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A Chromium(III)‐Superoxo Complex as a Three‐Electron Oxidant with a Large Tunneling Effect in Multi‐Electron Oxidation of NADH Analogues
Author(s) -
Devi Tarali,
Lee YongMin,
Jung Jieun,
Sankaralingam Muniyandi,
Nam Wonwoo,
Fukuzumi Shunichi
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201611709
Subject(s) - heterolysis , chemistry , electron transfer , kinetic isotope effect , reactivity (psychology) , photochemistry , hydride , bond cleavage , proton coupled electron transfer , metal , electron acceptor , redox , medicinal chemistry , stereochemistry , inorganic chemistry , organic chemistry , catalysis , deuterium , medicine , physics , alternative medicine , quantum mechanics , pathology
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 III ‐superoxo complex, [Cr III (O 2 )(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 IV ‐oxo complex, [Cr IV (O)(TMC)(Cl)] + ( 2 ), is formed by a heterolytic O−O bond cleavage of a putative Cr II ‐hydroperoxo complex, [Cr II (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 4 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.