Synthesis, structural characterization, antimicrobial and DNA binding studies of homoleptic zinc and copper complexes of NO Schiff bases derived from homoveratrylamine

Abstract

Four new homoleptic zinc (1 and 2) and copper (3 and 4) complexes of two Schiff base ligands (L1H and L2H) derived from 2-(3,4-dimethoxyphenyl)ethan-1-amine (5), a dimethyl derivative of dopamine were synthesized. All four complexes were well characterized by elemental analysis, FT-IR and UV–Vis., spectroscopy. Further, the zinc complexes (1 and 2) were characterized by 1H and 13C{1H} NMR spectroscopy while the copper complexes (3 and 4) by single crystal X-ray diffraction. The characterization data of complexes revealed strong coordination via azomethine nitrogen (N) and phenolate oxygen (O) of deprotonated ligands (L1 and L2) as NO donors of composition [Zn/Cu(L1-2)2] (1–4). The CT-DNA binding affinity of complexes 1, 2 and 4 was assessed using electronic absorption titration method which showed avid binding through intercalation mode and the binding constant (Kb) was found in the order of 105–106 M−1. The compounds (1–5) were screened for dose dependent antimicrobial activity by agar well diffusion method against pathogenic antibacterial strains, E. coli, S. aureus and antifungal strain, C. albicans. The compounds showed significant toxicity to these pathogens.