Synthesis, characterization, cytotoxicity and antimicrobial activity of copper complexes of N-imine pendant derivatives of 2-(methylthio)aniline

Abstract

NS-containing ligands with the 2-thioaniline motif and imine functional group linked phenyl, 2-pyridyl and 2-thienyl pendants were synthesized by imine condensation reactions with corresponding aldehydes. 2-(methylthio)-N-(2-thienylmethylene)-benzenamine is a new compound characterized by NMR, FTIR and UV–vis. Single crystal X-ray crystallographic data was obtained for all three ligands. The corresponding Cu(I) complexes were obtained by addition of CuBr in toluene/acetonitrile solutions affording the bis-bidentate NS- and SNS-complexes. Aerobic oxidation of one compound, the Cu(I) complex of 2-(methylthio)-N-(2-pyridylmethylene)-benzenamine, afforded the corresponding Cu(II) complex which was characterized by single crystal X-ray crystallography and presented a pentacoordinated CuBr2 adduct of 2-(methylthio)-N-(2-pyridylmethylene)-benzenamine with a distorted square pyramidal coordination environment. Free ligands and the Cu complexes were screened for antimicrobial activity and 2-(methylthio)-N-(2-pyridylmethylene)-benzenamine copper(II) dibromide showed activity against B. cereus and S. aureus. The cytotoxicity of ligands and Cu complexes on mammalian cell cultures was assessed by the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay on mouse macrophages cell line (J774.A1) and human breast cancer cell line (MCF7). The free NS-ligands showed good biocompatibility with both cell lines. Cu(I) and Cu(II) complexes showed significant effects on cell viability with dose-response dependency.