Hirokuni Jintoku

Enantioselective recognition by a highly ordered porphyrin-assembly on a chiral molecular gel

Enantioselective recognition of amino acids was achieved by using a highly ordered chiral assembly of achiral porphyrin on a chiral molecular gel. Exceptionally high enantioselectivity was observed for histidine derivatives by monitoring the CD patterns and fluorescence quenching, K(SV) (l): 26.3 × 10(3) M(-1); K(SV)(D)-enantiomer: 7.03 × 10(3) M(-1).

Chirally self-assembled porphyrin nanowires assisted by L-glutamide-derived lipid for excitation energy transfer

An L-glutamide-functionalized tetraphenylporphyrin () has been newly synthesized and its self-assembling behavior in organic solvents is reported. forms nanofibrous assemblies in a dilute solution to show specific induced circular dichroism at the absorption band around the porphyrin moiety. It enables us to observe the meso-stable and stepwise H- and J-like hierarchical aggregations. Energy transfer studies in a mixed system with a pyrene-functionalized L-glutamide reveal the promotion of energy transfer from the pyrene excimer to the porphyrin moiety.

Noncovalent One-to-One Donor–Acceptor Assembled Systems Based on Porphyrin Molecular Gels for Unusually High Electron-Transfer Efficiency

A new approach for fabricating donor-acceptor assembled systems is demonstrated, based on J-type ordered aggregation of a low-molecular zinc porphyrin derivative and subsequent integration of a pyridylated fullerene derivative with coordination and orientation onto the porphyrin aggregates. This system achieves unusually high efficiencies in fluorescence quenching during one-to-one mixing of the donor and acceptor. Moreover, the Stern-Volmer constant (K(SV)) and association constant (K) of this system are 2520 and 56 times higher, respectively, than those of the corresponding nonassembled system. The quenching efficiency is thermotropically switchable, since ordered-to-disordered transitions are essential characteristics of noncovalent low molecular assemblies.

Highly efficient and switchable electron-transfer system realised by peptide-assisted J-type assembly of porphyrin

We propose a new strategy for fabrication of a phase-separated bicontinuous system composed of low-molecular donor and acceptor that is built up through coordination-based orientation of pyridylated fullerene on a π-conjugated zinc-porphyrin J-type assembly. This complex system exhibits extremely efficient and switchable fluorescence quenching.

Versatile chiroptics of peptide-induced assemblies of metalloporphyrins

Zinc porphyrin functionalized with double long-chain alkylated L-glutamide (GTPP-Zn) was synthesized for the first time, and its self-assembling behaviour was investigated in nonpolar organic solvents. The uniqueness of this functionalized porphyrin is characterized by its drastic colour change from dark green to purple via the formation of chirally stacked structures through selective axial coordination on zinc with pyridine derivatives. In this paper, we report the versatility of the GTPP-Zn assembly process as a stimuli-responsive chiroptical switching system and describe the remarkable ligand-specific induction of secondary chirality accompanied by aggregation morphological change.

Tunable Stokes shift and circularly polarized luminescence by supramolecular gel

A new optical material based on the self-assembly of a low-molecular organogelator-linked anthracene derivative for the control of the fluorescence wavelength and polarization was developed. When the anthracene derivative was formed through self-assembly, the fluorescence wavelength was shifted by 100 nm (426 to 526 nm) and emitted circularly polarized luminescence. The control of the fluorescence wavelength and polarization was accomplished through the excimer formation of anthracene fluorophores, which can be tuned by the cooling process, temperature and solvent of the solution. Also, the fluorescence control in the solid state and the white-light emission in the gel state were accomplished by mixing the polymer matrix, and the addition of red-emitting dye, respectively. This material has possible potential for various applications such as a spectral conversion film, white light-emitting diodes and circularly polarized displays.

Creation of a polymer backbone in lipid bilayer membrane-based nanotubes for morphological and microenvironmental stabilization

We report a novel method for morphological and microenvironmental stabilization of single-walled bilayer nanotubes, which involves construction of a polymer backbone between the monolayers by intercalating a monomer, followed by in situ polymerization.

Self-assembling fullerene derivatives for energy transfer in molecular gel system

An L-glutamide-derived compound with a fullerene moiety was newly synthesized by the coupling of (6,6)-phenyl-C61 butyric acid with N,N-didodecyl L-glutamide containing an amino alkyl group. In this paper, we describe that the solubility to an organic solvent was sufficiently improved by functionalization with L-glutamide and these fullerene derivatives could form ordered aggregates in organic solvents. It is also reported that the fullerene-containing derivatives were evaluated as a donor-acceptor model with the corresponding porphyrine derivative.

Supramolecular gel-functionalized polymer films with tunable optical activity

We describe a new method for the fabrication of an optically active polymer film, involving the phase separation of self-assembled chiral nanofibres in a solid polymer matrix. The circular polarization properties of the films can be controlled by changing the morphology of the phase-separated nano domains.

Tuning of Molecular Orientation of Porphyrin Assembly According to Monitoring the Chiroptical Signals

Zinc tetraphenylporphyrin functionalized by an L-glutamide derivative as a self-assembling tool ( g -TP) was investigated from the viewpoint of chiral nanomaterials. As a result, it was found that g -TP in cyclohexane formed nano-size assemblies with unique chiroptical signals based on J-type stacking among the porphyrin moieties, which was very sensitive to axial coordination on zinc. In this paper, it is also described that the g -TP chiral assembly can recognize chirality and slight difference of chemical structures of ligands.