Primary Reactions in the Photochemistry of Hexahalide Complexes of Platinum Group Metals: A Minireview

Publication date: Available online 15 May 2015 Source:Journal of Photochemistry and Photobiology C: Photochemistry Reviews Author(s): Evgeni M. Glebov , Ivan P. Pozdnyakov , Victor F. Plyusnin , Igor Khmelinskii We review the results obtained for PtIVCl6 2−, PtIVBr6 2−, IrIVCl6 2−, IrIVBr6 2−, and OsIVBr6 2− complexes in aqueous and alcoholic solutions using ultrafast pump-probe spectroscopy, laser flash photolysis, ESR, and photoelectron spectroscopy. We discuss the correlations between the photophysics and the photochemistry of these complexes. The key reaction for PtIVCl6 2− is the inner-sphere electron transfer, which results in an Adamson radical pair that lives for several picoseconds, and the subsequent photoaquation in aqueous solutions and photoreduction in alcohols. The chlorine atom formed as the primary product escapes the solvent cage in aqueous solutions or oxidizes a solvent alcohol molecule via secondary electron transfer, producing secondary intermediates that react on the microsecond time scale. The photoexcitation of PtIVBr6 2− results in the formation of pentacoordinated PtIV intermediates, i.e., 3PtIVBr5 − and 1PtIVBr5 −, with characteristic lifetimes of approximately 1 and 10 ps, respectively. Subsequent reactions of these intermediates result in the complexation of a solvent molecule. Photoreduction is also possible in alcohols. Similar reactions occur with rather low quantum yields for IrIVCl6 2−, therefore, only the ground-...

Source: Journal of Photochemistry and Photobiology C: Photochemistry Reviews - May 16, 2015 Category: Chemistry Source Type: research