Bioactive mixed-ligand zinc(II) complexes with 1H-tetrazole-5-acetic acid and oligopyridine derivatives

1H-tetrazole-5-acetic acid is bifunctional ligand that was employed for the synthesis of zinc(II) complexes in the presence of secondary ligands such as oligopyridines (dmphen - 4,7-dimethyl-1,10-phenanthroline, phendione - 1,10-phenanthroline-5,6-dione, phen - 1,10-phenanthroline, dmbipy - 2,2'-bi-4-picoline, bipy - 2,2'-bipyridine). Five new mixed-ligand zinc(II) complexes [Zn(dmphen)L]center dot H2O (1), [Zn(phendione)(H2O)L]center dot 2H(2)O (2), [Zn(phen) L]center dot 0,5H(2)O (3), {[Zn(dmbipy)L]center dot H2O}(n) (4) and [Zn(bipy)L]center dot H2O (5) have been synthesized and characterized by elemental analysis, IR spectroscopy and powder X-ray diffraction. All complexes have shown to possess thermal stability up to 250 degrees C by thermogravimetric analysis, except for complexes 2 and 5, which have been stable up to 200 degrees C. Crystal structures of polymeric complexes {[Zn(dmphen)(H2O)(2)L]center dot 2H(2)O}(n) (1a) and 4 have been determined by single-crystal X-ray diffraction analysis. The effect of the compounds on viability of HepG-2, MCF-7 and MRC-5 cell lines has been investigated. Complex 2 was found to be the most cytotoxic with IC50 values of 6.4 +/- 0.9 mu M for HepG-2 cells and 2.6 +/- 1.1 mu M for MCF-7 cells. The antimicrobial activity of the complexes and ligands has been investigated against E. coli, S. aureus, P. italicum and C. steinii.