Interstate Vibronic Coupling Constants Between Electronic Excited States for Complex Molecules

TL;DR

This paper introduces a new method to accurately determine interstate vibronic coupling constants in complex molecules using time-dependent density functional theory and wavefunction overlaps, improving modeling of excited-state interactions.

Contribution

A novel protocol for extracting interstate vibronic coupling constants from excited-state wavefunction overlaps at the TDDFT level, enhancing the analysis of complex molecular systems.

Findings

Successfully applied to rhenium carbonyl complexes

Enables analysis of closely lying electronic states

Facilitates non-adiabatic quantum dynamics modeling

Abstract

In the construction of diabatic vibronic Hamiltonians for quantum dynamics in the excited-state manifold of molecules, the coupling constants are often extracted solely from information on the excited-state energies. Here, a new protocol is applied to get access to the interstate vibronic coupling constants at the time-dependent density functional theory level through the overlap integrals between excited-state adiabatic auxiliary wavefunctions. We discuss the advantages of such method and its potential for future applications to address complex systems, in particular those where multiple electronic states are energetically closely lying and interact. As examples, we apply the protocol to the study of prototype rhenium carbonyl complexes [Re(CO)$_3$(N,N)(L)]$^{n+}$ for which non-adiabatic quantum dynamics within the linear vibronic coupling model and including spin-orbit coupling have been reported recently.