Temperature study of the solution conformations of aqueous lanthanide(III) complexes containing monodentate ligands

Abstract

The conformations of the 1 : 1 lanthanide(III)–antipyrine and –tetrafluorophenol complexes in aqueous medium are proposed not to change significantly over the temperature range 5–95 °C. Whilst the Ln³⁺–antipyrine complexes contain the ligand only weakly bonded via a second-co-ordination-sphere interaction, the tetrafluorophenol ligand is proposed to be associated with Ln³⁺via an inner-sphere interaction. Anomalous shift data for Tm³⁺, Er³⁺, and Tb³⁺ are interpreted in terms of the assumption of axial symmetry being invalid; such anomalous behaviour decreases with increasing temperature.