Synthesis and Characterization of Three Novel Cation-Containing (NH4+/C3H7NH3+/NH3+C2H4NH3+) Aluminum Diphosphonates

Three new aluminum diphosphonates (C(3)H(7)NH(3))[AlF[(HO)O(2)PC(2)H(4)PO(3)]] (1) (orthorhombic, Pnma, a = 8.2048(1) A, b = 6.90056(6) A, c = 19.6598(4) A, Z = 4), (H(3)NC(2)H(4)NH(3))[Al(OH)(O(3)PC(2)H(4)PO(3))] (2) (monoclinic, P2(1)/n, a = 11.142(3) A, b = 7.008(2) A, c = 12.903(5) A, beta = 96.24(7) degrees, Z = 4), and (NH(4))(2)[AlF(O(3)PCH(2)PO(3))] (3) (orthorhombic, Cmcm, a = 16.592(2) A, b = 7.5106(9) A, c = 7.0021(9) A, 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 (AlO(4)F(2) for 1 and 3 and AlO(6) for 2) linked together through the bridging CPO(3) 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 O(3)PC- 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.