Interactions of water molecule in 2-(quinuclidinium)-propionic acid bromide hydrate

The structure of 2-(quinuclidinium)-propionic acid bromide hydrate (QNPr·H2O·HBr, 1) has been determined by X-ray diffraction, DFT calculations, and characterized by FTIR and NMR spectroscopy. The crystals are monoclinic, space group P21/n. The water molecule is engaged in three hydrogen bonds, one with the COOH group of 2.602(4) Å and two to the bromide anions of 3.244(3) and 3.340(3) Å. The molecule of 1 has a chiral center at C(9) and two isomers (R) and (S) form an eight-membered cyclamer. The structures of monomer (2a) and dimer (2b) of the title complex have been optimized by the B3LYP/6-31G(d,p) approach. The solid-state FTIR spectra of 1 and its deuterated analogue have been measured and compared with the theoretical spectra. The assignments of the observed and predicted bands are proposed. The interpretation of 1H and 13C NMR spectra of 1, dissolved in D2O, has been based of 2D experiments and calculated GIAO/B3LYP/6-31G(d,p) magnetic isotropic shielding tensors.