenes (NGs) for anchoring metal
nanoparticles (NPs) can open the door for their applications in catalysis.
Reported examples employ hydrophilic graphene oxides as substrates, making
it difficult to coexist with organic substrates in organic solvents. The
title NGs are metal NP-doped lipophilic NGs (M-NG1). Various metal cations
form NPs with a diameter of a few to tens of nanometers on the basal plane.
Owing to the lipophilic nature of NG1, M-NG1 is prepared by the reduction
of the basal plane with sodium in THF followed by the addition of metal
salts. Au-NPs on NG1 allow anchoring an organic thiol carrying an anthracene
fluorophore, which is a proof of concept of composite materials utilizing
the surface of NGs. The assessment of the catalytic function of Pd-NG1
reveals that chlorobenzene and bromobenzene yield a coupling product, and
fluorobenzene also undergoes the reactions, demonstrating the catalytic
function of Pd-NG1. Shusaku Takahashi, Ryo Sekiya, and Takeharu Haino Angew. Chem. Int. Ed.,2022,61, e202205514.(Hot Paper) ●Chirality Induction on a Coordination Capsule for Circularly Polarized
Luminescence By utilizing a confined space inside a coordination capsule consisting
of achiral components, we achieve trimeric structures composed of acetic
acid and 2,3-disubstituted tartaric acid derivatives. Steric and electronic
interactions between the substituents on the tartaric acid and 2,2′-bipyridyl
arms of the capsule permit the transfer of the chirality of the tartaric
acid to the capsule, resulting in diastereoenrichment of the host-guest
complexes of up to 92 % de. The chiral templates can be washed away with
diethyl ether, leaving an enantiomerically enriched capsule. The resulting
capsule biases the dynamic axial chirality of a 4,4′-diacetoxybiphenyl
guest carrying benzothiadiazole units, demonstrating guest-to-capsule and
capsule-to-guest chirality transfer. The induced chirality on the bound
guest enables it to emit circularly polarized luminescence in the NIR region,
demonstrating the application of induced chirality for confined spaces
for the generation of chiroptical properties. Kentaro Harada, Ryo Sekiya, and Takeharu Haino Angew. Chem. Int. Ed.,2022,61, e202209340. ●共沸化合物を簡単に分離する。ー繰り返し使える吸着材料ー (解説)平尾岳大（Hirao Takehiro）, 月刊「化学」2022年8月号, p64-65. ●Self-assembly of neutral platinum complexes controlled by thermal inputs In this report, we describe the self-assembly behavior of neutral platinum
complexes in toluene. The platinum complexes were seen to form two different
types of assemblies depending on the preparation temperature. Masaya Yoshida, Takehiro Hirao, and Takeharu Haino Chem. Commun.,2022,58, 8356-8359. ●Integration of Nanographenes and Organic Chemistry – Toward Nanographene-based
Two-Dimensional Materials Graphene and its relatives have received considerable attention from the
fields of physics and chemistry since the isolation of pristine graphene
sheets. Nanographenes (NGs) are graphene fragments that are a few to tens
of nanometers in diameter. Compared to graphene and its relatives, such
as graphene oxides, NGs can be handled more easily, and their large surface
and oxygen functional groups on the edge allow postsynthetic modifications.
The study of NGs is gradually shifting from the development of synthetic
procedures to postsynthetic modification. From the structural point of
view, NGs can be regarded as two-dimensional carbon polymers. Their unique
structures and affinity for organic molecules make NGs excellent scaffolds
for two-dimensional materials, which are now an important topic in organic
and polymer chemistry. In this conceptual article, we introduce the position
of NGs from the perspective of two-dimensional substances and briefly review
both the structural features of NGs and the effects of functionalization
on their physical properties. These are valuable when producing reasonable
strategies for their postsynthetic modifications. Ryo Sekiya and Takeharu Haino ChemPhysChem,2022,23, e202200311.(Very Important Paper, Front Cover) ●Supramolecular Ensembles Formed via Calix[5]arene-Fullerene Host-Guest
Interactions This minireview introduces the research directions for the synthesis of
supramolecular fullerene polymers. First, the discovery of host-guest complexes
of pristine fullerenes is briefed. We focus on progress in supramolecular
fullerene polymers directed by the use of calix[5]arene-fullerene interactions,
which comprise linear, networked, helical arrays of fullerenes in supramolecular
ensembles. The unique self-sorting behavior of right-handed and left-handed
helical supramolecular fullerene arrays is discussed. Thereafter, an extensive
investigation of the calix[5]arene-fullerene interaction for control over
the chain structures of covalent polymers is introduced. Takehiro Hirao and Takeharu Haino Chem. Asian. J.,2022,17, e202200344. ●Chirality Induction in a Hydrophilic Metallohelicate The title compound is a water-soluble triply stranded metallohelicate 1Fe
composed of TEG-chain-installed calix[4]arene-based bis-bidentate ligands
and Fe3+ cations. This compound can incorporate up to two molecules of
small chiral cations (G1 and G2). Interestingly, G1 shows positive cooperativity
for host-guest complexation, whereas G2 exhibits noncooperativity, despite
having a greater affinity for 1Fe than G1. Density functional theory (DFT)
calculations indicate the metallohelicate cavity expands upon encapsulation
of the first guest. This conformational change facilitates the entrapment
of the second guest and explains why the interaction parameters of G1 and
G2 are larger than 1, despite electrostatic repulsion between the guests.
The DFT calculation predicts an intermolecular interaction between the
phenyl groups of G1 in the cavity, whereas no such interaction is found
for G2. This difference can explain the distinct molecular recognition
of G1 and G2. CD spectroscopy shows that both (R)-G1 and (R)-G2 induce
(M)-helicity in 1Fe and vice versa. DFT calculations suggest that the chirality
of the guests is transmitted to 1Fe via CH/O hydrogen bonds between the
guest and the C=O bond on the calix[4]arene strand. The CD intensity of
1Fe is nonlinear in the ee% of (R)- and (S)-G1, indicating that the presence
of the first guest increases the affinity of 1Fe toward a second guest
with the same chirality due to preorganization by the first guest. Masayuki Morie, Ryo Sekiya, and Takeharu Haino Chem. Asian J.,2022,17, e202200275. ●Host–Guest Complexation of Bisporphyrin Cleft and Electron-Deficient Aromatic
Guests The host–guest complexation of a bisporphyrin cleft with various electron-deficient
guest molecules was studied in solution and in the solid-state. X-ray crystal
structures of a bisporphyrin cleft with naphthalene dianhydride and 2,4,7-trinitrofluorenone
reveal that these guest molecules were located within the bisporphyrin
cleft and formed ideal π–π stacking interactions in a host–guest ratio
of 1:1. Isothermal titration calorimetry determined the binding constants
and thermodynamic parameters for the 1:1 host–guest complexations in 1,2-dichloroethane
and toluene. Two types of enthalpy–entropy compensation effects were found:
(1) The tightly stacked host–guest structures restrict guest movement within
the cleft, which results in significant desolvation with large intrinsic
entropies. (2) The loosely bound guests maintain their molecular freedom
within the bisporphyrin cleft, which leads to less desolvation with small
intrinsic entropies. Chiral guest encapsulation directed the clockwise
and anticlockwise twisted conformations of the bisporphyrin units, which
induced bisignate CDs. Naoyuki Hisano and Takeharu Haino J. Org. Chem.,2022,87, 4001-4009. ●Chiral Supramolecular Polymer Formed via Host-Guest Complexation of an
Octaphosphonate Biscavitand and a Chiral Diammonium Guest Chiral supramolecular polymers were constructed through the host-guest
complexation of an octaphosphonate biscavitand and a chiral diammonium
guest. Isothermal titration calorimetry determined that host-guest complexation
was enthalpy- and entropy-favored with the high binding constants. Diffusion-ordered
NMR spectroscopy and viscometry of the host-guest solution revealed that
supramolecular polymerization occurred, which most likely followed a ring-chain
mechanism. The cyclic oligomers and the supramolecular polymer chains were
visualized by atomic force microscopy. Circular dichroism was observed
when the octaphosphonate biscavitand and the chiral diammonium guest were
mixed, which suggested that chirally twisted supramolecular polymers were
formed. A chiral supramolecular polymer was constructed through host-guest
complexation between an octaphosphonate biscavitand and a chiral diammonium
guest. A ring-chain mechanism participated in supramolecular polymerization,
where a certain amount of cyclic oligomers most likely competed with supramolecular
polymers. The cyclic oligomers and the supramolecular polymer chains were
visualized by atomic force microscopy. The stereogenic centers of the guest
chirally twisted the supramolecular polymer chains in solution. Koki Hamada, Daisuke Shimoyama, Takehiro Hirao, Takeharu Haino Bull. Chem. Soc. Jpn.,2022,95, 621-627. ●Electrochromism of Nanographenes in the Near-Infrared Region Nanographene (NG) is a potential candidate for organic EC materials because
of its large π-conjugated system, chemical stability, absorption band covering
the visible region, and tunable optical properties by postsynthetic modification.
We show that NGs carrying redox-active triphenylamine (TPA) units covalently
linked to the NG edge function as EC materials in the NIR region. The hybrid
materials can be obtained by the installation of TPA units onto the NG
edge and display changes in the absorption spectrum in the NIR region extending
to a wavelength of over 2000 nm upon one-electron oxidation and reduction
at low potentials (<1.1 V). Time-dependent unrestricted density
functional theory calculation of a model NG at the UB3LYP/6-31G(d,p) level
of theory suggests that a narrow energy gap between the basal plane and
the oxidized TPA unit is responsible for the observed EC function in the
NIR region. Ikuya Matsumoto, Ryo Sekiya, Hiroji Fukui, Ren-De Sun, and Takeharu Haino Angew. Chem. Int. Ed.,2022,61, e202200291.(Hot Paper, Back Cover) ●Non-Racemically Twisted Supramolecular Fullerene Polymers 平尾岳大（Hirao Takehiro）・灰野岳晴（Haino Takeharu） 高分子, 71巻, 1号, pp. 6-6, 2022 ●Nanographene – A Scaffold of Two-Dimensional Materials Substances can be divided into 0D to 3D species based on the number of
repeating units (atom, ion, and molecule) and their arrangements in space
(point, linear, layer, and solid). Discrete substances belong to 0D species,
polymers are examples of 1D species, and molecular crystals are 3D species.
Most of the substances belong to one of these species. On the other hand,
those categorized into 2D species wherein the repeating units organize
a layer are less explored. 2D species have a surface and edges. The incorporation
of these structural features into a molecular design can realize multifunctionalized
systems that are difficult to achieve by conventional organic synthesis.
The development of 2D species is, therefore, the frontier of organic, inorganic,
and polymer chemistry. Nanographenes (NGs) are suitable scaffolds for realizing
2D species due to several factors, such as chemical stability and oxygen-containing
functional groups on the surface and on the edge, allowing postsynthetic
modifications. Our group has utilized NGs with tens of nanometers in diameters
for developing 2D species. Carboxy groups on the edge enable us to install
various substituents into NGs, offering NG-based functional materials.
These studies demonstrate that the integration of NGs with organic chemistry
can widen the scope of their applications other than optical materials
that are a main application of NGs. We introduce our recent studies on
the development of NG-based functional materials realized by postsynthetic
modifications. We hope that this account will contribute to the development
of the chemistry of 2D species. Ryo Sekiya and Takeharu Haino Chem. Rec.,2022,22, e202100257.(Cover Picture) ●Resorcinarene-based Supramolecular Capsules – Supramolecular Functions
and Applications A resorcinarene is a synthetic macrocycle comprising four resorcinol molecules
covalently linked by methylene bridges. The interannular bridges produce
a cavitand, which possesses a bowl-shaped structure. We have developed
supramolecular capsules formed through Ag(I) and Cu(I) coordination-driven
self-assembly of cavitands possessing 2,2’-bipyridyl arms at the upper
rim. The self-assembled capsules accommodate various molecular guests and
supramolecular assemblies possessing acetoxy groups. The host-guest chemistry
of the molecular capsules is applied to fabricate supramolecular polymers.
This account describes the recent developments in supramolecular chemistry
of resorcinarene-based coordination capsules and describes the brief history
of resorcinarene-based capsules and related capsules. Ryo Sekiya, Kentaro Harada, Natsumi Nitta, and Takeharu Haino Synlett,2022,33, 518-530. 2021 ●Self-Sorting Behavior in Supramolecular Fullerene Polymerization Directed
by Host-Guest Complexation between Calix[5]arene and C60 We describe self-sorting supramolecular polymerization that uses chiral
calix[5]arene hosts and a dumbbell-shaped fullerene guest. In a solution
containing the racemic host and the guest, the (S)-host and the (R)-host
preferably formed their homomeric complexes to form helical supramolecular
fullerene polymers in a self-sorting manner. The self-sorting behavior
has been studied using diffusion-ordered 1H NMR (DOSY) and circular dichroism
(CD) studies. The present findings show that it is possible to accomplish
controlled supramolecular polymerization. Takehiro Hirao, Naoka Fujii, Yoshiki Iwabe, and Takeharu Haino Chemm.Commun.,2021,57, 11831-11834. ●Synthesis and Conformational Characteristics of Calix[4]arene Oligomers Lower- and/or upper-rim functionalization of calix[4]arene realized a variety
of calix[4]arene systems. Compared to these monomeric calix[4]arenes, covalently
linked calix[4]arene oligomers have not been studied well. Calix[4]arene
oligomers can be utilized as building blocks of supramolecular complexes
as well as for the synthesis of calix[4]arene polymers. This background
motivated us to develop synthetic procedures for calix[4]arene oligomers
and to conduct conformational analysis of these oligomers. We produce oligomers
ranging from the monomer to the pentamer. The coupling of the pentamer
with 2,3-dibenzyloxy-1,4-benzenedicarboxylic acid can access a decamer
and oligomers. NMR measurements, X-ray crystal structure analysis, and
computational studies demonstrate that calix[4]arene oligomers can regulate
their length by changing the conformations of the calix[4]arene cores. Masauki Morie, Ryo Sekiya, and Takeharu Haino Bull. Chem. Soc. Jpn,2021,94, 2792-2799.(Selected Paper) ●Gas-Phase UV Spectroscopy of Chemical Intermediates Produced in Solution:
Oxidation Reactions of Phenylhydrazines by DDQ In this study, we demonstrated cold gas-phase spectroscopy of chemical
intermediates produced in solution. Herein, we combined an electrospray
ion source with a T-shaped solution mixer for introducing chemical intermediates
in solution into the gas phase. Specifically, the oxidation reaction of
2-(4-nitrophenyl)hydrazinecarboxaldehyde (NHCA) by 2,3-dichloro-5,6-dicyano-p-benzoquinone
(DDQ) was initiated by mixing the methanol solutions of NHCA and DDQ in
the T-shaped mixer, and the chemical species were injected into the vacuum
apparatus for ultraviolet photodissociation (UVPD) spectroscopy. A cationic
intermediate was strongly observed at m/z 150 in the mass spectrum, and
the UVPD spectrum was observed under cold (∼10 K) gas-phase conditions.
The UVPD spectrum showed a strong, broad absorption at ∼38,000 cm–1, accompanied
by a relatively weak component at ∼34,000 cm–1. These spectral patterns
can be ascribed to a diazonium cation intermediate, whose existence has
been predicted in a previous study. This report indicates that cold gas-phase
UV spectroscopy can be a useful method for identifying the structure of
chemical intermediates produced in solution. Shiori Machida, Motoki Kida, Satoru Muramatsu, Takehiro Hirao, Takeharu
Haino, and Yoshiya Inokuchi J. Phys. Chem. A,2021,125, 6697-6702. ●Solvent-Directed Formation of Helically Twisted Stacking Constructs via
Self-Assembly of Tris(phenylisoxazolyl)benzene Dimers Ureido-pyrimidinone (UPy)-appended tris(phenylisoxazolyl)benzenes were
synthesized. The UPy moieties of the tris(phenylisoxazolyl)benzenes stably
formed self-complementary dimers in solution. The dimers self-assembled
to form helically twisted stacking constructs driven by π-π stacking interactions
of UPy dimer moieties and dipole-dipole interactions of isoxazole units.
Strong association affinity was seen within the stacking constructs compared
with the previously reported isoxazole derivatives owing to the auxiliary
π-π stacking interaction. Notably, tris(phenylisoxazolyl)benzenes showed
an environmentally responsive nature. The absorption band, emission intensity,
and size of ensembles significantly depended on the mixing ratio of CHCl3
and methylcyclohexazne (MCH). Also, a sharp on-off switching nature was
seen in their circular dichroism (CD) and circularly polarized luminescence
(CPL) spectra in response to the mixing ratio of CHCl3 and MCH. CD and
CPL were activated only at a certain mixing ratio of CHCl3/MCH, thus showing
potential for the creation of molecular sensors. Yudai Ono, Takehiro Hirao and Takeharu Haino Org. Biomol. Chem.,2021,19, 7165-7171. ●Self-Complementary Structure of Bisporphyrin Dimer The crystal structure of a bisporphyrin cleft molecule revealed that the
head-to-head dimeric structure is directed by the intermolecular self-complementary
hydrogen-bonding interactions of amide groups and π-π stacking interactions.
The UV/Vis absorption spectrum of the homodimeric structure in the solid-state
resulted in a broad Soret band. Time-dependent density functional theory
(TD-DFT) calculation of the dimer indicated that an intra- and intermolecular
charge transfer transition as well as a π-π* transition were responsible
for the observed broad Soret bandThe crystal structure of a self-complementary
bisporphyrin dimer is reported. The head-to-head dimeric structure was
maintained by the assistance of hydrogen bonding interactions and π-π stacking
interactions. The UV-Vis absorption spectrum of the dimer showed a broad
Soret band in the solid state. TD-DFT calculation of the dimeric structure
revealed that a local π-π* electronic transition and intra- and intermolecular
charge transfer electronic transition most likely contribute to band broadening
at the Soret band. Naoyuki Hisano ,Takehiro Hirao , and Takeharu Haino Chem. Lett.,2021,50, 1844-1847. ●Negative Coorperativity in Guest Binding of Ditopic Self-Folding Biscavitand A brand-new self-folding biscavitand was synthesized from a feet-to-feet-connected
bisresorcinarene. The X-ray crystal structure of the biscaivtand showed
that the two cavities are tightly connected with four butylene linkages.
The conformationally coupled two cavities accommodated two cationic guests,
showing a homotropic negative cooperativity in nonpolar solvents (toluene
and chloroform). A polar tetrahydrofuran solvent weakened the cyclic hydrogen
bonding interactions of the biscavitand, which resulted in noncooperative
guest binding. Haruna Fujimoto, Daisuke Shimoyama, Katsuo Katayanagi, Naomi Kawata, Takehiro
Hirao, and Takeharu Haino Org. Lett.,2021,23, 6217–6221.(Supplementary Journal Cover) DOI:10.1021/acs.orglett.1c01837 ●SUPRAMOLECULAR CHEMISTRY OF FULLERENES (Book Chapter) Takehiro Hirao and Takeharu Haino, Handbook of Fullerene Science and Technology ●Chemical Modification of Nanographenes and Their Functions Ryo Sekiya and Takeharu Haino Journal of Synthetic Organic Chemistry,2021,79, 743-753. DOI:10.5059/yukigoseikyokaishi.79.743 ●(ナノ)グラフェン (This paper is written in Japanese) Ryo Sekiya and Takeharu Haino Journal of Synthetic Organic Chemistry,2021,79, 792. ●トップダウン法により得られるナノグラフェンの有機化学 (This paper is written in Japanese) （解説）特集：ナノカーボン材料はどこまで進んだか？ 関谷亮（Sekiya Ryo）・灰野岳晴（Haino Takeharu） 化学と工業 , 2021年6月号,p409-411. ●Polymerization of a Biscalix[5]arene Derivative Recent decades have seen an increased interest in the preparation of polymers
possessing host or guest moieties as the end group, which has enabled new
polymeric materials such as self-healable, shape-memory, and stimuli-responsive
materials. Such polymers are commonly synthesized by tethering the host
or guest moieties to polymers. On the other hand, there are limited reports
demonstrating the preparation of host- or guest-appended polymers by directly
polymerizing the corresponding host- or guest-appended monomers, which
is valuable for easy access to diverse polymers from single molecular species.
However, reactive host and/or guest moieties of the monomer interfere with
the polymerization reaction. Here, we report that a biscalix[5]arene host-appended
molecule can be polymerized with various monomers to form the corresponding
host-appended polymers. The host-guest complexation behavior of calix[5]arene-appended
polymers with fullerene derivatives was studied by 1H NMR and UV/vis spectroscopic
techniques, which revealed that the long polymer chains did not prevent
host-guest complexation even when the fullerene derivative was equipped
with a polymer chain. Thus, the present study shows the potential for developing
polymers that have various combinations of polymer chains. Takehiro Hirao, Kazushi Fukuta, and Takeharu Haino RSC Adv.,2021,11, 17587-17594. ●Self-assembly of neutral platinum complexes possessing chiral hydrophilic
TEG chains Neutral platinum complexes that possess chiral triethylene glycol (TEG)
moieties were synthesized. The platinum complexes formed helically twisted
stacked assemblies in chloroform and toluene, which were studied by 1H
NMR, UV/vis spectroscopy, and emission spectroscopy. On the other hand,
emissive micellar aggregates were observed in a THF/water mixed solvent.
Dynamic light scattering (DLS) experiments revealed that micellar aggregates
with a diameter (d) of ≈100 nm emitted strong light, whereas the monomeric
form and large aggregates (d > 500 nm) did not show luminescence
efficiently. Furthermore, the micellar aggregates were twisted chirally,
where the twisted direction was determined by the chirality of the TEG
moieties. The assemblies were observed to be solvent responsive, which
allows for the modulation of the nanostructure by changing the solvent
polarity. Masaya Yoshida, Takehiro Hirao, and Takeharu Haino Org. Biomol. Chem.,2021,19, 5303-5311.(Cover Picture) ●Self-Assembling Behavior and Chiroptical Properties of Carbazole-Cored
Phenyl Isoxazolyl Benzenes Carbazole-cored phenyl isoxazolyl benzenes possessing chiral moieties were
synthesized. The molecules self-assembled to form stacked supramolecular
assemblies in an isodesmic fashion in chloroform, whereas the molecules
preferably assembled in a cooperative fashion in methylcyclohexane (MCH),
which was determined by spectroscopic methods, including UV–vis absorption,
fluorescence, and 1H NMR spectroscopy. Clear nucleation and elongation
processes were observed in the plot of the degree of aggregation (αagg)
against temperature, which allowed us to determine the elongation temperature
(Te), the enthalpic gain in the elongation process (ΔHe), the equilibrium
constant between nucleation and elongation (Ka), and the degree of polymerization
at the elongation temperature ([Nn(Te)]). Circular dichroism (CD) and circularly
polarized luminescence (CPL) studies revealed the formation of helically
stacked assemblies in solution. Moreover, the majority-rule effect was
clearly observed in the solutions of mixtures of (S)- and (R)-1, indicating
the chiral amplification behavior of the helically stacked assemblies consisting
of (S)- and (R)-1. AFM provided morphological insight into the assemblies
on mica, which clearly indicates the formation of polymeric assemblies
in the solid state. Yudai Ono, Takehiro Hirao, Toshiaki Ikeda, and Takeharu Haino J. Org. Chem.,2021,86, 5499-5505.(Supplementary Journal Cover) ●Self-Assembly of Nanographenes Suitably decorated small aromatic systems can organize stacked structures
that display interesting properties arising from their unique morphologies.
Although nanographenes produced by top-down methods have graphitic domains
and can in principle be applied for such supramolecular systems, to the
best of our knowledge, no such example has been reported thus far. This
is partly because of their limited solubility in organic solvents and partly
because of their wide lateral size distribution. To realize nanographene-based
supramolecular aggregates, nanographenes carrying alkyl chains with narrow
lateral size distributions are employed. We find that the nanographenes
undergo self-assembly and that self-assembly is regulated by concentration,
solvent polarity, temperature, and sonication. Optical measurements and
AFM images indicate that stacked structures are possible candidates for
aggregates. A molecular mechanics calculation suggests that graphitic domains
inside the nanographenes can contact those of the nearest neighbors in
the aggregates, while graphitic domains near the edge are difficult to
make contact due to steric congestion. This model can rationalize a unique
PL response to temperature. The nanographenes showed concentration-dependent
morphologies on mica, stacked structures at low concentrations and polymer-like
network structures on mica at higher concentrations. Ikuya Matsumoto, Ryo Sekiya, and Takeharu Haino Angew. Chem. Int. Ed.,2021,60, 12706-12711. (Hot Paper, Frontispiece) ●Helically Organized Fullerene Array in a Supramolecular Polymer Main Chain To date, supramolecular chemistry techniques have been applied to fullerene
polymer synthesis, enabling the development of main-chain fullerene polymers
whose primary structure is well regulated, including linear, dendritic,
and net-like fullerene arrays. These research achievements have led to
an intriguing scientific challenge to create main-chain fullerene polymers
with higher structural regulation. Here, we report the fabrication of a
helically organized fullerene array based on the supramolecular polymerization
of chiral ditopic tetrakiscalix[5]arene hosts and a dumbbell-shaped fullerene.
The molecular association between the chiral hosts and the dumbbell-shaped
fullerene resulted in sizable supramolecular polymers in solution, with
the highest degree of polymerization of more than 32. The achiral dumbbell-shaped
fullerene exhibited circular dichroism in the π-π* transition bands arising
from the fullerene moieties through supramolecular polymerization. End-capping
experiments of the supramolecular helical polymers showed that the chirally
twisted conformation of the dumbbell-shaped fullerene was directed by supramolecular
polymerization. Finally, the helical morphology of the supramolecular polymer
chain was visualized by atomic force microscopy. The successful development
of helical main-chain fullerene polymers would break new ground in fullerene
chemistry. Tekehiro Hirao, Yoshiki Iwabe, Naoka Fujii, Takeharu Haino J. Am. Chem. Soc.,2021,143, 4339-4345. ●Folding and Unfolding of Acetoxy Group-Terminated Alkyl Chains Inside
a Size Regulable Hemicarcerand A resorcinarene-based hemi-carcerand, which consists of two cavitands covalently
linked to each other by four alkyl chains, allows structural expansion
and contraction by demetalation and metalation of Cu(I) cations with a
size change of approx-imately 12 Å. This metal-mediated switching of the
two states regulates the conformations of acetoxy group-terminated alkyl
chains. A guest binding study reveals the encapsulation of heptyl to undecyl
chains in metal-free and Cu(I)-coordinated capsules. The chemical shifts
of the acetoxy groups of the bound guests are the same in the metal-free
capsule, while those in the Cu(I)-coordinated one differ from each other.
This indicates that the metal-free capsule regulates its size to the bound
guests, while the bound guests adopt their conformations to the cavity
of the Cu(I)-coordinated capsules. 1H NMR measurements and molecular mechanics
calculations suggest that the bound guests have extended conformations
in the metal-free capsule, while the Cu(I)-coordinated capsule forces the
bound guests to adopt folded conformations. The presence of folded conformations
is supported by the conformational study with structurally similar capsules
and a non-symmetric guest, allowing us to observe NOEs stemming from folded
conformations of the guest in the cavity. Kentaro Harada, Ryo Sekiya, and Takeharu Haino J. Org. Chem.,2021,86, 4440-4447.(Supplementary Journal Cover) ●Translational Isomers of N-sulfonylated [3]Catenane: Synthesis and Isomerization N-Sulfonylated [3]catenanes, which exist as two translational isomers,
were synthesized. The X-ray crystal structure of the distal isomer of [3]catenane,
which has higher symmetry, revealed hydrogen bonds involving the carboxylic
acid moieties on the terminal rings. The thermodynamic parameters of the
isomerization revealed that this hydrogen bonding influenced the isomerization
process. Hajime Iwamoto, Yuki Ishizu, Eietsu Hasegawa, Ryo Sekiya, and Takeharu
Haino Chem. Commun.,2021,57, 1915-1918. ●Nanographenes from Distinct Carbon Sources This article reports the production protocol of nanographenes and the effect
of the reaction conditions on their structures and optical properties.
These fundamental studies are of value for exploring suitable reaction
conditions for the production of nanographenes with desirable properties.
Graphite, finely crushed graphite powders, and artificial graphite, all
of which are commercially available, are employed. Nanographenes are produced
by the acid-assisted oxidative cleavage of the parent carbons followed
by neutralization and deionization. The use of dialysis membranes for the
size separation of nanographenes offers nanographenes with a specific size
distribution, thereby allowing their structures and optical properties
to be compared. Experiments demonstrate that small amounts of acids (60
ml of conc. H2SO4 and 20 mL of 60% HNO3) and oxidation for 12 h promotes
a more efficient and cost-effective production of nanographenes from 2
g of a carbon source. The functionalization of the nanographene edges with
p-propargyloxybenzyl amine confirms that the armchair edge with two carboxy
groups is the dominant edge structure, irrespective of the carbon source. Ikuya Matsumoto, Ryo Sekiya, and Takeharu Haino Bull. Chem. Soc., Jpn.,2021,94, 1394-1399.(Selected Paper, Inside Cover) ●Blueish-white-light-emitting Nanographenes Developed by Pd-Catalyzed Suzuki-Miyaura
Cross Coupling Reactions Top-down methods produce nanographenes with many carboxy groups on their
edges. These functional groups can be utilized for developing multichromophoric
systems. As proof of concept, pyrene is installed on the edges by Pd-catalyzed
cross-coupling reactions. The lack of monomer emissions from the functionalized
nanographenes indicates that the neighboring chromophores are sufficiently
distant to form the excimer. The pyrene-installed nanographene emits bluish-white-light.
Its lipophilic nature allows fabricating a nanographene-dispersed polymethyl
methacrylate film emitting visible light. Shohei Nishitani, Ryo Sekiya, Ikuya Matsumoto, and Takeharu Haino Chem. Lett.,2021,50, 664-667. ●Programmed Dynamic Covalent Chemistry System of Addition-Condensation
Reaction of Phenols and Aldehydes Application of a dynamic covalent chemistry strategy to the reversible
reaction system of resorcinol and α, ω-alkanedials [(CH2)m(CHO)2] (m =
2 ~ 10) in ethanol in the presence of hydrogen chloride (HCl) solution
as a catalyst at 80 °C for 48 h afforded the thermodynamically most stable
products with high selectivity. The reaction of 1,4-butanedial afforded
a ladder polymer containing calixarene skeletons in the main chain in quantitative
yield. 1,5-Pentanedial gave Noria, a water-wheel-like cyclic oligomer,
in high yield. Calixarene-dimer-type cyclic oligomers were formed selectively
from 1,6-hexanedial, 1,8-octanedial, 1,10-decanedial, and 1,12-dodecanedial,
while calixarene-trimer-type cyclic oligomers were obtained selectively
from 1,7-heptanedial, 1,9-nonanedial, and 1,11-undecanedial. The Noria
like macrocyles NoriaPY NoriaMP and NoriaEP could be also synthesized via
DCC system using pyrogallol, 3-methoxyphenol, and 3-ethoxyphenol. A triple-ringed[14]arene
could be synthesized via DCC system using the reaction of 2-methylresorcinol
and m-benzenedicarbaldehyde. Hiroto Kudo, Daisuke Shimoyama, Ryo Sekiya, and Takeharu Haino Chem. Lett.,2021,50, 825-831. ●Supramolecular fluorescent sensors: An historical overview and update Since as early as 1867, molecular sensors have been recognized as being
intelligent “devices” capable of addressing a variety of issues related
to our environment and health (e.g., the detection of toxic pollutants
or disease-related biomarkers). In this review, we focus on fluorescence-based
sensors that incorporate supramolecular chemistry to achieve a desired
sensing outcome. The goal is to provide an illustrative overview, rather
than a comprehensive listing of all that has been done in the field. We
will thus summarize early work devoted to the development of supramolecular
fluorescent sensors and provide an update on recent advances in the area
(mostly from 2018 onward). A particular emphasis will be placed on design
strategies that may be exploited for analyte sensing and corresponding
molecular platforms. Supramolecular approaches considered include, inter
alia, binding-based sensing (BBS) and indicator displacement assays (IDAs).
Because it has traditionally received less treatment, many of theillustrative
examples chosen will involve anion sensing. Finally, this review will also
include our perspectives on the future directions of the field. Chenxing Guo, Adam C. Sedgwick, Takehiro Hirao, and Jonathan L. Sessler Coord. Chem. Rev.,2021,427, 213560. ●A Light‐Harvesting/Charge‐Separation Model with Energy Gradient Made of
Assemblies of meta‐pyridyl Zinc Porphyrins Self‐assembly of porphyrins is a fascinating topic not only for mimicking
chlorophyll assemblies in photosynthetic organisms but also for the potential
of creating molecular‐level devices. Herein we have prepared zinc porphyrin
derivatives bearing a meta‐pyridyl group at the meso‐position and studied
their assemblies in chloroform. Among porphyrins studied, one with a carbamoylpyridyl
moiety (ZnPPyC) gave distinct 1H NMR spectrum in CDCl3, which allowed us
to probe the supramolecular structure in solution in detail. Ring‐current
induced chemical shift changes in 1H NMR, together with vapor pressure
osmometry and diffusion‐ordered NMR spectroscopy, among other evidence,
suggested that the porphyrin molecules form a trimer in a triangular cone
structure. Further incorporation of a directly‐linked porphyrin‐ferrocene
dyads with the same assembling properties in the assemblies lead to a rare
light‐harvesting/charge‐separation model, in which an energy gradient is
incorporated and reductive quenching occurs. Joe Otsuki, Takumi Okumura, Kosuke Sugawa, Shin-ichiro Kawano, Kentaro
Tanaka, Takehiro Hirao, Takeharu Haino, Yu Jin Lee, Seongsoo Kang, Dongho
Kim Chem. Eur. J.,2021,27, 4053-4063. ●Stereoselectivity in Dehydrative Cyclic Trimerization of Substituted 4-Alkylaminobenzoic
Acids Cyclic trimerization of substituted 4-alkylaminobenzoic acids were investigated.
From NMR analyses of DiMeO_C3A with two methoxy groups, which was obtained
by using SiCl4 as a dehydrative condensation reagent and purified by preparative
GPC, exhibited the syn/anti ratio of 60/40. On the other hand, 3Br_C3A
with one bromine group at the ortho-position relative to the amide nitrogen
was synthesized by using PPh3/Cl3CCCl3 as a dehydrative condensation reagent
and isolated by SiO2 colum chromatography. 3Br_C3A showed an inverse stereoselectivity,
namely, the syn/anti ratio of 25/75 was calculated based on the conprehensive
NMR analyses. The population of stereoisomers had no relationship with
the dehydrative condensation reagent and reaction temperature. Solvent
character also had a negligible influence on the syn/anti ratio in solution
reflecting the rigid structure of 3Br_C3A. Koji Takagi, Hinako Yamaguchi, Daiki Miyamoto, Yuka Deguchi, Takehiro Hirao
and Takeharu Haino New J. Chem.,2021,45, 1187-1193. ●Calix[4]arene-Based Triple-Stranded Metallohelicate in Water The title complex is a triple-stranded metallohelicate organized by the
self-assembly of 5,17-difunctionalized calix[4]arenes and metal cations
with octahedral coordination geometry. Due to hydrophilic triethylene glycol
chains on the lower rim of the calix[4]arene, the metallohelicate can encapsulate
cationic guests in water. NMR and UV-vis titration experiments reveal that
the metallohelicate captures a pyridinium guest with an alanine derivative
to form a host-guest complex with a host-guest ratio of 1:1. CD spectroscopy
confirms the bias of the P- and M-helical sense of the metallohelicate
by the captured guest. The metallohelicate captures two molecules of dicationic
N,N’-dimethyl-DABCO and monocationic N-methyl quinuclidine, exhibiting
a positive allosteric effect. 1H NMR titration experiments indicate that
the bound guests are in close proximately to the aromatic rings of the
ligands. Molecular mechanics calculations based on the UV-vis and NMR observations
suggest that the first guest preorganizes the conformation of the metallohelicate
to facilitate access of the second guest to the cavity. Masayuki Morie, Ryo Sekiya, and Takeharu Haino Chem. Asian J.,2021,16, 49-55.(Cover Picture) ● Edge Functionalized Nanographenes Nanographenes (NGs) have recently emerged as new carbon materials. Their
nanoscale size results in a size-dependent quantum confinement effect,
opening the band gap by a few eV. This energy gap allows NGs to be applied
as optical materials. This property has attracted researchers across multiple
scientific fields. The photophysical properties of NGs can be manipulated
by introducing organic groups onto their basal planes and/or into their
edges. In addition, the integration of organic functional groups into NGs
results in NG-based hybrid materials. These features make the postsynthetic
modification of NGs an active research area. Since obtainable information
on chemically functionalized NGs is limited due to their nonstoichiometry
and structural uncertainty, their structural characterization requires
a combination of multiple spectroscopic methods. Therefore, information
on the characterization procedures of recently published chemically functionalized
NGs is of value for advancing the field of NG-based hybrid materials. The
present review focuses on the structural characterization of chemically
functionalized NGs. We hope this review will help to advance this field. Ryo Sekiya and Takeharu Haino Chem. Eur. J.,2021,27, 187-199.(This article was selected as a Review Showcase.) 2020 ●Conformation of K+(Crown Ether) Complexes Revealed by Ion Mobility-Mass
Spectrometry and Ultraviolet Spectroscopy The conformation and electronic structure of dibenzo-24-crown-8 (DB24C8)
complexes with K+ ion were examined by ion mobility–mass spectrometry (IM–MS),
ultraviolet (UV) photodissociation (UVPD) spectroscopy in the gas phase,
and fluorescence spectroscopy in solution. Three structural isomers of
DB24C8 (SymDB24C8, Asym1DB24C8, and Asym2DB24C8) in which the relative
positions of the two benzene rings were different from each other were
investigated. The IM–MS results at 86 K revealed a clear separation of
two sets of conformers for the K+(SymDB24C8) and K+(Asym1DB24C8) complexes
whereas the K+(Asym2DB24C8) complex revealed only one set. The two sets
of conformers were attributed to the open and closed forms in which the
benzene–benzene distances in the complexes were long (>6 Å) and
short (<6 Å), respectively. IM–MS at 300 K could not separate the
two conformer sets of the K+(SymDB24C8) complex because the interconversion
between the open and closed conformations occurred at 300 K and not at
86 K. The crown cavity of DB24C8 was wrapped around the K+ ion in the complex,
although the IM–MS results availed direct evidence of rapid cavity deformation
and the reconstruction of stable conformers at 300 K. The UVPD spectra
of the K+(SymDB24C8) and K+(Asym1DB24C8) complexes at ∼10 K displayed broad
features that were accompanied by a few sharp vibronic bands, which were
attributable to the coexistence of multiple conformers. The fluorescence
spectra obtained in a methanol solution suggested that the intramolecular
excimer was formed only in K+(SymDB24C8) among the three complexes because
only SymDB24C8 could possibly assume a parallel configuration between the
two benzene rings upon K+ encapsulation. The encapsulation methods for
K+ ion (the “wraparound” arrangement) are similar in the three structural
isomers of DB24C8, although the difference in the relative positions of
the two benzene rings affected the overall cross-section. This study demonstrated
that temperature-controlled IM–MS coupled with the introduction of appropriate
bulky groups, such as aromatic rings to host molecules, could reveal the
dynamic aspects of encapsulation in host–guest systems. Sota Tanaka, Yomoyuki Ujihira, Mayuko Kubo, Motoki Kida, Daisuke Shimoyama,
Satoru Muramatsu, Manabu Abe, Takeharu Haino, Takayuki Ebata, Fuminori
Misaizu, Keijiro Ohshimo, and Yoshiya Inokuch J. Phys. Chem. A,2020,124, 9980–9990. ●Absorption of Chemicals in Amorphous Trisresorcinarene Abstract:Trisresorcinarene is an interesting class of macrocyclic hosts. Its insoluble
nature and conformationally flexible structure allow its application as
a solid absorbent. Various aromatic and aliphatic hydrocarbons are absorbed
into the amorphous solid of the trisresorcinarene, demonstrating the versatile
absorption capability of trisresorcinarene. Shimoyama, Daisuke; Sekiya, Ryo; Haino Takeharu Chem. Commun.,2020,56, 12582-12585. ●Feet‐to‐Feet‐Connected Multitopic Resorcinarene Macrocycles Abstract:The past three decades have witnessed extraordinary advances in the preparation
of macrocycles from a resorcinarene platform. Bridging two or more resorcinarene
units through multipoint connections produces multitopic resorcinarene‐based
hosts. The unique properties arising from multivalency offer diverse applications,
such as molecular flasks, molecular machines, and supramolecular polymers.
The face‐to‐face connection of two or more resorcinarenes results in a
convergent, expanded guest binding space in which many large guests can
be accommodated. In contrast, the feet‐to‐feet connection provides an extroverted,
ditopic feature that can lead to different applications. Herein, we highlight
the synthesis of extroverted, multitopic resorcinarene macrocycles and
discuss their fascinating functions, such as molecular recognition, allosteric
guest binding, and supramolecular polymerization. Shimoyama, Daisuke; Haino, Takeharu Asian. J. Org. Chem.,2020, 1718-1725. ●Prof. Haino's Author Profile has been published in Angew. Chem. Int. Ed. ●One-dimensional arrangement of NORIA in the solid-state Abstract:NORIA is a synthetic macrocycle consisting of twelve resorcinol rings.
The hydroxy groups surrounding the surface of NORIA make it difficult for
NORIA to be dissolved in organic solvents, except for polar solvents, a
property which is ideal for developing solid-state materials. For developing
solid-state materials, information about the effect of the crystallization
conditions on the crystal packing of NORIA is required, although only limited
examples have been reported so far. We find that the crystal packing of
NORIA depends heavily on the crystallization conditions. Single crystals
are grown in DMF solutions by the slow diffusion of pentane, cyclohexane,
methylcyclohexane, benzene, and toluene into the solution. X-ray diffraction
analysis demonstrates that the saturated hydrocarbon vapors induce the
molecules to organize into a triclinic crystal packing, whereas another
crystal packing, wherein NORIA is arranged linearly in the hexagonal crystal,
is formed in the case of aromatic vapors. In the five crystals, DMF molecules
are trapped by NORIA and interact with neighboring hosts through hydrogen
bonding, indicating that the DMF molecules function as linkers. The X-ray
crystal structures suggest that the planarity of the guests is a factor
behind the formation of the hexagonal crystal packing. Electron density
maps and the solvent accessible surface of NORIA suggest that small molecules,
such as water, can access the cavity. The large solvent-accessible volumes
in the unit cells of both crystal packings demonstrate that NORIA functions
as an excellent building block for lattice inclusion compounds. Shimoyama, Daisuke; Sekiya, Ryo; Maekawa, Hiroyuki; Kudo, Hiroto; Haino,
Takeharu CrystEngComm,2020,22, 4740-4747 ●A dual redox-responsive supramolecular polymer driven by molecular recognition
between bisporphyrin and trinitrofluorenone Abstract:A dual redox-responsive supramolecular polymer driven by molecular recognition
between bisporphyrin (bisPor) and trinitrofluorenone (TNF) has been developed.
The supramolecular polymer was degraded into monomers in response to both
oxidation and reduction stimuli. Hisano, Naoyuki; Hirao, Takehiro; Haino, Takeharu Chem. Commun.,2020,56, 7553-7556 ●Construction of Helically Stacked π‐Electron Systems in Poly(quinolylene‐2,3‐methylene)
Stabilized by Intramolecular Hydrogen Bonds Abstract:π‐Stacked polymers, which consist of layered π‐electron systems in a polymer,
can be expected to be used in molecular electronic devices. However, the
construction of a stable π‐stacked structure in a polymer is considerably
challenging because it requires sophisticated designs and precise synthetic
methods. Herein, we present a novel π‐stacked architecture based on poly(quinolylene‐2,3‐methylene)
bearing alanine derivatives as the side chain, obtained through the living
cyclo‐copolymerization of an o‐allenylaryl isocyanide. In the resulting
polymer, the neighboring quinoline rings of the main chain form a layered
structure with π–π interactions, which is stabilized by intramolecular
hydrogen bonds. The vicinal quinoline units form two independent helices
and the whole molecule is a twisted‐tape structure. This structure is established
on the basis of UV/CD spectra, theoretical calculations, and atomic‐force
microscopy. Kataoka, Yuki; Kanbayashi, Naoya; Fujii, Naoka; Okamura, Taka‐aki; Haino,
Takeharu; Onitsuka, Kiyotaka Angew. Chem. Int. Ed.,2020,59, 10286-10291 ●Self‐Healing Supramolecular Materials Constructed by Copolymerization
via Molecular Recognition of Cavitand‐Based Coordination Capsules Abstract:The repeating guest units of poly‐(R)‐2 were selectively encapsulated by
the self‐assembled capsule poly‐1 possessing eight polymer side chains
to form the supramolecular graft polymer (poly‐1 )n⋅poly‐(R)‐2 . The encapsulation
of the guest units was confirmed by 1H NMR spectroscopy and the DOSY technique.
The hydrodynamic radius of the graft polymer structure was greatly increased
upon the complexation of poly‐1 . The supramolecular graft polymer (poly‐1
)n⋅poly‐(R)‐2 was stably formed in the 1:1 host–guest ratio, which increased
the glass transition temperature by more than 10 °C compared to that of
poly‐1 . AFM visualized that (poly‐1 )n⋅poly‐(R)‐2 formed the networked
structure on mica. The (poly‐1 )n⋅poly‐(R)‐2 gelled in 1,1,2,2‐tetrachloroethane,
which led to fabrication of distinct viscoelastic materials that demonstrated
self‐healing behavior in a tensile test. Nitta, Natsumi; Takatsuka, Mei; Kihara, Shin‐ichi; Hirao, Takehiro;Haino,
Takeharu Angew. Chem. Int. Ed.,2020, accepted. ●Helicity of a polyacetylene directed by molecular recognition of biscalixarene
and fullerene Abstract:Chiral biscalixarenes and a C60-appended polyphenylacetylene have been
synthesized. The chiral biscalixarene encapsulated the C60 unit of the
phenylpolyacetylene, which induced the preferred helicity of the polyacetylene. Hirao, Takehiro; Iwabe, Yoshiki; Naoyuki Hisano; Haino, Takeharu Chem. Commun.,2020,56, 6672-6675 ●Columnar Organization of Carbo[5]helicene Directed by Peripheral Steric
Perturbation Abstract:Three carbo[5]helicenes ([5]CHs) containing benzylmaleimide groups displayed
columnar stacked organizations, including dislocated, parallel, and alternating
(P)- and (M)-helix molecular arrangements in the solid state. The peripheral
benzyl groups resulted in very small steric interactions that are responsible
for the formation of columnar stacked arrangements in the crystalline state. Hirao, Takehiro; Ono, Yudai; Kawata, Naomi; Haino,Takeharu Org. Lett.,2020, 22, 5294-5298 DOI:10.1021/acs.orglett.0c01421 ●A Supramolecular Approach to Polymer-Shape Transformation via Calixarene-Fullerene
Complexation Abstract:We synthesized fullerene-terminated polymethyl methacrylates (PMMAs), linear
ditopic calix[5]arene host, and branched tritopic calix[5]arene host. The
calix[5]arene hosts bound to the fullerene moieties of the PMMAs, inducing
shape transformation among three different polymer shapes, namely, short
PMMA, long PMMA, and star-shaped PMMA, in solution. The transformation
was studied using UV/vis spectroscopy, fluorescence spectroscopy, diffusion
ordered NMR spectroscopy, size-exclusion chromatography, viscometry, and
differential scanning calorimetry. Dynamic light scattering measurements
confirmed that the transformation between the individual shapes was induced
by application of external stimuli, including prechosen molecules and heating
of the solution. Of particular note is that atomic force microscopy revealed
that PMMA illustrated an additional shape, namely, a spherical shape, in
the solid state due to the cohesive nature of its fullerene moiety. The
present study illustrated that a supramolecular approach to polymer-shape
regulation allows access to multiple distinct polymer shapes in sequence. Hirao, Takehiro; Fukuta, Kazushi; Haino, Takeharu Macromolecules,2020,53, 3563–3570. DOI:10.1021/acs.macromol.0c00621 ●Chemically Functionalized Two-Dimensional Carbon Materials Abstract:Nanographenes (NGs), also known as graphene quantum dots, have recently
been developed as nanoscale graphene fragments. These nanocarbon species
can be excited with UV light and emit light from the UV‐to‐visible region.
This photoemission has received great attraction across multiple scientific
fields. NGs can be produced by cutting off carbon sources or fusing small
organic molecules to grow graphitic structures. Furthermore, the organic
synthesis of NGs has been intensely studied. Recently, the number of research
papers on postsynthetic modifications of NGs has gradually increased. Installed
organic groups can tune the properties of NGs and provide new functionalities,
opening the door for the development of sophisticated carbon‐based functional
materials. This review sheds light on recent progress in the postsynthetic
modification of NGs and provides a brief summary of their production methods. Sekiya, Ryo; Haino, Takeharu Chem. Asian J.,2020,15, 2316-2328. ●Supramolecular Polymerization and Functions of Isoxazole Ring Monomers Abstract:Head-to-tail dipole-dipole arrays of isoxazole rings lead to supramolecular
helical assemblies where the assembly and disassembly are regulable based
on temperature and solvent properties. The cooperative supramolecular polymerization
characterized by a two-step polymerization consisting of nucleation and
elongation is driven by the multiple dipole array as well as the induced
dipoles in the supramolecular organization. The helical supramolecular
assemblies are fabricated with the aid of multiple dipole–dipole interactions.
The chiroptical properties, such as CD and CPL, are determined by the right-handed
and left-handed helicities of the supramolecular organizations, which are
directed by the stereogenic side chains. The AIE and AIEE are established
in the supramolecular assemblies. The AIE feature of the platinum complex
is inherent in the supramolecular assemblies, which results in luminogenic
micelles. Emissive supramolecular micelles are fabricated. In this review,
these aspects are briefly described, emphasizing the importance of the
intermolecular dipole-dipole interactions in supramolecular chemistry. Haino, Takeharu; Hirao, Takehiro Chem. Lett.,2020,49, 574-584. ●Upper-Rim Functionalization and Supramolecular Polymerization of a Feet-to-Feet-Connected
Biscavitand Abstract:An octaiodobiscavitand was synthesized by an aromatic Finkelstein iodination
reaction in good yield. Sonogashira and Suzuki coupling reactions of the
octaiodobiscavitand gave rise to upper-rim-functionalized biscavitands
that self-assembled to form the supramolecular polymer in the solid state. Shimoyama, Daisuke; Sekiya, Ryo; Haino Takeharu Chem. Commun.,2020,56, 3733-3736. ●Folding control of a non-natural glycopeptide using saccharide-coded structural
information for polypeptides Abstract:We synthesized “glyco-arylopeptides”, whose folding structure significantly
changes depending on the kind of saccharide in their side chain. The saccharide
moiety interacts with the main chain via hydrogen bonding, and the non-natural
polypeptides form two well-defined architectures—(P)-31- and (M)-41-helices—depending
on the length of the saccharide chains and even the configuration of a
single stereo-genic center in the epimers. Ishido, Yuki; Kanbayashi, Naoya; Fujii, Naoka; Okayamura, Taka-aki; Haino,
Takeharu;Onitsuka Kiyotaka Chem. Commun.,2020,56, 2767-2770. ●A Regulable Internal Cavity Inside A Resorcinarene‐Based Hemi‐Carcerand Abstract:Covalent organic capsules, such as carcerands and hemi‐carcerands, constitute
an interesting class of molecular hosts. These container molecules have
confined spaces capable of hosting small molecules, although the size of
the inner cavities cannot be changed substantially, limiting the scope
of the applications. The title covalently linked container is produced
by metal‐directed dimerization of a resorcinarene‐based cavitand possessing
four 2,2’‐bipyridyl arms on the wide rim followed by olefin metathesis
at the vertexes of the resulting capsule with a second‐generation Grubbs
catalyst. The covalently linked bipyridyl arms permit expansion of the
inner cavity by demetalation. This structural change influences the molecular
recognition properties; the metal‐coordinated capsule recognizes only 4,4’‐diacetoxybiphenyl,
while a metal‐free counterpart can encapsulate not only 4,4’‐diacetoxybiphenyl
but also 2,5‐disubstituted‐1,4‐bis(4‐acetoxyphenylethynyl)benzene, which
is 9.4 Å longer than the former guest. Molecular mechanics calculations
predict that the capsule expands the internal cavity to encapsulate the
long guest by unfolding the folded conformation of the alkyl chains, demonstrating
the flexible and regulable nature of the cavity. The guest competition
experiments show that the preferred guest can be switched by metalation
and demetalation. Harada, Kentaro; Sekiya, Ryo; Haino, Takeharu Chem. Eur. J.,2020,26, 5810-5817. ●トップダウン法により得られる化学修飾ナノグラフェン Chemically Functionalized Nanographenes Produced by Top-down Method Abstract:Nanographenes, which are nanoscale graphene fragments, can be obtained
by cutting off carbonaceous materials. This procedure, so-called top-down
method, allows the gram-scale production of nanographenes. Our group has
utilized these nanographenes for developing carbon-based functional materials.
The installation of organic groups into the edge of nanographenes realized
functionalized nanographenes. These nanographenes exhibit interesting properties,
such as white-light emission, supramolecular polymerization and near-infrared
emission. Sekiya, Ryo; Haino, Takeharu ファインケミカル, 2020年, 1月 (This article is written in Japanese.) ●AIE-active Micells Formed by Self-assembly of an Amphiphilic Platinum
Complex Possessing Isoxazole Moieties Abstract:An increased interest in the use of platinum complex based luminescent
micelles for imaging biological tissues has emerged in recent years due
to their low cytotoxicity, synthetic flexibility, photostability, and high
emission efficiency. Here, we report a luminescent micelle that is prepared
through the self-assembly of an amphiphilic, neutral Pt(II) complex with
isoxazole moieties in THF/water on account of its aggregation-induced emission
(AIE) property. Hirao, Takehiro; Tsukamoto, Hidemi; Ikeda, Toshiaki;Haino,Takeharu Chem. Commun.,2020,56, 1137-1140. ●Entropy–driven Cooperativity in the Guest Binding of an Octaphosphonate
Biscavitand Abstract:Uncommon entropy‐driven cooperativity is reported in the guest binding
of an octaphosphonate biscavitand. Isothermal titration calorimetry analysis
determined the thermodynamic parameters for the 1:2 host‐guest binding
of biscavitands with ammonium guests in methanol, ethanol, isopropanol,
and chloroform. Chloroform drove uncommon entropy‐driven cooperative binding,
whereas the alcohols resulted in enthalpy‐driven noncooperative binding.
1H NMR studies revealed that each cavity possessed six water molecules
in chloroform, which were liberated upon the guest binding. The enthalpy‐entropy
compensation relationship produced a large positive intrinsic entropy in
chloroform, which implies that water desolvation causes a considerable
entropic gain by paying an enthalpic penalty due to breaking the hydrogen
bonding networks of the water clusters. Shimoyama, Daisuke; Haino, Takeharu Chem. Eur. J.,2020,26, 3074-3079. ●Chirality-Embedded Nanographene Abstract:The development of chiral nanographenes hasmostly been carried out by bottom-up
methods and examplesof species developed by the post-modification of nanogra-phenes
prepared by top-down methods remain limited. Weshow that the attachment
of chiral functional groups onto theedge of nanographenes generates chirality
on the surface. X-ray diffraction analysis and DFT calculations indicate
that thechirality of the functional groups is transferred to the surfacevia
steric interactions from the chiral center through the five-membered cyclic
imide to the nanographene edge. The excitoncoupling between the p-bromophenyl
groups confirms that thefunctional groups are arranged on the armchair
edges atdistances that permit exciton coupling, which provides infor-mation
about their relative orientation. These pieces ofinformation help to elucidate
the edge structure of nano-graphenes prepared by top-down methods. Nishitani, Shohei; Sekiya, Ryo; Haino Takeharu Angew. Chem. Int. Ed.,2020,59, 669-673.(Hot Paper) ●Feet-to-feet Connected Trisresorcinarenes Abstract:The macrocyclization of resorcinol and odd-numbered bisdioxolanes under
acidic conditions produced feet-to-feet connected trisresorcinarenes possessing
three resorcinarene units linked with odd-numbered alkyl chains. The formation
of trisresorcinarenes was confirmed using high-resolution mass spectrometry
and NMR spectroscopy. The trisresorcinarenes were isolated as protected
forms in moderate yields. The protected trisresorcinarenes exhibited D3h
symmetry in conformation in solution. Crystal structure analysis revealed
that the protected trisresorcinarenes possess large inner spaces surrounded
by three resorcinarene units. Shimoyama, Daisuke; Sekiya, Ryo; Kudo, Hiroto; Haino, Takeharu Org. Lett.,2020,22, 352-356. DOI:10.1021/acs.orglett.9b03693 2019 ●A Protocol for Separation of Nanographenes Abstract: Top-down methods are convenient preparative methods for nanographenes,
although the products consist of graphene fragments with a broad size distribution.
We show that a combination of dialysis membranes (50, 25, 15, 8, and 2
kD) can conveniently separate nanographenes into five size distributions.
The separated nanographenes can be employed as starting materials for carbon-based
functional materials. Matsumoto, Ikuya; Sekiya, Ryo;Haino, Takeharu RSC Adv.,2019,9, 33843-33846.(Hot Article) This article was adressed in RSC Advances Blogs. ●Conformational Characteristics of Feet-to-Feet-Connected Biscavitands Abstract: X-ray crystallography of an acetoxy-protected bisresorcinarene and biscavitands
possessing phosphonate and dialkylsilyl bridges revealed that the bisresorcinarene
and the biscavitands adopt helical forms in the solid state. Helical conformations
were also found in solution. The helix–helix interconversions of the biscavitands
occurred with high activation barriers of more than 50 kJ mol–1. The activation
parameters of the helix–helix interconversions were determined using exchange
spectroscopy (EXSY). The positive activation enthalpies and the negative
activation entropies suggest that the transition states of the helix–helix
interconversion process are most likely more strained and symmetric than
the ground states. The compensatory enthalpy–entropy correlation is found
in the series of activation parameters, giving rise to a compensation temperature
of 254 K. Shimoyama, Daisuke; Haino,Takeharu J. Org. Chem.,2019,84, 13483-13489. ●Intrinsic Emission from Nanographenes Abstract:Top‐down approaches have been widely used as convenient methods for the
production of nanographenes. To understand the photoemission properties
of nanographenes, their separation and the optical properties of the individual
fractions is important. By using a combination of size‐exclusion and silica‐gel‐adsorption
chromatography, we separated lipophilic nanographenes that contained para‐methoxybenzyl
groups. The mixture consisted of large (average 19.8 nm) and small (average
4.9 nm) nanographenes, whilst unreacted carboxy groups remained in the
latter group. Optical measurements revealed that oxygen‐containing functional
groups had little influence on the photoemission of the nanographenes,
thus indicating that the intrinsic emission, that is, emission from the
sp2 surfaces, was responsible for the photoemission. Two photoemission
bands were observed for all of the fractions, which likely originated from
the edge and inner parts of nanographene. Yamato, Kairi; Sekiya, Ryo; Nishitani, Shohei; Haino, Takeharu Chem. Asian. J.,2019,14, 3213-3220. ●Helical Assembly of a Dithienogermole Exhibiting Switchable Circularly
Polarized Luminescence Abstract:Dithienogermole derivatives S- and R-1 possessing phenylisoxazoles and
chiral side chains were synthesized. The helical assembly of 1 in methylcyclohexane
exhibited circularly polarized luminescence (CPL). The CPL signals of the
assembly in the elongation regime were inverted with respect to those in
the nucleation regime. Hirano, Kyohei;Ikeda, Toshiaki; Fujii, Naoka; Hirao, Takehiro; Nakamura,
Masashi; Adachi, Yohei; Ohshita, Joji; Haino, Takeharu Chem. Commun.,2019,55,10607-10610. ●Ring-Chain Competition in Supramolecular Polymerization Directed by Molecular
Recognition of Bisporphyrin Cleft Abstract:Increasing interest in innovative supramolecular materials has spurred
efforts to develop head-to-tail monomers possessing a host moiety as a
head and a guest moiety as a tail, making them capable of forming supramolecular
polymers through intermolecular associations while avoiding intramolecular
cyclization. This competition between the intramolecular cyclization and
the intermolecular association is influenced by conformational entropy,
relying on the flexibility of the linker chain that connects the host moiety
to the guest moiety in a head-to-tail monomer. However, there are limited
reports presenting a quantitative thermodynamic picture describing the
conformational entropy in ring–chain equilibrium processes. Here, we report
the quantitative evaluation of the role of conformational entropy in the
ring–chain equilibrium mechanism of the supramolecular polymerization of
a head-to-tail monomer possessing a bisporphyrin host and a trinitrofluorenone
guest connected with various alkyl chains as linkers. The supramolecular
polymerization of the head-to-tail monomers was studied using UV/vis, NMR,
and diffusion-ordered spectroscopy spectroscopic techniques and viscometry.
The thermodynamic parameters of the ring–chain equilibrium were determined
in the initial stage of the supramolecular polymerization. The conformational
entropy, which relies on the flexibility of the linker, had a significant
influence on the critical polymerization concentration. This quantitative
discussion of ring–chain competition is expected to provide a foundation
for the proper design of artificial head-to-tail monomers that form supramolecular
polymers. Hirao, Takehiro; Hisano Naoyuki; Akine Shigehisa; Kihara Shin-ichi; Haino,
Takeharu Macromolecules,2019,52, 6160-6168 DOI: 10.1021/acs.macromol.9b01012 ●Near-Infrared Emitting Nitrogen-Doped Nanographenes Abstract:The quantum‐size effect, which enables nanographenes to emit photoluminescence
(PL) in the UV to visible region, has inspired intense research. However,
the control of the PL properties of nanographenes through manipulation
of their π‐system by post‐modifications is not well developed. By utilizing
a ring‐closure reaction between an aromatic 1,2‐dicarboxylic acid and a
1,8‐naphthalenediamine derivative, which produces a perimidine framework,
nitrogen‐doped nanographenes were realized. Two nanographenes produced
by a one‐pot reaction of edge‐oxidized nanographene (GQD‐2) with 1,8‐naphthalenediamine
derivatives (GQD‐1a and GQD‐1b) displayed an absorption band extending
to >1000 nm; furthermore, the PL wavelength of GQD‐1a was significantly
red‐shifted into the near‐infrared (NIR) region in which it can be used
for bioimaging. Time‐dependent DFT calculations of model nanographenes
showed that the functional groups narrow the HOMO–LUMO gap, realizing the
NIR‐emitting nanographenes. Yamato, Kairi; Sekiya, Ryo; Suzuki, Kaho; Haino, Takeharu Angew. Chem. Int. Ed.2019,58, 9022-9026 ●Substituent-Controlled Racemization of Dissymmetric Coordination Capsules Abstract:We report the effect of substituents (methyl, isopropyl, methoxy, and methoxyphenyl)
at the 6′-position of the 2,2′-bipyridyl arms on the racemization of dissymmetric
coordination capsules 1a–d. When the capsules included (R)-4,4′-diacetoxy-2,2′-benzyloxycarboxyl-biphenyl
((R)-3), the (M)-helical conformer was enriched with a diastereomeric excess
(de%) of >98% for 1a, 31% for 1b, 81% for 1c and 75% for 1d. The entrapped
guests in 1a, 1c and 1d can be removed by washing the solid containing
the host–guest complexes with diethyl ether. The rate of racemization in
THF follows the order of 1c > 1d ≫ 1a. X-ray crystal structural analysis
and density functional theory calculation of model complex 4c indicate
a distorted tetrahedral coordination of the Cu(I) center, and UV-vis absorption
spectroscopy indicates similar coordination environments in 1c and 4c.
A series of experiments demonstrates that the racemization rate depends
on the dihedral angles of the bipyridyl arms, and the angles are regulated
by the substituents. The methoxy and methoxyphenyl substituents in 1c and
1d enlarge the dihedral angles of the bipyridyl arms. This facilitates
the access of solvent molecules to the Cu(I) centers and promotes racemization.
The slower racemization of 1d can be ascribed to the steric protection
of the Cu(I) centers from incoming solvent molecules by the p-methoxyphenyl
group. Harada, Kentaro; Sekiya, Ryo; Maehara, Takeshi; Haino, Takeharu Org. Biomol. Chem.,2019,17,4729-4735 ●Tunable Enforced Cavities inside Self-assembled Capsules Abstract: Controlling and tuning the molecular recognition properties is a crucial
task in host–guest chemistry. The size and dimension of the guest-binding
space inside self-assembled capsules 1a–c is successfully determined by
installing the substituents at the 6′-position of 2,2′-bipyridyl arms.
X-ray diffraction analysis and DFT calculations at the M06-2X/6-31G(d,p)+LanL2DZ
level of theory demonstrate that the p-methoxyphenyl group expands the
dihedral angle of the 2,2′-bipyridyl arms through its π-stacking interaction
to the 2,2′-bipyridyl arm, whereas the steric interaction of the isopropyl
group to the neighboring bipyridyl arm slightly reduces the dihedral angle
of the two bipyridyl groups. The Cu(I)-united 2,2′-bipyridyl arms function
as a hinge; accordingly, installing the p-methoxyphenyl group extends the
cavity by ca. 2 Å, whereas the isopropyl group shrinks the cavity more
than that of the capsule 1a with methyl groups at the 6′-positions. These
steric interactions influence the molecular recognition of the capsules
1a–c for rigid ditopic guest 2a as well as flexible ones 2b–f. The guest
selectivity inside the enforced cavity is determined by varying the substituents. Maehara, Takeshi; Sekiya, Ryo; Kentaro, Harada; Haino, Takeharu Org. Chem. Front.2019,6,1561-1566 ●Separation of Spectroscopically Uniform Nanographenes Abstract:Excitation‐dependent photoluminescence (PL) is a well‐known property of
graphene quantum dots (GQDs). For the development of carbon‐based photofunctional
materials, GQDs possessing uniform PL properties are in high demand. A
protocol has been established to separate spectroscopically uniform lipophilic
GQD‐1a from a mixture of GQD‐1 mainly composed of GQD‐1a and GQD‐1b. The
mixture of GQD‐1 was synthesized through the reaction of p‐methoxybenzylamine
with GQD‐2 prepared from graphite by common oxidative exfoliation. Size‐exclusion
chromatography gave rise to GQD‐1a and GQD‐1b, with diameters of 19.8 and
4.9 nm, respectively. Large GQD‐1a showed that the PL was fairly independent
of the excitation wavelengths, whereas the PL of small GQD‐1b was dependent
on excitation. The excitation‐dependent nature is most likely to be associated
with the structures of sp2 domains on the graphene surfaces. The large
sp2‐conjugated surface of GQD‐1a is likely to possess well‐developed and
large sp2 domains, the band gaps of which do not significantly vary. The
small sp2‐conjugated surface of GQD‐1b produces small sp2‐conjugated domains
that generate band gaps differing with domain sizes. Yamato, Kairi; Sekiya, Ryo; Abe, Manabu; Haino, Takeharu Chem. Asian. J.,2019,14, 1786-1791 ●Organogelators of 5,17-Difunctionalized Calix[4]arenes Abstract: 5,17-Difunctionalized calix[4]arenes 1a,b were found to function as low
molecular-weight organic gelators. They formed organogels with a variety
of organic solvents. SEM images showed 1a formed stacked structures in
the xerogels. Single-crystal X-ray analysis of 1c as well as AFM, XRD,
and SAXS measurements of 1a indicated that the xerogels contained lamellar
structures of the calix[4]arenes. Lai, Nang, Duy; Sekiya, Ryo; Tosaka, Masatoshi; Yamago, Shigeru; Matsumoto,
Takuya; Nishino, Takashi; Ichikawa, Takayuki; Haino, Takeharu. Chem. Lett.,2019,48, 43-46 ●Designer Supramolecular Polymers with Specific Molecular Recognitions Abstract: Supramolecular polymers are members of an emergent class of polymer materials
that exhibit designability and flexibility. This article describes how
supramolecular polymers can be synthesized by taking advantage of our host–guest
structures based on a calix[5]arene, a bisporphyrin, and a self-assembled
capsule. Linear and two-dimensional fullerene nanostructures can be fabricated
using the designed monomer structures. The porphyrin donor–acceptor interaction
directs the supramolecular polymerization, resulting in linear porphyrin
polymers that behave similarly to a conventional polymer chain in solution,
even though their structures are dynamic and time-averaged. The fragile
supramolecular polymer chains are cross-linked to fabricate a robust self-standing
film. The sequence reorganization of the supramolecular homopolymer is
established by competitive ditopic guest complexation. The sequence-controlled
terpolymer is fabricated via self-sorting behavior. The postmodifications
of the supramolecular polymer chains, as well as the polymer chains themselves,
are achieved by grafting and non-covalent cross-linking to regulate the
macroscopic properties and structures of the polymer main chains. These
uniquely organized polymers are fabricated on a nanoscale. Haino, Takeharu. Polym. J.,2019,51, 303-318 2018 ●Facile Synthesis of an Eight-Armed Star-Shaped Polymer via Coordination-Driven
Self-Assembly of a Four-Armed Cavitand Abstract:The polystyrene chains were installed at the lower rim of a resorcinarene-based
cavitand via reversible addition–fragmentation (RAFT) polymerization to
form a four-armed star-shaped polymer. A star-shaped polystyrene-functionalized
supramolecular capsule was prepared through the coordination-driven self-assembly
of the four-armed start-shaped polymer with silver ions. The eight-armed
start-shaped supramolecular capsule encapsulated 4,4′-diacetoxybiphenyl
as did a cavitand-based self-assembled capsule. A DOSY measurement indicated
that the eight-armed star-shaped polymer was twice as large as the four-armed
star-shaped polymer. The solution behaviors of these compounds resulted
in a difference in their zero-shear viscosities. Nitta, Natsumi; Mei, Takatsuka; Kihara, Shin-ichi; Sekiya, Ryo; Haino,
Takeharu ACS Macro. Lett.,2018,7, 1308-1311. DOI:10.1021/acsmacrolett.8b00669 ●Majority-Rules Effect and Allostery in Molecular Recognition of Calix[4]arene-Based
Triple-Stranded Metallohelicates Abstract:The triple‐stranded metallohelicates 1a,/1b–3a/3b possessing internal guest
binding cavities surrounded by calix[4]arene units were synthesized through
coordination‐driven self‐assembly. UV/Vis titration experiments verified
that the metallohelicates encapsulated N‐methyl pyridinium cations bearing
amino acid groups to form host–guest complexes. The guest chirality was
transferred to the helicity of the helicates through the steric contact
between the stereogenic center of the amino acid group and the metal cores.
The (M) helicity was induced when guests the (R)‐4‐‐(R)‐6 were accommodated
within the cavities. The multiple guest complexation within the self‐assembled
helicates 2a and 3a displayed large positive cooperative effects, indicating
that the first guest complexation preorganizes the rest of the cavities
to facilitate a subsequent guest binding. This cooperativity results in
the majority‐rules effect in the chiral guest binding for 2a and 3a. Yamasaki, Yutaro; Shio, Hidemi; Amimoto, Tomoko; Sekiya, Ryo; Haino, Takeharu Chem. Eur. J.,2018,24, 8558-8568. ●Supramolecular Properties of a Monocarboxylic Acid-Functionalized “Texas-Sized”
Molecular Box Abstract:A new carboxylic acid-functionalized “Texas-sized” molecular box TxSB-CO2H
has been prepared by combining two separate building blocks via an iodide-catalyzed
macrocyclization reaction. A single-crystal X-ray diffraction analysis
revealed a paired “clip-like” dimer in the solid state. Concentration-dependent
behavior is seen for samples of TxSB-CO2H as prepared, as inferred from
1H NMR spectroscopic studies carried out in DMSO-d6. However, in the presence
of excess acid (1% by weight of deuterated trifluoracetic acid; TFA-d1),
little evidence of aggregation is seen in DMSO-d6 except at the highest
accessible concentrations. In contrast, the conjugate base form, TxSB-CO2–,
produced in situ via the addition of excess triethylamine to DMSO-d6 solutions
of TxSB-CO2H acts as a self-complementary monomer that undergoes self-assembly
to stabilize a formal oligomer ([TxSB-CO2–]n) with a degree of polymerization
of approximately 5–6 at a concentration of 70 mM. Evidence in support of
the proposed oligomerization of TxSB-CO2– in solution and in the solid
state came from one- and two-dimensional 1H NMR spectroscopy, X-ray crystallography,
dynamic light scattering (DLS), and scanning electron microscopy (SEM).
A series of solution-based analyses carried out in DMSO and DMSO-d6 provide
support for the notion that the self-assembled constructs produced from
TxSB-CO2– are responsive to environmental stimuli, including exposure to
the acetate anion (as its tetrabutylammonium, TBA+, salt), and changes
in overall concentration, temperature, and protonation state. The resulting
transformations are thought to reflect the reversible nature of the underlying
noncovalent interactions. They also permit the stepwise interconversion
between TxSB-CO2H and [TxSB-CO2–]n via the sequential addition of triethylamine
and TFA-d1. The present work thus serves to illustrate how appropriately
functionalized molecular box-type macrocycles may be used to develop versatile
stimuli-responsive materials. It also highlights how aggregated forms seen
in the solid state are not necessarily retained under competitive solution-phase
conditions. Wu, Ren-Tsung;Chi, Xiaodongi; Hirao, Takehiro;Lynch, Vincent M. Lynch;
Sessler, Jonathan L. J. Am. Chem. Soc.,2018,140, 6823-6831 ●Control over Multiple Molecular States with Directional Changes Driven
by Molecular Recognition Abstract: Recently, ligand–metal coordination, stimuli-responsive covalent bonds,
and mechanically interlinked molecular constructs have been used to create
systems with a large number of accessible structural states. However, accessing
a multiplicity of states in sequence from more than one direction and doing
so without the need for external energetic inputs remain as unmet challenges,
as does the use of relatively weak noncovalent interactions to stabilize
the underlying forms. Here we report a system based on a bispyridine-substituted
calix[4]pyrrole that allows access to six different discrete states with
directional control via the combined use of metal-based self-assembly and
molecular recognition. Switching can be induced by the selective addition
or removal of appropriately chosen ionic guests. No light or redox changes
are required. The tunable nature of the system has been established through
a combination of spectroscopic techniques and single crystal X-ray diffraction
analyses. The findings illustrate a new approach to creating information-rich
functional materials. Hirao, Takehiro; Kim, Dong Sub; Chi, Xiaodong;Lynch Vincent M.;Ohara, Kazuaki;
Park, Jung Su; Yamaguchi, Kentaro; Sessler, Jonathan L. Nature Commun.,2018,9, 823 DOI:10.1038/s41467-018-03220-0 ●Supramolecular Copolymerization by Sequence Reorganization of a Supramolecular
Homopolymer Abstract:The homopolymeric sequence formed by the head‐to‐head association of tetrakisporphyrin
1 is completely dissociated by the competitive association of the ditopic
guest G2, resulting in the supramolecular copolymer poly‐1⋅G2 with an alternatingly
repeating host–guest sequence. The 1:1 stoichiometry of 1 and G2 is confirmed
by a Job plot using UV/Vis titration and diffusion‐ordered NMR spectroscopy
(DOSY). The solution viscometry for poly‐1 and poly‐1⋅G2 suggests that
the supramolecular chain of poly‐1 behaves like a rod, whereas the supramolecular
copolymer chain of poly‐1⋅G2 behaves like a swelled fat chain, which is
entangled in the semi‐dilute regime. Atomic force microscopy shows that
the supramolecular polymer poly‐1⋅G2 is highly oriented through the interdigitation
of the long alkyl chains. Nadamoto, Kouhei; Maruyama, Kei; Fujii, Naoka; Ikeda, Toshiaki; Kihara,
shin-ichi; Haino, Takeharu. Angew. Chem. Int. Ed.,2018,57, 7028-7033. ●Controllable Direction of Porphyrin Derivatives in Two Cyclodextrin Cavities Abstract:Porphyrin–trimethyl‐β‐cyclodextrin (TMe‐β‐CDx) complexes have pseudorotaxane
structures in which two meso‐phenyl and/or ‐pyridyl moieties penetrate
the upper rim of two TMe‐β‐CDx molecules. Porphyrin derivatives with one
to three pyridyl moieties at meso positions formed complexes with TMe‐β‐CDx
in which the penetration of the upper rim of the two TMe‐β‐CDxs by the
pyridyl moieties was minimized. In contrast, in TMe‐β‐CDx complexes formed
with porphyrin derivatives bearing two 2‐methoxyphenyl moieties and two
pyridyl moieties, the pyridyl moieties penetrate the upper rim of the two
molecules because steric hindrance prevents penetration by the 2‐methoxyphenyl
moieties. Horiguchi, Banri; Nakaya, Toshimi; Ueda, Masafumi; Sugisawa, Kouta; Mizuta,
Tsutomu; Haino, Takeharu; Kawata, Naomi; Ikeda, Atsushi. Eur. J. Org. Chem.,2018,18, 2138-2143. ●Pseudorotaxanes in the Gas Phase: Structure and Energetics of Protonated
Dibenzylamine-crown Ether Complexes Abstract: We observe UV spectra of protonated dibenzylamine (dBAMH+) and its complexes
with 15-crown-5 (dBAMH+–15C5), 18-crown-6 (dBAMH+–18C6), and 24-crown-8
(dBAMH+–24C8) under cold (∼10 K) gas-phase conditions by UV photodissociation
(UVPD) and UV–UV hole-burning (HB) spectroscopy. The UVPD spectrum of the
dBAMH+–15C5 complex shows an extensive low-frequency progression, which
originates from a unique conformation of the dBAMH+ part with benzene rings
facing closely to each other, while UVPD and calculation results suggest
open conformations of the dBAMH+ part for dBAMH+–18C6 and dBAMH+–24C8.
UV–UV HB spectra of the dBAMH+–24C8 complex indicate that there exist at
least two conformers; multiple conformations can contribute to high stability
of dBAMH+–24C8 pseudorotaxane due to “conformational” entropic effects.
The UVPD experiment indicates that the dissociation probability of dBAMH+–24C8
into dBAMH+ and 24C8 is substantially smaller than that of dBAMH+–15C5
and dBAMH+–18C6, which can be related to the barrier height in the dissociation
process. The energetics of the dBAMH+–24C8 complex is investigated experimentally
with NMR spectroscopy and theoretically with the global reaction route
mapping (GRRM) method. An energy barrier of ∼60 kJ mol−1 is present in
the pseudorotaxane formation in solution, whereas there is no barrier in
the gas phase. In the course of the photodissociation, excited dBAMH+–24C8
complexes can be trapped at many local minima corresponding to multiple
conformations. This can result in effective dissipation of internal energy
into degrees of freedom not correlated to the dissociation and decrease
the dissociation probability for the dBAMH+–24C8 complex in the gas phase.
The energy barrier for the pseudorotaxane formation in solution originates
not simply from the slippage process but rather from solvent effects on
the dBAMH+–24C8 complex. Kida, Motoki; Shimoyama, Daisuke; Ikeda, Toshiki; Sekiya, Ryo; Haino, Takeharu;
Ebata, Takayuki; Jouvet, Christophe; Inokuchi, Yoshiya. Phys. Chem. Chem. Phys.,2018,20, 18678-18687 ●A Supramolecular Polymer Network of Graphene Quantum Dots Abstract:Graphene quantum dot (GQD)–organic hybrid compounds (GQD‐2b–e) were prepared
by introducing 3,4,5‐tri(hexadecyloxy)benzyl groups (C16) and linear chains
terminated with a 2‐ureido‐4‐[1H]‐pyrimidinone (UPy) moiety onto the periphery
of GQD‐1. GQD‐2b–e formed supramolecular assemblies through hydrogen bonding
between the UPy units. GPC analysis showed that GQDs with high loadings
of the UPy group formed larger assemblies, and this trend was confirmed
by DOSY and viscosity measurements. AFM images showed the polymeric network
structures of GQD‐2e on mica with flat structures (ca. 1.1 nm in height),
but no such structures were observed in GQD‐2a, which only carries the
C16 group. GQD‐2c and GQD‐2d formed organogels in n‐decanol, and the gelation
properties can be altered by replacing the alkyl chains in the UPy group
with ethylene glycol chains (GQD‐3). GQD can thus be used as a platform
for supramolecular polymers and organogelators by suitable chemical functionalization. Uemura, Yuichiro; Yamato Kairi; Sekiya, Ryo; Haino, Takeharu Angew. Chem. Int. Ed.,2018,57, 4960-4964 ●Synthesis and Dimerization Studies of a Lipophilic Photoresponsive Aryl
Extended Tetraureacalix[4]pyrrole Abstract:We describe the syntheses of the lipophilic aryl‐extended α,α,α,α‐tetraurea‐phenyl‐calix[4]pyrrole
1, featuring four appended azo‐phenyl groups with two tert‐butoxy carbonyl
meta‐substituents and its photo‐inactive counterpart 2. In CD2Cl2 solutions,
both tetraurea‐calix[4]pyrroles self‐assemble into dimeric capsules by
encapsulating one molecule of a suitable bis‐N‐oxide or two molecules of
a mono‐N‐oxide. The dimeric capsules are mainly stabilized by a cyclic
array of sixteen hydrogen bonds established between the eight unidirectionally
oriented urea groups. Photoirradiation experiments demonstrated the trans‐to‐cis
isomerization of the azo‐phenyl groups and the formation of a plethora
of stereo isomeric cis‐azo‐enriched capsular assemblies. The highly cis‐azo
enriched capsular assemblies seem to show a reduced stability and their
involvement in equilibria with non‐capsular counterparts that also bind
the N‐oxides. The thermally induced cis‐to‐trans interconversion processes
demonstrated the reversibility of the photoisomerization and the photostability
of most binding partners. An equimolar mixture of the two tetraureas produced
two homodimeric capsules and the heterodimeric counterpart in a ratio close
to statistical distribution. Sekiya, Ryo; Díaz-Moscoso, Alejandro; Ballester, Pablo Chem. -Eur. J.,2018,24, 2182-2191 ●A Circularly Polarized Luminescent Organogel Based on a Pt(II) Complex
Possessing Phenylisoxazoles Abstract:A Pt(II)phenylbipyridine complex 1, possessing phenylisoxazoles, long alkyl
chains, and chiral alkyl chains, was synthesized. Complex 1 formed a stacked
assembly in chloroform, self-assembled in a cooperative manner in methylcyclohexane
(MCH), and gelled in higher alcohols and dodecane. In the nucleation regime,
1 assembled via a Pt–Pt interaction, which was demonstrated by the metal–metal-to-ligand
charge transfer (MMLCT) emission band of the assembly. In the elongation
regime, 1 displayed aggregation-induced emission enhancement (AIEE) character.
The assembly of 1 formed in MCH was chiroptically non-active, suggesting
that the assembly was non-helical. Complex 1 also exhibited strong AIEE
and circularly polarized luminescence (CPL) with an anisotropic factor
(glum) of 0.011 in 1-decanol gel, indicating that a chiral assembly was
formed in the gel. Ikeda, Toshiaki; Hirano, Kyohei; Haino, Takeharu Mater. Chem. Front.2018,2, 468-474. 2017 ●Synthesis and Sturcture of Feet-to-Feet Connected Bisresorcinarenes Abstract: Bisresorcinarenes 1a–d were obtained in excellent yields, and 1e was finally
obtained in 50% yield. X-ray diffraction analysis showed that 1a and 1b
adopted helical conformations, whereas the two resorcinarenes of 1c–e were
in parallel orientations in which the clefts of the aliphatic chains entrapped
one or two solvent molecules. The conformational study revealed that the
helix interconversion between the (P)- and (M)-helical conformers depended
on the length of the aliphatic chains. 1a had the largest energetic barrier
to helix interconversion, while in 1b, its more flexible aliphatic chains
lowered its energetic barriers. The P/M interconversion of 1a was coupled
with the clockwise/anticlockwise interconversion of the interannular hydrogen
bonding of the two resorcinarenes. The large negative entropic contributions
indicate that the transition state is most likely more ordered than the
ground states, suggesting that the transition state is most likely symmetric
and is solvated by water molecules. Calculations at the M06-2X/6-31G(d,p)
level revealed that the more stable (P)-conformation has clockwise interannular
hydrogen bonding between the two resorcinarenes. Shimoyama, Daisuke; Ikeda, Toshiaki; Sekiya, Ryo; Haino, Takeharu J. Org. Chem.,2017,82, 13220-13230 ●Hexameric Assembly of 5,17-di-Subsituted Calix[4]arene in the Solid State Abstract:Chiral 5,17-difunctionalized-25,26,27,28-tetrapropyloxycalix[4]arene possessing
(S)-mandelamide arms ((S,S)-1) afforded cocrystals (S,S)-1·(solvent) (solvent
= MeOH, EtOH, 1-PrOH, 2-PrOH, and CH3CN). X-ray diffraction analysis revealed
that (S,S)-1 formed head-to-tail columnar structures. In most cocrystals
(MeOH, EtOH, 1-PrOH, and CH3CN), the columnar structures were arranged
hexamerically to form a chiral hexagonal channel, which is a rare example
of calix[4]arene derivatives in the solid state. The fact that the branched
guest (2-PrOH) and the racemic mixture of the host formed different crystal
packings wherein no hexameric structure existed indicates that both the
linearity of the guest and the homochirality of the host are important
factors for driving the columnar structures to form the hexameric assembly.
Apohost (S,S)-1apo showed interesting adsorption behavior; it adsorbed
benzene among the organic molecules tested. The adsorption and desorption
processes were repeated several times, demonstrating the sponge-like character
of (S,S)-1apo. Yamasaki, Yutaro; Sekiya, Ryo; Haino, Takeharu CrystEngComm,2017,19, 6744-6751 ●Slow Intermolecular Complexation-Decomplexation Exchanges of Cyclodextrins
in Fullerene and Its Derivative Complexes Abstract:Fullerenes (C60 and C70) and several functionalized C60 derivatives can
be encapsulated in two γ‐cyclodextrins (γ‐CDxs). Although intermolecular
complexation–decomplexation exchange of γ‐CDx is known to be very slow,
the exchange rates have yet to be quantitatively measured. Herein, we determined
that the pseudo‐first‐order association and dissociation rate constants
for the γ‐CDx2•C70 complex were 4.3 and 0.6 s−1 at 23 °C, respectively.
In contrast, the intermolecular exchange rates for the γ‐CDx2•C60 and C60
derivative complexes were slower than the time scale of exchange spectroscopy
NMR experiments and the exchange rate constants were in the order of 10−4
s−1. Furthermore, a γ‐CDx2•C60 derivative complex was shown to have different
intermolecular exchange rates for the two γ‐CDxs depending on steric hindrance
from the substituent on the C60 derivative. Ikeda, Atsushi; Mae, Tomoya; Sugikawa, Kouta; Komaguchi, Kenji; Konishi,
Toshifumi; Hirao, Takehiro; Haino Takeharu ChemistrySelect,2017,2, 11322-11327 ●Sequence-Controlled Supramolecular Terpolymerization Directed by Specific
Molecular Recognitions Abstract:Nature precisely manipulates primary monomer sequences in biopolymers.
In synthetic polymer sequences, this precision has been limited because
of the lack of polymerization techniques for conventional polymer synthesis.
Engineering the primary monomer sequence of a polymer main chain represents
a considerable challenge in polymer science. Here, we report the development
of sequence-controlled supramolecular terpolymerization via a self-sorting
behavior among three sets of monomers possessing mismatched host–guest
pairs. Complementary biscalix[5]arene-C60, bisporphyrin-trinitrofluorenone
(TNF), and Hamilton’s bis(acetamidopyridinyl)isophthalamide-barbiturate
hydrogen-bonding host–guest complexes are separately incorporated into
heteroditopic monomers that then generate an ABC sequence-controlled supramolecular
terpolymer. The polymeric nature of the supramolecular terpolymer is confirmed
in both solution and solid states. Our synthetic methodology may pave an
avenue for constructing polymers with tailored sequences that are associated
with advanced functions. Hirao, Takehiro; Kudo, Hiroaki; Amimoto, Tomoko; Haino Takeharu Nat. Commun.,2017,8, Article No. 634 DOI: 10.1038/s41467-017-00683-5 ●Induced dipole-directed cooperative self-assembly of a benzotrithiophene Abstract:A benzotrithiophene derivative possessing phenylisoxazoles self-assembled
to form stacks. The molecule isodesmically self-assembled in chloroform,
whereas it self-assembled in a cooperative fashion in decalin and in methylcyclohexane.
Thermodynamic studies based on isodesmic, van der Schoot, and Goldstein–Stryer
mathematical models revealed that the self-assembly processes are enthalpically
driven and entropically opposed. An enthalpy–entropy compensation plot
indicates that the assembly processes in chloroform, decalin, and methylcyclohexane
are closely related. The enthalpic gains in less-polar solvents are greater
than those in more-polar solvents, resulting in the formation of large
assemblies in decalin and in methylcyclohexane. The formation of large
assemblies leads to cooperative assemblies. The elongation process is enthalpically
more favored than the nucleation process, which drives the cooperativity
of the self-assembly. DFT calculations suggested that a hexameric assembly
is more stable than tetrameric or dimeric assemblies. Cooperative self-assemblies
based on intermolecular interactions other than hydrogen bonding have rarely
been reported. It is demonstrated herein that van der Waals interactions,
including induced dipole–dipole interactions, can drive the cooperative
assembly of planar π-conjugated molecules. Ikeda, Toshiaki;Adachi, Hiroaki; Fueno, Hiroyuki; Tanaka, Kazuyoshi; Haino,
Takeharu J. Org. Chem.,2017,82, 10062-10069. ●Supramolecular Polymeric Assemblies of pi-Conjugated Molecules Possessing
Phenylisooxazoles Abstract:Supramolecular polymeric stacks of flat molecular components provide a
highly ordered molecular organization that results in unique functions.
The engineering of molecular organization, therefore, has attracted a great
deal of attention both in supramolecular chemistry and in material science.
The electronic and structural properties of molecular components determine
the forthcoming supramolecular organization structure and properties. Non-covalent
intermolecular interactions are responsible for directional growth in supramolecular
polymerization. We have discovered that a phenylisoxazole ring system drives
supramolecular polymerization in a directional way. π-Conjugated molecular
components possessing phenylisoxazole moieties constructively assemble
to form one-dimensional stacked assemblies via π–π stacking and dipole–dipole
interaction. The introduction of a chirality onto the molecular components
results in supramolecular helical organizations with unique photophysical
functions. Switchable circularly polarized luminescence (CPL) and circular
dichroism (CD) are developed in the supramolecular helical organizations.
The grown assemblies provide highly entangled fibrillar networks, giving
rise to organogels. The photo-responsive organogels and toroidal nanostructures
are fabricated with the assistance of a photo-addressable azobenzene group.
A light-harvesting system is developed in the organogels. Ikeda, Toshiaki; Haino, Takeharu Polymer,2017,128, 243-256 DOI: 10.1016/j.polymer.2017.02.059 ●Photoluminescence Response of Graphene Quantom Dots toward Organic Bases
and an Acid Abstract:Edge-modified graphene quantum dots (GQD-1) showed base-dependent photoluminescence
(PL) responses. DBN, DBU, and Et3N gradually enhanced the PL intensity
and then caused quenching, whereas quenching was not observed when pyridine
and pyrimidine were used. The quenching can be explained by the photoinduced
electron transfer from the anchored bases at the periphery to the emissive
sites of GQD-1. Suzuki, Kaho; Yamato, Kairi; Sekiya Ryo; Haino, Takeharu Photochem. Photobio. Sci.2017,16, 623-626 ●Supramolecular Graft Copolymerization of a Polyester via Guest-Selective
Encapsulation of a Self-Assembled Capsule Abstract:Repeating guest units of polyesters poly‐(R)‐2 were selectively encapsulated
by capsule 1(BF4)4 to produce supramolecular graft polymers. The encapsulation
of the guest units was confirmed by 1H NMR spectroscopy. The graft polymer
structures were confirmed by the increase in the hydrodynamic radii and
the solution viscosities of the polyesters upon complexation of the capsule.
After the capsule was formed, atomic force microscopy showed extension
of the polyester chains. The introduction of the graft chains onto poly‐(R)‐2
resulted in the main chain of the polymer having an M‐helical morphology.
The complexation of copolymers poly‐[(R)‐2‐co‐(S)‐2] by the capsule gave
rise to the unique chiral amplification known as the majority‐rules effect. Tsunoda, Yuta; Takatsuka, Mei; Sekiya, Ryo; Haino Takeharu Angew. Chem. Int. Ed.2017,56, 2613-2618 ●Site-Selective Encapsulation of Different Anions in a Quadruply Interlocked
Dimer Abstract: Interlocked dimer 2, which is composed of two physically interlocked monomers
1, has three cavities (cavity A × 2 and cavity B × 1) and can encapsulate
three anions, such as NO3− and BF4−, one anion per cavity. There are six
possible encapsulation patterns, A–F; two (A and F) contain only one kind
of anion and the others (B–E) contain both NO3− and BF4− at the same time
with different ratios and with different positions. Anion competition experiments
showed that in addition to F, which encapsulates three NO3− ions, C, in
which NO3− and BF4− ions are captured in cavities A and cavity B, respectively,
was selectively formed. Detailed investigations have revealed that B–E
were formed by dimerization, but three of the four were subjected to anion
exchange and converged into C or F. This selective formation can be explained
by the fact that NO3− is a better anion template than BF4−, as well as
the molecular structure of the interlocked dimer; cavities A are surrounded
by four bridging ligands and can be accessed by free anions, whereas no
space available for anion exchange is present around cavity B because this
cavity is surrounded by eight bridging ligands. Therefore, the BF4− ions
in cavities A are expelled by free NO3−, but the BF4− ion in cavity B is
not, resulting in the selection of C and F. We have found that the volume
of the cavity influenced anion recognition. New interlocked dimer 3, which
has smaller cavities than those of 2, captured three NO3− ions to form
F, whereas only a small amount of an interlocked dimer that contains both
NO3− and BF4− was formed. Sekiya Ryo; Fukuda Morihiko; Kuroda Reiko Org. Biomol. Chem.2017,15, 4328-4335 ●Vanadium(V) Complexes of Some Bidentate Hydrazone Ligands and Their Bromoperoxidase
Activity Abstract:Dinuclear methoxy bridged complexes of vanadium, [VO(µ-OMe)(OMe)(L)]2 (1–3)
have been synthesized from the reaction of VOSO4·H2O with triethylamine
and the respective hydrazone ligand. The compounds have been characterized
by spectroscopic methods and determination of single crystal X-ray structure
of one of them (1). DFT and TD-DFT calculations were used to understand
the electronic structures of the complexes and their electronic spectra
respectively. Though the dimeric complexes are stable in the solid state,
the ESI-MS spectra as well as 1H NMR spectra of the complexes suggest that
in solution the monomeric forms of the complexes are the major species.
The V(V) complexes in DMF were used to catalyze the oxidative bromination
of salicylaldehyde, in aqueous H2O2/KBr in the presence of HClO4 at room
temperature. The complexes show exceptionally high bromoperoxidase activity
with salicylaldehyde as a model substrate to produce 5-bromo salicylaldehyde
in good yield and high TOF and TON. Therefore, these complexes behave as
functional models of vanadate dependent bromoperoxidase enzyme. Adak, Piyali; Ghosh, Bipinbihari; Pakhira, Bholanath; Sekiya, Ryo; Kuroda,
Reiko Polyhedron,2017,127, 135-143 DOI:10.1016/j.poly.2017.01.054 ●Light-harvesting organogel based on tris(phenylisoxazolyl)benzene Abstract:A novel light-harvesting organogel based on tris(phenylisoxazolyl)benzene,
1, was developed. A pyrene derivative, 2, possessing four phenylisoxazole
substituents, was synthesised as an energy acceptor. The electronically
excited-state energy of 1 was transferred to a small portion of 2 in the
gel state, whereas the photo-induced energy transfer was not observed in
solution. The coassembled structures of 1 and 2, formed in the decalin
gel, exhibited light-harvesting behaviour. The study on the fluorescence
quantum yield revealed that one molecule of 2 accepts the excited-state
energy from approximately eight molecules of 1. Time-resolved fluorescence
decay experiments revealed that the fluorescence resonance energy transfer
is dominant in the energy transfer process in the gel state. Ikeda, Toshiaki; Ueda, Yuko; Komori, Naomitsu; Abe, Manabu; Haino, Takeharu Supramolecular Chem.2017,29, 471-476 DOI:10.1080/10610278.2016.1268692 2016 ●Allostery in Guest Binding of Rim-to-Rim-Connected Homoditopic Biscavitands Abstract: Rim‐to‐rim‐connected phosphonate biscavitands 1a and 1b were synthesized.
Crystal structure analysis and variable‐temperature NMR spectroscopy studies
reveal that 1a is more rigid in conformation than 1b. Biscavitands 1a and
1b bind cationic guests G1–G3 through hydrogen bonding and CH–π interactions,
demonstrating positive and negative allosteric effects, respectively. The
allosteric effects in guest binding are associated with the conformational
flexibilities of 1a and 1b. The positive allosteric effect of 1a is directed
by the tightly connected cavities, in which information of the first guest
binding is transferred to the remaining cavity, which becomes preorganized.
In contrast, a slightly negative allosteric effect is found in more‐flexible
1b. Shimoyama, Daisuke; Yamada, Hitomi; Ikeda, Toshiaki; Sekiya, Ryo; Haino,
Takeharu Eur. J. Org. Chem.2016, 3300-3303 (Front Cover) ●Synthesis and Properties of Novel Optically Active Platinum-containing
Poly(phenyleneethynylene)s Abstract: The dehydrochlorination coupling polymerization of N-(3,5-diethynylbenzoyl)-l-alanine
dodecylamide 1 with platinum (Pt) chlorides having pyridine, bipyridine,
and phenanthroline ligands 2a–2d gave novel optically active poly(phenyleneethynylene)s
[poly(1-2a)–poly(1-2d)] bearing Pt in the main chains. The Z-average diameters
of the polymers ranged from 453 to 1081 nm. Poly(1-2a) exhibited CD signals
assignable to aggregates, and formed regulated twisted structures with
height of 540 ± 70 nm and pitch of 62 ± 6 nm, which were confirmed by AFM
measurements. Otaki, Yoshinori; Marumoto, Manabu; Miyagi, Yu; Hieran, Takehiro; Haino,
Takeharu; Sanda, Fumio Chem. Lett.2016,45, 937-939 ●Cooperative Self-Assembly of Carbazole Derivatives Driven by Multiple
Dipole-Dipole Interactions Abstract:Carbazole possessing phenylisoxazoles self-assembled in a cooperative manner
in decalin. X-ray crystal structure analysis revealed that the isoxazole
dipoles align in a head-to-tail fashion. DFT calculations suggested that
the linear array of dipoles induced the polarization of each dipole, leading
to an increase in dipole–dipole interactions. This dipole polarization
resulted in cooperative assembly. Ikeda, Toshiaki; Iijima, Tatsuya; Sekiya, Ryo; Takahashi, Osamu; Haino,
Takeharu J. Org. Chem.2016,81, 6832-6837 ●Synthesis of a Pentacene-Type Silaborin via Double Dehydrogenative Cyclization
of 1,4-Diboryl-2,5-disilylbenzene Abstract:A new pentacene‐type silaborin, in which three benzene rings are bridged
by silicon and boron atoms, has been synthesized and characterized by using
NMR spectroscopy and X‐ray crystallographic analysis. The precursor, 1,4‐bis(dimesitylboryl)‐2,5‐bis(phenylsilyl)benzene
(4), was prepared by stepwise introduction of a silyl group and a boryl
group to a benzene ring starting from 1,4‐dibromobenzene. Double cyclization
of 4 proceeds by a H‐Mes exchange and a B‐H/C‐H dehydrogenative condensation
to afford pentacene‐type silaborin 5. X‐ray crystal structure analysis
reveals that 5 adopts a bent structure rather than a planar one. UV/Vis
spectra and DFT calculations for 5 reveal a lowering of the LUMO energy
level compared with corresponding anthracene‐type 3. Hirofuji, Tatsuya; Ikeda, Toshiaki; Haino, Takeharu; Yamamoto, Yohsuke;
Kawachi, Atsushi Chem. Eur. J.2016,22, 9734-973 ●Chemical Functionalisation and Photoluminescence of Graphene Quantum Dots Abstract:Chemical modification of graphene quantum dots (GQDs) can influence their
physical and chemical properties; hence, the investigation of the effect
of organic functional groups on GQDs is of importance for developing GQD–organic
hybrid materials. Three peripherally functionalised GQDs having a third‐generation
dendritic wedge (GQD‐2), long alkyl chains (GQD‐3) and a polyhedral oligomeric
silsesquioxane group (GQD‐4) were prepared by the CuI‐catalysed Huisgen
cycloaddition reaction of GQD‐1 with organic azides. Cyclic voltammetry
indicated that reduction occurred on the surfaces of GQD‐1–4 and on the
five‐membered imide rings at the periphery, and this suggested that the
functional groups distort the periphery by steric interactions between
neighbouring functional groups. The HOMO–LUMO bandgaps of GQD‐1–4 were
estimated to be approximately 2 eV, and their low‐lying LUMO levels (<−3.9 eV)
were lower than that of phenyl‐C61‐butyric acid methyl ester, an n‐type
organic semiconductor. The solubility of GQD‐1–4 in organic solvents depends
on the functional groups present. The functional groups likely cover the
surfaces and periphery of the GQDs, and thus increase their affinity for
solvent and avoid precipitation. Similar to GQD‐2, both GQD‐3 and GQD‐4
emitted white light upon excitation at 360 nm. Size‐exclusion chromatography
demonstrated that white‐light emission originates from the coexistence
of differently sized GQDs that have different photoluminescence emission
wavelengths. Sekiya, Ryo; Uemura, Yuichiro; Naito, Hiroyoshi; Naka, Kensuke; Haino,
Takeharu Chem. Eur. J .2016,22, 8198-8206 ●Hydrogen-bonded hexameric cluster of benzyl alchol in the solid state
polymeric organization of p-tert-Butylcalix[5]arene Abstract:An uncommon hydrogen-bonded hexameric cluster of benzyl alcohol (2) was
formed in hydrophobic space in the layered organisation of the one-dimensional
polymeric zigzag array of 1 in the solid state. The hexameric cluster adopted
a distorted cyclohexane-like (12) O–H⋯O hydrogen bond network. The formation
of the hexameric cluster was quite sensitive to a tiny structural difference
of guests; phenylethylalcohol (3), phenol (4), benzyl amine (5) and aniline
(6) did not form any hexameric cluster. The packing coefficient of 0.53
suggested that the hexameric cluster nicely filled the hydrophobic space,
which most likely resulted in the effective van der Waals contacts that
stabilised the supramolecular organisation composed of the hexameric cluster
and the polymeric array of 1 in the solid state. Kajiki, Yasunori; Sekiya, Ryo; Haino, Takeharu Supramolecular Chem.2016,28, 444-449 DOI:10.1080/10610278.2015.1117084 ●Photoresponsive Toroidal Nanostructure Formed by Self-assembly of Azobenzene-Functionalized
Tris(phenylisoxazolyl)benzene Abstract:The self-assembly of tris(phenylisoxazolyl)benzene 1b with photochemically
addressable azobenzene moieties produced toroidal nanostructures, the formation
and dissociation of which were reversibly regulated upon photoirradiation.
1b displayed a mesogenic behavior. In the solution, the stacked assemblies
along with their C3 axes were formed. In the mesophase, two molecules of
1b most likely adopted the antiparallel arrangement to stabilize the columnar
organization. This assembling behavior most likely triggered the development
of the supramolecular toroidal nanostructures. Adachi, Hiroaki; Hirai, Yuko; Ikeda, Toshiaki; Maeda, Makoto; Hori, Ryo;
Kutsumizu, Shoichi; Haino, Takeharu Org. Lett.2016,18, 924-927 DOI:10.1021/acs.orglett.5b03622 ●Frozen Dissymmetric Cavities in Resorcinarene-Based Coordination Capsules Abstract:By introducing slight structural modifications to a D4‐symmetric coordination
capsule, we succeeded in isolating the nearly enantiopure capsules (P)‐
and (M)‐2 a(BF4)4. Chiral guest, dibenzyl 4,4′‐diacetoxy‐6,6′‐dimethyl‐[1,1′‐biphenyl]‐2,2′‐dicarboxylate
(3) was encapsulated within the dissymmetric cavity of 2 a(BF4)4, resulting
in a high diastereoselectivity of >99 % de. The encapsulated guest was
successfully removed from the complex without racemization through precipitation
of the empty capsule. CD spectra confirmed that the chirality of the capsule
was maintained in THF and 1,4‐dioxane for long periods, whereas a small
amount of acetonitrile accelerated racemization of the empty capsule. The
activation parameters of the racemization reaction were determined in dichloromethane
and 1,2‐dichloroethane, resulting in positive enthalpic contributions and
large negative entropic contributions, respectively. Accordingly, the racemization
fits a first‐order kinetic model. Mechanically coupled Cu+‐2,2′‐bipyridine
coordination centers were responsible for the high‐energy barrier of racemization
and led to the unique chiral memory of the dissymmetric cavity, which was
turned off by the addition of acetonitrile. Imamura, Taisuke; Maehara, Takeshi; Sekiya, Ryo; Haino, Takeharu Chem. Eur. J .2016,22, 3250-3254 ●Induced-Fit Molecular Recognition of Alkyl Chains in p-tert-Butylcalix[5]arene
in the Solid state Abstract:p-tert-Butylcalix[5]arene 1 recognized conformationally flexible aliphatic
hydrocarbons (hexane 2, heptane 3, octane 4, nonane 5, decane 6, undecane
7, and dodecane 8) and monoalkyl benzenes (toluene 10, ethylbenzene 11,
propylbenzene 12, butylbenzene 13, hexylbenzene 14, and octylbenzne 15)
to form host–guest complexes. X-ray diffraction study has revealed that
the alkyl chains of 11–15 were selectively recognized by 1, whereas host
1 recognized the aromatic ring of 10. The alkyl chain termini of 3, 4,
6–8, 11–13, and 15 adopted unusual folded conformations in the cavity.
M06-2X/6-31G(d,p) level of calculations revealed that the mutual induced-fit
shape adjustments between the calix[5]arene cavity and the flexible guests
play a key role in maximizing the host–guest interactions directed by the
C(sp3)–H/π interactions, leading to the unusual conformations of the alkyl
chain termini of the guests and the selective binding of the alkyl chains
in the solid state. Kajiki, Yasunori; Sekiya, Ryo; Yamasaki, Yutaro; Uemura, Yuichiro; Haino,
Takeharu Bull. Chem. Soc. Jpn.2016,89, 220-225(Selected Paper) ●Synthesis of Linear [5]Catenanes via Olefin Metathesis Dimerization of
Pseudorotaxanes Composed of a [2]Catenane and a Secondary Ammonium Salt Abstract:[5]Catenanes were synthesized by olefin metathesis dimerization. The reaction
of pseudorotaxanes, which were derived from a [2]catenane and one equivalent
of an ammonium salt bearing two terminal olefins in dichloromethane, with
a catalytic amount of Grubbs catalyst afforded linear [5]catenanes in 12%
yield. Intermolecular and intramolecular olefin metathesis reactions were
controlled by the length of the alkyl chain of the ammonium salts. Iwamoto, Hajime; Tafuku, Shinji; Sato, Yoshihiko; Takizawa, Wataru; Katagiri,
Wataru; Tayama, Eiji; Hasegawa, Eietsu; Fukazawa, Yoshimasa; Haino, Takeharu Chem. Commun.2016,52, 319-322 ●Solvent-induced Emission of Organogels Based on Tris(phenylisoxazolyl)benzene Abstract:Luminescent organogels based on tris(phenylisoxazolyl)benzene possessing
perylenebisimide 1 were synthesized. The emission properties of the gels
varied depending on the solvent properties: 1,4-dioxane gel was highly
emissive, pyridine gel was moderately emissive, and benzene gel was non-emissive. Ikeda, Toshiaki; Masuda, Tetsuya; Takayama, Midori; Adachi, Hiroaki; Haino,
Takeharu Org. Biomol. Chem.2016,14, 36-39 (Front Cover) 2015 ●Supramolecular Porphyrin Copolymer Assembled through Host-Guest Interactions
and Metal-Ligand Coordination Abstract:Bisporphyrin cleft molecule 1 Zn possessing a guest moiety assembled to
form supramolecular polymers through host–guest interactions. Bispyridine
cross‐linkers created interchain connections among the supramolecular polymers
to form networked polymers in solution. Solution viscometry confirmed that
the cross‐linked supramolecular polymers were highly entangled. Frequency‐dependent
linear viscoelastic spectroscopy revealed that the supramolecular polymers
generated well‐entangled solutions with associating and networking polymers,
whereas the solid‐like aggregates moved individually without breaking and
reforming structures below the transition temperature of 9.6 °C. Morphological
transition of the supramolecular polymers was evidenced by AFM images;
the non‐cross‐linked polymer resulted in wide‐spread thin networks, while
the cross‐linked networks produced thicker worm‐like nanostructures. The
supramolecular networks gelled in 1,1,2,2‐tetrachloroethane, and an elastic
free‐standing film was fabricated with a Young’s modulus of 1 GPa. Kinjo, Kanashi; Hirao, Takehiro; Kihara, Shin-ichi; Katsumoto, Yukiteru;
Haino, Takeharu Angew. Chem. Int. Ed.2015,54, 14830-14834 ●Synthesis of Optically Active Conjugated Polymers Containing Platinum
in the Main Chain: Control of the Higher-Order Structures by Substituents
and Solvents Abstract:The Sonogashira–Hagihara coupling polymerization of d‐hydroxyphenylglycine‐derived
diiodo monomers 1–4 and platinum‐containing diethynyl monomer 5 gave the
corresponding polymers [poly(1–5)–(2–5)] with number‐average molecular
weights of 19,000–25,000 quantitatively. The polymers were soluble in CHCl3,
CH2Cl2, THF, and DMF. CD and UV–vis spectroscopic analysis revealed that
amide‐substituted polymers [poly(1–5) and poly(2–5)] formed chiral higher‐order
structures in solution, while ester‐substituted polymers [poly(3–5) and
poly(4–5)] did not. Poly(1–5) formed one‐handed helices in THF/toluene
mixtures, while it formed chiral aggregates in THF/MeOH mixtures. Poly(1–5)
emitted fluorescence with quantum yields ranging from 0.8 to 1.3%. The
polymers usually aggregated in the solid state. Miyagi, Yu; Hirao, Takehiro; Haino, Takeharu; Sanda, Fumio J. Polym. Sci. A Polym. Chem.2015,53, 2452-2461 (Front Cover) ●Supramolecular Polymerization Engineered with Molecular Recognition Abstract:Supramolecular polymeric assemblies represent an emerging, promising class
of molecular assemblies with enormous versatility compared with their covalent
polymeric counterparts. Although a large number of host–guest motifs have
been produced over the history of supramolecular chemistry, only a limited
number of recognition motifs have been utilized as supramolecular connections
in polymeric assemblies. This account describes the molecular recognition
of host molecules based on calix[5]arene and bisporphyrin that demonstrate
unique guest encapsulations; subsequently, these host–guest motifs are
applied to the synthesis of supramolecular polymers that display polymer‐like
properties in solution and solid states. In addition, new bisresorcinarenes
are developed to form supramolecular polymers that are connected via a
rim‐to‐rim hydrogen‐bonded dimeric structure, which is composed of two
resorcinarene moieties. Haino, Takeharu Chem. Rec.2015,15, 837-853 ●New Insights into Metal Ion-crown Ether Complexes Revealed by SEIRA Spectroscopy Abstract:We demonstrate a powerful spectroscopic technique, surface-enhanced infrared
absorption (SEIRA) spectroscopy, not only for detecting host–guest complexes
in solution but also for examining the relationship between the guest selectivity,
complex structure, and solvent effect. We synthesize thiol derivatives
of 15-crown-5 and 18-crown-6 [2-(6-mercaptohexyloxy)methyl-15-crown-5 (15C5-C1OC6-SH)
and 2-(6-mercaptohexyloxy)methyl-18-crown-6 (18C6-C1OC6-SH)], which are
adsorbed on gold surfaces through S–Au bonds. The IR difference spectra
of the M+·15C5-C1OC6 (M = Li, Na, K, Rb, and Cs) complexes on gold are
observed using aqueous solutions of MCl by SEIRA spectroscopy. The spectra
show a noticeable change in the C–O stretching vibration at around 1100
cm−1. The spectral patterns of M+·15C5-C1OC6 are similar for Li+ and Na+,
and for K+, Rb+, and Cs+; the interaction between the metal ions and 15C5-C1OC6
changes drastically between Na+ and K+ in the series of alkali metal ions.
On the other hand, the equilibrium constant for complex formation determined
by the IR intensity shows clear preference for Na+ ions. We also observe
the IR difference spectra of M+·18C6-C1OC6 in methanol and compare them
with those in water. The spectral patterns in methanol are almost the same
as those in water, but the equilibrium constant in methanol does not show
preference for any ion, different from the K+ preference in water. From
these findings we attribute the origin of the ion selectivity of 15C5 and
18C6 in solution to the interaction between the metal ions and the crown
ethers in the complexes or the solvation energy of free ions. In the case
of 15C5-C1OC6 in water, the preference of Na+ over K+, Rb+, and Cs+ can
be attributed to the strength of the interaction or the size matching between
metal ions and 15C5-C1OC6; the Na+ selectivity over Li+ ions is dominated
by the solvation energy of free ions. For 18C6-C1OC6 in methanol, the equilibrium
constant for complex formation becomes much bigger in methanol than that
in water and loses the selectivity in methanol, because the solvation energy
in methanol is fairly smaller than that in water, predominating the contribution
from the strength of the interaction between metal ions and 18C6-C1OC6.
The IR spectra measured by SEIRA spectroscopy are quite sensitive to properties
of host–guest complexes such as the intermolecular interaction, the structure,
and the orientation against the gold surface. However, the evidence for
guest selectivity emerges primarily in the intensity of the spectra, rather
than band positions or spectral patterns in the IR spectra. Inokuchi, Yoshiya;Ebata, Takayuki; Ikeda, Toshiaki; Haino, Takeharu; Kimura,
Tetsunari; Guo, Hao; Furutani, Yuji New J. Chem.2015,39, 8673-8680 ●UV Photodissociation Spectroscopy of Cryogenically Cooled Gas Phase Host-guest
Complex Ions of Crown Ethers Abstract:The geometric and electronic structures of cold host–guest complex ions
of crown ethers (CEs) in the gas phase have been investigated by ultraviolet
(UV) fragmentation spectroscopy. As host CEs, we chose 15-crown-5 (15C5),
18-crown-6 (18C6), 24-crown-8 (24C8), and dibenzo-24-crown-8 (DB24C8),
and as guests protonated-aniline (aniline·H+) and protonated-dibenzylamine
(dBAM·H+) were chosen. The ions generated by an electrospray ionization
(ESI) source were cooled in a quadrupole ion-trap (QIT) using a cryogenic
cooler, and UV spectra were obtained by UV photodissociation (UVPD) spectroscopy.
UV spectroscopy was complemented by quantum chemical calculations of the
most probable complex structures. The UV spectrum of aniline·H+·CEs is
very sensitive to the symmetry of CEs; aniline·H+·18C6 shows a sharp electronic
spectrum similar to aniline·H+, while aniline·H+·15C5 shows a very broad
structure with poor Franck–Condon factors. In addition, a remarkable cage
effect in the fragmentation process after UV excitation was observed in
both complex ions. In aniline·H+·CE complexes, the cage effect completely
removed the dissociation channels of the aniline·H+ moiety. A large difference
in the fragmentation yield between dBAM·H+·18C6 and dBAM·H+·24C8 was observed
due to a large barrier for releasing dBAM·H+ from the axis of rotaxane
in the latter complex. Inokuchi, Yoshiya; Haino, Takeharu; Sekiya, Ryo; Morishima, Fumiya; Dedonder,
Claude; Feraud, Geraldine; Jouvet, Christophe; Ebata, Takayuki. Phys. Chem. Chem. Phys.2015,17, 25925-25934 ●Liposome Collapse Resulting from an Allosteric Interaction between 2,6-Dimethyl-beta-Cyclodextrins
and Lipids Abstract:Although heptakis(2,6-di-O-methyl)-β-cyclodextrin (DMe-β-CDx) has been
reported to exhibit higher cytotoxicity than many other cyclodextrins because
of the way in which it abstracts cholesterols from liposomes, we have identified
another reason for its cytotoxicity based on its interaction with lipids.
These interactions exhibited nonlinear sigmoidal responses with Hill coefficient
values (n) in the range of 3.0–3.6, which indicated that this phenomenon
involves positive allosterism. Furthermore, analysis by mass spectroscopy
revealed that the lipid–DMe-β-CDx complexes had stoichiometric ratios in
the range of 1 : 1–1 : 4. Ikeda, Atsushi; Iwata, Noboru; Hino, Shodai; Mae, Tomoya; Tsuchiya, Yuki;
Sugikawa, Kouta; Hirao, Takehiro; Haino, Takeharu; Ohara, Kazuaki; Yamaguchi,
Kentaro. RSC Advances2015,5, 77746-77754 ●Novel Helical Assembly of a Pt(II) Phenylbipyridine Complex Directed by
Metal-metal Interaction and Aggregation-induced Circularly Polarized Emission Abstract: Pt(II) phenylbipyridine complexes possessing bis(phenylisoxazolyl)phenylacetylene
ligands self-assembled to form stacked aggregates via Pt–Pt, π–π stacking,
and dipole–dipole interactions. The assembled structures were influenced
by the solvent properties. Non-helical assemblies found in chloroform displayed
metal–metal-to-ligand charge transfer absorption and emission, whereas
helical assemblies formed in toluene showed aggregation-induced enhancement
of emission and aggregation-induced circularly polarized luminescence.
The rates of the association and dissociation of the assemblies were significantly
reduced in toluene, and the non-helical structures formed in chloroform
were surprisingly memorized. Ikeda, Toshiaki; Takayama, Midori; Kumar, Jatish; Kawai, Tsuyoshi; Haino,
Takeharu Dalton Trans.2015,44, 13156-13162 ●Facile Construction of Well-defined Fullerene-dendrimer Supramolecular
Nanocomposites for Bioapplications Abstract:Well-defined fullerene–dendrimer supramolecular nanocomposites exhibiting
uniform size, controlled morphology, high fullerene inclusion efficiency,
excellent water solubility, and non-toxicity were facilely fabricated through
complexation of carboxyfullerenes with poly(ethylene glycol)-modified poly(amidoamine)
dendrimers. Li, Xiaojie; Watanabe, Yasuo; Yuba, Eiji; Harada, Atsushi; Haino, Takeharu;
Kono, Kenji Chem. Commun.2015,51, 2851-2854 ●Molecular Recognition of Upper Rim Functionalized Cavitand and Its Unique
Dimeric Capsule in the Solid State Abstract:Cavitand 1 possesses four 2,2′-bipyridyl pillars on its upper rim that
encapsulates small guests, such as nitromethane, acetonitrile, methyl acetate,
ethyl acetate, and N-methylacetamide, into a deep cavity to form host–guest
complexes in a 1 : 1 ratio. Nitroethane, N,N-dimethylformamide, and N,N-dimethylacetamide
were not bound in this manner. A guest-binding study and molecular mechanics
calculations revealed that the four 2,2′-bipyridyl pillars of cavitand
1 created a steric boundary that is responsible for selective guest recognition.
In the solid state, cavitand 2 formed a unique chiral capsule 22 by π–π
stacking interactions between the 2,2′-bipyridyl pillars. A nitromethane
molecule was unusually placed deep inside the cavity, as directed by the
multiple hydrogen bonding interactions between the nitromethane oxygen
atoms, the C–H bonds of the bridge methylenes and the pillar phenyl groups. Kobayashi, Mutsumi; Takatsuka, Mei; Sekiya, Ryo; Haino, Takeharu Org. Biomol. Chem.2015,13, 1647-1653 ●Anomalous Cage Effect of the Excited State Dynamics of Catechol in the
18-Crown-6-Catechol Host-Guest Complex Abstract:We determined the number of isomers and their structures for the 18-crown-6
(18C6)–catechol host–guest complex, and examined the effect of the complex
formation on the S1 (1ππ*) dynamics of catechol under a supersonically
cooled gas phase condition and in cyclohexane solution at room temperature.
In the gas phase experiment, UV–UV hole-burning spectra of the 18C6–catechol
1:1 complex indicate that there are three stable isomers. For bare catechol,
it has been reported that two adjacent OH groups have an intramolecular
hydrogen (H) bond. The IR–UV double resonance spectra show two types of
isomers in the 18C6–catechol 1:1 complex; one of the three 18C6–catechol
1:1 isomers has the intramolecular H-bond between the two OH groups, while
in the other two isomers the intramolecular H-bond is broken and the two
OH groups are H-bonded to oxygen atoms of 18C6. The complex formation with
18C6 substantially elongates the S1 lifetime from 7 ps for bare catechol
and 2.0 ns for the catechol–H2O complex to 10.3 ns for the 18C6–catechol
1:1 complex. Density functional theory calculations of the 18C6–catechol
1:1 complex suggest that this elongation is attributed to a larger energy
gap between the S1 (1ππ*) and 1πσ* states than that of bare catechol or
the catechol–H2O complex. In cyclohexane solution, the enhancement of the
fluorescence intensity of catechol was found by adding 18C6, due to the
formation of the 18C6–catechol complex in solution, and the complex has
a longer S1 lifetime than that of catechol monomer. From the concentration
dependence of the fluorescence intensity, we estimated the equilibrium
constant K for the 18C6 + catechol ⇄ 18C6–catechol reaction. The obtained
value (log K = 2.3) in cyclohexane is comparable to those for alkali metal
ions or other molecular ions, indicating that 18C6 efficiently captures
catechol in solution. Therefore, 18C6 can be used as a sensitive sensor
of catechol derivatives in solution with its high ability of fluorescence
enhancement. Morishima, Fumiya; Kusaka, Ryoji; Haino, Takeharu; Ebata, Takayuki J. Phys. Chem. B2015,119, 2557-2565 2014 ●Conversion from Pillar[5]arene to Pillar[6-15]arenes by Ring Expansion
and Encapsulation of C60by Pillar[n]arenes with Nanosize Cavities Abstract:Conversion of ring size from pillar[5]arene to pillar[6–15]arenes and isolation
of pillar[n]arene homologues (n = 11–13) with known pillar[n]arene homologues
(n = 6–10) are demonstrated. Pillar[10]arene formed the most stable host–guest
complex with C60 among the pillar[5–14]arenes. Ogoshi, Tomoki; Ueshima, Naosuke; Sakakibara, Fumiyasu; Yamagishi, Tada-aki;
Haino, Takeharu Org. Lett.2014,16, 2896-2899 ●Supramolecular Fullerene Polymers and Networks Directed by Molecular Recognition
between Calix[5]arene and C60 Abstract:A biscalix[5]arene–C60 supramolecular structure was utilized for the development
of supramolecular fullerene polymers. Di‐ and tritopic hosts were developed
to generate the linear and network supramolecular polymers through the
complexation of a dumbbell‐shaped fullerene. The molecular association
between the hosts and the fullerene were carefully studied by using 1H NMR,
UV/Vis absorption, and fluorescence spectroscopy. The formation of the
supramolecular fullerene polymers and networks was confirmed by diffusion‐ordered
1H NMR spectroscopy (DOSY) and solution viscometry. Upon concentrating
the mixtures of di‐ or tritopic hosts and dumbbell‐shaped fullerene in
the range of 1.0–10 mmol L−1, the diffusion coefficients of the complexes
decreased, and the solution viscosities increased, suggesting that large
polymeric assemblies were formed in solution. Scanning electron microscopy
(SEM) was used to image the supramolecular fullerene polymers and networks.
Atomic force microscopy (AFM) provided insight into the morphology of the
supramolecular polymers. A mixture of the homoditopic host and the fullerene
resulted in fibers with a height of (1.4±0.1) nm and a width of (5.0±0.8) nm.
Interdigitation of the alkyl side chains provided secondary interchain
interactions that facilitated supramolecular organization. The homotritopic
host generated the supramolecular networks with the dumbbell‐shaped fullerene.
Honeycomb sheet‐like structures with many voids were found. The growth
of the supramolecular polymers is evidently governed by the shape, dimension,
and directionality of the monomers. Hirao, Takehiro; Tosaka, Masatoshi; Yamago, Shigeru; Haino, Takeharu Chem. Eur. J.2014,20, 16138-16146(Hot Paper) ●Guest Induced Head-to-tail Columner Assembly of 5,17-Difunctionalized
Calix[4]arene Abstract:Calix[4]arene possessing two catechol side arms 1 and organic molecules
(nPrOH, AcOH, AcOEt, and CH3CN) crystallized to afford cocrystals: 1·(nPrOH)4,
1·(AcOH)4, 1·(AcOEt), and 1·(CH3CN)2. In these cocrystals, calix[4]arene
1 is arranged one-dimensionally, forming head-to-tail columnar structures.
The organic guests settle in the residual space between the columnar structures;
they are captured by the catechol side arms through hydrogen bonding. In
the cocrystal 1·(H2O)2, a continuous zigzag array of 1 is formed instead
of the columnar assembly, demonstrating that the organic guests induced
the formation of the head-to-tail columnar structures in the crystal packing.
The crystalline apohost 1apo was prepared by the desorption of the MeOH
guests from the cocrystal 1·(MeOH)4; this compound adsorbed the MeOH vapour,
reconstructing the original crystal packing. When 1apo adsorbed the iPrOH
vapour, a cocrystal with a crystal structure similar to that of 1·(MeOH)4
was formed, suggesting that 1apo has a crystal structure similar to that
of 1·(MeOH)4. Sekiya, Ryo; Yamasaki, Yutaro; Tada, Wataru; Shio, Hidemi; Haino, Takeharu CrystEngComm2014,16, 6023-6032 ●High Diastereoselection of Dissymmetric Capsule by Chiral Guest Complexation Abstract:Encapsulation of chiral guests in the dissymmetric capsule 1⋅4 BF4 formed
diastereomeric supramolecular complexes G⊂1⋅4 BF4 (G: guest). When chiral
guests 2 a–q were encapsulated within the dissymmetric space of the self‐assembled
capsule 1⋅4 BF4, circular dichroism (CD) was observed at the absorption
bands that are characteristic of the π–π* transition of the bipyridine
moiety of the capsule, which suggests that the P and M helicities of the
capsule are biased by the chiral guest complexation. The P helicity of
diastereomeric complex (S)‐2 l⊂1⋅4 BF4 was determined to be predominant,
based on CD exciton coupling theory and DFT calculations. The diastereoselectivity
was highly influenced by the ester substituents, such that benzyl ester
moieties were good for improving the diastereoselectivity. A diastereomeric
excess of 98 % was achieved upon the complexation of 2 j. The relative
enthalpic and entropic components for the distereoselectivity were obtained
from a van’t Hoff plot. The enthalpic components were linearly correlated
with the substituent Hammett parameters (σp+). The electron‐rich benzyl
ester moieties generated donor–acceptor π–π stacking interactions with
the bipyridine moiety, which resulted in a significant difference in energy
between the predominant and subordinate diastereomeric complexes. Tsunoda, Yuta; Fukuta, Katsunori; Imamura, Taisuke; Sekiya, Ryo; Furuyama,
Taniyuki; Kobayashi, Nagao; Haino, Takeharu Angew. Chem. Int. Ed.2014,53, 7243-7247 ●White-Light-Emitting Edge-Functionalized Graphene Quantum Dots Abstract:Graphene quantum dots (GQDs) have received considerable attention for their
potential applications in the development of novel optoelectronic materials.
In the generation of optoelectronic devices, the development of GQDs that
are regulated in terms of their size and dimensions and are unoxidized
at the sp2 surfaces is desired. GQDs functionalized with bulky Fréchet’s
dendritic wedges at the GQD periphery were synthesized. The single‐layered,
size‐regulated structures of the dendronized GQDs were revealed by atomic
force microscopy. The edge‐functionalization of the GQDs led to white‐light
emission, which is an uncommon feature. Sekiya, Ryo; Uemura, Yuichiro; Murakami, Hideki; Haino, Takeharu Angew. Chem. Int. Ed.2014,53, 5619-5623 ●Development of Ultraviolet-Ultraviolet Hole-burning Spectroscopy for Cold
Gas Phase Ions Abstract:A new ultraviolet–ultraviolet hole-burning (UV–UV HB) spectroscopic scheme
has been developed for cold gas-phase ions in a quadrupole ion trap (QIT)
connected with a time-of-flight (TOF) mass spectrometer. In this method,
a pump UV laser generates a population hole for the ions trapped in the
cold QIT, and a second UV laser (probe) monitors the population hole for
the ions extracted to the field-free region of the TOF mass spectrometer.
Here, the neutral fragments generated by the UV dissociation of the ions
with the second laser are detected. This UV–UV HB spectroscopy was applied
to protonated dibenzylamine and to protonated uracil. Protonated uracil
exhibits two strong electronic transitions; one has a band origin at 31760
cm–1 and the other at 39000 cm–1. From the UV–UV HB measurement and quantum
chemical calculations, the lower-energy transition is assigned to the enol–keto
tautomer and the higher-energy one to the enol–enol tautomer. Féraud, Géraldine; Dedonder-Lardeux, Claude; Jouvet, Christophe; Inokuchi,
Yoshiya; Haino, Takeharu; Sekiya, Ryo; Ebata, Takayuki J. Phys. Chem. Lett.2014,5, 1236-1240 ●Formation of Host-Guest Complexes on Gold Surface Investigated by Surface-Enhanced
IR Absorption Spectroscopy Abstract:We apply surface-enhanced infrared absorption (SEIRA) spectroscopy to host–guest
complexes in liquid phase to examine the structural change in the complex
formation. Two thiol derivatives of 18-crown-6 (18C6) are chemisorbed on
a gold surface, and aqueous solutions of MCl salts (M = Li, Na, K, Rb,
and Cs) are put to form M+·18C6 complexes. Infrared spectra of these complexes
in the 900–2000 cm−1 region are obtained by SEIRA spectroscopy. The observed
IR spectra show noticeable peaks due to the complex formation, demonstrating
that SEIRA spectroscopy will be a powerful method to investigate the structure
of host–guest complexes in supramolecular chemistry. Inokuchi, Yoshiya; Mizuuchi, Takahiro; Ebata, Takayuki; Ikeda, Toshiaki;
Haino, Takeharu; Kimura, Tetsunari; Guo, Hao; Furutani, Yuji Chem. Phys. Lett.2014,592, 90-95 DOI:10.1016/j.cplett.2013.12.026 ●Self-Assembly of Oligo(phenylisoxazolyl)benzenes Induced by Multiple Dipole-Dipole
Interactions Abstract:We have demonstrated that oligo(phenylisoxazolyl)benzenes 3–6 formed polymeric
assemblies. The intermolecular associations were discussed using thermodynamic
parameters. The formation of the polymeric assemblies were confirmed by
DOSY and AFM measurements. The large polymeric structures were observed
both in solution and in the solid state. The multiple dipole–dipole interactions
were crucial for the supramolecular polymerization of the oligo(phenylisoxazolyl)benzenes. Haino, Takeharu; Ueda, Yuko; Hirao, Takehiro; Ikeda, Toshiaki; Tanaka,
Masahiro Chem. Lett.2014,43, 414-416 ●Ion-based Assemblies of Planer Anion Complexes and Cationic PtII Complexes Abstract:Because the metallophilicity of attractive PtII⋯PtII interactions helps
in the fabrication of columnar structures, terpyridine–PtII complexes were
used as planar counter cationic species for formation of charge-segregated
assemblies using π-conjugated receptor–Cl− complexes as planar anions. Sekiya, Ryo; TsuTsui, Yusuke; Choi, Wookjin; Sakurai, Tsuneaki; Seki, Shu;
Bando, Yuya; Maeda, Hiromitsu Chem. Commun.2014,50, 10615-10618 ●Synthesis, Characterization, X-ray Crystal Structurte, DFT Calculations
and Catalytic Properties of a Dioxovanadium(V) Complex Derived from Oxamohydrazide
and Pyridoxal - A model Complex of Vanadate Dependent Bromoperoxidase) Abstract:A vanadium(V) complex with the formula [Et3NH][VVO2(sox-pydx)] with a new
tridentate ligand 2-[2-[[3-hydroxy-5-(hydroxymethyl)-2-methylpyridin-4-yl]methylene]hydrazinyl]-2-oxoacetamide
(soxH-pydxH), obtained by condensation of oxamohydrazide and pyridoxal
(one of the forms of vitamin B6), has been synthesized. The compound was
characterized by various analytical and spectroscopic methods, and its
structure was determined by single-crystal X-ray diffraction technique.
Density functional theory (DFT) and time-dependent DFT calculations were
used to understand the electronic structure of the complex and nature of
the electronic transitions observed in UV–vis spectra. In the complex,
vanadium(V) is found to be pentacoordinated with two oxido ligands and
a bianionic tridentate ONO-donor ligand. The vanadium center has square-pyramidal
geometry with an axial oxido ligand, and the equatorial positions are occupied
by another oxido ligand and a phenolato oxygen, an imine nitrogen, and
a deprotonated amide oxygen of the hydrazone ligand. A DFT-optimized structure
of the complex shows very similar metrical parameters as determined by
X-ray crystallography. The O4N coordination environment of vanadium and
the hydrogen-bonding abilities of the pendant amide moiety have a strong
resemblance with the vanadium center in bromoperoxidase enzyme. Bromination
experiments using H2O2 as the oxidizing agent, with model substrate phenol
red, and the vanadium complex as a catalyst show a remarkably high value
of kcat equal to 26340 h–1. The vanadium compound also efficiently catalyzes
bromination of phenol and salicylaldehyde as well as oxidation of benzene
to phenol by H2O2. Das, Chandrima; Adak, Piyali; Mondai, Satyajit; Sekiya, Ryo; Kuroda, Reiko;
Gorelsky, Serge; Chattopadhyay, Shyamal Inorg. Chem.2014,53 ,11426-11437 ●Heteroleptic Ru(II) Complexes Containing Aroyl Hydrazone and 2,2'-bipyridyl:
Synthesis, X-ray Crystal Structure, Electrochemical and DFT Studies Abstract:Four heteroleptic Ru(II) complexes [Ru(bpy)2(L)]X (L = bidentate N, O−
donor hydrazone ligands, X = ClO4 or PF6) have been synthesized and characterized.
Single crystal X-ray structures of two of the complexes are also reported.
The complexes show strong absorptions in the 400–600 nm region of the visible
radiation, with very similar room temperature emission spectra to that
of reference [Ru(bpy)3]X2 but with the lowest energy MLCT (metal to ligand
charge transfer) band bathochromically shifted by about 50 nm. Results
obtained from both electrochemical experiments and DFT calculations show
remarkable differences in the HOMO–LUMO properties of the hydrazone complexes
compared to [Ru(bpy)3]X2. TDDFT calculations have been used to understand
the nature of the electronic transitions. Ghosh, Bipinbihari; Naskar, Sumita; Naskar, Subhendu; Espinosa, Arturo;
Hau, Sam; Mak, Thomas; Sekiya, Ryo; Kuroda, Reiko, Chattopadhyay, Shyama Polyhedron,2014,72 , 115－121 DOI:10.1016/j.poly.2014.01.031 2013 ●Supramolecular Chemistry: From Host-guest Complexes to Supramolecular
Polymers Abstract:Combining the concepts of supramolecular chemistry with material science
has led to the development of supramolecular polymer chemistry. Although
a large number of host-guest motifs have been produced, only a limited
number of recognition motifs have been utilized as supramolecular connections
within polymeric assemblies. In this account, we describe the molecular
recognition of host molecules based on a calix[5]arene and a bisporphyrin,
demonstrating unique guest encapsulations; subsequently, these host-guest
motifs were applied to the synthesis of supramolecular polymers that display
polymer-like properties in both solution and solid states. In addition,
we disclose that bisresorcinarenes form supramolecular polymers that are
connected via a hydrogen-bonded rim-to-rim dimeric structure, which is
composed of two resorcinarene moieties. Haino, Takeharu J. Synth. Org. Chem. Jpn.2013,71, 1172-1181 DOI:10.5059/yukigoseikyokaishi.71.1172 ●Head-to-tail Polymeric Columnar Structure of Calix[4]arene Possessing
Catechol Arms in the Solid State Abstract:Calix[4]arene 1 cocrystallized with methanol (MeOH), ethanol (EtOH), isopropanol
(iPrOH) and 1,4-butanediol (BDO) to afford clathrate compounds 1·(MeOH)4,
1·(EtOH)4, 1·(iPrOH)4, and 1·(BDO)2, respectively. The unique head-to-tail
polymeric columnar structures of 1 were found in the solid state. Sekiya, Ryo; Yamasaki, Yutaro; Katayama, Susumu; Shio, Hidemi; Haino, Takeharu CrystEngComm2013,15, 8404-8407 ●Synthesis of Optically Active Poly(m-phenyleneethynylene-aryleneethynylene)s
Bearing Hydroxy Groups and Examination of the Higher Order Structures Abstract:Novel optically active poly(m-phenyleneethynylene–aryleneethynylene)s bearing
hydroxy groups with various arylene units {poly[(S)-/(R)-1–3a]–poly[(R)-1–3e]
and poly[(S)-2–3a]} were synthesized by the Sonogashira–Hagihara coupling
polymerization of 3,5-diiodo-4-hydroxy-C6H4CONHCH(CH3)COXC12H25 [(S)-/(R)-1
(X = O), (S)-2 (X = NH)] with HC≡C–Ar–C≡CH [3a (Ar = 1,4-C6H4), 3b (Ar
= 1,4-C6H4-1,4-C6H4−), 3c (Ar = 1,4-C6H4-1,4-C6H4-1,4-C6H4−), 3d (Ar =
2,5-dihexyl-1,4-C6H2), 3e (Ar = 2,5-didodecyl-1,4-C6H2)]. The yields and
number-average molecular weights of the polymers were in the ranges 60–94%
and 7,000–29,500 with no correlation between the yield and the Mn. Circular
dichroism (CD), UV–vis, and fluorescence spectroscopic analyses indicated
that poly[(S)-1–3a]–poly[(S)-1–3c] and poly[(S)-2–3a] formed predominantly
one-handed helical structures in THF, while poly[(S)-1–3d] and poly[(S)-1–3e]
showed no evidence for forming chirally ordered structures. All polymers
emitted blue fluorescence. The solution state IR measurement revealed the
presence of intramolecular hydrogen bonding between the amide groups at
the side chains of poly[(S)-1–2a]. The helical structures and helix-forming
abilities of the polymers were analyzed by the molecular mechanics (MM),
semiempirical molecular orbital (MO) and density functional theory (DFT)
methods. Tube-like structures, presumably formed by perpendicular aggregation
of the helical polymers, were observed by atomic force microscopy (AFM). Sogawa, Hiromitsu; Shiotsuki, Masashi; Hirao, Takehiro; Haino, Takeharu;
Sanda, Fumio Macromolecules2013,46, 8161-8170 ●Size- and Orientation-Selective Encapsulation of C70by Cycloparaphenylenes Abstract:The size‐ and orientation‐selective formation of the shortest‐possible
C70 peapod in solution and in the solid state by using the shortest structural
unit of an “armchair” carbon nanotube (CNT), cycloparaphenylene (CPP),
has been studied. [10]CPP and [11]CPP exothermically formed 1:1 complexes
with C70, thereby giving the resulting peapods. A van′t Hoff plot analysis
revealed that the formation of these complexes in 1,2‐dichlorobenzene was
mainly driven by entropy, whereas the theoretical calculations suggested
that the formation of the complex in the gas phase was predominantly driven
by enthalpy. C70 was found to exist in two distinct orientations inside
the CPP cavity, namely “lying” and “standing”, depending on the specific
size of the CPP. The theoretical calculations and the X‐ray crystallographic
analysis revealed that the interactions between [10]CPP and the short axis
of C70 in its lying orientation were isotropic and similar to those observed
between [10]CPP and C60. However, the interactions between [11]CPP and
C70 in its standing orientation were anisotropic, thereby involving the
radial deformation of [11]CPP into an ellipsoidal shape. This “induced
fit” maximized the van der Waals interactions with the long axis of C70.
Theoretical calculations revealed that the deformation occurred readily
with low energy loss, thus suggesting that CPPs are highly radially elastic
molecules. These results also indicate that the same type of radial deformation
should occur in CNT peapods that encapsulate anisotropic fullerenes. Iwamoto, Takahiro; Watanabe, Yoshiki; Takaya, Hikaru; Haino, Takeharu;
Yasuda, Nobuhiro; Yamago, Shigeru Chem. Eur. J.2013,19, 14061-14068 ●超分子化学を用いる分子配列構造の制御 (This article is written in Japanese) 灰野岳晴 Organometallic News2013,2, 54-60 ●Selective Synthesis of [2]- and [3]Catenane Tuned by Ring Size and Concentration Abstract:The syntheses of [2]- and [3]catenanes by olefin metathesis and oxidative
acetylide coupling have been studied in detail. Pseudorotaxanes that were
obtained by mixing crown ether and ammonium salts containing two terminal
reactive end-groups were converted to [2]- and [3]catenane. Their yields
were influenced not only by the chain length of the ammonium salts but
also by the concentration of the crown ether and the ammonium salts. The
strain energies of [2]catenane were responsible for the formation of [2]catenane. Iwamoto, Hajime; Takizawa, Wataru; Itoh, Koji; Hagiwara, Tatsuya; Tayama,
Eiji; Hasegawa, Eietsu; Haino, Takeharu J. Org. Chem.2013,78, 5205-5217 ●Photoresponsive Two-Component Organogelators based on Trisphenylisoxazolylbenzene Abstract:Photochromic tris(phenylisoxazolyl)benzene 1 and bispyridine derivatives
2a–e were mixed in a certain ratio to generate stable gels in benzyl alcohol,
4-methoxybenzyl alcohol, and aniline. Supramolecular assembly of 1 in solution
was confirmed by 1H NMR study. The Tgel value was saturated in a 2 : 3
ratio of 1 and 2c. The intermolecular hydrogen bonds OH⋯N and salt bridge
O−⋯H–N+ between 1 and 2c coexisted evidently, and these hydrogen bonds
contributed to the stabilization of the gel networks. The lengths of alkyl
chains of 2a–e governed the stabilities of the gels. The gel formations
were driven by the morphological transition of 1 before and after the addition
of 2a–e. Mixtures of 1 and 2a–e led to the well developed fibrillar networks,
generating a lot of voids that are responsible for immobilizing solvent
molecules. When the benzyl alcohol gel was irradiated at 360 nm, the gel
turned to the sol. The sol was reversed to the gel by warming. This gel-to-sol
phase transition was completely reversible. Haino, Takeharu; Hirai, Yuko; Ikeda, Toshiaki; Saito, Hiroshi Org. Biomol. Chem.2013,11, 4164-4170 (Inside Front Cover) ●Molecular-recognition-directed formation of supramolecular polymers Haino, Takeharu Polym. J.2013,45, 363-383 DOI:10.1038/pj.2012.144
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