Crystal structure of penta-sodium hydrogen dicitrate from synchrotron X-ray powder diffraction data and DFT comparison.

The crystal structure of penta-sodium hydrogen dicitrate, NaH(CHO), has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Each of the two independent citrate anions is joined into a dimer by very strong centrosymmetric O-H⋯O hydrogen bonds, with O⋯O distances of 2.419 and 2.409 Å. Four octa-hedrally coordinated Na ions share edges to form open layers parallel to the plane. A fifth Na ion in trigonal-bipyramidal coordination shares faces with NaO octahedra on both sides of these layers.