Molecular structure of the 1:2 complex of 2-quinuclidinium-butyrate with p-hydroxybenzoic acid

The structure of the 1:2 complex of 2-quinuclidinium-butyrate, QNBu, with p-hydroxybenzoic acid, HBA, (1) has been determined by X-ray diffraction, DFT calculations, and the complex was characterized by FTIR and NMR spectroscopy. The crystals are triclinic, space group P 1 ¯ . The QNBu and HBA molecules are linked by medium-strong OH···O hydrogen bonds into a double strand related by two types of inversion centers, each inside different H-bonded rings. The O···O distances vary between 2.652(3) and 2.720(2) إ. The FTIR spectrum of the solid complex is consistent with the X-ray results. The second-derivative IR spectrum and calculated frequencies for the optimized structure of QNBu·2HBA were used to explain the FTIR spectrum in the carbonyl-carboxylate region. The interpretation of 1H and 13C NMR spectra has been based on 2D experiments and calculated GIAO/B3LYP/6-31G(d, p) magnetic isotropic shielding constants.