The violet color of Ft(bpy)(bdt) (bpy = 2,2-bipyridine; bdt = 1,2-benzenedithiolate) is due to a Pt/S-->diimine charge-transfer transition, the emission originates from the corresponding triplet state (tau = 460 ns). Photochemical oxidation of Pt(bpy)(bdt) occurs in the presence of oxygen in N,N-dimethylformamide, acetonitrile, or dimethyl sulfoxide solution; the reaction has been investigated by H-1 NMR and UV-risible absorption spectroscopy. Singlet oxygen produced by energy transfer from the excited complex is implicated as the active oxygen species, in sequential formation of sulfinate, Pt(bpy)(bdtO(2)), and disulfinate, Pt(bpy)(bdtO(4)), products. Both products have been characterized by X-ray crystallography. The rate of photooxygenation is strongly dependent on water concentration, and transient absorption spectra are consistent with the formation of at least one intermediate. As a whole, our data suggest that the photooxidation chemistry of platinum(II) diimine dithiolates is similar to that of organic sulfides.