Department of Chemistry and Nano Science, Ewha Womans University, Seoul, 03760, Korea.
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, China.
Angew Chem Int Ed Engl. 2017 Mar 20;56(13):3510-3515. doi: 10.1002/anie.201611709. Epub 2017 Mar 7.
Metal-superoxo species are involved in a variety of enzymatic oxidation reactions, and multi-electron oxidation of substrates is frequently observed in those enzymatic reactions. A Cr -superoxo complex, [Cr (O )(TMC)(Cl)] (1; TMC=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), is described that acts as a novel three-electron oxidant in the oxidation of dihydronicotinamide adenine dinucleotide (NADH) analogues. In the reactions of 1 with NADH analogues, a Cr -oxo complex, [Cr (O)(TMC)(Cl)] (2), is formed by a heterolytic O-O bond cleavage of a putative Cr -hydroperoxo complex, [Cr (OOH)(TMC)(Cl)], which is generated by hydride transfer from NADH analogues to 1. The comparison of the reactivity of NADH analogues with 1 and p-chloranil (Cl Q) indicates that oxidation of NADH analogues by 1 proceeds by proton-coupled electron transfer with a very large tunneling effect (for example, with a kinetic isotope effect of 470 at 233 K), followed by rapid electron transfer.
金属-过氧物种参与各种酶促氧化反应，并且在这些酶促反应中经常观察到底物的多电子氧化。描述了一种 Cr-过氧配合物，[Cr(O)(TMC)(Cl)]（1；TMC=1,4,8,11-四甲基-1,4,8,11-四氮杂环十四烷），它在二氢烟酰胺腺嘌呤二核苷酸（NADH）类似物的氧化中作为新型三电子氧化剂。在 1 与 NADH 类似物的反应中，通过假定的 Cr-过氧配合物[Cr(OOH)(TMC)(Cl)]的异裂 O-O 键断裂形成 Cr-氧合配合物[Cr(O)(TMC)(Cl)]（2），[Cr(OOH)(TMC)(Cl)]是通过从 NADH 类似物向 1 转移氢化物生成的。比较 NADH 类似物与 1 和对氯醌（Cl Q）的反应性表明，1 对 NADH 类似物的氧化通过具有非常大隧道效应的质子偶联电子转移进行（例如，在 233 K 时动力学同位素效应为 470），随后是快速电子转移。
