Synthesis, Crystal Structure, and Properties of a Binuclear Co(II)‐tpha Complex (tpha = Terephthalate Dianion)

Abstract

The binuclear complex [Co₂(tpha)(phen)₄(H₂O)₂]·(NO₃)₂·2C₂H₅OH, (tpha = terephthalate dianion; phen = 1,10‐phenanthroline) has been synthesized by the reaction of H₂tpha, phen and Co(NO₃)₂·6H₂O in a mixed solvent of DMF/C₂H₅OH. Its structure was solved at 296 K. The compound crystallizes in the monoclinic system, space group P2₁/c: a = 0.9687(1) nm, b = 1.2988(3) nm, c = 2.2627(3) nm, β = 97.49(1)°, Z = 2. The final agreement factors are R = 0.052 and wR = 0.062. The binuclear entity is centrosymmetric and each Co(II) ion is 6‐coordinate, distorted octahedral. The tpha ligand bridges two Co(II) ions in a bis‐monodentate fashion. The cations and anions are linked through intramolecular hydrogen bonds. The result of the variable temperature magnetic susceptibility measurement revealed antiferromagnetic interaction between the two Co(II) ions. The analysis of the magnetic data finds: 2J = −0.45 cm⁻¹ and g = 1.94. Also, the ESR spectra and the color of the complex markedly vary with temperature. The IR and UV‐Vis‐NIR spectra of the complex have been determined and assigned.

Keywords:

• Binuclear Co(II)‐tpha complex
• Synthesis
• Characterization
• Magnetic properties

Acknowledgment

This work was supported by the National Natural Science Foundation (No. 20071016), and the State Key Laboratory of Inorganic Synthesis and Preparative Chemistry at Jilin University of China. We are grateful to Professor Y. G. Zheng at Jilin University of China for assistance in collecting and analyzing the ESR data.