Synthesis, structure and characterization of two new open-framework gallium phosphite-oxalates of varying dimensionality

Using N, N-dimethyl-piperazine as structure directing agent, two new gallium phosphite-oxalates [Ga₂(HPO₃)₂(H₂PO₃)₂(C₂O₄)](C₆N₂H₁₆) (I) and [Ga₂(HPO₃)₂(H₂PO₃)(C₂O₄)](C₆N₂H₁₆)_0.5 (II) have been synthesized under solvothermal and hydrothermal conditions, respectively and further characterized by powder X-ray diffraction, IR spectroscopy, TGA, ICP-AES and elemental analyses. Single crystal X-ray diffraction reveals that the striking feature of I and II is that they possess the same second building unit (SBU) Ga₂P₂ constructed from two GaO₆ octahedra and two [HPO₃^2-] pseudo-pyramids sharing oxygen atoms. However, due to the different connecting fashions of SBUs, [C₂O₄^2-] groups and [H₂PO₃^-] pseudo-pyramids, the final frameworks of them are distinctly different. Compound I shows 2D layered structures with 8-membered ring (8-MR) windows in the ab plane while compound II presents a 3D open-framework with 8-MR channels along the b axis.