Skinner Kevin C, Kammeraad Josh A, Wymore Troy, Narayan Alison R H, Zimmerman Paul M
Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109, United States.
Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
J Phys Chem B. 2023 Nov 30;127(47):10097-10107. doi: 10.1021/acs.jpcb.3c06120. Epub 2023 Nov 17.
Single-electron transfer (SET) promotes a wide variety of interesting chemical transformations, but modeling of SET requires a careful treatment of electronic and solvent effects to give meaningful insight. Therefore, a combined constrained density functional theory and molecular mechanics (CDFT/MM) tool is introduced specifically for SET-initiated reactions. Mechanisms for two radical-polar crossover reactions involving the organic electron donors tetrakis(dimethylamino)ethylene (TDAE) and tetrathiafulvalene (TTF) were studied with the new tool. An unexpected tertiary radical intermediate within the TDAE system was identified, relationships between kinetics and substitution in the TTF system were explained, and the impact of the solvent environments on the TDAE and TTF reactions were examined. The results highlight the need for including solvent dynamics when quantifying SET kinetics and thermodynamics, as a free energy difference of >20 kcal/mol was observed. Overall, the new method informs mechanistic analysis of SET-initiated reactions and therefore is envisioned to be useful for studying reactions in the condensed phase.
单电子转移（SET）能促进各种各样有趣的化学转化，但对SET进行建模需要仔细处理电子效应和溶剂效应，才能得出有意义的见解。因此，专门引入了一种结合约束密度泛函理论和分子力学（CDFT/MM）的工具来研究由SET引发的反应。利用这种新工具研究了涉及有机电子供体四（二甲氨基）乙烯（TDAE）和四硫富瓦烯（TTF）的两个自由基-极性交叉反应的机理。在TDAE体系中鉴定出了一个意想不到的叔自由基中间体，解释了TTF体系中动力学与取代之间的关系，并研究了溶剂环境对TDAE和TTF反应的影响。结果突出了在量化SET动力学和热力学时纳入溶剂动力学的必要性，因为观察到自由能差>20 kcal/mol。总体而言，这种新方法为SET引发反应的机理分析提供了信息，因此有望用于研究凝聚相中的反应。
