Two new 3-D Cd(II) metal–organic frameworks based on flexible cyclohexane-1,2,4,5-tetracarboxylic acid ligand

•Two new 3D Cd(II) complexes were synthesized and characterized.•The ligand adopt same conformation and diverse coordination modes in two complexes.•Complexes 1 and 2 exhibit rare purple emission at ambient temperature.

Two new metal–organic frameworks, {[Cd2(CTA)(bpea)(H2O)3] (H2O)5}n (1) and {[Cd2(CTA)(bpe)1.5(H2O)2] (H2O)7}n (2) (H4CTA = cyclohexane-1,2,4,5-tetracarboxylic acid, bpea = 1,2-bis(4-pyridyl)ethane, bpe = 1,2-bis(4-pyridyl)ethylene), have been synthesized and characterized by elemental analysis, IR and X-ray powder diffraction. Single-crystal X-ray investigation reveals that two complexes possess three-dimensional frameworks, in which the carboxylate oxygen atoms on the H4CTA ligand display different coordination modes and all ligands exclusively keep same conformation. Thermogravimetric analysis shows that 1 and 2 represent favorable thermal stability. Moreover, two complexes exhibit purple emission in the solid state at ambient temperature.

Graphical abstractIn this work, two new 3D Cd(II) complexes were synthesized and characterized. Single-crystal X-ray investigation reveals that two complexes possess three-dimensional frameworks, in which the carboxylate oxygen atoms on the H4CTA ligand display different coordination modes and all ligands exclusively keep same conformation. Two complexes represent favorable thermal stability and rare purple emission.Figure optionsDownload full-size imageDownload as PowerPoint slide