The time evolution of NiN and CNNC is displayed in Figure . The bond elongation and the planarization start both around the same time ∼ 200 fs. This delayed onset coincides with the one observed in the 3 MC population (Figure ). The synchronous evolution reflects the steric constraints induced by mismatch between the ionic radius of the Ni(II) center and the porphyrin cavity, which is responsible for the initial ruffling. However, a temporal dichotomy sets in: the monotonous bond elongation spans over more than a 1 ps while the ruffling increases slightly until 300 fs before decreasing to yield a planarization of the ring that completes by ∼ 600 fs. The asynchronicity between the time evolution of the structural parameters is a definite signature of multi-modal dynamics. Close examination of the average nuclear displacements along the vibrational normal modes extracted from the trajectories reveals several predominant modes, namely v 1 (32.6 cm -1 ), v 2 (52.0 cm -1 ), v 14 (221.7 cm -1 ), v 29 (386.8 cm -1 ) and v 38 (514.5 cm -1 ) (S.I.2). Although these modes clearly dominate, it should be stressed that smaller contributions from other normal modes within the existing 141 ones could nevertheless add up to become significant.