Open-Framework Zinc Phosphates Synthesized in the Presence of Structure-Directing Organic Amines

Abstract

Four open-framework zinc phosphates have been synthesized in the presence of structure-directing organic amines. Crystal data: compound I, [NH3(CH2)2NH3·Zn2(HPO4)2(H2PO4)2], monoclinic, space group=P21/c (No. 14), a=16.420(2) Å, b=7.826(1) Å, c=14.640(1) Å, β=116.47(1)°, V=1684.05(2) Å3, Z=4, M=578.8(1), Dcalc=2.22 g cm−3, MoKα, RF=0.05; compound II, [NH3(CH2)2NH3·Zn(HPO4)2], monoclinic, space group=P21/c (No. 14), a=5.161(1) Å, b=15.842(2) Å, c=12.027(2) Å, β=92.36(2)°, V=982.41(1) Å3, Z=4, M=319.45(1), Dcalc=2.16 g cm−3, MoKα, RF=0.06; compound III, [NH3CH2CH(OH)CH2NH3·Zn2(HPO4)3], monoclinic, space group=P21/c (No. 14), a=8.615(1) Å, b=9.648(1) Å, c=17.209(1) Å, β=93.02(1)°, V=1428.4(2), Z=4, M=510.8(1), Dcalc=1.79 g cm−3, MoKα, RF=0.03; compound IV, [NH3(CH2)6NH3·Zn3(HPO4)4H2O], monoclinic, space group=C2/c (No. 15), a=16.815(1) Å, b=8.970(1) Å, c=15.080(1) Å, β=97.25(1)°, V=2256.4(1), Z=4, M=734.3(1), Dcalc=2.16 g cm−3, MoKα, RF=0.05. The compounds are made up of ZnO4 and PO4 tetrahedra that share vertices. The connectivity between the ZnO4 and PO4 units gives rise to layers in I, III, and IV and a chain architecture in II. The structure-directing organic amine holds the chains and the layers in position through multi-point hydrogen bonding. The layers in I and III consist of bifurcated 12-membered rings, and those in IV, of 8-membered rings. The phosphate units occur either as hydrogen phosphate (HPO4) or dihydrogen phosphate (H2PO4) moieties. These and other novel features in these materials suggest that further exploration may lead to many new solids with interesting structures. As a guide to understanding the formation of different ring structures in Zn phosphates and allied materials, a possible pathway involving the basic 4-membered ring is suggested.