Research Article SN -Donor Methylthioanilines and Copper(II) Complexes: Synthesis, Spectral Properties, and In Vitro Antimicrobial Activity Temitope E. Olalekan , 1,2 Adeniyi S. Ogunlaja, 3 and Gareth M. Watkins 1 1 Department of Chemistry, Rhodes University, P.O. Box 90, Grahamstown 6140, South Africa 2 Department of Chemistry, University of Ibadan, Ibadan 200285, Nigeria 3 Department of Chemistry, Nelson Mandela University, Port Elizabeth 6001, South Africa Correspondence should be addressed to Temitope E. Olalekan; topeolalekan11@yahoo.com Received 12 November 2018; Revised 24 January 2019; Accepted 5 February 2019; Published 3 March 2019 Academic Editor: Bartolo Gabriele Copyright © 2019 Temitope E. Olalekan et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Methylthioanilines, a series of sulfur-nitrogen donor ligands substituted with OCH 3 , CH 3 , Cl, and Br, and their copper(II) complexes have been synthesized and characterized by 1 H and 13 C NMR, elemental analysis, FTIR, UV-Vis and EPR spectra, molar conductance, and magnetic susceptibility measurements. Te NMR spectra of the ligands revealed that the para/ortho protons and para carbon were sensitive to the electronic efect of substituents. Te CHNS analysis presented CuLCl 2 (L = OCH 3 , CH 3 , Cl) and CuL 2 Cl 2 (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. Te electronic spectra have suggested square planar and octahedral geometries for these complexes. Te EPR spectra demonstrated that the solid state copper(II) complexes possess d x 2 –y 2 orbital ground state and g ‖ > g ⊥ > 2.0023 in a tetragonal environment. Te compounds were evaluated for in vitro antimicrobial activity against S. aureus, B. subtilis, E. coli, and C. albicans. Te copper complexes showed higher activity than the parent ligands against S. aureus and B. subtilis; the electron-donating OCH 3 and CH 3 derivatives were more active than the withdrawing Br- and Cl-substituted compounds. 1. Introduction Tiomethylated anilines belong to a class of nitrogen- sulfur (SN) donor groups. Tey fnd application in prepa- ration of sulfoxides [1] which are desulfurized to generate methylated anilines [2] and as starting materials [3] for deriving aminobenzaldehydes which are also useful pre- cursors to many important heterocyclics. By coupling 2- (methylthioaniline) with another suitable aromatic polymer, a suitable chelating resin [4] has been derived for use in preconcentration of metal ions such as Cd, Hg, Ni, Co, Cu, and Zn for analytical purposes. Substituted 2- (methylthio)anilines were synthesized from the reaction of corresponding anilines with aliphatic disulfdes in the pres- ence of Lewis acid catalysts, particularly aluminum chloride and copper iodide at high temperatures of >100 ∘ C; mixtures of ortho- and para- substituted methylthiolated products resulted [5]. A two-pot synthetic route can also be used to generate substituted 2-(methylthio)anilines. 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]. Te biological relevance of Cu(I)/Cu(II) in living systems includes their presence as cuproproteins to transport molec- ular oxygen and acts as good catalysts in related oxidation- reduction processes. Substituted 6-(methylthio)aniline lig- ands are potential SN bidentate ligands of which bioactiv- ity has not been investigated. Te 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. Hindawi Heteroatom Chemistry Volume 2019, Article ID 9203435, 7 pages https://doi.org/10.1155/2019/9203435