ChemistrySelect, vol.5, no.31, pp.9730-9735, 2020 (SCI-Expanded)
Four Schiff bases, (3/4/2/4)-{[(2-hydroxy-5-methylphenyl)imino]methyl}benzene-1,2/1,3/1,4/1,2-diols (H3L1-H3L4), derived from 2,3/2,4/2,5/3,4-dihydroxybenzaldehydes and 2-amino-4-methylphenol, and their CoCl2, PdCl2, CuCl(2)and ZnCl(2)complexes were synthesized and characterized. The structures of the complexes were suggested on the basis of elemental analysis, TGA, molar conductivity, magnetic moment, FT-IR, UV-vis and NMR spectroscopy. According to the analytical and spectral data, the ligandsH(3)L(1),H(3)L(2)andH(3)L(3)acted as tridentate, giving chelate structures in the complexes, via the C=N nitrogen and two phenolate oxygen atoms whereasH(3)L(4)acted as bidentate. In addition, the crystal structure ofH(3)L(1)was determined by X-ray diffraction. The spectral data show that there is keto-enol tautomerization in the ligands and keto form is dominant inH(3)L(1)andH(3)L(3)while enol form is inH(3)L(2)andH(3)L(4). Antimicrobial activities of the compounds were tested against six bacteria and three fungi. [Zn(H2L1)Cl].4H(2)O showed superior activity toward the fungiC. albicans,C. parapsilosisandC. tropicaliscompared toH(3)L(1)and the other compounds. Strong activity ofH(3)L(1),H(3)L(2)andH(3)L(3)was observed towardS. aureuswhereas they showed weak activity to the other microorganisms.