Redox Potentials of Cobalt Corrinoids with Axial Ligands Correlate with Heterolytic Co-C Bond Dissociation Energies

Yoshitsugu Morita, Koji Oohora, Akiyoshi Sawada, Takashi Kamachi, Kazunari Yoshizawa, Takashi Hayashi

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

We investigate the correlations between the redox potentials of nonalkylated cobalt corrinoids and the Co-C bond dissociation energies (BDEs) of the methylated species with an aqua or histidine axial ligand. A set of cobalt corrinoids, cobalamin, and its model systems, which include new version of myoglobin reconstituted with cobalt didehydrocorrin, are investigated. The Co(III)/Co(II) and Co(II)/Co(I) redox potentials of myoglobin reconstituted with cobalt tetradehydrocorrin and didehydrocorrin and the bare cofactors were determined. Density functional theory (DFT) calculations were performed to estimate the Co-C BDEs of the methylated species. It is found that the redox potentials correlate well with the heterolytic BDEs, which are dependent on the electronegativity of the corrinoid frameworks. The present study offers two important insights into our understanding of how enzymes promote the reactions: (i) homolysis is promoted by strong axial ligation and (ii) heterolysis is controlled by the redox potentials, which are regulated by the saturated framework and axial ligation in the enzyme.

Original languageEnglish
Pages (from-to)1950-1955
Number of pages6
JournalInorganic chemistry
Volume56
Issue number4
DOIs
Publication statusPublished - Feb 20 2017

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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