Vibronic Effects on Rates of Excitation Energy Transfer and Their Temperature Dependence

Vibronic effects on rate constants governing excitation energy transfer between different electronic states have been studied within the adiabatic regime and the harmonic oscillator approximation, possibly including bulk solvent effects with the polarizable continuum model. A recent implementation in the Gaussian package has been extended for this purpose, with the possibility of taking into account frequency shifts and mode mixing effects between ground and excited electronic states. The potentialities of the new computational tool have been analyzed for a number of case studies, including excimers of naphthalene and zinc porphyrin complexes. In all cases, the change of rate constants with temperature arising from the inclusion of vibronic effects is in good qualitative agreement with the available experimental data.