Environment effects on triplet–triplet energy transfer in DNA

We present a quantum-chemical study of the impact of the environment on triplet exciton migration in polyA–polyT DNA sequences. Electronic couplings are estimated by combining the fragment excitation difference scheme with the polarizable continuum model. Conformational fluctuations are taken into account by considering 500 structures extracted from a classical molecular dynamics trajectory. In contrast to singlet transfer, we find that the environment effect is not strongly correlated with the coupling magnitude in vacuum, and can significantly enhance or reduce its value in individual conformations. Conformational averaging, however, leads to a net cancellation of medium effects on the overall transfer rate.