INTERSYSTEM-CROSSING DYNAMICS IN HETERODINUCLEAR POLYPYRIDYL-BRIDGED COMPLEXES

The excited-state properties of [(L)4MII(dpp)RuII(bpy)2](PF6)n (bpy = 2,2‘-bipyridine; dpp = (2,3-bis(2-pyridyl)pyrazine); (L)4MII = (NH3)4RuII (n = 4) or (CN)4FeII (n = 0)) have been investigated by steady-state and time-resolved picosecond and nanosecond transient luminescence and absorption spectroscopic methods. The [(NH3)4RuII(dpp)RuII(bpy)2]4+* complex is nonemissive in room-temperature H2O solution. Picosecond laser flash photolysis of [(NH3)4RuII(dpp)RuII(bpy)2]4+ reveals the formation of a transient species that decays exponentially (τ = 290 (±80) ps) independent of excitation wavelength. The excited-state behavior of [(NC)4FeII(dpp)RuII(bpy)2]* display a complicated dependence on excitation wavelength. Following 591-nm pulsed laser excitation into the 1[(dπ) (π*) ] ← 1[(dπ) ] metal-to-ligand charge transfer (MLCT) band, a short-lived transient is formed with τ 200 ns. One...