Synthesis, structure and biological properties of the zinc(II) complexes with 5-(4-chlorophenyl)-1H-tetrazole and oligopyridine derivatives

In this work, we present six new zinc(II) complexes with the general formulas [Zn2(oligopyridine)2L4] and [Zn (oligopyridine)2L2], where L- = 5-(4-chlorophenyl)-1H-tetrazolate anion, and oligopyridine = 1,10-phenanthroline or 2,2 '-bipyridine derivatives (dmphen - 4,7-dimethyl-1,10-phenanthroline, phen - 1,10 phenanthroline, dmbipy - 2,2 '-bi-4-picoline, bipy - 2,2 '-bipyridine), which have been synthesized with high yield and characterized by IR spectroscopy, elemental, thermogravimetric, single crystal and powder X-ray analyses. A distorted square-pyramidal and octahedral geometry of zinc(II) ion have been demonstrated by single crystal Xray diffraction analysis. The tetrazolate ligand exhibits two types of coordination: monodentate, and bidentatebridging via the N(2), N(3) or N(1), N(2) atoms. The behavior of all complexes in solution has been investigated by UV-Vis and the 1H, 13C NMR spectroscopy, conductometry, and mass spectrometry. The antimicrobial study of the compounds has been carried out against E. coli, St. aureus, P. italicum, and C. steinii, and [Zn2(dmbipy)2L4] has been shown to possess significant protistocidal properties. According to the cytotoxicity study,all complexes don't have cytotoxic properties in 1-100 mu M concentration range against tumor human cell lines (larynx carcinoma Hep2, hepatocellular carcinoma HepG2 and breast adenocarcinoma MCF-7) with the exception of complex 5 which has displayed significant cytotoxic effect (LC50 = 19.8 +/- 2.4 mu M) against Hep2 cells. However, obtained compounds have a pronounced cytostatic effect on all tumor cell lines.