Synthesis, Spectral Characterization, Density Functional Theory Studies and Antidiabetic Activities of Copper(II) Complexes of Schiff Bases Derived from N-Benzoyl Glycylhydrazide

Two new Schiff bases, (E)-N-(2-(2-(2-hydroxy-3-methoxybenzylidene)hydrazineyl)-2-oxyethyl)benzylidene)hydrazineyl)-2-oxyethyl)-benzamide (H2L1), (E)-N-(2-((2-hydroxynapthalen-1-yl)methylene)hydrazineyl)-2-oxyethyl)benzamide (H2L2) and their Cu(II) complexes were synthesized and characterized by elemental analyses, molar conductance, thermal analysis, magnetic susceptibility, UV-Vis, IR, EPR and mass spectroscopic data. Formation of Cu(II) complexes having 1:1 metal: ligand stoichiometry was ascertained from the elemental and thermogravemetric analyses. The observed magnetic moment is consistent with the expected value for Cu(II) (d9) complexes, which typically exhibit one unpaired electron. Spectral and DFT studies suggest pentacoordinated geometries for the complexes in which the ligands act as a tridentate species bonding through the carbonyl-O, azomethine-N and phenolate/phenolic-O. The molecular geometries of the complexes were thoroughly optimized using the Global Hybrid Minnesota functional M06, with the Pople 6-31+G(d,p) basis set for oxygen and nitrogen and the Def2-SVP basis set for hydrogen, carbon and heavy transition metal copper atom in the DFT calculations to improve the balance between accuracy and computational cost. The antidiabetic properties of the ligands and their Cu(II) complexes were investigated, revealing that the complexes exhibited significant enzyme inhibition activity.