Spectroscopic and structural investigation of 2,5-dicarboxy-1-methylpyridinium inner salt

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• 作者：P. Barczy艅ski ; A. Komasa ; A. Katrusiak ; Z. Dega-Szafran ; 艁. Nowaczyk ; M. Ratajczak-Sitarz ; M. Szafran
• 关键词：2 ; 5-Dicarboxy-1-methylpyridinium inner salt ; X-ray diffraction ; FTIR and NMR spectra ; DFT calculations ; Hydrogen bonds
• 刊名：Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
• 出版年：5 March, 2014
• 年：2014
• 卷：121
• 期：Complete
• 页码：586-595
• 全文大小：981 K

文摘

The structure of 2,5-dicarboxy-1-methylpyridinium inner salt (1), has been studied by X-ray diffraction, B3LYP/6-311G(d,p) calculations, FTIR, Raman and NMR spectroscopy. The molecules are linked by short intermolecular and asymmetric OH鈰疧 hydrogen bonds of 2.486(2) 脜 between carboxyl and carboxylate groups of neighboring molecules into infinite chains. The hydrogen bonds in the molecules optimized by the B3LYP/6-311G(d,p) approach in trimer (2) and dimer (3) are slightly longer than in the crystal. The FTIR spectrum of the investigated inner salt is dominated by a broad and intense absorption in the 1500-800 cm^鈭? region attributed to the 谓_as(OHO) and 纬(OHO) vibrations of the strong hydrogen bond. In the Raman spectrum the broad absorption is absent. Linear correlations, m>未m>_exp = m>am> + m>b 蟽m>_calc between the experimental ¹H and ¹³C NMR chemical shifts (m>未m>_exp) of the investigated inner salt in D₂O and the calculated magnetic isotropic shielding constants (m>蟽m>_calc) for the optimized monomer (4a) solvated in water are reported. The pm>Km>_a value for 1 of 2.31 卤 0.02 was determined by the potentiometric titration.