Short-Time Events, Coherence, and Structural Dynamics in Photochemistry of Aqueous Halogenated Transition Metal Dianions

A.N Tarnovsky,A.S Mereshchenko,S.L Johnson,I.L Zheldakov,T Pascher,S.K Pal,P Z El-Khoury,C.J Milne,J Uhlig,E.V Butaeva,M.N Ryazantsev

doi:10.1051/epjconf/20134105038

Abstract

Ultrafast pump-probe spectroscopy, time-resolved x-ray absorption, and computational photochemistry elucidate the photochemical pathway of hexabromoplatinate dianions that propagates through distortions of nascent penta- bromoplatinate anions caused by Jahn-Teller conical intersections and terminates at aquated product complexes.

Highlights

Aqueous PtBr62- was excited into the mixed 1T2g ligand-field/charge-transfer state (LF/CT) and the dissociative lowest excited triplet 3T1g LF state at 420 nm and 530 nm, respectively
The photochemical reaction path involves separation of negative charges (PtBr62- → PtBr5- + Br-), distortions of a nascent penta-bromoplatinate anion caused by a Jahn-Teller (JT) C4v conical intersection (CI), and hydration to form PtBr5(H2O)
The assignment of the UVvis spectrum of aqueous PtBr62- has been carried out using CASPT2 calculations of vertical electronic transitions (VETs), [2]

Summary

Introduction

Aqueous PtBr62- was excited into the mixed 1T2g ligand-field/charge-transfer state (LF/CT) and the dissociative lowest excited triplet 3T1g LF state at 420 nm and 530 nm, respectively. To characterize the reaction pathways, intermediates and products, we used ultrafast pump-probe and time-resolved x-ray absorption spectroscopies, in concert with CASPT2 and DFT/TDDFT calculations. The 1T1g LF/CT state and the dissociative 3T1g LF state of PtBr62- both give rise to the same 500-nm absorption band, Fig. 1.

Results

Conclusion