The simulations revealed that upon photoexcitation, the Fe-CO bond undergoes coherent oscillations with a period of 42 fs and an amplitude of approximately 1 Å (Figure ). These nuclear motions drive irreversible CO dissociation and initiate sequential spin transitions, with the system relaxing into a triplet metal-to-ligand charge transfer (MLCT) state within ~75 fs and reaching the quintet state in ~430 fs. These computational findings demonstrated the crucial role of vibronic couplings in the ultrafast photodynamics of organometallic complexes. Reprinted (adapted) with permission from Ref. Copyright 2023 American Chemical Society.