Photoinduced bond oscillations in ironpentacarbonyl(FeCO)5 give delayed, synchronous bursts of carbonmonoxide(CO) release

This is the authors' abstract. We don't add key points for this paper.

The early excited state dynamics in the photodissociation of transition metal carbonyls determines the chemical nature of short-lived catalytically active reaction intermediates. However, time-resolved experiments have not yet revealed the mechanistic details in the sub-picosecond regime. Hence in this study, the photoexcitation of ironpentacarbonyl Fe(CO)5 has been simulated by semi-classical surface-hopping excited state molecular dynamics based on time-dependent density functional theory. We �find that the bright metal-to-ligand charge-transfer (MLCT) transition induces Fe-C oscillations in the trigonal bipyramidal complex leading to periodically reoccurring release of predominantly axial CO. Metaphorically the photoactivated Fe(CO)5 acts as a CO geyser, which we explain in terms of dynamics in the potential energy landscape of the axial Fe-C distances and non-adiabatic transitions between manifolds of bound MLCT and dissociative metal-centered(MC) excited states. The predominant release of axial CO ligands and a delayed release of equatorial CO ligands are explained in an unified mechanism based on the (sigma*)(Fe-C) anti-bonding character of the receiving orbital in the dissociative MC states both in the Franck-Condon region and at distorted geometries.