Luminescent properties of diketonates of trivalent europium with dimethyl sulfoxide

Photoluminescent properties of the tris(thenoyltrifluoroacetonate)europium(III) dihydrate with dimethyl sulfoxide (DMSO), in the solid state, are reported. The compound Eu(TTA)(3). 2DMSO and the precursor salt were characterized by IR spectroscopy, differential scanning calorimetry and elemental analysis. The emission data indicate that the substitution of the two water molecules by DMSO ligand in the complex causes an intensification of luminescence corresponding to the D-5(0) --> F-7(J) (J = 0-4) transitions associated with one of the site symmetries. Large values of the Omega(2) intensity parameter (35.2 x 10(-20) cm(2)) were obtained, reflecting the hypersensitive character of the D-5(0) --> F-7(2) transition and indicating that Eu3+ ion is in a highly polarizable chemical environment. This is consistent with systems containing sulfoxide ligands DBSO and PTSO. The DMSO complex also shows a higher value for the Omega(4) parameter (6.8 x 10(-20) cm(2)) as a consequence of the difference in the basicity of the oxygen donor ligand. Lifetime measurements (tau = 0.72 ms) confirm that the Eu3+ luminescence has a higher efficiency than in the case of the hydrated compound. (C) 2000 Elsevier Science S.A. All rights reserved.