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2022
●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.
●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.
●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.(Cover Picture)
●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)