Ma Zheng, Lin Zhiwei, Lawrence Candace M, Rubtsov Igor V, Antoniou Panayiotis, Skourtis Spiros S, Zhang Peng, Beratan David N
Department of Chemistry , Duke University , Durham , North Carolina 27708 , USA.
Department of Chemistry , Tulane University , New Orleans , Louisiana 70118 , USA.
Chem Sci. 2018 Jun 27;9(30):6395-6405. doi: 10.1039/c8sc00092a. eCollection 2018 Aug 14.
A UV-IR-Vis 3-pulse study of infra-red induced changes to electron transfer (ET) rates in a donor-bridge-acceptor species finds that charge-separation rates are slowed, while charge-recombination rates are accelerated as a result of IR excitation during the reaction. We explore the underpinning mechanisms for this behavior, studying IR-induced changes to the donor-acceptor coupling, to the validity of the Condon approximation, and to the reaction coordinate distribution. We find that the dominant IR-induced rate effects in the species studied arise from changes to the density of states in the Marcus curve crossing region. That is, IR perturbation changes the probability of accessing the activated complex for the ET reactions. IR excitation diminishes the population of the activated complex for forward (activationless) ET, thus slowing the rate. However, IR excitation increases the population of the activated complex for (highly activated) charge recombination ET, thus accelerating the charge recombination rate.
一项对供体-桥-受体体系中红外诱导电子转移（ET）速率变化的紫外-红外-可见三脉冲研究发现，在反应过程中，由于红外激发，电荷分离速率减慢，而电荷复合速率加快。我们探究了这种行为的潜在机制，研究了红外诱导的供体-受体耦合变化、康登近似的有效性以及反应坐标分布。我们发现，在所研究的体系中，红外诱导的主要速率效应源于马库斯曲线交叉区域态密度的变化。也就是说，红外微扰改变了电子转移反应进入活化络合物的概率。红外激发减少了正向（无活化）电子转移活化络合物的数量，从而减慢了速率。然而，红外激发增加了（高度活化）电荷复合电子转移活化络合物的数量，从而加快了电荷复合速率。
