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

Abstract

We demonstrate that spin-vibronic coupling is the most significant mechanism in vibrational coherence transfer (VCT) from the singlet (S 1 ) to the triplet (T 1 ) state of the [Pt 2 (P 2 O 5 H 2 ) 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 S 1 →T 2 (τ ISC = 1.084 ps) is much faster than the S 1 → T 1 (τ ISC = 763.4 ps) and S 1 → T 3 (τ ISC = 13.38 ps) in CH 3 CN solvent, indicating that VCT is possible from the low-lying excited singlet (S 1 ) to the triplet (T 1 ) state through the intermediate T 2 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.

Ultrafast proton transfer of the aqueous phenol radical cation

“…The transfer of vibrational coherence between different electronic states was recently observed in transition metal complexes after ultrafast intersystem crossing. 91,92 As discussed below, our experimental results favor the mechanism involving vibrational coherence transfer.…”

Spin-vibronic interaction induced reverse intersystem crossing: A case study with TXO-TPA and TXO-PhCz molecules

“…They have observed that this coupling vector largely depends on the nature of the two triplet or singlet states and the energy gap between them. On the other hand, Marian et al 65 and Karak et al 68 have considered the spin-vibronic interaction through the explicit calculation of the derivative of the direct SOC with respect to the normal mode coordinates and successfully applied the method for calculating the rate constant of intersystem crossing. Nevertheless, in the present work, we have adopted the method developed by Kim et al 26 .…”

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