Article pubs.acs.org/JPCA
Potential Energy Mapping of the Excited-States of (η6-Arene)Cr(CO)3 Complexes: the Evolution Toward CO-Loss or Haptotropic Shift Processes Conor Long* School of Chemical Sciences, Dublin City University, Dublin 9, Ireland S Supporting Information *
ABSTRACT: The potential energy profiles of the optically accessible excited states of two model (η6-arene)Cr(CO)3 systems were explored using Time-Dependent Density Functional Theory. Two photochemical reactions were investigated, CO-loss and the haptotropic or ring-slip of the arene ligand. In both cases the photochemical reaction requires the surmounting of a small thermal barrier in the lowest energy excited state. In the case of (η6-benzene)Cr(CO)3 only one excited state is populated following 400 nm excitation and this leads to the release of CO. The calculated energy barrier to this process is 13 kJ mol−1. In the case of (η6-thiophenol)Cr(CO)3 two excited states are accessible one leading to CO-loss while the other results in the ring-slip process. The calculated barrier to the ring-slip process is 11 kJ mol−1. The calculations are consistent with the results of picosecond time-resolved infrared studies.
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INTRODUCTION Ligand loss is a fundamental process in many photochemical reactions of organometallic complexes.1 In particular, photoinduced CO-loss has achieved the status of a prototypal reaction, and this reaction has been the subject of many studies both experimental2−18 and computational.19−30 These investigations have mainly focused on symmetric homoleptic complexes such as Cr(CO)6. For this system the photoinduced CO-loss occurs on an ultrafast (
