| Abstract
| - The hybrid configuration interaction singles/time dependent density functional theory approach of Dreuwand Head-Gordon [Dreuw, A.; Head-Gordon, M. J. Am. Chem. Soc.2004, 126, 4007] has been applied tostudy the potential energy landscape and accessibility of the charge-transfer ππ* excited state in the dimerof 7-azaindole, which has been traditionally considered a model for DNA base pairing. It is found that thecharge-transfer ππ* excited state preferentially stabilizes the product of a single proton transfer. In this situation,the crossing between this state and the photoactive electronic state of the dimer is accessible. It is found thatthe charge-transfer ππ* excited state has a very steep potential energy profile with respect to any singleproton-transfer coordinate and, in contrast, an extremely flat potential energy profile with respect to the stretchof the single proton-transfer complex. This is predicted to bring about a pair of rare fragments of the 7-azaindoledimer, physically separated and hence having very long lifetimes. This could have implications in the DNAbase pairs of which the system is an analogue, in the form of replication errors.
|
