Shin-ichi Kugimiya

Synthesis and chromophoric interactions of an ‘ortho-gable-porphyrin.’ a novel tetraphenylporphyrin dimer

A newly synthesized ‘ortho-gable-porphyrin,’ a tetraphenylporphyrin-type dimer with an ortho-phenylene bridge, provided a model for closer porphyrin–porphyrin separation.

Electron transport across artificial liposomal membranes aided by phase-transfer of the movable electron carrier: correlationship between hydrophobicity and carrier efficiency

Abstract Electron transport across single wall, bimolecular lecithin liposomal membranes from exterior S2O4 = to interior ferricyanide or FMN (riboflavin 5′-phosphate) were investigated. A series of alkylviologens were used as electron carriers. The overall electron trasport rates increased with the carbon number of the alkyl chain for C1 – C4′ then decreased monotonically until C18. Measurement of the distribution of tne viologens, and the corresponding viologen cation radicals, between H2O/CH2Cl2 or H2O/lecithin liposome were carried out independently. These results, together with the rate measurements, clearly demonstrate that the overall electron transport rates are primarily controlled by the phase-transfer of the alkylviologen cation radicals from the exterior aqueous phase to the membrane for C1 – C4′ and by the phase-transfer of the cation radicals from the membrane to the interior aqueous phase for C4 – C18. This leads to optimal electron transport for the C4 viologen.

Fluorescence characteristics of unsymmetrical metal complexes of “gable porphyrin”

Abstract Mono and mixed metal complexes of “gable” porphyrin, i.e., meta-phenylene bridged porphyrin dimer, were synthesized. Picosecond time resolving fluorescence spectra identified the very rapid rate process in the order of 1011 s-1 for energy as well as electron transfers from the S1 state of Zn-TPP to the free or Fe(III)-TPP unit.

Electron conduction across vesicular bilayer membranes induced by a caroviologen molecular wire

The zwitterionic caroviologen 12±, incorporated into vesicle bilayer membranes, functions as a molecular wire mediating electron transfer from an external reducing phase to an internal oxidising phase.

Gable porphyrin metal complex as a double recognition model

A new metalloreceptor, a gable porphyrin metal complex, recognizes aromatic heterocycles regiospecifically by the use of double recognition, which is necessary for advanced molecular recognition.

Allosteric behavior of artificial compounds.

The artificial allosteric molecules were prepared by connecting two independent metal porphyrin molecules by covalent bond. These molecules as fragments behave very similarly to the monomeric metal porphyrins except adsorption dissociation characteristics. In this paper we would like to discuss mostly on interesting and useful cooperativity or cooperative binding dissociation of small molecules like CO, O2, or base to both of porphyrin metals. The original structure of the dimeric porphyrin, especially when they are very strongly cooperative, usually needs chemical strain between two porphyrin rings and this strain is released by the first binding of small molecule which causes coordinating change of the metal porphyrin.