Issue 7, 2015

Modulation of electronic and redox properties in phenolate-rich cobalt(iii) complexes and their implications for catalytic proton reduction

Abstract

We investigate the redox, spectroscopy and catalytic reactivity of new cobalt(III) complexes based on phenolate-rich [N2O3] ligands. These complexes are described as [CoIII(LX)MeOH], where X indicates the presence of chloro (1), bromo (2), iodo (3), or tert-butyl (4) substituents in the 3rd and 5th positions of each phenolate ring. These substituents modulate the Co(III) ← PheO LMCT bands of the parent complexes with 1 (451) > 2 (453) > 3 (456) > 4 (468 nm) and the redox potentials involved with the Co(III)/Co(II) and ligand reduction and with the phenolate/phenoxyl oxidation processes. The influence of the substituents on the phenolate pendant arms was also observed on the kinetic parameters; 1 presented a rate constant of 1.0 × 10−3 s−1 whereas 4 showed a considerably slower rate (5.3 × 10−5 s−1). Species 1 and 4 are electrocatalysts towards proton reduction in the presence of weak acid in acetonitrile. A TON of 10.8 was observed for 1 after 3 h of bulk electrolysis at −2.20 VFc/Fc+ using a mercury pool as the working electrode.

Graphical abstract: Modulation of electronic and redox properties in phenolate-rich cobalt(iii) complexes and their implications for catalytic proton reduction

Supplementary files

Article information

Article type
Paper
Submitted
31 Oct 2014
Accepted
02 Jan 2015
First published
07 Jan 2015

Dalton Trans., 2015,44, 3454-3466

Modulation of electronic and redox properties in phenolate-rich cobalt(III) complexes and their implications for catalytic proton reduction

D. Basu, M. M. Allard, F. R. Xavier, M. J. Heeg, H. B. Schlegel and C. N. Verani, Dalton Trans., 2015, 44, 3454 DOI: 10.1039/C4DT03337J

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