Spectroscopic and structural elucidation of 4-dimethylaminopyridine and its hydrogensquarate
A distortion of the aromatic character and stabilization of the imino-form as a result of the protonation of 4-dimethylaminopyridine was established by IR-, UV- and 1H NMR-spectral analysis of 4-diaminopyridinium hydrogensquarate. Quantum chemical calculations were carried out at MP2 and B3LYP level...
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Veröffentlicht in: | Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2008-11, Vol.71 (2), p.695-702 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | A distortion of the aromatic character and stabilization of the imino-form as a result of the protonation of 4-dimethylaminopyridine was established by IR-, UV- and
1H NMR-spectral analysis of 4-diaminopyridinium hydrogensquarate. Quantum chemical calculations were carried out at MP2 and B3LYP levels of theory and a 6-311++G** basis set with a view to determining the changes in geometrical parameters and IR-spectroscopic characteristics resulting from N
py protonation. Linear-dichroic IR-spectroscopy coupled with the orientation techniques of solid samples as liquid crystal suspensions and melted solid polycrystalline films was applied for the identification of the IR-bands, characteristic for the structural fragments of the neutral and imino-form of the pyridine derivative. The spectral results were compared with the structure, obtained by a single crystal X-ray analysis. The salt contains dimmers of hydrogensquarate anions and N
py protonated cations of which the former are stabilized by strong intermolecular OH…O interactions (2.552
Å and 143.1(2)°). The 4-diaminopyridinium cation interacts with the anion through moderate NH…O bonds (2.729
Å and 165.0(0)°). Individual cations are π–π stacked with their neighbors at a distance of 3.406
Å. |
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ISSN: | 1386-1425 |
DOI: | 10.1016/j.saa.2008.01.033 |