New ON Schiff bases and their homoleptic Zn, Ni, and Cu complexes - Synthesis, structural characterization and DNA binding studies

Abstract

New Schiff base ligands (L1H, L2H and L3H) and their homoleptic Zn(II) (1, 2 and 3), Ni(II) (4, 5 and 6), and Cu(II) (7, 8 and 9) complexes have been synthesized. The ligands were obtained by the reaction of 2-(3,4-dimethoxyphenyl)ethanamine with 5-chlorosalicylaldehyde, 5-bromosalicylaldehyde and 3-methoxysalicylaldehyde respectively. All these compounds were characterized by CHN analysis, FT-IR and UV–Vis spectroscopy. The structures of ligands and zinc complexes were also confirmed by 1H and 13C{1H} NMR spectroscopy. The molecular structures of L1H, L2H and 6 were determined by single crystal X-ray diffraction studies. In all complexes the monobasic ligands (L1, L2 and L3) act as ON donors by coordinate through azomethine nitrogen and phenolate oxygen to form complexes of composition [M(L1–3)2] (1–9). The crystal structures of L1H, L2H and 6 features CH…π and CH…O types of intermolecular secondary bonding interactions. The calf thymus-DNA binding interaction of ligands and complexes have been assessed by electronic absorption titrations which showed avid binding through intercalative mode and the binding constant (Kb) found in the order of 107M−1.