title: Crystal structures, spectroscopic and theoretical study of novel Schiff bases of 2-(methylthiomethyl)anilines.
abstract: New Schiff bases derived from p-methoxysalicylaldehyde and 2-(methylthiomethyl)anilines (substituted with methyl, methoxy, nitro) were synthesized and characterized by elemental analyses, FT-IR, NMR, electronic spectra and quantum chemical calculations. X-ray crystallography of two compounds showed the solid structures are stabilized by intramolecular and intermolecular H-bonds. The effect of OH⋯N interaction between the phenolic hydrogen and imine nitrogen on the proton and carbon NMR shifts, and the role of CH⋯O and CH⋯S contacts are discussed. The bond lengths and angles, (1)H and (13)C NMR data, E(LUMO-HOMO), dipole moments and polarizability of the compounds were predicted by density functional theory, DFT (B3LYP/6-31G∗∗) method. The experimental geometric parameters and the NMR shifts were compared with the calculated values, which gave good correlations. The electronic effects of aryl ring substituents (methyl, methoxy and nitro) on the properties of the resulting compounds, such as the color, NMR shifts, electronic spectra and the calculated energy band gaps, dipole moments and polarizability are discussed. Increase in electron density shifted the phenolic proton resonance to lower fields. The methoxy-substituted compound has a small dipole moment and subsequent large polarizability value. Highest polarity was indicated by the nitro compound which also showed high polarizability due to its larger size. The energy gaps obtained from E(LUMO-HOMO) calculations suggest these compounds may have applications as organic semiconducting materials.
authors.affiliation: Department of Chemistry and Centre for Chemico- and Biomedicinal Research, Rhodes University, Grahamstown 6140, South Africa. Electronic address: topeolalekan11@yahoo.com.
authors.forename: Temitope E
authors.initials: TE
authors.lastname: Olalekan
authors.affiliation: Department of Chemistry, University of Ibadan, 200285 Oyo State, Nigeria.
authors.forename: Isaiah A
authors.initials: IA
authors.lastname: Adejoro
authors.affiliation: Department of Chemistry, Nelson Mandela Metropolitan University, Port Elizabeth 6001, South Africa.
authors.forename: Bernardus
authors.initials: B
authors.lastname: VanBrecht
authors.affiliation: Department of Chemistry and Centre for Chemico- and Biomedicinal Research, Rhodes University, Grahamstown 6140, South Africa.
authors.forename: Gareth M
authors.initials: GM
authors.lastname: Watkins
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004583:Electrons; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D012545:Schiff Bases / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D000814:Aniline Compounds; D012545:Schiff Bases; C023650:aniline
keywords: 2-(Methylthiomethyl)anilines; Crystal structures; DFT calculations; NMR shifts; Schiff base