Tetranuclear CoII 4O4 Cubane Complex: Effective Catalyst Toward Electrochemical Water Oxidation
INORGANIC CHEMISTRY（2024）
Abstract
The reaction of Co(OAc)(2)6H(2)O with 2,2 '-[{(1E,1 ' E)-pyridine-2,6-diyl-bis(methaneylylidene)bis(azaneylylidene)}diphenol](LH2) a multisite coordination ligand and Et3N in a 1:2:3 stoichiometric ratio forms a tetranuclear complex Co-4(L)(2)(mu-eta(1):eta(1)-OAc)(2)(eta(2)-OAc)(2)] 1.5 CH3OH 1.5 CHCl3 (1). Based on X-ray diffraction investigations, complex 1 comprises a distorted Co4O4 cubane core consisting of two completely deprotonated ligands [L](2-) and four acetate ligands. Two distinct types of Co-II centers exist in the complex, where the Co(2) center has a distorted octahedral geometry; alternatively, Co(1) has a distorted pentagonal-bipyramidal geometry. Analysis of magnetic data in 1 shows predominant antiferromagnetic coupling (J = -2.1 cm(-1)), while the magnetic anisotropy is the easy-plane type (D-1 = 8.8, D-2 = 0.76 cm(-1)). Furthermore, complex 1 demonstrates an electrochemical oxygen evolution reaction (OER) with an overpotential of 325 mV and Tafel slope of 85 mV dec(-1), required to attain a current density of 10 mA cm(-2) and moderate stability under alkaline conditions (pH = 14). Electrochemical impedance spectroscopy studies reveal that compound 1 has a charge transfer resistance (R-ct) of 2.927 Omega, which is comparatively lower than standard Co3O4 (5.242 Omega), indicating rapid charge transfer kinetics between electrode and electrolyte solution that enhances higher catalytic activity toward OER kinetics.
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