Luminescent lanthanide complexes with phosphoramide and arylphosphonic diamide ligands

The sensitization of Eu(III) luminescence by the phosphoramide and arylphosphonic diamide ligands OP(NMe)Ind, OP(NMe)Cbz, OP(NMe)Ph, OP(NMe)(1-Naph) and OP(NMe)(2-Naph) (Ind = indol-1-yl; Ph = phenyl; Cbz = carbazol-9-yl; 1-Naph = naphtalen-1-yl; 2-Naph = naphtalen-2-yl) was verified by coordination to the [Eu(NO)] metal fragment. The emission spectra of the corresponding complexes showed only the D -> F transitions of the metal centre, with the exception of the carbazolyl derivative. Some of the ligands were also able to sensitize Tb(III) luminescence, in agreement with the triplet state energies estimated from the phosphorescence spectra of the analogous Gd(III) nitrates. On the basis of the photoluminescence results achieved using nitrate as ancillary ligand, heptacoordinate Eu(III) complexes having general formula [Eu(?-dike)L] (?-dike = dibenzoylmethanate, tenoyltrifluoroacetonate; L = phosphoramide or arylphosphomic diamide ligand) were prepared and characterized. All the complexes exhibited bright red emission upon excitation with near-UV and violet-blue light, with intrinsic quantum yields ranging between 18 and 36%.