Orientations of water molecule and hydronium ion in 1-methylquinolinium-3-carboxy chloride monohydrate studied by X-ray diffraction, DFT calculations, NMR, FTIR and Raman spectra

The structure of 1-methylquinolinium-3-carboxy chloride monohydrate, 3QBWHCl, has been studied by X-ray diffraction, B3LYP/6-31G(d,p) calculations, NMR, FTIR and Raman spectra. The crystals are triclinic, space group P1¯. The unit cell comprises six symmetry-independent complexes denoted by letters A-F. Each of those 1-methylquinolinium-3-carboxylate is hydrogen-bonded to a water molecule (in four complexes) or a hydronium ion (in two complexes), O-H···O(W) = 2.556-2.585 Å. The water molecules and hydronium ions are hydrogen bonded to two Cl− anions, O(W)-H···Cl− = 3.093-3.119 Å. The Cl− anions and water molecules additionally interact electrostatically with the positively charged nitrogen atom, N+···Cl− = 3.375-3.394 Å, N+···O(W) = 4.027-4.081 Å. Structures of eight most stable complexes (G-N) have been optimized by the B3LYP/6-31G(d,p) level of theory and the results have been compared with the X-ray data. Linear correlations between the experimental 1H and 13C NMR chemical shifts (δexp) of 3QBHCl in D2O and DMSO-d6, and the GIAO/B3LYP/6-31G(d,p) calculated magnetic isotropic shielding tensors (σcalc) using the screening solvation model (COSMO), δexp = a + bσcalc, are reported. The probable assignments of the anharmonic experimental solid state vibrational frequencies of anhydrous complexes L (3QBHCl and 3QBDCl) based on the calculated B3LYP/6-31G(d,p) harmonic frequencies have been proposed.