Spin crossover dynamics studies on the thermally activated molecular oxygen binding mechanism on a model copper complex

Abstract

The theoretical description of the primary dioxygen (O₂) binding and activation step in many copper or iron enzymes, suffers from the intrinsically electronic non-adiabaticity of the spin flip events of the triplet dioxygen molecule (³O₂), mediated by spin–orbit couplings. In this work, we presented the early-stage ultrafast spin flip dynamics of O₂ binding for a simplified monocopper complex, involving the coupled singlet and triplet electronic states. The on-the-fly trajectory surface hopping (TSH) simulations have identified the dynamical effects that may influence the mode of O₂ coordination (end-on vs. side-on), and the electronic structures can be viewed as complexes of molecular O₂ with Cu(I) or as Cu(II)-superoxide compounds. In addition, significant spin flip events are obversed within the sub-picosecond regime. We hope this work may provide complimentary insights on the traditional interpretation of O₂ binding on copper complexes and subsequent catalytic reaction mechanisms.