Toshikazu Hirao

Conjugated systems composed of transition metals and redox-active π-conjugated ligands

Abstract A combination of transition metals and π-conjugated molecules or polymers as redox-active ligands leads to the hybrid conjugated complexes. A variety of structural designs are possible based on the coordination number and geometry, affording an efficient multi-redox system. This review focuses mostly on conjugated complexes with p-quinone, p-quinonediimine, and polyaniline derivatives to give bimetallic, metallocyclic, and polymeric complexes. Complexes with polyanilines are used in the catalytic oxidation reactions, for example, the Wacker oxidation, in which the π-conjugated polymers serve as a redox-active ligand.

Hydrogen-bonding-directed molecular assembly of ferrocene bearing dipeptide chains (-l-Ala-l-Pro-NHPyMe) as an organometallic crystal architecture

Abstract The ferrocene 1 bearing the dipeptide chains, - l -Ala- l -Pro-NHPyMe, which was characterized by two intramolecular interchain hydrogen bondings between CO (Ala) and NH (another Ala) of each dipeptide chain to induce the chirality organized structure, was demonstrated to form a 1:2 complex with (1R,3S)-camphoric acid (CA). The single-crystal X-ray structure determination revealed a polymeric cocrystal composed of alternating units of 1 and two CA, which are linked by a network of hydrogen bonds to create the double-helical-like hydrogen-bonded molecular arrangement.

Conjugated complexes via oxidative complexation of polyaniline derivatives to vanadium(III)

Abstract The emeraldine base of poly( o -toluidine) and N,N ′-bis(4′-dimethylaminophenyl)-1,4-quinonediimine were demonstrated to undergo oxidative complexation to VCl 3 , affording the corresponding conjugated complexes. The complexation proceeds via reduction of the quinonediimine moiety with oxidation of V(III)–V(IV), in which the vanadium species is considered to play an important role in both the complexation and reduction.

Synthesis and characterization of p-phenylenediamine derivatives bearing a thiadiazole unit

New p-phenylenediamine derivatives bearing a thiadiazole unit were synthesized by palladium-catalyzed amination. Cyclic voltammetry revealed that the electrochemical properties depend on the position of the benzothiadiazole ring.

Conjugated complex system composed of quinonediimine unit

A combination of transition metals and π-conjugated molecules or polymers as redox-active ligands affords the hybrid conjugated complexes. A variety of structural design is possible based on the coordination number and geometry to construct an efficient multi-redox system.