| Abstract
| - Photoinduced hole injection by an acridine derivative X+ within the complex 5‘-TG-2TX+TG2T-3‘ has beenstudied using quantum chemical calculations. The probability of charge shift from the excited state of theintercalated chromophore, (X+)*, to the guanine acceptors, G-2 and G2, is computed for 24 differentconformations of the complex generated by rotation of the chromophore about the DNA axis. Because thefree energies and the reorganization energies for the charge shift in both direction are very similar, theprobability of G-2 or G2 oxidation is determined by the ratio of squared electronic couplings between (X+)*and the diabatic states with a hole on the guanine bases. To estimate the electronic couplings we employ themultistate generalized Mulliken−Hush method and electronic adiabatic states of the system calculated withinthe multiconfigurational INDO/S approach. We show that the rate of the charge shift reaction critically dependson the chromophore position and that there are well-separated regions in the conformational space, where thehole charge is mainly injected either into G-2 or into G2 or is unlikely. Thus, the direction of the hole injectioncan be switched by rotation of the intercalated chromophore and the photocleavage efficiency of the acridinederivative and related species can be modulated by the conformational changes.
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