Electrochromic properties of mixed valence binuclear ruthenium complexes adsorbed on nanocrystalline SnO2 films

The electrochromic properties of two new mixed valence ruthenium complexes: K[(NC5H4CH2PO3H2)RuIII(NH3)4(NC)RuII(CN)5] and K[(NC5H4PO3H2)RuIII(NH3)4(NC)RuII(CN)5], where phosphonic acid groups have been introduced at the pyridine ligand, have been studied in homogeneous solution and adsorbed on transparent nanocrystalline SnO2 electrodes. These species exhibit a superior stability with respect to the previously studied, K[(NC5H4CO2H)RuIII(NH3)4NCRuII(CN)5] complex, showing negligible optical density changes after cycling 20 000 times the electrodes between −0.5 and 0.5 V versus SCE.