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American Chemical Society, The Journal of Physical Chemistry A, 2(117), p. 361-369, 2013

DOI: 10.1021/jp3106502

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X-ray Absorption Spectroscopy of Ground and Excited Rhenium-Carbonyl Diimine-Complexes: Evidence for a Two-Center Electron Transfer

This paper is available in a repository.
This paper is available in a repository.

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Abstract

Steady-state and picosecond time-resolved X-ray absorption spectroscopy is used to study the ground and lowest triplet states of [ReX(CO)3(bpy)]n+, X = Etpy (n=1), Cl or Br (n=0). We demonstrate that the transient spectra at both the Re L3- and Br K-edges show the emergence of a pre-edge feature, absent in the ground state spectrum, which is associated with the electron hole created in the highest occupied molecular orbital following photoexcitation. Importantly, these features have the same dynamics and this conrms previous predictions that the low lying excited states of these complexes involve a two-centre charge transfer from both the Re and the ligand, X. We also demonstrate that the DFT optimised ground and excited structures allow us to reproduce the experimental XANES and EXAFS spectra. The ground state structural renement shows that the Br atom contributes very little to the latter, while the Re-C-O scattering paths are dominant due to the so-called focusing eect. For the excited state spectrum, the Re-X bond undergoes one of the largest changes, but still remains a weak contribution to the photoinduced changes of the EXAFS spectrum.