Proton-Coupled Electron Transfer Enhances the Electrocatalytic Reduction of Nitrite to NO in a Bioinspired Copper Complex
Proton-Coupled Electron Transfer Enhances the Electrocatalytic Reduction of Nitrite to NO in a Bioinspired Copper Complex
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DOI：
10.1021/acscatal.8b00361
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发表时间：
2018-06-01
期刊：
影响因子：
12.9
通讯作者：
Symes, Mark D.
中科院分区：
文献类型：
--
作者：
Cioncoloni, Giacomo;Roger, Isolda;Symes, Mark D.
选择性和有效的电催化还原亚硝酸盐为一氧化氮（NO）是非常重要的，无论是用于生物医学应用的NO释放系统的发展和从环境中去除氮氧化物污染物。在自然界中，这种转化是由（除其他外）被称为含铜亚硝酸盐还原酶的酶介导的。因此，能够将亚硝酸盐还原为NO的合成铜络合物的开发引起了相当大的兴趣。然而，有没有研究描述质子耦合电子转移在亚硝酸盐还原过程中的关键作用时，使用这样的合成配合物。在这里，我们描述了两个以前未报道的铜配合物（3和4）的电催化还原亚硝酸盐NO，其中质子中继单元的作用，在第二次协调领域的金属可以探测的合成和表征。配合物4带有紧邻铜中心的侧链羧酸酯基团，而配合物3缺乏这种功能性。我们的研究结果表明，配合物4是有效的亚硝酸盐还原的电催化剂的两倍比配合物3和配合物4是最好的铜基分子电催化剂，这个反应尚未发现。3和4之间的反应性的差异，探测使用一系列的电化学，光谱和计算方法，这揭示了可能的催化机制4和牵连的质子中继能力，其悬垂羧酸基团在增强的反应性，这种复杂的显示。这些结果突出了质子耦合电子转移在亚硝酸盐还原为NO的关键作用，并具有重要的影响，仿生催化剂的设计，为氮氧化物的选择性相互转化。
The selective and efficient electrocatalytic reduction of nitrite to nitric oxide (NO) is of tremendous importance, both for the development of NO-release systems for biomedical applications and for the removal of nitrogen oxide pollutants from the environment. In nature, this transformation is mediated by (among others) enzymes known as the copper-containing nitrite reductases. The development of synthetic copper complexes that can reduce nitrite to NO has therefore attracted considerable interest. However, there are no studies describing the crucial role of proton-coupled electron transfer during nitrite reduction when such synthetic complexes are used. Herein, we describe the synthesis and characterization of two previously unreported Cu complexes (3 and 4) for the electrocatalytic reduction of nitrite to NO, in which the role of proton-relaying units in the secondary coordination sphere of the metal can be probed. Complex 4 bears a pendant carboxylate group in close proximity to the copper center, while complex 3 lacks such functionality. Our results suggest that complex 4 is twice as effective an electrocatalyst for nitrite reduction than is complex 3 and that complex 4 is the best copper-based molecular electrocatalyst for this reaction yet discovered. The differences in reactivity between 3 and 4 are probed using a range of electrochemical, spectroscopic, and computational methods, which shed light on the possible catalytic mechanism of 4 and implicate the proton-relaying ability of its pendant carboxylate group in the enhanced reactivity that this complex displays. These results highlight the critical role of proton-coupled electron transfer in the reduction of nitrite to NO and have important implications for the design of biomimetic catalysts for the selective interconversions of the nitrogen oxides.