Strong Photoluminescence and Thermal Stability of Eu(III) Coordination Polymers with Thiophene-Based Bridge

Abstract

Lanthanide coordination compounds, composed of lanthanide ions (Ln(III)) and specific organic ligands, are widely known to show sharp and strong emission due to the nature of f-f transition in lanthanide ions.1They are promising candidates for LEDs, chemical sensors, and solar cells applications. In order to compensate the small absorption coefficients of Ln(III) ions, various types of antenna ligands have been developed to harvest and transfer the energy from the light source to the Ln(III) ions through ligand to metal energy transfer upon excitation. Our group have previously reported that the Ln(III) coordination polymers with phenylene-based bridging ligands show thermal stability above 300˚C due to the intermolecular CH/F and CH/π interactions.2 In this presentation, we demonstrate the design and synthesis of novel Ln(III) coordination polymers composed of Eu(III) ions, beta-diketonates, and thiophene-based bridging ligands in order to estabilish both high emission quantum yields and thermal stability. The decomposition temperature of these coordination polymers are estimated to be above 300˚C. According to the single crystal X-ray analyses, multiple intermolecular CH/F interactions are observed between single polymer chains because of the zig-zag coordination structure. They also exhibit intense red emission which is detectable to the naked eye under daylight. Emission spectra, quantum yields (Φ total, Φ Ln), and lifetimes (τ obs) are also measured to estimate the photophysical parameters such as radiative and non-radiative constants (k r and k nr, respectively).