Synthesis and characterization of 1h-imidazo [5, 6-f][1, 10] phenanthroline-2(3h)-thione and its ni (ii) and cu (ii) complexes and their antibcterial activity

Abstract

Heterocyclic compounds are compounds that have a broad spectrum of biological activities. 1,10-phenanthroline derivatives have attracted considerable interest from both synthetic and medicinal chemists. The aim of this study was to synthesize, characterize and evaluate antibacterial activity of 1H-imidazo [5, 6-f][1, 10] phenanthroline-2(3H)-thione and its Ni (II) and Cu (II) complexes. 1H-imidazo [5, 6-f][1, 10] phenanthroline-2(3H)-thione was synthesized by direct reaction of 1, 10- phenanthroline-5.6-dione (PD) and thiourea (TU). The complexes of Ni (II) and Cu (II) with this ligand were prepared by direct reactions of the chloride salts of the metals and ligand (1:2) mole ratios in ethanol. The structures of synthesized ligand and metal complexes were characterized and confirmed by elemental analyses (C, H, N and S), FT-IR, 1 HNMR, 13 C-NMR, Atomic absorption spectroscopy, UV-Vis spectra and molar conductivity measurement. The data from the elemental analysis suggest a good agreement between the calculated and the experimental values for the elements and the IR studies revealed that ligand acted as bidentate through nitrogen atoms in synthesized complexes. The metal complexes were isolated in good yield and are thermally stable. The molar conductivity measurements of the complexes indicates that their electrolytic nature and geometry structure. On the basis of spectral studies an octahedral geometry for Ni (II) complex and distorted octahedral geometry for Cu (II) complex. A comparative antibacterial study test was performed using the disk diffusion method against on two gram positive bacterial (Staphylococcus aureus (ATCC 25923), Bacillus subtillus (ATCC 6633) and two gram negative bacteria (Escherichia coli (ATCC 35218) and pseudomonas aeruginosa (ATCC 27853). Ni (II) complex shows higher bioactivity than Gentamicin against Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 27853) while Cu (II) complex is more bioactive than Ni (II) complex against Bacillus subtilis. The Cu (II) and Ni (II) complexes exhibit higher antibacterial activities than the free ligand.