Isotopic effect and temperature dependent intramolecular excitation energy transfer in a model donor–acceptor dyad

Abstract

We consider here the non-adiabatic energy transfer dynamics for a model bi-chromophore system consisting of a perylenemonoimide unit linked to a ladder-type poly(para-phenylene) oligomer. Starting from a semi-empirical parameterization of a model electron/phonon Hamiltonian, we compute the golden-rule rate for energy transfer from the LPPP5 donor to the PMI acceptor. Our results indicate that the non-adiabatic transfer is promoted by the out-of-plane wagging modes of the C–H bonds even though theses modes give little or no contribution to the Franck–Condon factors in this system. We also predict a kinetic isotope effect of k^(H)/k^(D) = 1.7–2.5 depending upon the temperature.