Mitsutoshi Okano

Electrochemical synthesis of polygermanes

Abstract Five dialkyl-substituted and three phenyl substituted polygermanes were electrochemically synthesized. Among them, dibutyl-, dipentyl-, and dihexyl-substituted polygermanes gave the best synthetic results, i.e., relatively high yields (25–45%), high current efficiency (25–50%), high molecular weights ( M w : 10,000–25,000), and long absorption maxima ( λ max : 324–327 nms). Thus obtained polygermanes showed the discontinuous thermochromic changes known for the polymers. Syntheses of the corresponding polysilanes under the same conditions gave better yields (50–70%), better current efficiency (50–80%), slightly larger molecular weights ( M w : 15,000–35,000), but shorter absorption maxima ( λ max : 313–316 nms). The reaction mechanism was discussed in detail. It was suggested in the discussion that more back-biting reactions, which is one of the causes for the decrease of the yield and the molecular weight, occur in the later stages of electrolysis. In order to know if molecular weights and yields are decreasing in the later stages of electropolymerization, syntheses with 40, 60, 80, and 100% electricity of the theoretical value were carried out. Synthesis with 80% electricity of the theoretical value gave the best results.

Electrochemical synthesis of stannane–silane and stannane–germane copolymers

Abstract Poly(dibutylstannylene-co-dibutylsilylene) and poly(dibutylstannylene-co-dibutylgermylene) were synthesized for the first time, by electrochemical reduction of dibutyldichlorostannane together with dibutyldichlorosilane and dibutyldichlorogermane, respectively, in a one-compartment cell equipped with a platinum cathode and a silver anode, using tetrabutylammonium perchlorate and 1,2-dimethoxyethane as the supporting electrolyte and the solvent, respectively. Most of absorption peaks observed for the copolymers were located between those of polystannylene and polysilylene/polygermylene. A copolymer with relatively high stannane content had a relatively long absorption peak, which is close to that of a homopolymer polydibutylstannylene. A copolymer with a higher stannane content was more sensitive to the moisture in air.

Electrochemical synthesis of germane–germane and germane–silane copolymers

Poly(dibutylgermylene-co-dihexylgermylene), poly(dibutylsilylene-co-dihexylsilylene), poly(dihexylgermylene-co-dihexylsilylene), poly(dibutylgermylene-co-diphenylgermylene) and poly(methylphenylgermylene-co-dipentylgermylene) were synthesized electrochemically by introducing two corresponding monomers in starting electrolyte solution. The monomer ratio in the copolymers was successfully controlled by changing the ratio of monomers in the starting electrolyte solutions. However, the monomer ratio in the resulting copolymers were different from those in the starting electrolyte solutions. One monomer, which gives a better yield and a higher molecular weight than the other monomer in the homopolymer syntheses, was found in a larger proportion in the copolymer than was expected from the monomer ratio in the starting electrolyte solution. Thermochromic behaviors of the copolymers depended upon the ratio of monomers in the copolymers. It was concluded that random copolymerization was taking place in all the copolymer syntheses studied here.

Electrochemical synthesis of network polygermanes and polysilanes

Abstract Network σ-conjugated polymers, i.e., a butyl substituted network polygermane, (BuHxGe)n (x=0–2), a butyl substituted network polysilane, (BuHxSi)n (x=0–2), and an octyl substituted network polysilane, (OctHxSi)n (x=0–2), were synthesized by electrochemical reduction of butyltrichlorogermane, butyltrichlorosilane, and octyltrichlorosilane, respectively, for the first time. A polymer of (BuHxGe)n (x=0–2) had absorption which extended to 900 nm, while a polymer of (BuHxSi)n (x=0–2) and a polymer of (OctHxSi)n (x=0–2) had absorption which extended to 500 and 800 nms, respectively. It was found that the reported electrochemical method gave σ-conjugated polymers with more highly developed network structures compared to the other synthetic pathways. The structure of the polymers was successfully controlled from linear to highly developed network structures by controlling the charge for electrosynthesis.

Area‐selective deposition of organic conducting polymers on semiconductors: Polypyrrole‐ZnO system

Area‐selective deposition of polypyrrole was successfully performed by three different procedures with electrochemical and photoelectrochemical techniques. These methods are important as tools for organic conducting pattern generation and functionalization of electrode surfaces.

Back-Biting Reactions of σ-Conjugated Polymers in Electrochemical Systems

σ-Conjugated polymers (polysilanes and polygermanes) have been the subject of considerable interest in recent years because of their unique physical and chemical properties. Electrochemical reduction of dihalogeno-silanes and -germanes is one of the best pathways to the polymers. However, only relatively small molecular weight polymers are obtained by electrochemical method compared to those obtained by Wurtz-type coupling reaction.

NMR Study on the electrogenerated triphenylmethyl anion

NMR spectra of electrogenerated triphenylmethyl anions were successfully measured. Carbon-13 chemical shifts, which were essential to understand the nature of the anion, were obtained. Proton NMR gave quantitative data on the anion in the catholyte solution.