Heterobimetallic Complexes with M(III)-(μ-OH)-M(II) Cores (M(III) = Fe, Mn, Ga; M(II) = Ca, Sr, and Ba): Structural, Kinetic, and Redox Properties.
Heterobimetallic Complexes with M(III)-(μ-OH)-M(II) Cores (M(III) = Fe, Mn, Ga; M(II) = Ca, Sr, and Ba): Structural, Kinetic, and Redox Properties.
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DOI：
10.1039/c2sc21400h
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发表时间：
2013-02
期刊：
影响因子：
8.4
通讯作者：
Borovik AS
中科院分区：
文献类型：
--
作者：
Park YJ;Cook SA;Sickerman NS;Sano Y;Ziller JW;Borovik AS
使用含有具有 3 个磺酰胺基的三足配体的新型 FeII 络合物探索了氧化还原惰性金属离子对双氧活化的影响。该铁络合物比其 MnII 类似物表现出更快的 O2 还原初始速率。 FeII 和 MnII 配合物的第 2 族金属离子存在时，初始速率也有所增加，遵循 NMe4+ < BaII < CaII = SrII 的趋势。这些研究分离出含有 FeIII-(μ-OH)-MII 核心（MII = Ca、Sr 和 Ba）和具有 [SrII(OH)MnIII]+ 基序的异双金属配合物。还制备了类似的[CaII(OH)GaIII]+配合物，其固态分子结构与[CaII(OH)FeIII]+体系几乎相同。核磁共振研究表明，抗磁性 [CaII(OH)GaIII]+ 络合物在溶液中保留了其结构。对异质双金属体系的电化学测量表明，[CaII(OH)FeIII]+ 和 [SrII(OH)FeIII]+ 配合物具有相似的单电子还原电势，比 [BaII(OH)FeIII]+ 观察到的电势更正。异质双金属 MnII 配合物也得到了类似的结果。这些发现表明，在评估第 2 族离子对氧化还原过程（包括光系统 II 的放氧复合物内的氧化还原过程）的影响时，路易斯酸度并不是唯一需要考虑的因素。
The effects of redox-inactive metal ions on dioxygen activation were explored using a new FeII complex containing a tripodal ligand with 3 sulfonamido groups. This iron complex exhibited a faster initial rate for the reduction of O2 than its MnII analog. Increases in initial rates were also observed in the presence of group 2 metal ions for both the FeII and MnII complexes, which followed the trend NMe4+ < BaII < CaII = SrII. These studies led to the isolation of heterobimetallic complexes containing FeIII-(μ-OH)-MII cores (MII = Ca, Sr, and Ba) and one with a [SrII(OH)MnIII]+ motif. The analogous [CaII(OH)GaIII]+ complex was also prepared and its solid state molecular structure is nearly identical to that of the [CaII(OH)FeIII]+ system. Nuclear magnetic resonance studies indicated that the diamagnetic [CaII(OH)GaIII]+ complex retained its structure in solution. Electrochemical measurements on the heterobimetallic systems revealed similar one-electron reduction potentials for the [CaII(OH)FeIII]+ and [SrII(OH)FeIII]+ complexes, which were more positive than the potential observed for [BaII(OH)FeIII]+. Similar results were obtained for the heterobimetallic MnII complexes. These findings suggest that Lewis acidity is not the only factor to consider when evaluating the effects of group 2 ions on redox processes, including those within the oxygen-evolving complex of Photosystem II.