Film electrochemistry of a diruthenium complex at an electrode modified with various matrices in aqueous media

The three metal-centered reactions of Ru 2 (2-CH 3 ap) 4 Cl (1), where 2-CH 3 ap is 2-(2-methylanilino)pyridinate anion, were electrochemically investigated in three different cationic matrices at a basal plane pyrolytic graphite (BPG) electrode immersed in 0.5 M aqueous KCl solution. The matrices were tetra-n-octylphosphonium bromide (4C 8 P + Br - ), tetra-n-octylammonium bromide (4C 8 N + Br - ), or tetra-n-heptylammonium bromide (4C 7 N + Br - ). Complex 1 was also examined in a cast film of an artificial lipid, di-n-hexadecyldimetllylammonium poly(styrene sulfonate), 2C 1 6 N + PSS - , which has a phase-transition between the crystalline and the liquid crystalline phase at 26.6°C. Here, the Ru 5 + / 4 + 2 reaction shows a strong phase-transition temperature dependence, suggesting the possibility of a temperature-driven, "on-off" switching for the electrochemistry of 1.