Binuclear Zn(II) Schiff base complexes: Synthesis, spectral characterization, theoretical studies and antimicrobial investigations

Abstract Binuclear zinc(II) Schiff base complexes were synthesized through the reaction of ONNO tetradentate Schiff base ligands derived from the condensation of 2,2-dimethyl-1,3-propanediamine and 5-chlorosalicylaldehyde or 5-bromosalicylaldehyde with zinc acetylacetonate salt. The structures of synthesized products were explored spectroscopically through the FT-IR, 1H NMR and elemental analysis. Structural analysis of the complexes revealed that the compound is a centrosymmetric dimer in which the five coordinated Zn(II) atoms are linked to the opposite metal center by making μ-phenoxo bridges through one of the phenolic oxygen atoms of Schiff base ligands. The nature and types of non-covalent interactions present among the sample molecules were also investigated by using the quantum theory of atoms in molecules and non-covalent interactions calculations. The theoretical calculations, performed by density functional theory using the B3LYP/Def2-TZVP level of theory, direct that the intended outcomes are in compliance with the actual consequences. Furthermore, from antimicrobial screenings it was revealed that the zinc complexes are more active as compared to the ligands.