Structure of 3-aminopyridine betaine hydrochloride studied by X-ray diffraction, DFT calculations, FTIR and NMR spectroscopy

The structure of 3-aminopyridine betaine hydrochloride (1-carboxymethyl-3-aminopyridinium chloride), 3-NH2PBH·Cl, has been studied by X-ray diffraction, B3LYP/6-311G(d,p) calculations, FTIR and NMR spectra. The compound crystallized in monoclinic, space group P21/c in the crystal, the Cl− anion is connected with protonated betaine via the hydrogen bond O-H⋯Cl of 2.946(3) Å. Both protons of the NH2 group are engaged in hydrogen bonds with the neighboring molecules: N(2)–H(2B)⋯O(2) of 2.905(6) Å and N(2)–H(2B)⋯Cl(1) of 3.324(3) Å. The Cl− ion interacts electrostatically with three neighboring molecules. The probable assignments of the anharmonic experimental solid state vibrational frequencies of the investigated compound, based on the calculated frequencies in vacuum at the same level of theory for optimized structure, have been made. Correlations between the experimental 13C and 1H NMR chemical shifts (δexp) and the GIAO/B3LYP/6-311G(d,p) calculated magnetic isotropic shielding (σcal) in DMSO and D2O, δexp = a + b · σcalc, are reported.