New Cu(II) complexes with polydentate chelating Schiff base ligands: Synthesis, structures, characterisations and biochemical activity studies

We have reported herein the synthesis of three new Cu(II) complexes of tri- and tetradentate Schiff base ligands containing N-3 or N-4 donor set along with terminal NNN- or SCN- ligands: [(LCu)-Cu-1(NCS)]ClO4 (1), [(LCu)-Cu-2 (NCS)(2)] (2) and [(LCu)-Cu-3(NNN)]ClO4 (3) [L-1 = NC5H4C (CH3)=N(CH2)(3)N=C(CH3)C5H4N, L-2 = Me2N-(CH2)(3)-N=C(CH3)C5H4N and L-3 = NC5H4CH=N-(CH2)(4)-N=CHC5H4N]. The complexes have been systematically characterised by elemental, spectroscopic and electrochemical techniques. Antimicrobial activities of the Schiff base ligands. and their metal complexes have been studied using the disc diffusion method on the strains of Candida tropicalis and Bacillus megaterium. Structures of all the complexes have been unequivocally established from single crystal X-ray diffraction analyses that show the monomeric units containing a five-coordinated copper center in highly distorted square pyramidal geometry with thiocyanate or azide anion coordinated as terminal ligand. The complexes 1 and 3 crystallise in monoclinic (P2(1)/c) and 2 in triclinic (P-1) space group, respectively.