Homochiral Porous Lanthanide Phosphonates with 1D Triple-Strand Helical Chains: Synthesis, Photoluminescence, and Adsorption Properties

Four homochiral porous lanthanide phosphonates, [Ln(H2L)3]·2H2O, (H3L = (S)-HO3PCH2-NHC4H7-CO2H, Ln =
Tb (1), Dy (2), Eu (3), Gd (4)), have been synthesized under hydrothermal conditions. These compounds are
isostructural, and they possess a 3D supramolecular framework built up from 1D triple-strand helical chains. Each
of the helical chain consists of phosphonate groups bridging adjacent Ln(III) ions. The helical chains are stacked
through hydrogen bonds to form 1D tubular channels along the c axis. Moreover, helical water chains are located
in the 1D channels, and after removal of these water chains, the compounds exhibit selective adsorption capacities
for N2, H2O, and CH3OH molecules. Compounds 1 and 3 show strong green and red fluorescent emissions,
respectively, in the solid state at room temperature. Crystal data for 1:  TbP3O17N3C18H37, tetragonal (No.76), space
group P41, a = 12.4643(3) Å, b = 12.4643(3) Å, c = 18.7577(5) Å, V = 2914.17(13) Å3, and Z = 4. For 2: 
DyP3O17N3C18H37, a = 12.4486(3) Å, b = 12.4486(3) Å, c = 18.7626(5) Å, V = 2907.60(13) Å3, and Z = 4. For
3, EuP3O17N3C18H37, a = 12.4799(3) Å, b = 12.4799(3) Å, c = 18.8239(5) Å, V = 2931.78(13) Å3, and Z = 4.
For 4:  GdP3O17N3C18H37, a = 12.4877(18) Å, b = 12.4877(18) Å, c = 18.824(4) Å, V = 2935.5(8) Å3, and Z =
4.