Comparative 4f–4f absorption spectral study for the interactions of Pr(III) with selected urea and thiourea: Energy and electric dipole intensity parameters

N. Yaiphaba

Abstract

The complexation of urea and thiourea with Pr(III) has been studied in different organic solvents like methanol (CH3OH), acetonitrile (CH3CN), dioxane (C4H8O2) and DMF (C3H7NO) and their equimolar mixtures by employing absorption difference and comparative absorption spectrophotometry. The complexation of Pr(III) with ureas and thioureas is indicated by the changes in the absorption intensity following the subsequent changes in the oscillator strength of different 4f–4f bands and Judd-Ofelt intensity (Tl) parameters. The other spectral parameters like energy interaction parameters namely Slater–Condon (Fk), Racah (Ek), Lande ( x 4f), Nephelauxetic ratio (b) and bonding parameters (b1/2) are further computed to explain the nature of complexation. The difference in the energy parameters with respect to donor atoms and solvents reveal that the chemical environment around the lanthanide ions has great impact on f–f transition and any change in the environment result in modification of the spectra. Various solvents and their equimolar mixtures are also used to discuss the participation of solvents in the complexation.