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

The framework gallium diphosphonates Ga 2 [O 3 PC 2 H 4 PO 3 ](H 2 O) 2 F 2 ·2H 2 O ( 1 ) (triclinic, P 1̄, a = 5.0432(2) Å, b = 7.2468(3) Å, c = 8.3499(4) Å, α = 107.489(2)°, β = 92.444(2)°, γ = 109.338(2)°, Z = 1) and Ga 2 [O 3 PCH 2 (C 6 H 4 )CH 2 PO 3 ](H 2 O) 2 F 2 ( 2 ) (triclinic, P 1̄, a = 4. 9673(1) Å, b = 7. 0898(2) Å, c = 10. 1220(3) Å, α = 92. 698(2)°, β = 93.153(2)°, γ = 109. 122(2)°, Z = 1) and the solid-solution series Ga 2 {[O 3 PCH 2 (C 6 H 4 )CH 2 PO 3 ] 1 - x (HPO 3 ) 2 x }(H 2 O) 2 F 2 (0 ≤ x ≤ 0.146) x = 0.541 ( 3 ) and x = 0.144 Ga 2 {[O 3 PCH 2 (C 6 H 4 )CH 2 PO 3 ] 0.853(6) (HPO 3 ) 0.29(1) }(H 2 O) 2 F 2 ( 4 ) (triclinic, P 1̄, a = 4.959(2) Å, b = 7.078(2) Å, c = 10.024(3) Å, α = 92.404(5)°, β = 92.955(5)°, γ = 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 GaO 4 F 2 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.