Elucidating the contribution of solvent on the catecholase activity in a mononuclear Cu(II) system: An experimental and theoretical approach

Abstract A new mononuclear copper(II) complex, [Cu(H2tea)(N3)] (T-2) is synthesized and characterized by crystallographic, spectral and theoretical studies. The synthesized complex adopts penta coordinate tbp geometry around the Cu(II) center. The ligand (triethanolamine, H3tea) binds the metal as monoanionic species (H2tea‒). Supporting ligand (N3‒) satisfies the coordination geometry through monodentate mode. Several non-covalent interactions (such as O—H and N—H) integrate the whole framework and these interactions are well quantified with Hirshfeld surface analysis. The present complex exhibited excellent catecholase activity (solvent dependent) with Kcat(MeOH) = 903.6 h‒1. UV-Visible spectral study indicated a notable effect of solvent nature on the catecholase activity of Cu(II) complex which is attributable to the coordinating capability of the diverse solvents used. The maximum catalytic efficiency is observed in MeOH and then tailed by MeCN for T-2; while no such activity in DMSO was observed. The catecholase activity of T-2 is well corroborated by DFT calculations which reveal that higher difference in charge contributions between HOMOs and LUMOs along with metal and ligands of copper complex is the factor to the enhanced catecholase activity. The present work deals with the determination of structure-activity interrelation of mononuclear coordination compounds.