Tignor Steven E, Shaw Travis W, Bocarsly Andrew B
Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
Dalton Trans. 2019 Sep 7;48(33):12730-12737. doi: 10.1039/c9dt02060h. Epub 2019 Aug 7.
Complexes of the general form [Mn(X)(CO)bpy] (X = a variety of monodentate ligands, bpy = 2,2'-bipyridine) have been reported to act as electrocatalysts for the reduction of CO to CO. In this work, a series of phenol and anisole substituted bipyridine ligands were synthesized and ligated to a manganese metal center in order to probe for an intramolecular hydrogen-bonding interaction in the transition state of CO reduction. Ligands without the ability to intramolecularly hydrogen bond displayed decreased catalytic current density compared to those with the ability to hydrogen bond with CO. Electrocatalysis was studied by performing voltammetric and bulk electrolysis experiments under argon or CO environments. Measurements of catalytic rates using hydrogen vs. deuterium for the intramolecular H/D-bonding step show that there is an isotope effect associated with the catalysis. The data presented herein suggest a mechanism involving two subsequent equilibrium isotope effects in combination with a primary kinetic isotope effect.
据报道，通式为[Mn(X)(CO)bpy]（X = 多种单齿配体，bpy = 2,2'-联吡啶）的配合物可作为将CO还原为CO的电催化剂。在这项工作中，合成了一系列苯酚和苯甲醚取代的联吡啶配体，并将其连接到锰金属中心，以探究CO还原过渡态中的分子内氢键相互作用。与具有与CO形成氢键能力的配体相比，没有分子内氢键形成能力的配体显示出催化电流密度降低。通过在氩气或CO环境下进行伏安法和本体电解实验来研究电催化作用。使用氢气与氘对分子内H/D键合步骤的催化速率测量表明，催化作用存在同位素效应。本文给出的数据表明了一种涉及两个连续平衡同位素效应与一级动力学同位素效应相结合的机制。
