The excited states of [Ru(bpy)(2)(deeb)](PF6)(2), where bpy is 2,2-bipyridine and deeb is 4,4'-(CO2CH2CH3)(2)- 2,2'-bipyridine, were found to be efficiently quenched by triiodide (I-3(-)) in acetonitrile and dichloromethane. In dichloromethane, I-3(-) was found to quench the excited states by static and dynamic mechanisms; Stern - Volmer analysis of the time-resolved and steady-state photoluminescence data produced self-consistent estimates for the I-3(-) + Ru(bpy)(2)(deeb)(2+) reversible arrow [Ru-II(bpy)(2)(deeb)(2+),(I-3(-))](+) equilibrium, K = 51,000 M-1, and the bimolecular quenching rate constant, k(q) = 4.0 x 10(10) M-1 s(-1). In acetonitrile, there was no evidence for ion pairing and a dynamic quenching rate constant of k(q) = 4.7 x 10(10) M-1 s(-1) was calculated. Comparative studies with Ru(bpy)(2)(deeb)(2+) anchored to mesoporous nanocrystalline TiO2 thin films also showed efficient excited-state dynamic quenching by I-3(-) in both acetonitrile and dichloromethane, k(q) = 1.8 x 10(9) and 3.6 x 10(10) M-1 s(-1), respectively. No reaction products for the excited-state quenching processes were observed by nanosecond transient absorption measurements from 350 to 800 nm under any experimental conditions. X-ray crystallographic, IR, and Raman data gave evidence for interactions between I-3(-) and the bpy and deeb ligands in the solid state.