Design of Two Homoleptic Co(III) Complexes Derived from Flexible Salicylamine and Bulky 3,5-Di-tert-butylsalicylaldehyde Ligands as Efficient Electrocatalysts for Oxygen Evolution Reaction

Developing efficient and sustainable electrocatalysts for the oxygen evolution reaction (OER) is essential for advancing renewable energy technologies, particularly in terms of achieving cost-effective and scalable solutions. In this work, two homoleptic cobalt(III) complexes (complex 1 and complex 2) were synthesized using a Schiff base derived from flexible salicylamine derivatives and bulky 3,5-ditert-butylsalicylaldehyde. This ligand-engineering strategy creates a favorable balance between electronic stability and conformational flexibility, facilitating the generation of catalytically active sites under operating conditions. Structural analysis by single-crystal X-ray diffraction revealed that both complexes crystallize as homoleptic species, [LOMe2Co]− and [LOEt2Co]−, featuring a cobalt center in a distorted octahedral geometry with a +3 oxidation state, while triethylammonium ions act as counterions. Electrochemical studies demonstrated promising OER activity for both systems: complex 1 required an overpotential of 334 mV at 10 mA cm–2 with a Tafel slope of 63 mV dec–1, whereas complex 2 showed an overpotential of 348 mV with a Tafel slope of 70 mV dec–1. These findings highlight the potential of cobalt-based molecular complexes as cost-effective, earth-abundant electrocatalysts for sustainable energy applications.