Synthesis, crystal structure and antibacterial activity of azido complexes of cobalt(III) containing heteroaromatic Schiff bases

Three new Schiff base complexes of cobalt(III) viz. [Co(L1)(N3)]2 (1), [Co(L2)2(N3)2]NO3 (2) and [Co(L3)2(N3)2]ClO4 (3), where H2L1 = N,N'-propane-1,3-diylbis[1-(pyrrol-2-yl)methanimine], L2 = 1-[(thiophen-2-ylmethylidene)amino]propan-2-amine and L3 = 1-[(3-methylthiophen-2-ylmethylidene)amino]propan-2-amine, have been prepared and characterized. The syntheses have been achieved by the reaction of cobalt(II) nitrate or perchlorate with the tetradentate Schiff base (H2L1) or the bidentate ligands L2 and L3 in presence of azide. All the complexes 1-3 have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that all the complexes contain CoN6 chromophore in which the central Co(III) ions adopt distorted octahedral geometry. While 1 is a binuclear end-on bis(μ-azido) complex, both of 2 and 3 are mononuclear with two terminal azide ions disposed in cis positions. Structural studies reveal that weak intermolecular H-bonding or π…π interactions are operative to bind the complex units or the anions in the solid state. The antibacterial activity of all the complexes and their constituent Schiff base ligands has been tested against some Gram(+) and Gram(-) bacteria.