Hydrothermal Synthesis and Crystal Structure of Zn4(PO4)2(HPO4)2·0.5(C10H28N4)·2H2O, a New Layered Zinc Phosphate with 12-Ring Cavities

Abstract

Using 1, 4, 8, 11-tetraazacyclotetradecane (cyclam) as a template, a new layered zinc phosphate Zn4(PO4)2(HPO4)2·0.5(C10H28N4)·2H2O (defined as ZnPO-cyclam) with 12-ring cavities was synthesized under hydrothermal conditions in a molar ratio ZnO:P2O5:cyclam:H2O=1:2.2:0.5:284.7 at 140°C for 3 days. The gel had a pH 4 at the starting period. The ZnPO-cyclam crystal structure is solved using single-crystal X-ray diffraction data at 293 K. It crystallizes in monoclinic space group P21/c (no.14) with lattice parameters a=15.758(3) Å, b=9.0292(15) Å, c=15.543(3) Å, β=111.070 (16). V=2063.7(7) Å3, Z=4, R=0.0392, wR=0.0472, 4166 collected reflections, 2794 observed reflections with I>2σ(I). The structure of ZnPO-cyclam consists of alternating inorganic and organic layers. The inorganic layers are built up from ZnO4, ZnO3(H2O)2, PO4, and HPO4 with Zn–O–Zn and Zn–O–P bonds. The protonated cyclam molecules in which the four nitrogen atoms are all protonated form the organic layers. Strong hydrogen bonding exists between the inorganic–organic layers, and there are 12-ring cavities in the inorganic layers, in which the template cyclam molecules reside.