Synthesis, characterization, and antimicrobial activity of Cu(II) and Zn(II) complexes with N,N-bis(4-methoxybenzylidene)ethylenediamine or N-(4-methoxybenzylidene)ethylenediamine Schiff base

Seven mononuclear complexes were synthesized by mixing N,N'-bis(4-methoxy benzaldehyde)ethylenediamine (L) or N-(4-methoxybenzylidene)ethylenediamine (L1) and copper or zinc salts. These compounds were characterized by IR, 1H NMR, UV-vis, fluorescence spectroscopy, molar conductimetric, and elemental (CHN) analysis techniques. The crystal structures of the zinc complexes were determined by single crystal X-ray diffraction studies. Crystal data for C18H20I2N2O2Zn: Monoclinic, space group P21/c (no. 14), a = 10.45670(10) Å, b = 13.28610(10) Å, c = 15.43490(10) Å, β = 96.4300(10)°, V = 2130.86(3) Å3, Z = 4, Dcalc = 1.919 g/cm3, 46801 reflections measured (8.51° ≤ 2Θ ≤ 145.92°), 4231 unique (Rint = 0.0565, Rsigma = 0.0185) which were used in all calculations. Crystal data for C18H20Br2N2O2Zn: Monoclinic, space group P21/c (no. 14), a = 10.30071(17) Å, b = 13.00839(18) Å, c = 15.0084(2) Å, β = 97.3057(14) °, V = 1994.74(5) Å3, Z = 4, Dcalc = 1.737 g/cm3, 103282 reflections measured (4.158° ≤ 2Θ ≤ 59.492°), 5360 unique (Rint = 0.0394, Rsigma = 0.0161) which were used in all calculations. Crystal structures show a distorted tetrahedral geometry around the zinc metal. The ligand is bidentate chelating with imine nitrogen atoms. Fluorescence spectroscopy shows a reduction in the fluorescence intensity of the complexes relative to the ligand. This reduction is due to the presence of metal-coordinated halides. The in vitro antimicrobial activities of the ligand and complexes were elaborated by screening them against Gram(+) bacteria (Streptococcus pyogenes), Gram(-) bacteria (Pseudomonas aeruginosa), and a fungus (Candida albicans). All compounds showed weak activity against the tested bacterial and fungal strains.