The photoelectrochemical study of a series of ionically combined bischromophore transition metal complexes in LB films

Abstract

Five transition metals were selected as the central ions to coordinate with 4,5-dimercapto-1,3-dithiole-2-thione to form five complex anions which were combined with hemicyanine dye to form five complexes, bis{[(E)-N-octadecyl-4-[2-(4-dimethylaminophenyl)ethenyl]pyridinium}bis(4,5-dimercapto-1,3-dithiole-2-thionato)metalate [D₂M(dmit)₂, where M = Ni, Pd, Cu, Cd, Hg]. Data show that D₂Cd(dmit)₂ is the best in terms of the photoelectric conversion among the five complexes. The quantum yield of D₂Cd(dmit)₂ is 5 times greater than that of (E)-N-octadecyl-4-[2-(4-dimethylaminophenyl)ethenyl]pyridinium iodide (DI) itself. UV-vis and fluorescent spectroscopy were used to characterize the compounds and study the interaction of the ions. A semiempirical quantum chemical calculation by PM3 was used to elucidate the role of the counter anions. By combining the experimental and theoretical results, it was found that the electronic configuration of the transition metals and the geometric configuration of the counter anion play important roles in the photoelectric conversion system.