Multifunctional Luminescent Material Eu(III) and Tb(III) Complexes with Pyridine-3,5-Dicarboxylic Acid Linker: Crystal Structures, Tunable Emission, Energy Transfer, and Temperature Sensing

A series of lanthanide organic complexes, namely, [Ln 2 PDC 3 (H 2 O) 3 ]H 2 O (Ln = Eu, Tb, Eu x Tb 2– x, H 2 PDC: pyridine-3,5-dicarboxylic acid), were synthesized via hydrothermal method. Eu-PDC was characterized by single-crystal X-ray diffraction. The powder X-ray diffraction, Fourier transform infrared spectra, and thermogravimetric analysis illustrate that Eu-PDC, Tb-PDC, and Eu x Tb 2– x -PDC complexes are isostructural. All the complexes exhibit strong emission even though water molecules coordinated in the structure. Tunable emission color from green, yellow to red is realized by adjusting the Eu/Tb ratio in mixed Eu x Tb 2– x -PDC complexes. Energy transfer from Tb 3+ to Eu 3+ is discussed in detail via fluorescence decay and time resolution spectra. The detailed energy transfer process sees that the emitting color of Eu 0.15 Tb 1.85 -PDC shifts from green to orange in a time interval of 153–790 μs. In addition, temperature-dependent emission of the Eu 0.05 Tb 1.95 -PDC complex indicates that it is a potential solid state material for a luminescence thermometer in the range of 293–333 K. The temperature resolution is less than 0.16 K. The optical properties of the EuTb-PDC complex indicate that it is a multifunctional luminescent material with promising applications in temperature sensing, time resolution imaging, lighting, and displaying.