The crystal structure and characterization of a co-product in the synthesis of a Schiff base give evidence of its zwitterionic nature in the solid state

During the synthesis of the Schiff base 2-methoxy-6-{[(tiophen-2-methyl)imino]methyl}phenol ( o -HVATPNH2), a co-product was isolated and characterized. The crystal structure of this molecule, 4,10-dimethoxy-13-(thiophen-2-ylmethyl)-6,12-dihydro-6,12-epiminodibenzo[ b , f ][1,5]dioxocane, namely ( o...

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Bibliographic Details
Published in:New journal of chemistry 2022-02, Vol.46 (7), p.3130-3139
Main Authors: Rodríguez, M. R., Espino, G. A., Piro, O. E., Echeverría, G. A., Parajón-Costa, B. S., González-Baró, A. C.
Format: Article
Language:English
Subjects:
Chirality
Crystal structure
Crystallography
Imines
Molecular structure
Protons
Reaction mechanisms
Solid state
Structural analysis
Synthesis
Unit cell
Zwitterions
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Summary:During the synthesis of the Schiff base 2-methoxy-6-{[(tiophen-2-methyl)imino]methyl}phenol ( o -HVATPNH2), a co-product was isolated and characterized. The crystal structure of this molecule, 4,10-dimethoxy-13-(thiophen-2-ylmethyl)-6,12-dihydro-6,12-epiminodibenzo[ b , f ][1,5]dioxocane, namely ( o -VA) 2 TPNH2 for short, was determined by X-ray diffraction methods. The chiral compound crystallizes as a racemate in the triclinic space group P 1̄ with 2 molecules per unit cell. The ( o -VA) 2 molecular fragment in ( o -VA) 2 TPNH2 shows a non-crystallographic two-fold axis that enables the two molecular stereogenic centers to have the same chirality. The formation reaction mechanism for ( o -VA) 2 TPNH2 is proposed and the structural properties of the Schiff base o -HVATPNH2 were revised. Evidence of the presence of the zwitterionic form of a Schiff base in the solid state was found.
ISSN:1144-0546
1369-9261
DOI:10.1039/D1NJ04537G