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Hydrogen Bonds in the 1:1 and 2:1 Complexes of 1-Methylquinolinium-3-carboxylate with Mineral Acids Studied by NMR, FTIR and Raman Spectra and DFT Calculations

Barczyński P., Szafran M.

Polish Journal of Chemistry

2009

Vol. 83, nr 5

1061-1074

The 1:1 and 2:1 complexes of 1-methylquinolinium-3-carboxylate (benzotrigonelline), 3QB, with HCl, HBr, HNO3, HClO4 and HBF4 have been synthesized and their FTIR, Raman, 1H and 13C NMR spectra have been analyzed. The 1:1 complexes with HCl and HBr crystallize as monohydrates and water molecule is localized between the betaine and counter-ions (Cl– and Br–). In the complexes with HNO3, HClO4 and HBF4 the anions are connected with the protonated 3QB via O–HźźźX– hydrogen bonds. The 2:1 complexes with HCl, HBr, HNO3 and HClO4 crystallize with one water molecule while with HBF4 as an hydrous. Their FTIR spectra show a broad and intense absorption in the 1500–400 cm–1 region, typical of hydrogen bonds shorter than 2.5 A. The water molecule in the 2:1 complexes, except perchlorate, forms hydrogen bonds with anions. The influence of counter-ions on proton and carbon-13 chemical shifts is very small and comparable with the experimental error. The protonation of 3QB causes deshielding of all protons and most carbons, except C-3, C-9 and COO, which are shielded. The 2:1 complexes in D2O dissociate to the 1:1 complexes and 3QB. Five 1:1 (2–6) and six 2:1 (7–12) complexes have been analyzed by the B3LYP/6-31G(d,p) calculations in order to determine the influence of conformation of COOH groups on hydrogen bond and homoconjugation.

Hydrogen Bonds in the 1:1 and 2:1 Complexes of Trigonelline with Mineral Acids studied by FTIR, 1H and 13 C NMR Spectroscopies

Szafran M., Dega-Szafran Z., Grunwald-Wyspiańska M., Barczyński P., Pankowski M.

Polish Journal of Chemistry

2002

Vol. 76 / nr 9

1191-1197

The 1:1 and 2:1 complexes of trigonelline (TRG) with HBr, HI, HNO3, HClO4 and HBF4 have been synthesized and their FTIR, 1H and 13C NMR spectra were analyzed. The 1:1 complexes are divided into two groups. The first group includes complexes with HBr,HI andHNO3, in which a proton is transferred from the acid to TRG and the anions are bonded with the carboxylic group, COOHźźźX- (1). The second comprises complexes with HClO4 and HBF4, with two molecules of protonated TRG forming dimer, like benzoic acid, and the anions interacting exclusively with the positively charged nitrogen atoms (2). All 2:1 complexes crystallized with one water molecule and their FTIR spectra are of Had4i type iii, characterized by an intense broad (continuum) absorption below 1600 cm-1 typical of a short-strong hydrogen bond (SSHB) with a delocalized proton and a single _C=O band. In these complexes the water molecule interacts electrostatically with one positively charged nitrogen atom and the anions with the second one (3). The water molecule additionally forms a hydrogen bond with Br, I and NO3 ions. The proton and carbon chemical shifts of the complexes in D2O have been determined and discussed.