Synthesis, characterization and DFT studies of Schiff bases of p-methoxysalicylaldehyde

ABSTRACT. Five new Schiff bases synthesized by the reaction between 2-(methylthio)aniline derivatives and p-methoxysalicylaldehyde are presented as  MtH-1 (R = H), MtH-2 (R = CH3), MtH-3 (R = OCH3), MtH-4 (R = Cl) and MtH-5 (R = Br). They were characterized by CHNS analyses, NMR (1H, 13C, DEPT135, COSY and HSQC), FTIR and UV-Vis spectroscopic techniques. FT-IR, elemental analyses and NMR data supported the formation of the Schiff bases, with the chemical shifts of azomethine and phenol protons showing sensitivity to ring substitution. The crystal structure of MtH-1 featured the alignment of the phenyl rings to each other and to the C=N group with dihedral angles >170o. The DFT calculations corroborated the bond lengths and angles of MtH-1. The HOMO-LUMO energies, dipole moments and other reactivity parameters were calculated. The methyl-substituted MtH-2 was the least polar of the compounds. With calculated energy band gaps of almost 4 eV, the compounds may have applications in the semiconductors field.   KEY WORDS: Schiff bases, p-methoxysalicylaldehyde, Crystal structure, Spectroscopic properties, DFT calculations   Bull. Chem. Soc. Ethiop. 2023, 37(3), 675-688.                                                          DOI: https://dx.doi.org/10.4314/bcse.v37i3.11