Geoffroy-Neveux Antoine, Labet Vanessa, Alikhani M Esmail
MONARIS UMR 8233 CNRS, Sorbonne Université, 4 place Jussieu, 75252 Paris Cedex 05, France.
J Phys Chem A. 2022 May 26;126(20):3057-3071. doi: 10.1021/acs.jpca.1c10553. Epub 2022 May 11.
The double proton transfer (DPT) reaction between pyrazole and guanidine, a concerted reaction but strongly asynchronous and presenting a "plateau transition region", has been theoretically reinvestigated in the presence of an external uniform electric field. First, we computed the reaction path by DFT and proposed a very detailed description of the constitutive electronic events, based on the ELF topology and the bond evolution theory. Then, we studied the effect of an oriented external electric field (OEEF) on the reaction mechanism, for an OEEF oriented along the proton transfer axis. We observe that in one direction, the DPT reaction can be transformed into a stepwise reaction, going through a stabilized single proton transferred intermediate. Contrarily, the two proton transfers occur simultaneously when the electric field is applied in the opposite direction. In the latter case, the order in which the two protons are transferred in the same elementary step can even be reversed if the OEEF is intense enough. Finally, it has been shown that the evolution of the double proton transfer reaction in the presence of an electric field could be quantitatively anticipated by analyzing the ELF value at the bifurcation point between V(A, H) proton donor and V(B) proton acceptor of the double hydrogen bonded complex in the entrance channel.
吡唑与胍之间的双质子转移（DPT）反应是一个协同反应，但具有很强的非同步性且存在一个“平台过渡区域”，本文在外部均匀电场存在的情况下对其进行了理论再研究。首先，我们通过密度泛函理论（DFT）计算了反应路径，并基于电子定域函数（ELF）拓扑结构和键演化理论，对构成电子事件进行了非常详细的描述。然后，我们研究了沿质子转移轴方向的定向外部电场（OEEF）对反应机理的影响。我们观察到，在一个方向上，DPT反应可以转变为分步反应，经过一个稳定的单质子转移中间体。相反，当电场沿相反方向施加时，两个质子转移同时发生。在后一种情况下，如果OEEF强度足够大，两个质子在同一基元步骤中转移的顺序甚至可以颠倒。最后，研究表明，通过分析入口通道中双氢键复合物的V(A, H)质子供体和V(B)质子受体之间分叉点处的ELF值，可以定量预测电场存在下双质子转移反应的演化。
