Synthesis, crystal structure, and photophysical and magnetic properties of dimeric and polymeric lanthanide complexes with benzoic acid and its derivatives

A new family of lanthanide carboxylate complexes with benzoic acid and its derivatives was synthesised and characterised. The structures of the complexes were established by X-ray crystallography, which revealed that various chelating modes of the carboxylate ligands are present on the metal ion, resulting in the formation of dimeric and polymeric skeletons. The photophysical properties of the Eu and Tb complexes were studied: the complexes exhibited sensitised luminescence in the visible spectral region, but the luminescence intensities and lifetimes were very sensitive to quenching by the OH groups of methanol molecules. The solid-state magnetic properties of the Gd and Tb complexes demonstrated the presence of weak antiferromagnetic exchange interactions at very low temperatures, caused by interaction between the neighbouring ions along the chain.