Structural and antimicrobial studies of coordination compounds of VO(II), Co(II), Ni(II) and Cu(II) with some Schiff bases involving 2-amino-4-chlorophenol

Complexes of tailor-made ligands with life essential metal ions may be an emerging area to answer the problem of multi-drug resistance (MDR). The coordination complexes of VO(II), Co(II), Ni(II) and Cu(II) with the Schiff bases derived from 2-hydroxyacetophenone/2-chlorobenzaldehyde with 2-amino-4-chlorophenol were synthesized and characterized by elemental analysis, molar conductance, electronic spectra, FT-IR, ESR, FAB mass, thermal and magnetic susceptibility measurements. The FAB mass and thermal data show degradation of the complexes. The ligand A (2-hydroxyacetophenone-2amino-4-chlorophenol) behaved as tridentate and ligand B (2-chlorobenzylidene-2-amino-4-chlorophenol) as bidentate, coordinating through O and N donors. The complexes [VO(A)(H2O)]⋅xH2O, [M(A)(H2O)n]⋅xH2O for Co and Ni, [Cu(A)(H2O)] and [VO(B)2]⋅xH2O, [M(B)2(H2O)n] for Co and Cu and [Ni(B)2] exhibited coordination numbers 4, 5 or 6. X-ray powder diffraction data (a = = 11.00417 Å, b = 11.706081 Å and c = 54.46780 Å) showed that [Cu(CACP)2(H2O)2], complex 8, crystallized in the orthorhombic system. The in vitro biological screening effects of the investigated compounds were tested against the bacteria Escherichia coli, Staphylococcus aureus and Streptococcus fecalis and the fungi Aspergillus niger, Trichoderma polysporum and Candida albicans by the serial dilution method. A comparative study of the MIC values of the Schiff base and their [M(B)2(H2O)2] complexes (Co(II), complex 6 and Cu(II), complex 8), indicated that the metal complexes exhibited a higher or lower antimicrobial activity than 2-chlorobenzylidene-2-amino-4-chlorophenol as the free ligand (B).