SU-79: a novel germanate with 3D 10- and 11-ring channels templated by a square-planar nickel complex†
An open-framework germanate denoted as SU-79 with the chemical formula [Ge12.5O26(OH)2][Ni(C3N2H10)2]1.1(NH4)0.8(C3N2H12)0.5(C3N2H10)1.5(H2O)2 has been synthesized under hydro/solvothermal conditions using [Ni(1,2-pda)2]2+ (1,2-pda = 1,2-diaminopropane) and 1,2-pda as templates. Owing to the complicated pseudo-merohedral twinning in the crystals, the rotation electron diffraction (RED) method was used for the unit cell and space group determination. The structure of SU-79 was solved and refined based on synchrotron single crystal X-ray diffraction data. SU-79 exhibits a 3D open germanate framework built with Ge13 clusters, consisting of a 3D channel system with interconnected 10- and 11-ring channels. Interestingly, helical GeO4 tetrahedral chains with left-handed/right-handed chirality were found in the structure. The [Ni(1,2-pda)2]2+ complexes, adopting in a square-planar geometry, show a structure directing role on the SU-79 framework via hydrogen bonds. Comparing with its related structure, SU-67, the formation of the pseudo-merohedric twinning in SU-79 was also discussed.