Synthesis, Crystal Structures, and Modifications of Novel Framework Gallium Diphosphonates

The framework gallium diphosphonates Ga2[O3PC2H4PO3](H2O)2F2·2H2O (1) (triclinic, P, a = 5.0432(2) A, b = 7.2468(3) A, c = 8.3499(4) A,(alpha)= 107.489(2),(beta)= 92.444(2),(gamma)= 109.338(2), Z = 1) and Ga2[O3PCH2(C6H4) CH2PO3](H2O)2F2 (2) (triclinic, P, a = 4. 9673(1) A, b = 7. 0898(2) A, c = 10. 1220(3) A,(alpha)= 92. 698(2),(beta)= 93.153(2),(gamma)= 109. 122(2), Z = 1) and the solid-solution series Ga2{[O3PCH2(C6H4)CH2PO3]1-x(HPO3)2x}(H2O)2F2 (0 <= x<= 0.146) x = 0.541 (3) and x = 0.144 Ga2{[O3PCH2(C6H4)CH2PO3]0.853(6) (HPO3)0.29(1)}(H2O)2F2 (4) (triclinic, P, a = 4.959(2) A, b = 7.078(2) A, c = 10.024(3) A,(alpha)= 92.404(5),(beta)= 92.955(5),(gamma)= 109.187(5), Z = 1) have been synthesized by solvothermal methods and their structures determined using X-ray diffraction data. All the materials contain linear chains of corner-sharing GaO4F2 octahedra that are linked by the diphosphonate groups to form framework structures. The channels of 1 are found to contain two water molecules per unit cell while those in 2 are too narrow to contain extraframework species. The apertures created in the phosphite-substituted derivatives of 2 (3 and 4) are shown, by crystallographic methods, to be considerably larger than those in 2 and, by thermogravimetric methods, to create more open structures. The synthetic conditions or form of the diphosphonate group are found to play a defining role in the adoption of this particular configuration of the inorganic component in the reported compounds and provide an additional strategy for the rational design of framework hybrid organic-inorganic solids.