This result is rather stunning in the view of some of the so-far established mechanisms, and compelled us to explore further mechanistic intricacies of the photorelaxation, in particular, the involvement of 3 MC states. In Figure , we present more detailed excited-state population dynamics, unweaving the two 3 MC components: the lower-energy 3 T 1g and the higher-energy 3 T 2g , focusing on the timescale on which the ISC dynamics occur (0-500 fs). We can now clearly identify that the quintet state is populated via a branching mechanism involving the two 3 MC components: a faster 3 MLCT → A key component of our simulated dynamics is the non-exponential nature of the quintet population rise shown in Figures and. This is due to dynamics via the 3 MC states, which is in line with the interpretation of ballistic dynamics observed experimentally in ref. 9; note that without the 3 MC, no such ballistic dynamics are observed, see Figure . The driving force for this non-exponential behaviour is the nuclear dynamics in the 3 MC states, dominated by the impulsive expansion of the Fe-N bonds (see Figure ). These structural dynamics drive the molecule toward the intersection of the 3 MC-5 MC PESs, at which efficient ISC occurs owing to direct 3 MC-5 MC SOC. This also explains why the direct pathway is not operative in the presence of 3 MC states: the nuclear dynamics on the steep 3 MC surface promptly move the molecule away from the region where the 3 MLCT → 5 MC transition could be possible via large energetic overlap.