1.2- Dithioles, 3- photochemistry

An important aspect of the photophysics of the Pt(diimine)(dithiolate) photochemistry that has received increasing attention is the ability of the excited-state complexes to undergo self-quenching. Initial work by Connick and Gray (111) showed that the lifetime of the complex Pt(bpy)(bdt) (bdt = benzene-1,2-dithiolate, 31) decreased with increasing solution concentration. The bimolecular self-quenching rate constant, calculated from a Stem-Volmer quenching analysis, was found to be 9.5 x 109 A/-1 s-1 in acetonitrile and 4 x 109 M 1 s 1 in chloroform. However, no evidence of excimer formation... 

The long lifetimes of CT excited states of the Pt(diimine)(dithiolate) complexes allow for bimolecular photochemistry, often involving oxidation of the complex. The earliest report of photoreactivity of these complexes dealt with the photooxidation of Pt(bpy)(tdt) (20) following excitation at 577 nm in chloroform (118). The reaction proceeds with a quantum yield of < ) = 0.03 and was attributed to ET to the halocarbon solvent (Eq. 8) similar to the CTTS photooxidation chemistry of the platinum bis(dithiolate) dianions described above. 

De Mayo and co-workers have studied the photochemistry of 1,2-dithiole-3-thiones in connection with general studies of the photochemistry of thioketones. 56 5-Aryl-substituted compounds were photochemically stable, whereas 4-aryl-substituted isomers gave dimers 109 as the main product. Minor amounts of compounds not containing the 1,2-dithiole nucleus 110, 111, and 112 were isolated.15 6... 

Reviews on dithioles, thienothiophens, fluoro-azoles, luminescence and photochemistry of azoles may be noted. 

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