Novel thiophene-benzothiazole derivative azomethine and amine compounds: Microwave assisted synthesis, spectroscopic characterization, solvent effects on UV–Vis absorption and DFT studies

Abstract

In this study, the novel thiophene-benzothiazole derivative azomethine compounds [(2-((benzo[d]thiazol-2-ylimino)methyl)-4-(thiophen-2-yl)phenol (3a), 2-(((6-methylbenzo[d]thiazol-2-yl)imino)methyl)-4-(thiophen-2-yl)phenol (3b) and 2-(((6-methoxybenzo[d]thiazol-2-yl)imino)methyl)-4-(thiophen-2-yl)phenol (3c)] were successfully synthesized in excellent yields by using conventional heating and microwave assisted synthesis methods. In addition, the new thiophene-benzothiazole derivative amin compounds [(2-((benzo[d]thiazol-2-ylamino)methyl)-4-(thiophen-2-yl)phenol (4a), 2-(((6-methylbenzo[d]thiazol-2-yl)amino)methyl)-4-(thiophen-2-yl)phenol (4b) and 2-(((6-methoxybenzo[d]thiazol-2-yl)amino)methyl)-4-(thiophen-2-yl)phenol (4c)] were obtained in good yields by reduction reaction of 3a-3c. The characterization of all compounds were performed by FTIR, 1H and 13C NMR spectroscopic techniques and elemental analysis. The chemical structure of 3a was also confirmed by single crystal X-ray diffraction method. The effect of solvents with different polarity on electronic absorption behaviors of all compounds was examined in detail. The optimized molecular structures and intramolecular hydrogen bonding, 1H and 13C NMR chemical shift values, UV–Vis spectroscopic parameters, HOMO-LUMO energies, Mulliken (MPA) and natural (NBO) atomic charges, molecular electrostatic potential (MEP) maps and solvent accessible surfaces (SASs) for 3a-3c and 4a-4c were calculated by using DFT/B3LYP/6-311G(2d,p) method. The theoretical results were compared to the experimentally obtained data and all results were found to be compatible.