Three novel functional Cd^II dicarboxylates with nanometer channels: Hydrothermal synthesis, crystal structures, and luminescence properties

Three novel functional transition-metal complexes with H₂A (H₂A = 9-ethylcarbazole-3,6-dicarboxylic acid), Cd(HA) ₂-(H₂O)₂ (1), [Cd(A)(phen)]·1.5H ₂O (2) (phen = 1,10-phenanthroline), and Cd(HA)₂(bipy) (3) (bipy = 4,4′-bipyridine), have been successfully synthesized by a hydrothermal synthetic method and characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, thermogravimetric analysis, and photoluminescence. The results show that all of the complexes contain nanometer channels, while the coordination modes were changed by the addition of the mixed ligands. The 2D supramolecular open-framework 1 is constructed through hydrogen-bond and aromatic π-π interactions. 2D coordination polymer 2 is constructed by π-π interactions between adjacent metal-organic polymeric coordination chains. Interestingly, the 3D supramolecular architecture of 3 first formed 2D grid layers from 1D chains by intermolecular hydrogen bonds and then extended into a 3D structure through aromatic π-π interactions. Furthermore, strong emissions from these complexes were also changed by the coordination modes in the solid state. However, complexes 1-3 show high thermal stability.