Eu benzoylacetonate

For Eu-dibenzoylmethide, they find at 77°K around 500 /nsec for the 5D0 level and less than 10 /nsec for the 5DX level. In Eu-benzoylacetonate at 77°K the lifetime of the 5D0 level is around 550 /isec, dropping to 530 /zsec at 300°K. The 5D level is less than 10 /nsec at 77°K. 

In spite of the difficulties, some specific studies involving absorption spectra of complexes such as oxydiacetates of Pr(III), Nd(III), Eu(III) and Er(III), benzoylacetonates of Eu(III) and monodiketonates of Eu(III) have been made with some success [184-186]. The experimental and calculated absorption spectra of oxydiacetate (ODA) complexes of Pr(III) are shown in Fig. 8.36. 

Both the hydrated and anhydrous forms of the chelate give a red fluorescence (characteristic of the Eu " ion) when exposed to ultraviolet radiation. Fluorescence is also shown in solution. Interest in the fluorescence behavior of europium chelates is prompted by the use of these compounds in optical maser (laser) devices. Optical maser action has been demonstrated for europium chelates derived from benzoylacetone (though not for the tris chelate reported here ). 

Similar examples for energy transfer from ligand localized levels to highly localized 4f levels are represented by the rare-earth chelates. Voloshin and Savutskii (1976) studied europium benzoylacetonate imder pressures up to 6 GPa. Exciting the triplet level they could observe the luminescence from the Eu " " ion. It was possible to describe the observed initial increase in the quantum yield of the Eu " " luminescence up to 2.5 GPa and the following decrease by the exchange resonance theory (Dexter, 1953). A more detailed study on different Tris chelates of Sm +, Eu +, Gd " ", and Tb " with -diketonates was performed by Hayes and Drickamer (1982), where the most dramatic effects of pressure on energy transfer phenomena were found for the Eu + chelates. 

The most conunonly used solvents for the study of the laser action are a 2 1 1 mixture of jS-ethoxypropionitrile, j8-ethojgfethanol and acetonitrile (EAA), a 1 1 1 mixture of proprion-itrile, butyronitrile and isobutyronitrile ( nitrile solvent ), a 3 1 ethanol-methanol mixture, a 3 1 ethanol-DMF mixture, and acetonitrile. Some of the mixed solvent systems remain liquid to temperatures as low as -150 °C. However, the /3-diketonate complexes are not always stable for a long time in such solutions. For instance, Schimitschek et al. (1965b) mention that emopimn(III) j8-diketonate complexes degrade in the 3 1 ethanol methanol mixture. Fry and Pirie (1965) foimd that in this alcohol mixture, [Eu(bzac)3(H20)] decomposed upon heating the solution to 70 °C or upon irradiation with ultraviolet radiation. The main decomposition products were ethyl acetate and acetophenone, which indicates that benzoylacetonate underwent a reverse Claisen condensation. Brecher et al. (1965) discussed the dissociation in solution of the tetrakis complexes into mixtures of non-lasing tris complexes and free jS-diketonate anions. 

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