The effect of ligand symmetry on the ratiometric luminescence characteristics of lanthanides

Yoshinori Okayasu, Hajime Kamebuchi, Junpei Yuasa

Index: 10.1039/C8DT00898A

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Abstract

This work demonstrated that the ligand symmetry of europium(III) complexes controls the ratiometric luminescence characteristics of the lanthanide. Nona-coordinated europium(III) complexes having unsymmetrical β-diketonate ligands (CS) exhibit distinctive ratiometric spectral variations in the extremely narrow f-f transition bands over the temperature range 253 to 323 K. Conversely, no such ratiometric change can be observed in a series of nona-coordinated europium(III) complexes containing symmetrical β-diketonate ligands (C2V). The remarkable difference depending on the ligand symmetry (CS vs C2V) suugests that coordination rearrenegment of the β-diketonate in the complex causes the ratiometric spectral variations in the extremely narrow f-f transition bands, where two europium(III) complex isomers exist in the solution equilibrium. A self-calibration method using dual iso-emissive points is reported, where self-calibration using the two emission intensities at the iso-emissive points reduces the coefficient of variation in the luminensece thermometry.