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

The crystal structure of dirubidium hydrogen citrate, 2Rb·HCHO, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The un-ionized carb-oxy-lic acid group forms helical chains of very strong hydrogen bonds (O⋯O ∼ 2.42 Å) along the axis. The hy-droxy group participates in a chain of intra- and inter-molecular hydrogen bonds along the axis. These hydrogen bonds result in corrugated hydrogen-bonded layers in the plane. The Rb cations are six-coordinate, and share edges and corners to form layers in the plane. The inter-layer contacts are composed of the hydro-phobic methyl-ene groups.