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Issue 10, 2015
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Stepwise double excited-state proton transfer is not possible in 7-azaindole dimer

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Abstract

The nature of the excited-state double proton transfer in 7-azaindole (7AI) dimer—whether it is stepwise or concerted—has been under a fierce debate for two decades. Based on high-level computational simulations of static and dynamic properties, we show that much of the earlier discussions was induced by inappropriate theoretical modelling, which led to biased conclusions towards one or other mechanism. A proper topographical description of the excited-state potential energy surface of 7AI dimer in the gas phase clearly reveals that the stepwise mechanism is not accessible due to kinetic and thermodynamic reasons. Single proton transfer can occur, but when it does, an energy barrier blocks the transfer of the second proton and the dimer relaxes through internal conversion. Double proton transfer takes place exclusively by an asynchronous concerted mechanism. This case-study illustrates how computational simulations may lead to unphysical interpretation of experimental results.

Graphical abstract: Stepwise double excited-state proton transfer is not possible in 7-azaindole dimer

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Publication details

The article was received on 27 May 2015, accepted on 06 Jul 2015 and first published on 08 Jul 2015


Article type: Edge Article
DOI: 10.1039/C5SC01902H
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Citation: Chem. Sci., 2015,6, 5762-5767
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    Stepwise double excited-state proton transfer is not possible in 7-azaindole dimer

    R. Crespo-Otero, N. Kungwan and M. Barbatti, Chem. Sci., 2015, 6, 5762
    DOI: 10.1039/C5SC01902H

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