Synergistic Complexation of Eu^{3+} by a Polydentate Ligand and a Bidentate Antenna to Obtain Ternary Complexes with High Luminescence Quantum Yields

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2002-04, Vol.106, p.3681-3689
• Main Authors: Klink, Stephen I., Hebbink, Gerald A., Grave, Lennart, Oude Alink, Patrick G. B., van Veggel, Frank C. J. M., Werts, Martinus H. V.
• Format: Article
• Language: English
• Subjects: Chemical Sciences; Physics
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp012617o

A series of ternary Eu 3+ complexes are presented consisting of a polydentate m-terphenyl-based Eu 3+ complex(Eu)1 and different antenna chromophores possessing lanthanide(III) ion coordinating properties. The seriesof investigated antenna chromophores consist of 1,10-phenanthroline, tetraazatriphenylene, and threeβ-diketonates, namely dibenzoylmethane, benzoyltrifluoroacetylacetonate, and hexafluoroacetylacetonate. Asa result of the synergistic complexation of Eu^{3+} by the polydentate ligand and the bidentate antenna, the distance between the antenna and lanthanide ion has been minimized and the Eu^{3+} ion has been shielded completely from the solvent. These are two important requirements to obtain efficiently emitting lanthanide(III) complexes. The formation of the ternary complexes and their photophysical properties, in particular the population of the Eu^{3+} excited states and the efficiency of the sensitization process, have been studied in detail. Based on these measurements, it can be concluded that the aforementioned strategy of synergistic complexation has indeed led to the construction of efficiently emitting Eu^{3+} complexes. The β-diketonate ternary Eu^{3+} complexes combine a high stability (K = 3.8 +/- 0.2 × 10^7 M^-1 ) with high overall luminescence quantum yields of up to 0.29. The energy transfer from the sensitizer to the Eu^{3+} is exclusively to the ^{5}D_{1} level, from which the ^{5}D_{0} level is populated.