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 [S2Mo18O62](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 [S2Mo18O62](4-) were photostable. Photophysical studies suggest that the quenching of the [Ru(bPY)(3)](2+) excited state by [S2Mo18O62](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 [S2Mo18O62](4-) with the presence of a novel, luminescent, inter-ion charge-transfer transition. The identity of the transition is confirmed by resonance Raman spectroscopy.