Photooxidation of Platinum(II) Diimine Dithiolates

Abstract

The violet color of Pt(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 (τ = 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 ^1H NMR and UV−visible 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.

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