New heteroleptic Zn(II) complexes of thiosemicarbazone and diimine Co-Ligands: Structural analysis and their biological impacts

A thiosemicarbazone ligand HL appended new Zn(II) complexes [Zn(L)(bpy)] (1) and [Zn(L)(phen)] (2) (where, HL = (2-(3-bromo-5-chloro-2-hydroxybenzylidene)-N-phenylhydrazinecarbothioamidel, bpy = 2, 2'-bipyridine and phen = 1, 10-phenanthroline) have been synthesized and well characterized using conventional spectroscopic techniques viz, H-1 NMR, FTIR and UV-Vis spectra. The crystal structures of complexes 1 and 2 have been determined by single crystal X-ray diffraction studies. Both the complex 1 (tau = 0.5) and 2 (tau = 0.37) possesses square based pyramidally distorted trigonal bipyramidal geometry. The ground state electronic structures of complexes 1 and 2 were investigated by DFT/B3LYP theoretical analysis using 6-311G (d,p) and LANL2DZ basis set level. The superior DNA binding ability of complex 2 has been evaluated using absorption and fluorescence spectral titration studies. Antimicrobial evaluation reveals that complex 2 endowed better screening than HL and complex 1 against both bacterial as well as fungal species. Consequently, complex 2 possesses highest antibacterial screening against Staphylococcus aureus (MIC = 3.0 +/- 0.23 mM) and antifungal screening against Candida albicans (MIC = 6.0 +/- 0.11 mM). Furthermore, the anticancer activity of the ligand HL, complexes 1 and 2 have been examined against the MCF-7 cell line (Human breast cancer cell line) using MTT assay. It is remarkable that complex 2 (12 +/- 0.67 mu M)show highest anticancer activity than HL (25.0 +/- 0.91 mu M) and complex 1 (15 +/- 0.88 mu M) due to the presence of phen ligand moiety. (C) 2017 Elsevier B.V. All rights reserved.