Solvent motion and excited state decay in solutions of Cr(III) complexes

Thermal quenching of 2E in Cr(bpy)33+ (bpy = 2,2′-bipyridine) solutions where back-intersystem crossing is not important is compared with the quenching of Cr(NCS)63− and trans-Cr(NH3)2(NCS)4− in several solvents. Solvent motion enhances excited state relaxation whether or not back-intersystem crossing is a significant relaxation pathway. The relationship between motionally induced decay and the exponential or nonexponential character of the decay is discussed.