Shaw Wendy J, Helm Monte L, DuBois Daniel L
Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Biochim Biophys Acta. 2013 Aug-Sep;1827(8-9):1123-39. doi: 10.1016/j.bbabio.2013.01.003. Epub 2013 Jan 11.
This review discusses the development of molecular electrocatalysts for H2 production and oxidation based on nickel. A modular approach is used in which the structure of the catalyst is divided into first, second, and outer coordination spheres. The first coordination sphere consists of the ligands bound directly to the metal center, and this coordination sphere can be used to control such factors as the presence or absence of vacant coordination sites, redox potentials, hydride donor abilities and other important thermodynamic parameters. The second coordination sphere includes functional groups such as pendent acids or bases that can interact with bound substrates such as H2 molecules and hydride ligands, but that do not form strong bonds with the metal center. These functional groups can play diverse roles such as assisting the heterolytic cleavage of H2, controlling intra- and intermolecular proton transfer reactions, and providing a physical pathway for coupling proton and electron transfer reactions. By controlling both the hydride donor ability of the catalysts using the first coordination sphere and the proton donor abilities of the functional groups in the second coordination sphere, catalysts can be designed that are biased toward H2 production, oxidation, or bidirectional (catalyzing both H2 oxidation and production). The outer coordination sphere is defined as that portion of the catalytic system that is beyond the second coordination sphere. This coordination sphere can assist in the delivery of protons and electrons to and from the catalytically active site, thereby adding another important avenue for controlling catalytic activity. Many features of these simple catalytic systems are good models for enzymes, and these simple systems provide insights into enzyme function and reactivity that may be difficult to probe in enzymes. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
本综述讨论了基于镍的用于氢气产生和氧化的分子电催化剂的发展。采用了一种模块化方法，其中催化剂的结构分为第一、第二和外层配位球。第一配位球由直接与金属中心结合的配体组成，该配位球可用于控制诸如是否存在空配位位点、氧化还原电位、氢化物供体能力和其他重要热力学参数等因素。第二配位球包括诸如悬垂酸或碱等官能团，它们可与诸如H2分子和氢化物配体等结合底物相互作用，但不与金属中心形成强键。这些官能团可发挥多种作用，如协助H2的异裂、控制分子内和分子间的质子转移反应，以及为耦合质子和电子转移反应提供物理途径。通过使用第一配位球控制催化剂的氢化物供体能力以及第二配位球中官能团的质子供体能力，可以设计出偏向于氢气产生、氧化或双向（催化氢气氧化和产生）的催化剂。外层配位球定义为催化体系中超出第二配位球的部分。该配位球可协助质子和电子往返于催化活性位点的传递，从而为控制催化活性增加了另一条重要途径。这些简单催化体系的许多特性是酶的良好模型，并且这些简单体系为酶的功能和反应性提供了见解，而这些在酶中可能难以探究。本文是名为《生物能量学和仿生系统中的金属》特刊的一部分。
