Karmalkar Deepika G, Lim Hyeongtaek, Sundararajan Mahesh, Lee Yong-Min, Seo Mi Sook, Bae Dae Young, Lu Xiaoyan, Hedman Britt, Hodgson Keith O, Kim Won-Suk, Lee Eunsung, Solomon Edward I, Fukuzumi Shunichi, Nam Wonwoo
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.
School of Chemical Sciences, Goa University, Taleigao, Goa 403206, India.
J Am Chem Soc. 2025 Feb 5;147(5):3981-3993. doi: 10.1021/jacs.4c11751. Epub 2025 Jan 24.
A series of Ni complexes bearing a redox and acid-base noninnocent tetraamido macrocyclic ligand, H-(TAML-4) {H-(TAML-4) = 15,15-dimethyl-5,8,13,17-tetrahydro-5,8,13,17-tetraaza-dibenzo[]cyclotridecene-6,7,14,16-tetraone}, with formal oxidation states of Ni, Ni, and Ni were synthesized and characterized structurally and spectroscopically. The X-ray crystallographic analysis of the Ni complexes revealed a square planar geometry, and the [Ni(TAML-4)] complex with the formal oxidation state of Ni was characterized to be [Ni(TAML-4)] with the oxidation state of the Ni ion and the one-electron oxidized TAML-4 ligand, TAML-4. The Ni oxidation state and the TAML-4 radical cation ligand, TAML-4, were supported by X-ray absorption spectroscopy and density functional theory calculations. The reversible interconversions between [Ni(TAML-4)] and [Ni(TAML-4)] and between [Ni(TAML-4)] and [Ni(TAML-4)] were demonstrated in spectroelectrochemical measurements as well as in chemical oxidation and reduction reactions. The reactivities of [Ni(TAML-4)] and [Ni(TAML-4)] were then investigated in hydride transfer reactions using NADH analogs. Hydride transfer from 9,10-dihydro-10-methylacridine (AcrH) to [Ni(TAML-4)] was found to proceed via electron transfer (ET) from AcrH to [Ni(TAML-4)] with no deuterium kinetic isotope effect (/ = 1.0(2)). In contrast, hydride transfer from AcrH to [Ni(TAML-4)] proceeded much more slowly via a concerted proton-coupled electron transfer (PCET) process with / = 7.0(5). In the latter reaction, an electron and a proton were transferred to the Ni center and the TAML-4 ligand, respectively. The mechanisms of the ET by [Ni(TAML-4)] and the concerted PCET by [Ni(TAML-4)] were ascribed to the different redox potentials of the Ni complexes.
合成了一系列带有氧化还原和酸碱非无辜四酰胺大环配体H-(TAML-4) {H-(TAML-4) = 15,15-二甲基-5,8,13,17-四氢-5,8,13,17-四氮杂二苯并[]环十三碳烯-6,7,14,16-四酮}的镍配合物，并通过结构和光谱进行了表征。镍配合物的X射线晶体学分析显示为平面正方形几何结构，形式氧化态为Ni的[Ni(TAML-4)]配合物被表征为具有Ni离子氧化态和单电子氧化的TAML-4配体TAML-4的[Ni(TAML-4)]。镍的氧化态和TAML-4自由基阳离子配体TAML-4得到了X射线吸收光谱和密度泛函理论计算的支持。在光谱电化学测量以及化学氧化和还原反应中证明了[Ni(TAML-4)]与[Ni(TAML-4)]之间以及[Ni(TAML-4)]与[Ni(TAML-4)]之间的可逆相互转化。然后使用NADH类似物在氢化物转移反应中研究了[Ni(TAML-4)]和[Ni(TAML-4)]的反应活性。发现从9,10-二氢-10-甲基吖啶(AcrH)到[Ni(TAML-4)]的氢化物转移通过从AcrH到[Ni(TAML-4)]的电子转移(ET)进行，没有氘动力学同位素效应(/ = 1.0(2))。相反，从AcrH到[Ni(TAML-4)]的氢化物转移通过协同质子耦合电子转移(PCET)过程进行得慢得多，/ = 7.0(5)。在后者的反应中，一个电子和一个质子分别转移到镍中心和TAML-4配体上。[Ni(TAML-4)]的ET机制和[Ni(TAML-4)]的协同PCET机制归因于镍配合物的不同氧化还原电位。
