Synthesis, structure and photoluminescence properties of a three-dimensional cadmium(II) (4,5)-connected coordination...

The assembly of coordination polymers from metal ions and organic moieties is currently attracting considerable attention in crystal engineering due to their intriguing architectures and potential applications as functional materials. A new coordination polymer, namely poly[[μ₂-trans-1,2-bis(pyridin-3-yl)ethylene-κ²N:N']bis(μ₄-4,4'-oxydibenzoato-κ⁶O:O,O':O'':O'',O''')dicadmium(II)], [Cd₂(C₁₄H₈O₅)₂(C₁₂H₁₀N₂)]_n or [Cd₂(4,4'-OBB)₂(3,3'-BPE)]_n, has been synthesized by the the self-assembly of Cd(NO₃)₂·4H₂O, 4,4'-oxydibenzoic acid (4,4'-H₂OBB) and trans-1,2-bis(pyridin-3-yl)ethene (3,3'-BPE) under hydrothermal conditions. The title compound was structurally characterized by IR spectroscopy, elemental analysis and single-crystal X-ray diffraction analysis. Each Cd^II centre is coordinated by six carboxylate O atoms from four different 4,4'-OBB^2- ligands and by one pyridyl N atom form a 3,3'-BPE ligand. Adjacent crystallographically equivalent Cd^II ions are bridged by 4,4'-OBB^2- ligands, affording a two-dimensional [Cd(4,4'-OBB)]_n net extending in the ac plane. Neighbouring [Cd(4,4'-OBB)]_n nets are interlinked by 3,3'-BPE along the b axis to form a three-dimensional (3D) [Cd₂(4,4'-OBB)₂(3,3'-BPE)]_n coordination network. In the network, each Cd^II centre is linked by four different 4,4'-OBB^2- ligands and one 3,3'-BPE ligand. Meanwhile, each 4,4'-OBB^2- ligand connects four separate Cd^II ions. Therefore, if the 4,4'-OBB^2- ligands and Cd^II ions are considered as 4- and 5-connecting nodes, the structure of the title compound can be simplified as a 3D (4,5)-connected binodal framework with the rare (4⁴6²)(4⁴6⁶) TCS topology (Pearson, 1985; Blake et al., 2011). The thermal stability and photoluminescence properties of the title compound have also been investigated.