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Updated: Jul 19, 2025

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Published on: July 19, 2019
Concerted versus stepwise proton transfer reactions in the [2, 2'-bipyridyl]-3-3'-diol molecule: A static and dynamic
Lorenzo Briccolani-Bandini1, Eric Brémond2, Marco Pagliai1
1Dipartimento di Chimica "Ugo Schiff", Università degli Studi di Firenze, Sesto Fiorentino, Italy.
Abstract:
The double proton transfer (PT) reaction has been investigated in the [2,2'-bipyridyl]-3-3'-diol, a complex molecule where the proton movements is coupled to significant rearrangement of the electronic structure. Moreover, the reaction could be concerted, that is the two protons are exchanged simultaneously, or stepwise, where the two protons are transferred sequentially. To this end, a static exploration of the potential energy surface (PES) was carried together with the analysis of the free-energy surface (FES), both surfaces being evaluated at density functional theory level and different exchange-correlation functionals. While the concerted mechanism has been clearly discharged, the characteristics of the stepwise PT significantly depends on the chosen functionals, some suggesting a clear stepwise mechanism characterized by a stable reaction intermediates and two transitions states, whereas other approaches propend for a asynchronous PT, with a single TS. These features appear on both PES and FES, albeit some differences appears due to their different nature.
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