A Chromium(III)-Superoxo Complex as a Three-Electron Oxidant with a Large Tunneling Effect in Multi-Electron Oxidation of NADH Analogues

Tarali Devi, Yong Min Lee, Jieun Jung, Muniyandi Sankaralingam, Wonwoo Nam, Shunichi Fukuzumi

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

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 CrIII-superoxo complex, [CrIII(O2)(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 CrIV-oxo complex, [CrIV(O)(TMC)(Cl)]+ (2), is formed by a heterolytic O−O bond cleavage of a putative CrII-hydroperoxo complex, [CrII(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 (Cl4Q) 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.

Original languageEnglish
Pages (from-to)3510-3515
Number of pages6
JournalAngewandte Chemie - International Edition
Volume56
Issue number13
DOIs
StatePublished - 20 Mar 2017

Bibliographical note

Publisher Copyright:
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Keywords

  • NADH analogues
  • chromium(III)-superoxo complexes
  • hydride transfer
  • hydrogen atom transfer
  • three-electron oxidant

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