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

TY - JOUR

T1 - A Cobalt(III)−Hydroxo Complex Bearing a Pentadentate Amidate Ligand as an Electrocatalyst for Water Oxidation

AU - Lepcha, Panjo

AU - Biswas, Sachidulal

AU - Chowdhury, Srijan Narayan

AU - Bose, Suranjana

AU - Debgupta, Joyashish

AU - Paul, Satadal

AU - Biswas, Achintesh N.

N1 - 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.

PY - 2023/3/1

Y1 - 2023/3/1

N2 - 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.

AB - 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.

KW - Cobalt

KW - Electrochemistry

KW - Kinetics

KW - Redox-active ligand

KW - Water oxidation

UR - http://www.scopus.com/inward/record.url?scp=85144984967&partnerID=8YFLogxK

U2 - 10.1002/ejic.202200611

DO - 10.1002/ejic.202200611

M3 - Article

AN - SCOPUS:85144984967

SN - 1434-1948

VL - 26

JO - EUROPEAN JOURNAL OF INORGANIC CHEMISTRY

JF - EUROPEAN JOURNAL OF INORGANIC CHEMISTRY

IS - 7

M1 - e202200611

ER -