Variable Luminescence and Chromaticity of Homoleptic Frameworks of the Lanthanides together with Pyridylpyrazolates.

Homoleptic, 3D coordination polymers of the formula [Ln(3-PyPz) ] and [Ln(4-PyPz) ], (3-PyPz) =3-(3-pyridyl)pyrazolate anion, (4-PyPz) =3-(4-pyridyl)pyrazolate anion, both C H N , Ln=Sm, Eu, Gd, Tb, Dy, were obtained as highly luminescent frameworks by reaction of the lanthanide metals (Ln) with the aromatic heterocyclic amine ligands 3-PyPzH and 4-PyPzH. The compounds form two isotypic series of 3D coordination polymers and exhibit fair thermal stability up to 360 °C. The luminescence properties of all ten compounds were determined in the solid state, with an antenna effect through ligand-metal energy transfer leading to high efficiency of the luminescence displayed by good quantum yields of up to 74 %. The emission is mainly based on ion-specific lanthanide-dependent intra 4 f-4 f transitions for Tb : green, Dy : yellow, Sm : orange-red, Eu : red. For the Gd -containing compounds, the yellow emission of ligand triplet-based phosphorescence is observed at room temperature and 77 K. Co doping of the Gd-containing frameworks with Eu and Tb allow further shifting of the chromaticity towards white light emission.