Synthesis and characterizations of two NbO topological gallium phosphites with low framework density

• Two novel 3D open-framework gallium phosphites have been synthesized.
• Right- and left-handed helical chains construct the 3D framework.
• Both compounds show low framework density.

Two new 3D open-framework gallium phosphites Ga(HPO3)F2·(H2A)0.5, where A = C5N2H12(1) and C6N2H14 (2) have been solvothermally synthesized in the presence of 2-methyl piperazine and N,N′-dimethyl piperazine as template, respectively. Single crystal X-ray diffraction reveals that these two compounds have the similar inorganic framework structures, which may be viewed as the assembly of a second building unit (SBU), Ga2F2O4(HPO3)2 containing one dimer Ga2F2O8 and two HPO3 groups. The SBUs are linked with each other via vertex-sharing oxygen atoms to form a new 3D open-framework which possesses the left- and right-handed helical chains along c axis. With the SBU as 4-connected nodes, the structure can be simplified into a uninodal NbO topology. Moreover, compounds 1 and 2 show low framework density value of 9.4 and 9.7, respectively. Crystal data: compound 1, Trigonal, R-3 (148), a = b = 18.315(3) Å, c = 13.136(4) Å, γ = 120°, V = 3815.9(13) Å3 and Z = 9; compound 2, Trigonal, R-3 (148), a = b = 17.8476(4) Å, c = 13.5159(6) Å, γ = 120°, V = 3728.5(2) Å3 and Z = 18.

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