Photoinduced ligand isomerization in Dimethyl Sulfoxide Complexes of Ruthenium(II)

Abstract

Upon exposure to sunlight or UV irradiation, a DMSO solution of [Ru(bpy)2(DMSO)2]2+ (1) (bpy = 2,2’-bipyridine; DMSO = dimethyl sulfoxide) turns rapidly from yellow to red, but subsequently slowly reverts to yellow in the dark. The photochemical sequence is explained in terms of a photopromoted linkage isomerization of the DMSO ligands from Sto O-bound, with a relaxation back to the thermodynamically stable yellow S-bound form in the dark by an intermolecular mechanism. The ‘‘dark’’ reaction has been studied by UV/Vis spectrophotometry, NMR and IR spectroscopy. The S-bound ligation of DMSO in the yellow cation was established by Xray crystallographic studies of cis-[Ru(bpy)2(DMSO)2]-(CF3SO3)2.