X-ray and ab initio studies of the structure, vibrational and NMR spectra of 1-methyl-3-hydroxypyridinium chloride

The crystal and molecular structure of 1-methyl-3-hydroxypyridinium chloride, MePY3OHCl, has been characterized by X-ray diffraction, FTIR and NMR spectra and ab initio calculations. The crystals are orthorhombic, space group Pnma, with four formula units in a cell of the dimensions a = 15.1698(11), b = 6.8029(7), c = 7.0298(6) Å. The Cl− anion is engaged in a medium-strong hydrogen bond with the O–H group (O⋯Cl− = 2.985(2) Å) and in three N+⋯Cl− intermolecular electrostatic interactions. The calculated O⋯Cl− distances are shorter than in the crystal. The experimental solid-state vibrational spectra of MePY3OHCl and MePY3ODCl have been tentatively assigned on the basis of B3LYP/6-31G(d,p) calculated frequencies and intensities. Correlations between the experimental 1H and 13C NMR chemical shifts for MePY3OHCl and GIAO calculated magnetic isotropic shielding tensors (σ), δexp = a + bσcal, are reported.