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

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)]<bold></bold>3(NO3)<bold></bold>6H(2)O} (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 (2)-(1):(1) 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. [GRAPHICS] .