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

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posted on 12.03.2003, 00:00 by Howard G. Harvey, Simon J. Teat, Chiu C. Tang, Lachlan M. Cranswick, Martin P. Attfield
Three new aluminum diphosphonates (C3H7NH3){AlF[(HO)O2PC2H4PO3]} (1) (orthorhombic, Pnma, a = 8.2048(1) Å, b = 6.90056(6) Å, c = 19.6598(4) Å, Z = 4), (H3NC2H4NH3)[Al(OH)(O3PC2H4PO3)] (2) (monoclinic, P21/n, a = 11.142(3) Å, b = 7.008(2) Å, c = 12.903(5) Å, β = 96.24(7)°, Z = 4), and (NH4)2[AlF(O3PCH2PO3)] (3) (orthorhombic, Cmcm, a = 16.592(2) Å, b = 7.5106(9) Å, c = 7.0021(9) Å, 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 (AlO4F2 for 1 and 3 and AlO6 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 13 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.