Three Ln^III coordination compounds based on 1,1′,1″-(benzene-1,3,5-triyltris(methylene))tris(4-carboxypyridinium)tribromide: Synthesis, structures, and properties

Abstract

An exploration of reactions of 1,1′,1″-(benzene-1,3,5-triyltris(methylene))tris(4-carboxypyridinium)-tribromide (H₃LBr₃) with Ln^III salts has led to the formation of three complexes, {[LnL(H₂O)₂]·3(NO₃)·6H₂O} (Ln = Eu (1), Gd (2), and Tb (3)). Single-crystal X-ray analyses revealed that these complexes are isomorphous and have 3-D, channel-like structures, in which the carboxylic acids are fully deprotonated with syn–syn μ₂-η¹:η¹ type bridging modes and L ligands in a chair-shaped configuration. Both 1 and 3 showed strong luminescence upon excitation. Magnetic measurements were performed for 2 and 3. The magnetic studies show that very weak antiferromagnetic couplings exist between Gd^III and Gd^III in 2. Moreover, powder X-ray diffraction, infrared spectroscopy, and elemental analysis were also performed.

Keywords:

• Photoluminescence property
• lanthanide
• magnetic property
• metal-organic framework
• zwitterionic ligand