期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：2
页码：419-422
DOI：10.1073/pnas.0306721101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A theoretical analysis of the double proton transfer (PT) in a hydrogen-bonded N-heterocyclic base pair is presented. The calculated (time-dependent density functional theory) double PT barrier calculated for the concerted process of the 7-azaindole C2h dimer in the first excited singlet electronic state S1 conforms well to the kinetic data and the photophysical evidence reported in this article. The calculated PT energy barrier of 4.8 kcal/mol height, and the corresponding zero point energy value, yield for the S1 state an activation energy barrier of 0.3 kcal/mol. This finding implies that the double PT concerted process is almost barrierless, confirming previous experiments. Upon N-H deuteration of the 7-azaindole dimer, the theoretical excited-state activation energy for the double deuterium transfer is determined to be 1.4 kcal/mol, in agreement with experiment, which in low-temperature spectroscopy is shown to negate excited-state double-deuteron transfer.
