Demystifying the Origin of Vibrational Coherence Transfer Between the S1 and T1 States of the Pt-pop Complex

We demonstrate that spin-vibronic coupling is the most significant mechanism in vibrational coherence transfer (VCT) from the singlet (S1) to the triplet (T1) state of the [Pt2(P2O5H2)4]4– complex. Our time-dependent correlation function-based study shows that the rate of intersystem crossing (k ISC) through direct spin–orbit coupling is negligibly small, making VCT vanishingly small due to the ultrashort decoherence time (2.5 ps). However, the inclusion of the spin-vibronic contribution to the net k ISC in selective normal modes along the Pt–Pt axis increases the k ISC to such an extent that VCT becomes feasible. Our results suggest that k ISC for the S1 →T2 (τISC = 1.084 ps) is much faster than the S1 → T1 (τISC = 763.4 ps) and S1 → T3 (τISC = 13.38 ps) in CH3CN solvent, indicating that VCT is possible from the low-lying excited singlet (S1) to the triplet (T1) state through the intermediate T2 state. This is the first example where VCT occurs solely due to spin-vibronic interactions. This finding can pave the way for new types of photocatalysis.