Photophysical and novel charge-transfer properties of adducts between [RuII(bpy)3]2+ and [S2Mo18O62]4-

The photophysical properties of acetonitrile solutions of Ru(bpy)(3)](2+) and S(2)Mo(18)O(62)](4-) are described. We discuss evidence for ion cluster formation in solution and the observation that despite the strong donor ability of the excited state of Ru(bpy)(3)](2+) and its inherent photolability, adducts with S(2)Mo(18)O(62)](4-) were photostable. Photophysical studies suggest that the quenching of the Ru(bpy)(3)](2+) excited state by S(2)Mo(18)O(62)](4-) occurs via a static mechanism and that binding is largely electrostatic in nature. Evidence is provided from difference spectroscopy and luminescence excitation spectroscopy for good electronic communication between Ru(bpy)(3)](2+) and S(2)Mo(18)O(62)](4-) with the presence of a novel, luminescent, inter-ion charge-transfer transition. The identity of the transition is confirmed by resonance Raman spectroscopy.