Liu Jiale, Liao Rong-Zhen, Heinemann Frank W, Meyer Karsten, Thummel Randolph P, Zhang Yaqiong, Tong Lianpeng
School of Chemistry and Chemical Engineering/Institute of Clean Energy and Materials, Guangzhou University, No. 230 Wai Huan Xi Road, Higher Education Mega Center, Guangzhou, 510006, PR China.
Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei Key Laboratory of Bioinorganic Chemistry and Materia Medica, Hubei Key Laboratory of Materials Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Inorg Chem. 2021 Dec 6;60(23):17976-17985. doi: 10.1021/acs.inorgchem.1c02539. Epub 2021 Nov 22.
Novel cobalt and zinc complexes with the tetradentate ppq (8-(1″,10″-phenanthrol-2″-yl)-2-(pyrid-2'-yl)quinoline) ligand have been synthesized and fully characterized. Electrochemical measurements have shown that the formal monovalent complex [Co(ppq)(PPh)] () undergoes two stepwise ligand-based electroreductions in DMF, affording a [Co(ppq)DMF] species. Theoretical calculations have described the electronic structure of [Co(ppq)DMF] as a low-spin Co(II) center coupling with a triple-reduced ppq radical ligand. In the presence of triethylammonium as the proton donor, the cobalt complex efficiently drives electrocatalytic hydrogen evolution with a maximum turnover frequency of thousands per second. A mechanistic investigation proposes an EECC H-evolving pathway, where the second ligand-based redox process (E), generating the [Co(ppq)DMF] intermediate, initiates proton reduction, and the second proton transfer process (C) is the rate-determining step. This work provides a unique example for understanding the role of redox-active ligands in electrocatalytic H evolution by transition metal sites.
已合成并全面表征了新型钴和锌与四齿配体ppq（8-(1″,10″-菲咯啉-2″-基)-2-(吡啶-2'-基)喹啉）形成的配合物。电化学测量表明，形式上的一价配合物[Co(ppq)(PPh)]（）在N,N-二甲基甲酰胺（DMF）中经历两步基于配体的电还原，生成[Co(ppq)DMF]物种。理论计算将[Co(ppq)DMF]的电子结构描述为低自旋Co(II)中心与三重还原的ppq自由基配体耦合。在三乙铵作为质子供体存在的情况下，钴配合物能高效驱动电催化析氢，最大周转频率可达每秒数千次。机理研究提出了一种EECC析氢途径，其中基于配体的第二个氧化还原过程（E）生成[Co(ppq)DMF]中间体，引发质子还原，第二个质子转移过程（C）是速率决定步骤。这项工作为理解氧化还原活性配体在过渡金属位点电催化析氢中的作用提供了一个独特的例子。
