3D-Frameworks and 2D-networks of lanthanide coordination polymers with 3-pyridylpyrazole: photophysical and magnetic properties.

A series of 15 lanthanide-containing coordination polymers, both 3D- and 2D-networks, as well as complexes of Ln-trichlorides with 3-(3-pyridyl)pyrazole (3-PyPzH), were synthesized. A large structural diversity is observed depending on the ligand content: 3∞[Ln(3-PyPzH)Cl 3 ], Ln = Eu and Gd, of sra topology, 2∞[Sm(3-PyPzH)Cl 3 ], 2∞[Ln 2 (3-PyPzH) 3 Cl 6 ]·2solv, Ln = Eu 3+ , Tb 3+ , Dy 3+ , Ho 3+ and Er 3+ , solv = Tol and MeCN, of sql topology and 2∞[Ln(3-PyPzH 2 )Cl 4 ], Ln = La and Nd, of hcb topology with salt like complexes of the formula [(3-PyPzH 2 )][Ln(3-PyPzH) 2 Cl 4 ], Ln = Eu, Tb, Dy and Ho. The products were characterized by single-crystal and powder X-ray diffraction, high-temperature X-ray diffraction, differential thermal analysis and thermogravimetry (DTA/TG) combined with mass spectrometry, differential scanning calorimetry (DSC), IR-spectroscopy, UV-visible spectrophotometry, photoluminescence spectroscopy, and magnetic susceptibility. Absorption spectroscopy shows ion-specific 4f-4f transitions that can be assigned to Sm 3+ , Eu 3+ , Dy 3+ , Ho 3+ and Er 3+ in a wide range from the UV-VIS to NIR region. An excellent antenna effect through ligand-metal energy transfer was observed in 2∞[Tb 2 (3-PyPzH) 3 Cl 6 ]·2solv, leading to high efficiency of the luminescence indicated by a quantum yield up to 76%. Direct current magnetic susceptibility studies reveal the absence of interatomic interaction for Dy 3+ and Er 3+ and weak ferromagnetic interaction for Ho 3+ . Thermal analysis shows good stability up to 365 °C for 2∞[Ho 2 (3-PyPzH) 3 Cl 6 ]·2MeCN.