Université Paris-Saclay, CNRS, Institut de chimie moléculaire et des matériaux d'Orsay, 91405, Orsay, France.
Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198, Gif-sur-Yvette, France.
Angew Chem Int Ed Engl. 2020 Dec 7;59(50):22451-22455. doi: 10.1002/anie.202010859. Epub 2020 Oct 7.
The manipulation of the second coordination sphere for improving the electrocatalytic CO reduction has led to breakthroughs with hydrogen bonding, local proton source, or electrostatic effects. We have developed two atropisomers of an iron porphyrin complex with two urea functions acting as multiple hydrogen-bonding tweezers to lock the metal-bound CO in a similar fashion found in the carbon monoxide dehydrogenase (CODH) enzyme. The αα topological isomer with the two urea groups on the same side of the porphyrin provides a stronger binding affinity to tether the incoming CO in comparison to the αβ disposition. However, the electrocatalytic activity of the αβ atropisomer outperforms its congener with one of the highest reported turnover frequencies at low overpotential. The strong H/D kinetic isotope effect (KIE) observed for the αα system indicates the existence of a tight water hydrogen-bonding network for proton delivery which is disrupted by addition of an acid source. The small H/D KIE for the αβ isomer and the enhanced electrocatalytic performance on addition of stronger acid indicate the free access of protons to the bound CO on the opposite side of the urea arm.
通过对第二配位层的操控来改善电催化 CO 还原性能，从而产生了氢键、局部质子源或静电效应等突破。我们开发了两种具有两个脲基官能团的铁卟啉配合物的对映异构体，这些脲基官能团充当多个氢键夹，以类似一氧化碳脱氢酶（CODH）中发现的方式锁定金属结合的 CO。与卟啉同一侧具有两个脲基的 αα 拓扑异构体与αβ 构象相比，提供了更强的结合亲和力来固定进入的 CO。然而，αβ 对映异构体的电催化活性优于其同类物，具有最低过电势下报告的最高周转率频率之一。αα 体系观察到的强 H/D 动力学同位素效应（KIE）表明存在紧密的水氢键网络，用于质子传递，而添加酸源会破坏该网络。αβ 异构体的小 H/D KIE 以及在添加更强酸时增强的电催化性能表明，质子可以自由进入脲臂另一侧的结合 CO。
