Synthesis and characterization of three novel cation-containing (NH4+/C3H7NH3+/NH3+C2H4NH3+) aluminum diphosphonates

Three new aluminum diphosphonates (C3H7NH3){AIF[(HO)O2PC2H4PO3]} (1) (orthorhombic, Pnma, a = 8.2048(l) Angstrom, b = 6.90056(6) Angstrom, c = 19.6598(4) Angstrom, Z = 4), (H3NC2H4NH3)[AI(OH)(O3PC2H4PO3)] (2) (monoclinic, P2(1)/n, a = 11.142(3) Angstrom, b = 7.008(2) Angstrom, c = 12.903(5) Angstrom, = 96,24(7)degrees, Z = 4), and (NH4)2[AIF(O3PCH2PO3)](3) (orthorhombic, Cmcm, a = 16.592(2) Angstrom, b = 7.5106(g) Angstrom, c = 7.0021 (9) Angstrom, Z = 4) have been synthesized by solvothermal methods in the presence of linear organic ammonium cations (for 1 and 2) and ammonium cations (for 3) and their structures determined using powder, microcrystal, and single-crystal X-ray diffraction data, respectively. All three materials contain a similar one-dimensional chain motif which is related to that found in the mineral Tancoite. This chain motif consists of corner-sharing octahedra (AIO(4)F(2) for 1 and 3 and AIO(6) for 2) linked together through the bridging CPO3 tetrahedra of the diphosphonate groups. These chains are unusual in that each diphosphonate moiety acts as a bisbidentate ligand that is coordinated to the same two metal centers through both of the O3PC-groups of the diphosphonate ligand. The arrangement of the Tancoite-like chains and charge compensation cations in the structures of compounds 1-3 is seen to be dependent upon the nature of the diphosphonic acid and organoammonium/ammonium cations. Careful selection of these two components may provide a method to design future materials in this system.