MIXED-LIGAND LANTHANIDE COMPLEXES .11. ABSORPTION-SPECTRA AND HYPERSENSITIVITY IN THE COMPLEXES OF PR-III, ND-III, HO-III AND ER-III IN NONAQUEOUS SOLUTIONS

Absorption spectra are reported for the mixed-ligand complexes of Pr-I II, Nd-III, Ho-III, and Er-III containing ligands having nitrogen dono rs, in four different solvents (pyridine, DMSO, DMF and methanol). The solvents differ with respect to their donor atoms. The oscillator str engths for the hypersensitive and non-hypersensitive transitions have been determined and variations in the oscillator strengths and band sh apes with respect to solvent type is rationalized in terms of ligand ( solvent) structures and ligand coordination properties. Pyridine has b een found most effective in promoting 4f-4f intensity and is the stron gest ligand in a nephelauxetic sense among the solvents studied. (C) 1 997 Elsevier Science Ltd.