A new twofold interpenetrated two-dimensional cadmium(II) coordination polymer constructed from...

In recent years, much initial interest and enthusiasm has focused on the self-assembly of coordination polymers due to the aesthetics of their crystalline architectures and their potential applications as new functional materials. As part of an exploration of chiral coordination polymers, a new twofold interpenetrated two-dimensional (2D) coordination polymer, namely, poly[[tetraaquabis[μ₃-(2R,2'R)-2,2'-(benzene-1,4-dicarboxamido)dipropionato-κ⁵O,O':O'',O''':O'']dicadmium(II)] trihydrate], {[Cd₂(C₁₄H₁₄N₂O₆)₂(H₂O)₄]·3H₂O}_n, has been synthesized by the reaction of Cd(CH₃COO)₂·2H₂O with the designed ligand (2R,2'R)-2,2'-(benzene-1,4-dicarboxamido)dipropionic acid (H₂L). The compound has been structurally characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction and single-crystal X-ray diffraction analysis. In the crystal structure, each Cd^II cation binds to three carboxylate groups from two crystallographically independent L^2- dianions. Four carboxylate groups link two crystallographically independent cadmium cations into a 4,4-connected secondary building unit (SBU). The resulting SBUs are extended into a two-dimensional folding sheet via the terephthalamide moiety of the ligand as a spacer, which can be simplified as a (4,4)-connected 4,4L15 net with the point symbol (3.5³.6²)(3².5².6²). In the lattice, two independent folding sheets interpenetrate each other to yield a double-sheet layer. The resulting 2D layers pack in parallel arrays through intermolecular hydrogen bonds and interlayer π-π interactions. The thermal stability and photoluminescence properties of the title compound have been investigated and it exhibits an enhanced fluorescence emission and a longer lifetime compared with free H₂L.