Why Is Cobalt the Best Transition Metal in Transition-Metal Hangman Corroles for O鈥揙 Bond Formation during Water Oxidation?

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• 作者：Wenzhen Lai ; Rui Cao ; Geng Dong ; Sason Shaik ; Jiannian Yao ; Hui Chen
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2012
• 出版时间：September 6, 2012
• 年：2012
• 卷：3
• 期：17
• 页码：2315-2319
• 全文大小：278K
• 年卷期：v.3,no.17(September 6, 2012)
• ISSN：1948-7185

文摘

O鈥揙 bond formation catalyzed by a variety of 尾-octafluoro hangman corrole metal complexes was investigated using density functional theory methods. Five transition metal elements, Co, Fe, Mn, Ru, and Ir, that are known to lead to water oxidation were examined. Our calculations clearly show that the formal Co^V catalyst has a Co^IV鈥揷orrole^鈥? character and is the most efficient water oxidant among all eight transition-metal complexes. The O鈥揙 bond formation barriers were found to change in the following order: Co(V) Fe(V) < Mn(V) < Ir(V) < Co(IV) < Ru(V) < Ir(IV) < Mn(IV). The efficiency of water oxidation is discussed by analysis of the O鈥揙 bond formation step. Thus, the global trend is determined by the ability of the ligand d-block to accept two electrons from the nascent OH鈥?/sup>, as well as by the OH鈥?/sup> affinity of the TM(IV)鈺怬 species of the corresponding TM(V)鈺怬路H₂O complex. Exchange-enhanced reactivity (EER) is responsible for the high catalytic activity of the Co(V) species in its S = 1 state.

Keywords:

O鈭扥 bond formation; density functional theory; hangman corrole; water oxidation; transition metal; nucleophilic attack