Spectra and quantum states of europium β-diketone chelates in polymethylmethacrylate

Abstract

An analysis of the absorption spectra of different Eu β-diketone chelates led to a detailed spectroscopic investigation of Eu tris (4,4,4-trifluoro-1,2 thienyl-1,3 butanedione) chelate dissolved in polymethylmethacrylate and other hosts, at different temperatures and concentrations. The mechanism responsible for the line fluorescence is attributed to an intramolecular energy transfer from the triplet states of the organic chelate to the 5 D 0 and 5 D 1 resonance energy levels of the central europium ion. The concentration, temperature and host dependent fluorescence spectrum of Eu chelate have been investigated and interpreted. The absorption and phosphorescence spectra of the identical gadolinium chelate in different hosts were related to the overall transfer mechanism and the lowest-lying triplet states. The “molecular field splitting” effects are observed at low temperatures for the 7 F 0 → 5 D 2 transition and interpreted based on structural criteria. The intramolecular energy transfer has been tentatively formulated based on the admixture of the biradical triplet state of the chelate with the emitting levels of the europium ion.