Thermodynamic and structural aspects on the solvation steric effect of lanthanide(III)—dependence on the ionic size

Abstract

Thermodynamic and structural aspects on the solvation steric effect for yttrium(III) and lanthanide(III) ions in DMF, DMA and their mixtures will be reviewed. The yttrium(III) and lanthanide(III) ions form outer- and inner-sphere bromo complexes in N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA), respectively, and an equilibrium geometry is established in the mixture. This is ascribed to the solvation steric effect of DMA, i.e. the simultaneous coordination of bulky DMA molecules around the metal ion causes a severe steric hindrance among them, allowing replacement of the solvent molecule with the penetrating bromide ion into the first-coordination sphere. Solvation steric effects for the metal(III) ion bring about appreciable changes in the bond length and solvation number. The results from titration calorimetry, EXAFS, 89Y-NMR and titration Raman spectroscopy will be discussed.