A Quantum Chemical Study of Intramolecular Charge Transfer in a Closely-Spaced, Donor−Acceptor Molecule

Abstract

This investigation explores the use of contemporary quantum chemistry to mimic the light-induced, intramolecular charge-transfer processes that occur in 2-methyl-2,3-dihydrobenz[d,e]isoquinoline (DHBIQ) in polar solvents. Thus, the computed excited-state manifold, comprising two locally excited π,π* singlets, a locally excited π,π* triplet, and a charge-transfer (CT) state, is in excellent agreement with the experimental findings. It is shown that, whereas the energies of the various locally excited states are insensitive to molecular geometry and environment, the energy of the CT state depends markedly on structure and solvent polarity. The most favorable charge-transfer interactions occur within a distorted geometry that is midway between the axial and equatorial conformers identified for the ground state. The calculated nuclear and solvent reorganization energies are in good agreement with prior experimental work. Molecular dynamics simulations were employed to estimate the change in Gibbs free energy ...