Poly[[tetra-deca-kis-(μ-propionato)hepta-barium] propionic acid monosolvate tetra-hydrate]

The title compound, {[Ba₇(C₃H₅O₂)₁₄]·0.946C₃H₆O₂·4H₂O} , is represented by a metal-organic framework structure that is held together by Ba-O-Ba bonds, as well as by O-H⋯O hydrogen bonds of moderate strength. The structure comprises of four independent Ba²⁺ cations (one of which is situated on a twofold rotation axis), seven independent propionate and two independent water mol-ecules. The bond-valence sums of all the cations indicate a slight overbonding. There is also an occupationally, as well as a positionally disordered propionic acid mol-ecule present in the structure. Its occupation is slightly lower than the full occupation while the disordered mol-ecules occupy two positions related by a rotation about a twofold rotation axis. In addition, the methyl group in the symmetry-independent propionic acid mol-ecule is also disordered, and occupies two positions. Each propionic acid mol-ecule coordinates to just one cation from a pair of symmetry-equivalent Ba²⁺ sites and is simultaneously bonded by an O-H⋯O_propionate hydrogen bond. This means that on a microscopic scale, the coordination number of the corresponding Ba²⁺ site is either 9 or 10. The methyl as well as hy-droxy hydrogen atoms of the disordered propionic acid mol-ecule were not determined.