Phenylcyanamide Ligand Control of Photo-Induced Linkage Isomerism

The photo- and electrochemically induced linkage isomerism of six new complexes [Ru(bpy)2(L)(dmso-S)]+, where dmso is dimethylsulfoxide, bpy is 2,2′-bipyridine, and L– is pentachloro-, 2,3,5,6-tetrachloro-, 2,4,5-trichloro-, 2,4-dichloro-, 4-chloro-, and unsubstituted phenylcyanamide anion, were investigated. The quantum yields of linkage isomerism forming the metastable [Ru(bpy)2(L)(dmso-O)]+ complexes are shown to decrease with increasing donor properties of the phenylcyanamide ligand, and it is suggested that the donor properties of the cyanamide ligand stabilize the [Ru(bpy)2(L)(dmso-S)]+ complexes in the 3MLCT excited state. The cyclic voltammetry of these complexes showed two oxidation processes: a phenylcyanamide L(0/-) couple (an assignment supported by density functional theory (DFT) calculations) and a Ru(III/II) couple at more positive potential. Upon oxidation to Ru(III), the complexes rearranged to form Ru–O linkage isomers, and the scan rate dependent voltammograms permitted estimates of the rates of linkage isomerism.