Ligand concentration-dependent supramolecular complexes with uncoordinated carbonyl groups based on a new pyrazole carboxylic acid ligand

• Published in: Journal of coordination chemistry 2015-05, Vol.68 (10), p.1688-1704
• Main Authors: Xia, Qinghong, Ren, Yanqiu, Cheng, Mei-Ling, Liu, Xiuxiu, Chen, Sheng, Zhai, Changwei, Liu, Qi
• Format: Article
• Language: English
• Subjects: Cadmium(II); Coordination compounds; Crystal structure; Isomers; Ligands; Luminescence; N-Heterocyclic ligand; Optical properties; Photoluminescence; Pyrazole; Structural analysis; Supramolecular isomers; Three dimensional
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2015.1020305

One new pyrazole-based ligand, 1-carboxymethyl-3,5-dimethyl-1H-pyrazole-4-carboxylic acid (H 2 cmdpca), has been synthesized and characterized. Structural analysis reveals that H 2 cmdpca crystallizes in the monoclinic system and adopts a 3-D supramolecular network via the interaction of intermolecular hydrogen bonds. The reactions of Cd(II) ions with H 2 cmdpca and 4,4′-bipyridine (4,4′-bpy) afforded three metal complexes, [Cd(4,4′-bpy)(Hcmdpca) 2 (H 2 O) 3 ]·H 2 O (1), [Cd(4,4′-bpy)(Hcmdpca) 2 (H 2 O)]·3H 2 O (2), and [Cd(4,4′-bpy)(Hcmdpca) 2 (H 2 O)] (3). Structural analyses reveal that these complexes are all monoclinic and 1, 2, and 3 exhibit mononuclear, 1-D chain, and 1-D with binuclear loop structures, respectively, which are further assembled into 3-D supramolecular frameworks through non-covalent interactions. 1 and 2 are true supramolecular isomers, while 2 and 3 are "pseudo-supramolecular" isomers. In addition, the thermal stability and luminescent properties of the complexes are also investigated. One new ligand, (H 2 cmdpca), and three supramolecular complexes, [Cd(4,4′-bpy)(Hcmdpca) 2 (H 2 O) 3 ]·H 2 O (1), [Cd(4,4′-bpy)(Hcmdpca) 2 (H 2 O)]·3H 2 O (2), and [Cd(4,4′-bpy)(Hcmdpca) 2 (H 2 O)] (3), have been synthesized and characterized.