Solvent effect on optical properties of hydrated lanthanide tris-acetylacetone

We have studied the optical absorption spectra of trivalent lanthanide(III) beta-diketones. The enhancement in intensity of the hypersensitive transitions of Eu(III) D-5(0) -> F-7(2) and Tb(III) D-5(4) -> F-7(5) and D-5(4) -> F-7(2) complexes was observed in various solution mediums. The oscillator strength for the intraconfigurational transitions has been determined using Judd-Ofelt theory. The change in the oscillator strength and band shape with respect to solvent type is rationalized in terms of ligand (solvent) structure and coordination properties. The intensity of hypersensitive transitions is found to be highly influenced in DMF solution. Electronic spectral studies of the Pr(III) and Nd(III) complexes in different solvents, which differ with respect to donor atoms, reveal that the chemical environment around the lanthanide ion has great impact on f-f transitions and any change in the environment in terms of solvent results in modifications of the spectra. (C) 2007 Elsevier B.V. All rights reserved.