Hydro/Solvothermal Synthesis and Structures of New Zinc Phosphates of Varying Dimensionality

Hydro/solvothermal reactions of ZnO, HCl, H3PO4, 1,4-diazacycleheptane (homopiperazine), and H2O under a variety
of conditions yielded three new organic−inorganic hybrid materials, [C5N2H14][Zn(HPO4)2]·xH2O (x = ∼0.46), I,
[C5N2H14][Zn3(H2O)(PO4)2(HPO4)], II, and [C5N2H14][Zn2(HPO4)3]·H2O, III. While I has a one-dimensional structure,
II possesses a two-dimensional layered structure, and III has a three-dimensional structure closely related to the
ABW zeolitic architecture. All the compounds consist of vertex linking of ZnO4, PO4, and HPO4 tetrahedral units.
The fundamental building unit, single four-membered ring (S4R), is present in all the cases, and the observed
differences in their structures result from variations in the connectivity between the S4R units. Thus I has a corner-shared S4R forming an infinite one-dimensional chain, II has two corner-shared chains fused through a 3-coordinated
oxygen atom forming a strip and a layer with eight-membered apertures, and III has S4R units connected via
oxygen atoms to give rise to channels bound by eight T atoms (T = Zn, P) in all crystallographic directions. Crystal
data:  I, monoclinic, space group = P21/n (No. 14), a = 8.6053(3) Å, b = 13.7129(5) Å, c = 10.8184(4) Å, β =
97.946(1)°, V = 1264.35(8) Å3, Z = 4; II, monoclinic, space group = P21/c (No. 14), a = 11.1029(1) Å, b =
17.5531(4) Å, c = 8.2651(2) Å, β = 97.922(2)°, V = 1595.42(5) Å3, Z = 4; III, monoclinic, space group = P21
(No. 4), a = 8.0310(2) Å, b = 10.2475(3) Å, c = 10.570(3) Å, β = 109.651(1)°, V = 819.24(3) Å3, Z = 2.