Synthesis, characterization and antimicrobial activity of copper(II) complexes of some ortho-substituted aniline Schiff bases; crystal structure of bis(2-methoxy-6-imino)methylphenol copper(II) complex

Abstract

This study presents the synthesis, characterization and antimicrobial activity of copper(II) complexes of some ortho-substituted aniline Schiff bases (L1–L8). The Schiff bases and their respective copper(II) complexes were characterized by a combination of elemental analysis, infrared and UV/Visible studies. The structures of the ligands were also confirmed from 1H- and 13C-NMR spectral data. The infrared and electronic transition studies showed that the ligands are bidentate coordinating via the imine nitrogen and the phenolic oxygen atoms in a planar configuration. Introduction of aqueous ammonia to the ethanolic solution of L3/L4 and Cu(OAc) 2 .H 2 O aliquot yielded an ammonia-based complex due to the hydrolysis of the imine bond. The crystal structure of the resulting complex indicated a square planar geometry. The copper(II) ion crystallizes in the monoclinic system with a space group of P21/c having a = 10.9309, b = 4.85600, c = 17.7030, a = a = 90 ° and â = 119.658 °. The geometry is slightly distorted from planarity with O1-Cu1-N1 bond angles of 92.19 ° and 87.8 °. The Schiff base ligands and their respective copper(II) complexes were screened for their in vitro antibacterial and antifungal activity against Escherichia  coliATCC ® 8739™*, Staphylococcus aureus subsp. aureus ATCC ® 6538™*, Bacillus subtilis subsp. spizizeniiATCC® 6633™* and Candida albicansATCC ® 2091™*. The o-vanillin-based ligands exhibited higher activity than the salicylaldehyde derivatives which were virtually non-active against the tested organisms. KEYWORDS : o-Vanillin, substituted-aniline, Schiff bases, Cu(II) complexes, antimicrobial activity.