Synthesis and characterization of two novel pyridine-containing framework gallium ethylenediphosphonates

Two novel gallium diphosphonates, (C5H5N)Ga3F(O3PC2H4PO3)2 (I) (triclinic, P-1, a=8.2880(12) A, b=11.7197(16) A, c=11.7601(17) A, α=71.589(3)o, β=70.577(3)o, γ=77.313(3)o, V=1013.7(2) A3, Z=2, R 1=0.0352, wR 2=0.0980) and (C5H5NH)2[Ga4F2(O3PC2H4PO3)3] (II) (triclinic, P-1, a=8.670(4) A, b=9.742(3) A, c=10.406(2) A, α=81.44(3)o, β=65.83(5)o, γ=67.16(3)o, V=739.0(4) A3, Z=2, R 1=0.0600, wR 2=0.1495) have been synthesised by solvothermal methods in the presence of pyridine and their structures determined using single-crystal X-ray diffraction data. Both compounds I and II are composed of various Ga-centered polyhedra and ethylenediphosphonate groups that link together to form framework materials with one- and two-dimensional channel systems, respectively. The two structures are formed in the presence of structure-directing pyridine molecules that are directly bound to some of the Ga atoms in I, and are protonated as pyridinium cations in II. Compounds I has a charge-neutral framework, while compound II has an anionic framework. Both materials provide rare examples of organically structure-directed framework metal diphosphonate materials. - Graphical abstract: (C5H5N)Ga3F(O3PC2H4PO3)2 (I) and (C5H5NH)2[Ga4F2(O3PC2H4PO3)3] (II) are novel gallium diphosphonate materials composed of Ga-centered polyhedra and ethylenediphosphonate groups that link together to form framework materials with one- and two-dimensional channel systems, respectively. The two structures are formed in the presence of structure-directing pyridine molecules or pyridinium cations and are examples of organically structure-directed framework metal diphosphonates