Theoretical Investigation of Transient Species following Photodissociation of Ironpentacarbonyl in Ethanol Solution

Photodissociation of ironpentacarbonyl in solution generates transient species in different electronic states, which we have studied theoretically. From ab initio molecular dynamics simulations in ethanol solution, the closed-shell parent compound Fe(CO)5 is found to interact weakly with the solvent, whereas the irontetracarbonyl (Fe(CO)4) species, formed after photodissociation, has a strongly spin-dependent behavior. It coordinates a solvent molecule tightly in the singlet state and weakly in the triplet state. From the simulations, we have gained insight into intersystem crossing in solvated irontetracarbonyl, based on the distinct structural differences induced by the change in multiplitity. Alternative forms of coordination between Fe(CO)4 and functional groups of the ethanol molecule are simulated and a quantum chemical investigation of the energy landscape for the coordinated irontetracarbonyl give information about the interconversion of different transient species in solution. Furthermore, insights from the simulations, in which we find evidence of a solvent exchange mechanism, challenge the previously proposed mechanism of chain walking for undercoordinated metal carbonyls in solution.