Synthesis, characterization, luminescent properties and biological activities of zinc complexes with bidentate azomethine Schiff-base ligands

Abstract

A series of zinc complexes with a bidentate azomethine Schiff base ligands derived from 2-tosylaminobenzaldehyde, 2-hydroxy-, 2-hydroxy-5-methoxybenzaldehydes, 2-hydroxynaphthaldehyde and 3,4-dimethoxyphenylethylamine were synthesized by chemical and electrochemical methods. All compounds were characterized on the basis of C, H, N elemental analysis, FT-IR, 1H NMR, UV-vis and photoluminescence studies. The local atomic structures of complexes were determined from analysis of EXAFS and XANES of Zn K-edges. The molecular structure of bis{2-[(E)-2-(3,4-dimethoxyphenyl)ethyliminomethyl]-4-methoxyphenol}zinc(II) was determined by X-ray single-crystal diffraction. The fluorescence spectra show that these complexes in DMSO solutions at room temperature emit bright blue and green luminescence at 428–497 nm. The assignment and the nature of the bands in experimental UV–Vis spectra of complexes were analyzed using time-dependent (TD) DFT calculations. The azomethines and complexes of zinc have been screened for their antibacterial, protistocidal, and fungistatic activities against Penicillium italicum, Colpoda steinii, Escherichia coli 078 and Staphylococcus aureus P-209, and the results are compared with the activity of sulfadimethoxine, toltrazuril and fundazol.