Synthesis, crystal structure, luminescent and magnetic properties of bimetallic complex and hydrogen-bonded ionic framework of 1,2,4,5-benzenetetracarboxylate

A new bimetallic complex and a new hydrogen-bonded ionic framework (HIF) containing 1,2,4,5-benzenetetracarboxylate of the formulae [Co(C₁₀H₂O₈)(H₂O)₄][Ni(H₂O)₆] (1) and [C₁₀H₄O₈]₂[Ni(H₂O)₆][Zn(H₂O)₆] (2) were synthesized. The compounds were characterized by elemental analysis, atomic absorption spectroscopy, single-crystal X-ray diffraction, powder X-ray diffraction, infrared spectroscopy and thermal analysis. The crystal structure shows that 1 belongs to the triclinic system, $P\bar{1}$ space group, in which Co²⁺ is coordinated with O atom of carboxylate on 1,2,4,5-benzenetetracarboxylate, while Ni²⁺ is coordinated with six water molecules. The water molecules on [Ni(H₂O)₆]²⁺ are connected with 1,2,4,5-benzenetetracarboxylate through hydrogen bonds. 2 belongs to monoclinic system, C2/c space group, in which Ni²⁺ and Zn²⁺ are respectively coordinated with six water molecules, forming a slightly twisted octahedral structure, and are connected with each other by hydrogen bonds. Fluorescence experiments show that 1 and 2 have fluorescence properties. Variable-temperature magnetic susceptibility study (2–300 K) indicates the existence of antiferromagnetic interactions in 1 and 2.