Very short OHO hydrogen bond in bis(2-quinuclidinium-propionate) hydrobromide

The molecular structure of bis(2-quinuclidinium-propionate) hydrobromide, (QNPr)2HBr (1), has been characterized by single crystal X-ray diffraction, infrared spectroscopy and DFT calculations. The crystals (1) are triclinic, space group P 1 ¯ . The two QNPr moieties are joined by a very short O⋯H⋯O hydrogen bond of 2.449(3) Å, over the inversion centre. The short OHO hydrogen bond is confirmed by the broad absorption band below 1500 cm−1, with the centre of gravity, νH, at ca. 900 cm−1, in the FTIR spectrum. In the structure of (QNPr)2HBr (2) optimized at the B3LYP/6–31G(d,p) level of theory, the 2-quinuclidinium-propionate units are non-equivalent. The 2-quinuclidinium-propionic acid interacts with the QNPr inner salt by the O–H⋯O hydrogen bond of 2.533 Å.