Ultrafast Deactivation Processes in Aminopyridine Clusters: Excitation energy dependence and isotope effects.
Samoylova, E.; Smith, V. R.; Ritze, H. H. etc.,
Journal of the American Chemical Society, 128 15652 - 15656 (2006)
Fast excited-state relaxation in H-bonded aminopyridine clusters occurs via hydrogen transfer in the excited state. We used femtosecond pump-probe spectroscopy to characterize the excited-state reaction coordinate. Considerable isotope effects for partially deuterated clusters indicate that H-transfer is the rate-limiting step and validate ab initio calculations in the literature. A nonmonotonous dependence on the excitation energy, however, disagrees with the picture of a simple barrier along the reaction coordinate. An aminopyridine dimer serves as a model for Watson-Crick base pairs, where similar reactions have been predicted by theory.