Switching of the Electronic Communication between Two {Ru(trpy)(bpy)} (trpy = 2,2:6,2"Terpyridine and bpy = 2,2-Bipyridine) Centers by Protonation on the Bridging Dimercaptothiadiazolato Ligand

A stable Ru(II)/Ru(III) mixed-valence state was observed in acetonitrile for the ruthenium binuclear complex bridged by dimercaptothiadiazolate ((delta)E1/2 = 220 mV for Ru2(II,II)/Ru2(II,III) and Ru2(II,III)/Ru2(III,III) processes; Kcom = 5.3 × 103). Upon protonation of the bridging ligand by the addition of equimolar p-toluenesulfonic acid, however, the mixed-valence state diminished ((delta)E1/2 = 0 mV). The bridging ligand operates as a proton-induced switch of the electronic communication in the dimeric complex.