Synthesis, Characterization and Crystal Structures of Zinc(II) and Cobalt(III) Complexes Derived from Tridentate NNO- and NON-Schiff Bases with Antibacterial Activities

Two new polynuclear zinc complexes [Zn2Br2 (L-1)(2) ] (1) and [Zn(mu(1,5)-dca)L-2](n) (2), and two new mononuclear cobalt(III) complexes [(CoLN3)-N-1 (Brsal)] (3) and [CoL2 (HL2)] (4), where L-1 = 5-bromo-2-(((2-dimethylamino)ethyl)imino)methyl) phenolate, L-2 = 5-bromo-2-(((2-hydroxyethyl)imino)methyl)phenolate, dca = dicyanoamide, Brsal = 5-bromo-2-formyl-phenolate, have been synthesized and characterized. The complexes were characterized by elemental analyses, IR, UV-Vis spectra, molar conductivity, and single crystal X-ray diffraction. X-ray analysis indicates that the Zn atoms in complex 1 are in distorted square pyramidal coordination, the Zn atoms in complex 2 are in distorted trigonal bipyramidal coordination, and the Co atoms in complexes 3 and 4 are in octahedral coordination. The molecules of the complexes are stacked through pi...pi interactions and hydrogen bonds. The complexes were assayed for antibacterial activities against three Gram-positive bacterial strains (B. subtilis, S. aureus, and St. faecalis) and three Gram-negative bacterial strains (E. coli, P. aeruginosa, and E. cloacae) by MTT method.