Synthesis, crystal structure and antibacterial activities of mixed ligand copper(II) and cobalt(II) complexes of a NNS Schiff base

Abstract Two new copper(II) complexes of different nuclearities, viz. mononuclear [CuL 2 (H 2 O)](ClO 4 ) 2 ( 1 ), binuclear [Cu 2 L 2 (NCS) 2 (NO 3 ) 2 ] ( 2 ) and a mononuclear cobalt(II) complex, [CoL 2 (NCS) 2 ] ( 3 ), where HL = 2-{[pyridin-2-ylmethylidene]amino}benzenethiol, a tridentate Schiff base derived from 2-aminothiophenol and pyridine-2-al have been prepared. The complexes have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1 is a mononuclear copper(II) complex with distorted square pyramidal geometry. But, 2 is a thiocyanato-bridged binuclear species in which each copper(II) ion adopts an irregular octahedral geometry containing chelating nitro groups. Complex 3 is comprised of a mononuclear octahedral unit containing two thiocyanato groups in cis positions around the central cobalt(II) ion. The complex units in 1 – 3 are held together by H-bonding, π⋯π or O⋯π interactions to develop supramolecular network in their respective solid states. The antibacterial activity of all the complexes along with the constituent Schiff base ligand has been evaluated against some Gram(+) and Gram(−) bacteria.