Positional isomeric triphenylphosphine appended tetrahedral Cu(I) 2-/3-/4-methylpyridyldithiocarbonates as heterogeneous molecular electrocatalysts for OER and HER

Three Cu(I) complexes with positional isomeric methylpyridyldithiocarbonates as main ligands and two triphenylphosphine as co-ligands with compositions [Cu{(P(C₆H₅)₃}₂(2-Py-CH₂OCS₂)] (2PyCu), [Cu{(P(C₆H₅)₃}₂(3-Py-CH₂OCS₂)] (3PyCu) and [Cu{(P(C₆H₅)₃}₂(4-Py-CH₂OCS₂)] (4PyCu) (Py = Pyridyl) are reported herein. The single crystal X-ray diffraction investigations for all three complexes suggest a distorted tetrahedral geometry around Cu(I) that is satisfied by two S centers of methylpyridyldithiocarbonate ligand in bidentate chelating mode and two PPh₃ phosphorus centers. All three complexes exhibits interesting supramolecular frameworks sustained by C∙∙∙H, O∙∙∙H, S∙∙∙H and N∙∙∙H non-covalent interactions. The nature of these interactions have been assessed with the aid of Hirshfeld surface analyses and energy framework calculations. These complexes have been employed as molecular heterogeneous electrocatalysts in the oxygen/hydrogen evolution reactions (O/HERs). The electrocatalytic results indicate that 2PyCu exhibits the best electrocatalytic performance with onset potential of 1.67 V, η¹⁰ of 705.5 mV and a Tafel slope of 220 mV·dec^‑1 for OER. For HER also 2PyCu displays superior performance with an onset potential, η¹⁰, and a Tafel slope of -0.507 V, -658 mV and 168 mV·dec^‑1, respectively. Overall, because of the presence of Cu(I)-center, the electrocatalytic HER performances of all three complexes have been observed to be superior than their corresponding electrocatalytic OER performances.