COMPARISON OF ELECTRIC-DIPOLE INTENSITY PARAMETERS FOR A SERIES OF STRUCTURALLY RELATED ND(III) COMPLEXES WITH UREAS AND THIOUREAS IN NONAQUEOUS MEDIA

Absorption difference and comparative absorption spectrophotometric st udies involving 4f-4f transitions on neodymium(III) and different urea s [phenyl urea (pu), diphenyl urea (dpu), allyl urea (au), ethylene ur ea (eu) and tetramethyl urea (tmu)] and thioureas [phenyl thiourea (pt u), diphenyl thiourea (dptu), allyl thiourea (atu) and tetramethyl thi ourea (tmtu)] have been carried out in DMF and CH3OH as well as in DMF -CH3OH, DMF-CH3CN, DMF-Dioxane, CH3OH-CH3CN and CH3CN-Dioxane mixtures . The small chemical and structural differences due to the ligands and solvents are shown to produce significant variation in the intensitie s of observed 4f-4f absorption bands and their relative perturbation o n 4f-4f transition intensities are readily apparent in the Judd-Ofelt electric dipole (T-lambda) parameters determined for these complexes. Some correlations have also been made from the plots of oscillator str engths (P) against T-lambda parameters, which represent the relative s ensitivities of different 4f-4f transitions.