Synthesis, characterization and anti-fungal activity of Cu(II), Ni(II) and Cd(II) complexes of 5-Bromosalicylidene -2-Nitroaniline

Abstract

The synthesis, characterization and the antifungal activities of some selected transition metal complexes (Cu²⁺, Ni²⁺ and Cd²⁺) were carried out. The salts of these metals were complexed with the Schiff base obtained from 5-Bromosalicylaldehyde and 2-Nitroaniline yielding the compound; 5 – Bromosalicylidene – 2- nitroaniline complexes of Cu(II), Ni(II) and Cd(II). The new compounds were characterized on the basis of physicochemical properties, spectral analysis (FTIR, UV-visible), molar conductance, magnetic susceptibility and PXRD analysis. The metal complexes exhibited various range of colours such as dark green, dark brown and milk white with the Schiff base being dark yellow; giving yields of 69.2, 56.7 and 62.5 % respectively; high melting points (126, 320 and 128 ⁰C) and molar conductance values (591, 620 and 631 Ω^-1cm²mol^-1) for the Cu(II), Ni(II) and Cd(II) complexes respectively. The synthesized complexes were soluble in ethanol, methanol, DMSO, acetone, slightly soluble in DMF but insoluble in water and n-Hexane. The IR spectra of the synthesized complexes showed bands characteristic of azomethine (C=N) vibration mode as well as evidence of azomethine carbons, protons and formation of the M-N, M-O, O-H bonds. The spectral study also showed the complexes obtained as monomeric structures and the central metal moieties are four-coordinated, with tetrahedral geometry, except for the Cu(II) and Ni(II) complexes, which had square planar geometries. The complexes formed were of the general formula ML where L is the ligand and M is the respective metal ions. The PXRD studies revealed average crystallite size of 34.75, 69.75 and 39.11; the FWHM value of 0.23, 0.13 and 0.21; the hkl value of 101and 201. The antimicrobial activities of the ligand and its complexes were tested using Agar-well diffusion techniques for zone of inhibition while Agar dilution techniques were used for minimum inhibitory concentration and fungicidal concentration. The metal complexes of Schiff base showed broad spectrum antifungal activity against certain range of fungi; A. flavus, A. fumigates, A. niger, R. stolonifer, R. bataicola and C. albicans. The results showed that the complexes exhibited a higher fungicidal property than the ligand.