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 center dot Cl, has been studied by X-ray diffraction, B3LYP/6-311G(d,p) calculations, FUR and NMR spectra. The compound crystallized in monoclinic, space group P2(1)/c in the crystal, the Cl- anion is connected with protonated betaine via the hydrogen bond O-H center dot center dot center dot Cl of 2.946(3) angstrom. Both protons of the NH2 group are engaged in hydrogen bonds with the neighboring molecules: N(2)-H(2B)center dot center dot center dot O(2) of 2.905(6) angstrom and N(2)-H(2B)center dot center dot center dot Cl(1) of 3.324(3) angstrom. 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 C-13 and H-1 NMR chemical shifts (delta(exp)) and the GIAO/B3LYP/6-311G(d,p) calculated magnetic isotropic shielding (sigma(cal)) in DMSO and D2O, delta(exp) = a + b center dot delta(calc) are reported. (C) 2010 Elsevier B.V. All rights reserved.