X-ray, DFT, NMR, FTIR and Raman study of 1-methylquinolinium-3-carboxylate monohydrate

The structure of 1-methylquinolinium-3-carboxylate (benzotrigonelline) monohydrate has been studied by X-ray diffraction, B3LYP/6-31G(d,p) calculations, NMR, FTIR and Raman spectra. The crystals are monoclinic, space group P21/c, with a = 6.6716(2), b = 12.8422(4), c = 11.3638(5) Å, β = 99.925(4)°, V = 959.06(6) Å3, and Z = 4. Two 1-methylquinolinium-3-carboxylate molecules are linked by a pair of water molecules into a centro-symmetric dimer via two O(W)–H ⋯ O(1) bifurcated hydrogen bonds of lengths 2.867(2) and 3.046(2) Å. Structures of two of the most stable conformers of dimer, two of hydrated monomer and one anhydrous molecule have been analyzed by the B3LYP/6-31G(d,p) level of theory and the results have been compared with the X-ray data. The probable assignments of the anharmonic experimental solid state vibrational frequencies of the investigated compound, based on the calculated harmonic frequencies in vacuum at the same level of theory for the optimized structure, have been made. Correlations between experimental chemical shifts and GIAO/B3LYP/6-31G(d,p) calculated magnetic isotropic shielding constants, δexp = a + bσcalc, are reported.