Molecular structure of quinuclidine betaine hydrate studied by X-ray diffraction, DFT, FTIR, Raman, NMR methods

A new quinuclidine betaine (1-carboxymethyl-quinuclidinium inner salt), QNB, has been synthesized and characterized by X-ray diffraction, FTIR, NMR, and Raman spectra, and DFT calculations. QNB crystallized as monohydrate in monoclinic space group P21/n. Two water molecules link two QNB molecules into a cyclic system by two O-H···O hydrogen bonds of 2.731(1) and 2.760(1) Å. The optimized structure of (QNB·H2O)2 by the B3LYP/6-31G(d,p) method is more bent than in the crystal. The FTIR spectrum of the solid compound is consistent with the X-ray structure.