Synthesis, characterization and biological study of Cu(II) complexes of aminopyridine and (aminomethyl)pyridine Schiff bases

Abstract

The synthesis, characterization and antimicrobial activity determination of some aminopyridine- and (aminomethyl)pyridine–salicylaldimine copper(II) complexes were realized. The ligands, L1–L6, were prepared by condensing salicylaldehyde and o-vanillin with 2- and 3-amino- and (aminomethyl)pyridine, respectively. The complexes were characterized by micro-analytical, electronic, infrared and conductivity data. The structures of the Schiff base ligands were further confirmed from 1H- and 13C-NMR spectral data. This study established that salicylaldimine ligands could coordinate as neutral species via the imine-N and the undeprotonated phenolic-O. The complexes have the molecular formula: [CuLCl], [Cu(LH)2Cl2]·xH2O or [Cu(LH)Cl(H2O)]Cl. The X-ray crystal structure of [CuL6Cl] indicated a square planar geometry with the Schiff base ligand coordinated to the Cu(II) ion as a tridentate monobasic, N2O, ligand. The crystals crystallized in a monoclinic system with P21/c space group. All the ligands and their Cu(II) complexes were screened for their antimicrobial activity against Staphylococcus aureus subsp. aureus ATCC® 6538™*, Bacillus subtillis subsp. spizizenii ATCC® 6633™*, Escherichia coli ATCC® 8739™* and Candida albicans ATCC® 2091™* using agar diffusion and broth dilution techniques. The presence of the methoxyl group enhanced the antimicrobial activity of the salicylaldimine Schiff base ligands.

Keywords

• salicylaldimine
• crystal structure
• square planar
• Schiff bases
• in vitro
• chelates