Synthesis, crystal structure and antibacterial activity of manganese(III) and cobalt(III) complexes containing pentadentate Schiff bases of a common amine and thiocyanate

Four new mononuclear Schiff base manganese(III) and cobalt(III) complexes viz. [Mn(L-1)(NCS)] (1), [Mn(L-2)(NCS)] (2), [Co(L-3)(NCS)] (3), and [Co(L-4)(NCS)]center dot 0.5CH(3)OH center dot 0.5H(2)O (4), containing thiocyanate as a common pseudohalide ion are reported. The pentadentate Schiff base ligands H2L1, H2L2, H2L3, and H2L4 were obtained by the condensation of substituted salicylaldehydes with N-(3-aminopropyl)-N-methylpropane-1,3-diamine. The syntheses of the complexes have been achieved by the reaction of manganese(II) perchlorate or cobalt(II) perchlorate with the respective Schiff bases in the presence of thiocyanate in methanol medium. Complexes 1-4 have been characterized by microanalytical, spectroscopic, single-crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1-4 adopt nearly similar structures containing the MN4O2 (M = Mn, Co) chromophore in which each central M(III) ion adopts a distorted octahedral geometry. Weak intermolecular H-bonding interactions are operative in these complexes to bind the molecular units. The antibacterial activity of 1-4 and their constituent Schiff bases has been tested against some common bacteria.