Spectroscopic characterization, crystallographic elucidation and DFT investigation of 5-fluoro-6-(4-methylpiperazin-1-yl)benzo[d]thiazol-2-amine

The spectroscopic features and molecular structure of 5-fluoro-6-(4-methylpiperazin-1-yl)benzo[d]thiazol-2-amine (2-ABT) have been determined. Single-crystal X-ray analysis and vibrational spectroscopy have revealed the existence of 2-ABT in the amino tautomeric form in the solid state. Properties o...

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Bibliographic Details
Published in:Journal of molecular structure 2019-01, Vol.1176, p.614-621
Main Authors: Al-Harthy, Thuraya S., Shongwe, Musa S., Husband, John, Stoll, Raphael, Merz, Klaus, Abdel-Jalil, Raid J.
Format: Article
Language:English
Subjects:
2-aminobenzothiazole
Amino-imino tautomer
DFT calculations
H-bonding interactions
Single-crystal X-ray
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Summary:The spectroscopic features and molecular structure of 5-fluoro-6-(4-methylpiperazin-1-yl)benzo[d]thiazol-2-amine (2-ABT) have been determined. Single-crystal X-ray analysis and vibrational spectroscopy have revealed the existence of 2-ABT in the amino tautomeric form in the solid state. Properties of 2-ABT in solution have been investigated using 1H and 13C NMR spectroscopy along with electronic absorption spectroscopy. The experimental data are complemented by DFT and TD-DFT calculations at the B3LYP/6–311 + g(2d,p) level. TD-DTF-predicted spectroscopic and structural properties for both amino and imino tautomers of 2-ABT are compared with the measured data; no strong evidence for the presence of the imino tautomer is found within the experimental data. Calculated energy differences between the tautomers strongly favour the amino tautomer over the other. Indeed, X-ray crystallography has unequivocally shown the amino tautomer which co-crystallized with one water molecule in the orthorhombic space group Pnna. Analysis of the crystal packing reveals an interesting structural motif which comprises an assemblage of the 2-ABT molecules through π···π stacking interactions. Furthermore, there exist hydrogen-bonding interactions involving the lattice solvent and the amino group along with the benzothiazole nitrogen atom. [Display omitted] •Amino (CNH2)–imino (–CNH) tautomerism.•Spectroscopy and X-ray structure determination.•Density functional and time-dependent DFT calculations.
ISSN:0022-2860
1872-8014
DOI:10.1016/j.molstruc.2018.08.080