Dynamical Electron Mechanism of Double Proton Transfer in Formic Acid Dimer

作者：Okuyama Michihiro; Takatsuka Kazuo^*

来源：Bulletin of the Chemical Society of Japan, 2012, 85(2): 217-227.

DOI：10.1246/bcsj.20110237

We study the dynamical electron mechanism of "double proton transfer" in formic acid dimer, which is a prototype of many double proton transfers in chemical and biological systems. Since the present double proton transfer takes place in a cyclic molecular system (a ring structure of dimerizing formic acids), and since the molecular structures before and after the double proton transfer are isomorphic to each other, the pathway of electron flow associated with the reaction cannot be determined in principle within the adiabatic electronic structures based on the Born-Oppenheimer approximation. It is also hard to determine whether "protons" are shifted in formic acid dimer or "hydrogen atoms" are migrated. The general distinction between them is often controversial in experimental studies, too. We identify the mechanism of such dynamics by highlighting the electron current and its pathway. To extract such information of dynamical electrons, we apply the semiclassical Ehrenfest theory, which takes an explicit account of all nuclei nonadiabatic electron wave packet dynamics. It turns out that the reaction proceeds in a concerted manner so that the chance of radical separation is very low and as though the net electronic flow is kept as low as possible to minimize the charge separation within a molecular complex.

• 出版日期2012-2-15