Xu Song, Ashley Daniel C, Kwon Hyuk-Yong, Ware Gabrielle R, Chen Chun-Hsing, Losovyj Yaroslav, Gao Xinfeng, Jakubikova Elena, Smith Jeremy M
Department of Chemistry , Indiana University , 800 E. Kirkwood Ave. , Bloomington , Indiana 47401 , USA . Email:
Department of Chemistry , North Carolina State University , 2620 Yarbrough Dr. , Raleigh , NC 27695 , USA . Email:
Chem Sci. 2018 May 15;9(22):4950-4958. doi: 10.1039/c8sc00721g. eCollection 2018 Jun 14.
The cobalt macrocycle complex [Co(DIM)Br] (DIM = 2,3-dimethyl-1,4,8,11-tetraazacyclotetradeca-1,3-diene) is an electrocatalyst for the selective reduction of nitrate to ammonia in aqueous solution. The catalyst operates over a wide pH range and with very high faradaic efficiency, albeit with large overpotential. Experimental investigations, supported by electronic structure calculations, reveal that catalysis commences when nitrate binds to the two-electron reduced species Co(DIM), where cobalt and the macrocycle are each reduced by a single electron. Several mechanisms for the initial reduction of nitrate to nitrite were explored computationally and found to be feasible at room temperature. The reduced DIM ligand plays an important role in these mechanisms by directly transferring a single electron to the bound nitrate substrate, activating it for further reactions. These studies further reveal that the DIM macrocycle is critical to nitrate reduction, specifically its combination of redox non-innocence, hydrogen-bonding functionality and flexibility in coordination mode.
钴大环配合物[Co(DIM)Br]（DIM = 2,3 - 二甲基 - 1,4,8,11 - 四氮杂环十四碳 - 1,3 - 二烯）是一种用于在水溶液中将硝酸盐选择性还原为氨的电催化剂。该催化剂在很宽的pH范围内起作用，且法拉第效率非常高，尽管过电位较大。在电子结构计算的支持下进行的实验研究表明，当硝酸盐与双电子还原物种Co(DIM)结合时催化开始，其中钴和大环各自被一个电子还原。通过计算探索了几种将硝酸盐初始还原为亚硝酸盐的机制，发现它们在室温下是可行的。还原的DIM配体在这些机制中起着重要作用，通过直接将一个电子转移到结合的硝酸盐底物上，使其活化以进行进一步反应。这些研究进一步表明，DIM大环对于硝酸盐还原至关重要，特别是其氧化还原非无害性、氢键功能和配位模式灵活性的组合。
