Metal–organic Coordination Polymers Assembled from Divalent Transition Salts with a Flexible Spacer Ligand: Hydrothermal Syntheses, Crystal Structures, and Luminescent and Magnetic Properties

Abstract

Seven new metal-organic coordination polymers, [M(tzda)(H₂O)₄] _n [M = Co(1), Ni (2) and Zn(3)], [Zn(tzda)(4,4′-bipy)] _n (4), [Cd(tzda)(4,4′-bipy)_0.5(H₂O)] _n (5) and [M(tzda)(4,4′-bipy)(H₂O)] _n [M = Co(6), Ni(7)] [H₂tzda = (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid, 4,4′-bipy = 4,4′-bipyridine] have been hydrothermally synthesized and structurally characterized by X-ray single crystal diffraction. Compounds 1–3 display similar 1D zigzag chain structure. Compound 4 possesses a 2D-layered architecture generated from [Zn(tzda)] _n moiety with double-chain structure cross-linking 4,4′-bipy spacers, while compound 5 consists of –Cd–OCO–Cd–OCO– chains cross-linked through –CH₂SC₂N₂SSCH₂– spacers of tzda anions and 4,4′-bipy, also showing a 2D-layered structure. The structures of 6 and 7 seem more complicated, in which the [M(tzda)] _n layered subunits are extended to unique 3D framework by the bridging 4,4′-bipy ligand. Photoluminescence investigations reveal that 4 and 5 both display strong blue emissions in the solid state at room temperature, which could be significant in the field of luminescent materials. The magnetic studies of 6 and 7 show both display the characteristics of a weak antiferromagnetic coupling between metal ions in the system mediated by carboxylate bridges.

Keywords:

• Flexible carboxylate ligands
• Coordination polymers
• Hydrothermal synthesis
• Luminescent property
• Magnetic property

Acknowledgements

This work was sponsored by the National Natural Science Foundation of China (No. 90610001, 20471053), the China National Key Basic Research Special Funds (No. 2005CB214501, 2006CB708407) and the Energy & Technology Program from Zhengzhou University.