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Ligand dechelation effect on a [Co(tpy)2]2+ scaffold towards electro-catalytic proton and water reduction

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Abstract

This study presents the synthesis of the 4-(2,6-di(pyridin-2-yl)pyridin-4-yl)quinoline (4Ql-tpy) ligand and its corresponding cobalt complexes, i.e. [Co(4Ql-tpy)2]Cl2 and [Co(4Ql-tpy)2](PF6)3. The [Co(4Ql-tpy)2]Cl2 complex has been employed for electro-catalytic reduction of protons in DMF/H2O (95 : 5 v/v) as well as in phosphate buffer (pH 4.0–7.0). The spectroscopic investigations reveal the dissociation of one of the 4Ql-tpy ligands from the [Co(4Ql-tpy)2]Cl2 complex in the presence of excess AcOH in organic medium. However, in phosphate buffer it is evident that the dechelation of one of the peripheral pyridine rings followed by the protonation of pyridine-N occurs with the subsequent coordination of one water molecule. The aqueous electrochemical studies reveal that the Co(I) species is dependent on the proton concentration and the gradient for potential vs. pH indicates that a PCET (1H+/1e) is involved between [CoII(4Ql-tpy)(24Ql-tpy)(OH2)]2+ and [CoI(4Ql-tpy)(24Ql-tpyH)(OH2)]2+ in the pH range 2.8 to 8.0. The plausible mechanism has been described based on the spectroscopic and electrochemical investigations.

Graphical abstract: Ligand dechelation effect on a [Co(tpy)2]2+ scaffold towards electro-catalytic proton and water reduction

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Publication details

The article was received on 10 Nov 2018, accepted on 04 Feb 2019 and first published on 05 Feb 2019


Article type: Paper
DOI: 10.1039/C8NJ05712E
Citation: New J. Chem., 2019, Advance Article

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    Ligand dechelation effect on a [Co(tpy)2]2+ scaffold towards electro-catalytic proton and water reduction

    K. Majee and S. K. Padhi, New J. Chem., 2019, Advance Article , DOI: 10.1039/C8NJ05712E

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