Supramolecular and electrocatalytic OER properties of new heteroleptic fluoro- and trifluoromethyl-substituted Ni(ii)-dithiolates: effects of substituents and dihedral angle on the electrocatalytic performance

Abstract

Four new heteroleptic Ni(II) complexes with the general formula [Ni(dppe)(L)] (dppe = 1,2-bis-(diphenylphosphino)ethane; L = 4-fluoro-benzyl cyanide dithiolate (Ni-1); 2-trifluoromethyl benzyl cyanide dithiolate (Ni-2); 3-trifluoromethyl benzyl cyanide dithiolate (Ni-3) and 4-trifluoromethyl benzyl cyanide dithiolate (Ni-4)) have been synthesized and characterized spectroscopically as well as by employing single crystal X-ray diffraction. Single crystal X-ray diffraction analyses for Ni-1 and Ni-3 reveal a distorted square planar geometry around the Ni(II) center satisfied by two sulfur and two phosphorus centers of dithiolate and dppe ligands, respectively. Both Ni-1 and Ni-3 form interesting supramolecular arrays sustained by C–H⋯F, C–S⋯H, C⋯H(Ar), CN⋯H and (Ar)C⋯F intermolecular interactions. These interactions have further been investigated using Hirshfeld surface analysis. These complexes have been used as heterogeneous electrocatalysts for oxygen evolution reaction (OER) studies and the results suggest that the electrocatalytic activity of Ni-1 outperforms the electrocatalytic activities of the other three complexes and it displays an η¹⁰ value of 814 mV and a Tafel slope of 94 mV dec⁻¹. The study unveils the effects of fluoro- and trifluoromethyl substituents and the dihedral angle on the electrocatalytic properties towards the OER of these newly developed complexes.