Four 3D “brick-wall”-like metal–organic frameworks with a flexible ligand of (S,S,R,R)-1,2,3,4-cyclopentanetetracarboxylic acid: crystal structures, luminescent and magnetic properties

Abstract

To investigate the conformation of cyclopentanetetracarboxylic acid, four new “brick-wall”-like metal–organic frameworks have been synthesized from hydrothermal reactions with different metal salts, (S,S,R,R)-1,2,3,4-cyclopentanetetracarboxylic acid (H₄cptc) and auxiliary N-donor ligands, namely, Cu₂(S,S,R,R-cptc)(bpe)(H₂O)₂·2H₂O (1), Co₂(S,S,R,R-cptc)(bpe)_0.5(H₂O)₂·2H₂O (2), Cd₄(S,S,R,R-cptc)₂(bpa)₂(H₂O)₅·2H₂O (3) and Co₂(S,S,R,R-cptc)(bpy)_0.5(H₂O)₂·2(H₂O) (4) (bpe = 4-(2-(pyridine-4-yl)vinyl)pyridine, bpa = 4-(2-(pyridine-4-yl)ethyl)pyridine, bpy = 4-(pyridine-4-yl)pyridine). The complexes were further characterized by single-crystal X-ray diffraction, power X-ray diffraction, FT-IR spectra, fluorescent measurements and variable-temperature magnetic susceptibility measurements. The results of the structural investigations show that 1 is a charming (3,3,4)-trinodal architecture, 3 is an interesting trinodal (3,4,5)-connected architecture, and 2 and 4 are isostructural, which are both (4,5)-connected networks. In addition, the magnetic measurements indicate that 2 and 4 show weak antiferromagnetic interactions, and the fluorescent measurement shows the strong solid-state fluorescent emission at room temperature for 3.