Abstract
Methylthioanilines, a series of sulfur-nitrogen donor ligands substituted with OCH3, CH3, Cl, and Br, and their copper(II) complexes have been synthesized and characterized by 1H and 13C NMR, elemental analysis, FTIR, UV-Vis and EPR spectra, molar conductance, and magnetic susceptibility measurements. The NMR spectra of the ligands revealed that the para/ortho protons and para carbon were sensitive to the electronic effect of substituents. The CHNS analysis presented CuLCl2 (L = OCH3, CH3, Cl) and CuL2Cl2 (L = Br) stoichiometries for the copper complexes. FTIR spectra showed that the bidentate ligands were coordinated to the copper ion through their nitrogen and sulfur atoms. The electronic spectra have suggested square planar and octahedral geometries for these complexes. The EPR spectra demonstrated that the solid state copper(II) complexes possess dx2–y2 orbital ground state and g∥ > g⊥ > 2.0023 in a tetragonal environment. The compounds were evaluated for in vitro antimicrobial activity against S. aureus, B. subtilis, E. coli, and C. albicans. The copper complexes showed higher activity than the parent ligands against S. aureus and B. subtilis; the electron-donating OCH3 and CH3 derivatives were more active than the withdrawing Br- and Cl-substituted compounds.
Highlights
Thiomethylated anilines belong to a class of nitrogensulfur (SN) donor groups
Substituted 2(methylthio)anilines were synthesized from the reaction of corresponding anilines with aliphatic disulfides in the presence of Lewis acid catalysts, aluminum chloride and copper iodide at high temperatures of >100∘C; mixtures of ortho- and para- substituted methylthiolated products resulted [5]
The synthesis, NMR, FTIR, UV/Vis, electron paramagnetic resonance (EPR), molar conductance, magnetic measurements, and in vitro antimicrobial studies of ortho-substituted-6(methylthio)anilines and their copper(II) complexes are reported in this study
Summary
Thiomethylated anilines belong to a class of nitrogensulfur (SN) donor groups. They find application in preparation of sulfoxides [1] which are desulfurized to generate methylated anilines [2] and as starting materials [3] for deriving aminobenzaldehydes which are useful precursors to many important heterocyclics. Substituted 2(methylthio)anilines were synthesized from the reaction of corresponding anilines with aliphatic disulfides in the presence of Lewis acid catalysts, aluminum chloride and copper iodide at high temperatures of >100∘C; mixtures of ortho- and para- substituted methylthiolated products resulted [5]. By alkaline hydrolysis of the appropriate 2-aminobenzothiazoles at a high temperature and subsequent methylation with methyl iodide, the crude substituted 2-(methylthio)anilines were derived [6]. The synthesis, NMR, FTIR, UV/Vis, EPR, molar conductance, magnetic measurements, and in vitro antimicrobial studies of ortho-substituted-6(methylthio)anilines and their copper(II) complexes are reported in this study
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