New copper(II) complexes with benzimidazole and benzoxazole heterocyclic ligands: synthesis, spectral characterization, FMO, MEP, NBO, and DFT study

3-Ethoxy salicylaldehyde on reaction with 1,2-phenylenediamine and 2-aminophenol yielded heterocyclic ligands (HLBIZ and HLBOZ) under ultrasonic irradiation in ethanol solvent. The reaction of these ligands with copper(II) acetate monohydrate salt led to the related Cu(L)2 complexes in methanol solvent. FT-IR, 1H 13C NMR, and elemental analysis were used to investigate the structures of the synthesized ligands, while the copper(II) complexes were characterized by CHN analysis and FT-IR spectroscopy. The imino nitrogens and phenolic oxygens are involved in the coordination of the ligands to the Cu^2+ ions to generate the complex. The parameters estimated by DFT at the B3LYP/Def2-TZVP level of theory show that the theoretical values are consistent with the experimental findings.