School of Molecular Sciences and Department of Physics, Arizona State University, P.O. Box 871504, Tempe, Arizona 85287-1504, United States.
Chemistry Department, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973-5000, United States.
J Phys Chem B. 2021 Nov 11;125(44):12264-12273. doi: 10.1021/acs.jpcb.1c06949. Epub 2021 Oct 29.
The pathway of activationless proton transfer induced by an electron-transfer reaction is studied theoretically. Long-range electron transfer produces highly nonequilibrium medium polarization that can drive proton transfer through an activationless transition during the process of thermalization, dynamically altering the screening of the electron-proton Coulomb interaction by the medium. The cross electron-proton reorganization energy is the main energy parameter of the theory, which exceeds in magnitude the proton-transfer reorganization energy roughly by the ratio of the electron-transfer to proton-transfer distance. This parameter, which can be either positive or negative, is related to the difference in p values in two electron-transfer states. The relaxation time of the medium is on the (sub)picosecond time scale, which establishes the characteristic time for activationless proton transfer. Microscopic calculations predict substantial retardation of the collective relaxation dynamics compared to the continuum estimates due to the phenomenology analogous to de Gennes narrowing. Nonequilibrium medium configuration promoting proton transfer can be induced by either thermal or photoinduced charge transfer.
理论研究了电子转移反应引发的无活化质子转移途径。长程电子转移会产生高度非平衡的介质极化，这种极化可以在热化过程中通过无活化跃迁驱动质子转移，从而动态改变介质对电子-质子库仑相互作用的屏蔽。交叉电子-质子重组能是该理论的主要能量参数，其大小大致超过质子转移重组能，比值约为电子转移距离与质子转移距离之比。该参数可以为正或负，与两个电子转移态中 p 值的差异有关。介质的弛豫时间在（亚）皮秒时间尺度上，这为无活化质子转移建立了特征时间。微观计算预测，由于类似于德热纳变窄的现象，与连续体估计相比，集体弛豫动力学会大大延迟。通过热或光诱导的电荷转移，可以诱导促进质子转移的非平衡介质构型。
