A Cobalt(III)−Hydroxo Complex Bearing a Pentadentate Amidate Ligand as an Electrocatalyst for Water Oxidation

Panjo Lepcha, Sachidulal Biswas, Srijan Narayan Chowdhury, Suranjana Bose, Joyashish Debgupta, Satadal Paul, Achintesh N. Biswas*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


A Co(III)−hydroxo complex, [CoIII(dpaq)OH]ClO4 (1-OH) bearing a pentadentate ligand, H-dpaq, (H-dpaq=(2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate]) catalyses water oxidation in mildly alkaline medium (pH 8.0) at a potential of 1.4 VNHE with an average Turn-Over-Frequency (TOFmax) of 2.8×104 s−1 and faradaic efficiency of 88 %. Post-electrolysis characterization of the electrode rules out the formation of any heterogeneous electroactive species. Electrochemical results and theoretical calculations confirm the occurrence of both metal and ligand centered PCET processes during anodic scanning. The resulting formally Co(V)−oxo/oxyl intermediate undergoes water nucleophilic attack to install the O−O bond. The role of axial ligand in water oxidation by Co(III)−dpaq system has been examined by comparing the reactivity of the Co-hydroxide complex (1-OH) with that of its chloride-ligated counterpart, [CoIII(dpaq)Cl]Cl (1-Cl). The results confirm the ability of the Co-dpaq complexes to bind water/or water derived ligands over chloride or non-aqueous solvents. The interplay of ligand redox non-innocence and σ-donating ability of the N5-carboxamido ligand helps to store oxidizing equivalents and triggers O−O bond formation.

Original languageEnglish
Article numbere202200611
Issue number7
Early online date12 Dec 2022
Publication statusPublished - 1 Mar 2023

Bibliographical note

Funding Information:
This work was supported by grants from the Science and Industrial research Board (SERB, Project No. CRG/2021/002064 to A.N.B.). We also thank NIT Sikkim for doctoral research fellowship allocated to S. N. C.

Publisher Copyright:
© 2022 Wiley-VCH GmbH.


  • Cobalt
  • Electrochemistry
  • Kinetics
  • Redox-active ligand
  • Water oxidation

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