Electrocatalytic hydrogen production by dinuclear cobalt(ii) compounds containing redox-active diamidate ligands: a combined experimental and theoretical study

Papanikolaou, M. G., Elliott, A., McAllister, J. , Gallos, J. K., Keramidas, A. D., Kabanos, T. A., Sproules, S. and Miras, H. N. (2020) Electrocatalytic hydrogen production by dinuclear cobalt(ii) compounds containing redox-active diamidate ligands: a combined experimental and theoretical study. Dalton Transactions, 49(44), pp. 15718-15730. (doi: 10.1039/D0DT02617D) (PMID:33146215)

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Abstract

The chiral dicobalt(II) complex [CoII2(μ2-L)2] (1) (H2L = N2,N6-di(quinolin-8-yl)pyridine-2,6-dicarboxamide) and its tert-butyl analogue [CoII2(μ2-LBu)2] (2) were synthesized and structurally characterized. Addition of one equivalent of AgSbF6 to the dichloromethane solution of 1 and 2 resulted in the isolation of the mixed-valent dicobalt(III,II) species [CoIIICoII(μ2-L)2]SbF6 (3) and [CoIIICoII(μ2-LBu)2]SbF6 (4). Homovalent 1 and 2 exhibited catalytic activity towards proton reduction in the presence of acetic acid (AcOH) as the substrate. The complexes are stable in solution while their catalytic turnover frequency is estimated at 10 and 34.6 h−1 molcat−1 for 1 and 2, respectively. Calculations reveal one-electron reduction of 1 is ligand-based, preserving the dicobalt(II) core and activating the ligand toward protonation at the quinoline group. This creates a vacant coordination site that is subsequently protonated to generate the catalytically ubiquitous Co(III) hydride. The dinuclear structure persists throughout where the distal Co(II) ion modulates the reactivity of the adjacent metal site by promoting ligand redox activity through spin state switching.

Item Type:Articles
Additional Information:The research work was supported by the Hellenic Foundation for Research and Innovation (HFRI) under the HFRI PhD Fellowship grant (Fellowship Number: 1213).
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Sproules, Dr Stephen and Moiras, Dr Haralampos and Elliott, Mr Alexander and McAllister, Mr James
Authors: Papanikolaou, M. G., Elliott, A., McAllister, J., Gallos, J. K., Keramidas, A. D., Kabanos, T. A., Sproules, S., and Miras, H. N.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Dalton Transactions
Publisher:Royal Society of Chemistry
ISSN:1477-9226
ISSN (Online):1477-9234
Published Online:28 October 2020
Copyright Holders:Copyright © 2020 The Royal Society of Chemistry
First Published:First published in Dalton Transactions 49(44):15718-15730
Publisher Policy:Reproduced under a Creative Commons License

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