Structure of 6-hydroxy-1-methylquinolinium chloride hydrate studied by X-ray, DFT calculations, FTIR and NMR spectroscopes

The crystal structure of 6-hydroxy-1-methylquinolinium chloride hydrate (1), 6QBWHCl, is monoclinic, space group P21/n and Z = 4. 1-Methyl-6-oxyquinolinium betaine, 6QB, is protonated and its OH group participates in a moderate hydrogen bond with water molecule (O(1)–H⋯O(W1) = 2.636(2) Å). The water molecule is further connected by a hydrogen bond to chloride ion (O(W1)–H(W2)⋯Cl(1) = 3.090(3) Å). Structures of five complexes (2–6) have been optimized by the B3LYP/6-311G(d, p) level of theory and the results have been compared with the X-ray data of 1. Linear correlations between the experimental 1H and 13C NMR chemical shifts (δexp) of complexes 2–5 and the magnetic isotropic shielding constants (σcal) calculated by the GIAO/B3LYP/6-311G(d, p) approach, using the screening solvation model (COSMO), δexp = a + bσcal, are reported. The probable assignments of the anharmonic experimental solid state vibrational frequencies of anhydrous complex, 6QBHCl, based on the calculated B3LYP/6-311G(d, p) harmonic frequencies have been proposed.