Ultrafast deactivation processes in aminopyridine clusters: excitation energy dependence and isotope effects.
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Journal of the American Chemical Society, ISSN: 0002-7863, Vol: 128, Issue: 49, Page: 15652-6
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- Chemistry; PROTON-TRANSFER PROCESSES; BASE-PAIRS; AB-INITIO; MOLECULAR-DYNAMICS; ADENINE-THYMINE; STATE; SPECTROSCOPY; 2-AMINOPYRIDINE; SELECTIVITY
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.