Synthesis, Crystal Structure, and Solid State NMR Spectroscopy of (C10N4H28)[Zn6(HPO4)2(PO4)4]·2H2O, a New Zinc Phosphate with a Layer Structure

A new zinc phosphate, (C10N4H28)[Zn6(HPO4)2(PO4)4]·2H2O, with a layered architecture has been synthesized, for the first time, in the presence of 1,4-bis(3-aminopropyl)piperazine as the structure-directing agent. The structure comprises a network of ZnO4 and phosphate tetrahedra forming macroanionic layers with eight-membered apertures. Charge compensation is achieved by the quadruply protonated amine occupying interlamellar space and interacts with the inorganic layers via hydrogen bonding. The title compound is related to several other zinc phosphates in framework stoichiometry or crystal structure. Crystal data: (C10N4H28)[Zn6(HPO4)2(PO4)4]·2H2O, triclinic, space group P (No. 2), a=8.3343(9) ?, b= 12.413(1) ?, c=17.363(2) ?, =75.269(2)°, =78.868(2)°, =76.270(2)°, V=1670.7(5) ?3, Z=2, R1=0.0584, wR2=0.153. Proton-decoupled 31P MAS NMR reveals six 31P resonances with nearly equal intensities, which is in good agreement with the six distinct crystallographic phosphorus sites in the framework as indicated from X-ray structural analysis. 1H31P CP/MAS is used to obtain more details of the proximity between hydrogen and phosphorus atoms, and in combination with 2D RFDR NMR to assign the six phosphorus sites.