Triplet-quintet spin-crossover efficiency in fl-hydrogen transfer between Fe (C2H5)+ and HFe(C2H4)+

Many reactions including an iron atom show two-state reactivity, involving a change in the spin state induced by relativistic spin-orbit coupling. In this work, we theoretically study the efficiency of a typical spin-crossover reaction, Fe(C2H5)+ -> HFe(C2H4)+ fl-hydrogen transfer. We have constructed three-dimensional potential en-ergy surfaces and calculated triplet-quintet spin-orbit couplings. Using the spin-diabatic representation, we performed nonadiabatic transition state wave packet simulations to calculate the cumulative reaction proba-bility. The obtained cumulative reaction probability is much larger than that estimated from the one-dimensional single-passage Landau-Zener model. This indicates that the nonadiabatic dynamics is determined by a large number of passage dynamics, where the nuclear vibrational trajectory or quantum resonance state with a long lifetime can repeatedly traverse the crossing points.