Regulation of film electrochemistry and CO binding of a diruthenium complex embedded in artificial lipids on an electrode

Film electrochemistry of Ru2(2-CH3ap)4Cl (1), where 2-CH3ap is 2-(2-methylanilino)pyridinate anion, and their carbon monoxide (CO) binding ability were electrochemically investigated in three different cationic matrices at a basal plane pyrolytic graphite (BPG) electrode immersed in 0.5 M aqueous KCl solution under CO atmosphere. The matrices employed in this study were tetra-n-octylphosphonium bromide (4C8P+Br−), tetra-n-octylammonium bromide (4C8N+Br−), or tetra-n-heptylammonium bromide (4C7N+Br−). The complex 1 at the lipids modified electrodes was able to bind CO molecules in the Ru24+, Ru23+ and Ru22+ reduced forms. Regulation of CO binding reaction of the complex 1 was also examined in a cast film of an artificial lipid, di-n-hexadecyldimethylammonium poly(styrene sulfonate), 2C16N+PSS−, which has a phase transition between the crystalline and the liquid crystalline phase at 26.6 °C. Here, the Ru25+/Ru24+ and Ru24+/Ru23+ reactions under CO atmosphere showed a strong phase transition temperature dependence, suggesting the possibility of a temperature-driven regulation for the electrochemistry of complex 1 upon CO binding.