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

The crystal structure of dirubidium hydrogen citrate, 2Rb(+)·HC(6)H(5)O(7) (2−), has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The un-ionized carb­oxy­lic acid group forms helical chains of very strong hydrogen bonds (O⋯O ∼ 2.42 Å) along the b axis. The hy­droxy group participates in a chain of intra- and inter­molecular hydrogen bonds along the c axis. These hydrogen bonds result in corrugated hydrogen-bonded layers in the bc plane. The Rb(+) cations are six-coordinate, and share edges and corners to form layers in the ab plane. The inter­layer contacts are composed of the hydro­phobic methyl­ene groups.