Redox processes in photochemistry of Pt(iv) hexahaloid complexes

Abstract

Ultrafast pump–probe spectroscopy (λ_pump = 405 nm) was applied to study the primary photochemical processes for PtCl₆²⁻ and PtBr₆²⁻ complexes in aqueous and alcohol solutions. For PtCl₆²⁻, an intermediate with a lifetime of ca. 200 ps was registered and identified as an Adamson radical pair [Pt^IIICl₅²⁻⋯Cl˙]. The transformations of the primary intermediate give rise to successive formation of different Pt(III) species. The reactions of Pt(III) results in chain photoaquation in aqueous solutions and reduction of Pt(IV) to Pt(II) in alcohol solutions. For PtBr₆²⁻ complex, the previously reported (I. L. Zheldakov, M. N. Ryazantsev and A. N. Tarnovsky, J. Phys. Chem. Lett., 2011, 2, 1540; I. L. Zheldakov, PhD thesis, Bowling Green State University, 2010) formation of active ³PtBr₅⁻ intermediate is followed by very fast (15 ps) aquation of Pt(IV) in aqueous solutions and parallel reactions of solvation and reduction of Pt(IV) to Pt(II) in alcohol solutions. All the processes in alcohols are finished within 0.5 ns. The data of ultrafast experiments are supported by nanosecond laser flash photolysis and stationary photolysis.