Synthesis, Characterization, Molecular Modeling and Preliminary Biochemical Evaluation of New Copper (II) Mixed-Ligand Complexes

Three new Cu(II) mixed-ligand complexes of the type [Cu(primary ligand)(secondary co-ligand)], were synthesized, characterized and preliminary tested for their biochemical activities. The primary ligand (HL) was derived from condensation of p-toluidine with 2-hydroxy-naphthalhyde. Three different N-heterocyclic compounds, 8-hydroxy-quinoline (HQ), 2-(1H-benzimidazol-2-yl)phenol (HB), and 2-(4,5-diphenyl-1H-imidazol-2-yl)phenol (HI), were used as secondary co-ligands. Inhibitory capacity of the synthesized compounds were screened against the growth of pathogenic bacteria [E. coli (G(-)) and B. cereus (G(+))] and fungi (A. fumigatus), in terms of inhibition zone (IZ, mm), and minimum inhibitory concentration (MIC, mu g/mL) using the disc diffusion method. Furthermore, the complexes were tested for their phenoxazinone synthase-like activity in terms of K-cat. Density functional theory (DFT) calculations based on B3LYP with LanL2DZ level of theory were performed to prove the proposed geometry of the complexes as well as evaluate the electronic parameters responsible for their reactivity. Structure activity relationship formula was derived by correlating the experimental data (MIC or K-cat) with the calculated electronic parameters. (C) 2020 Elsevier B.V. All rights reserved.