Structure of 1-methylpyridinium-4-carboxylate monohydrate studied by X-ray, FT-IR, Raman, NMR and ab initio methods

The structure of 1-methylpyridinium-4-carboxylate monohydrate has been studied by X-ray diffraction, MP2 and B3LYP calculations, FT-IR, Raman, 1H and 13C NMR spectra. The crystals are triclinic, space group Pī, with a = 6.747(1), b = 7.6164(8), c = 7.709(1) Å, α = 72.30(1)°, β = 72.26(2)°, γ = 89.81(1)°, V = 357.7(1) Å3, and Z = 2. Two 1-methylpyridinium-4-carboxylate monohydrate molecules related by a crystallographic centre of symmetry are linked by a pair of water molecules into a dimer via two O(3W)–H···O hydrogen bonds of lengths 2.786(2) and 2.957(1) Å. The calculated molecular geometry is in good agreement with the X-ray data, except for the conformation of the COO·HOH species. The O(3W)···O hydrogen bond in the optimised half of a dimer structures is shorter in comparison with that in the crystal. In optimised structures of dimer the hydrogen bond lengths vary with the applied method and they are longer than those in the crystal. The O(3W)···O distances in dimer calculated by the B3LYP/6-31G(d,p) method are comparable (2.868 and 2.854 Å) but in the MP2/cc-pVDZ method they are different (2.955 and 3.132 Å). perimental solid-state vibrational spectra of the title compound and its deuterated analogue have been tentatively assigned on the basis of the MP2/cc-pVDZ calculated frequencies. Correlations between the experimental 1H and 13C NMR chemical shifts for the investigated complex and the GIAO calculated magnetic isotropic shielding tensors (σ), δexp = a + bσcal, are reported.