Crystal structure of dicesium hydrogen citrate from laboratory single-crystal and powder X-ray diffraction data and DFT comparison

The crystal structure of dicesium hydrogen citrate, 2Cs(+)·C(6)H(6)O(7) (2−), has been solved using laboratory X-ray single-crystal diffraction data, refined using laboratory powder X-ray data, and optimized using density functional techniques. The Cs(+) cation is nine-coordinate, with a bond-valence sum of 0.92 valence units. The CsO(9) coordination polyhedra share edges and corners to form a three-dimensional framework. The citrate anion is located on a mirror plane. Its central hy­droxy/carboxyl­ate O—H⋯O hydrogen bond is short, and (unusually) inter­molecular. The centrosymmetric end-end carboxyl­ate hydrogen bond is exceptionally short (O⋯O = 2.416 Å) and strong. These hydrogen bonds contribute 16.5 and 21.7 kcal mol(−1), respectively, to the crystal energy. The hydro­phobic methyl­ene groups occupy pockets in the framework.