Lanthanide phenolates with heterocyclic substituents. Synthesis, structure and luminescent properties

The complexes of trivalent lanthanides Ce, Sm, Eu, Gd, Tb, Dy with 2-(2-benzoxyazol-2-yl)phenolate (OON), 2-(2-benzothiazol-2-yl)phenolate) (SON) and 2-(2-benzoimidazol-2-yl)phenolate (NON) ligands were synthesized by the reactions of silylamides Ln[N(SiMe3)2]3 with respective phenol. Heteroleptic complex Tb(NON)2(SON) was obtained when Tb[N(SiMe3)2]3 was treated simultaneously with NONH and SONH. X-ray analysis of Ce(OON)3, Eu(OON)3, Sm(SON)3, Gd(NON)3, Dy(NON)3 and Tb(NON)2(SON) revealed that all the compounds are dimers with two bridging and four terminal XON ligands (XON)2Ln(μ-XON)2Ln(XON)2. In the heteroleptic complex the SON ligands are bridging but the NON groups are terminal. The molecules of the complexes in crystals are stacked with short intra- and intermolecular distances between planar ligands. This feature is reflected in the luminescence spectra of Gd, Tb (with SON ligands) and Dy complexes. Photo- and electroluminescence spectra of Ce, Gd and Dy derivatives showed only ligands emission in the region from 430 to 530 nm. The spectra of Sm and Tb complexes contain as well the bands of f-f transitions typical for corresponding metal ion. The complexes of Eu revealed no luminescence.