Europium chelate lasers

E. Reichstein, Y. Shami, M. Ramjeesingh, and E. P. Diamandis, Laser-excited time-resolved solid-phase fluoroimmunoassays with the new europium chelate 4,7-bis(chlorosulfophenyl)-l,10-phenanthroline-2,9-dicarboxylic acid as label, Anal. Chem. 60, 1069-1074 (1988). 

D. L. Ross and J. Blanc, Europium Chelates as Laser Materials, in Lanthanide/Actinide Chemistry, Advances in Chemistry Series (Ed. R. E. Gould), Vol. 71, Am. Chem. Soc., Washington, 1967, p. 155. 

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 ). 

Ross, D. L., Blanc, J., Europium Chelates as Laser Materials, Adv. Chem. 

Lempicki and Samelson (160) in their first paper reporting laser oscillation in europium made use of europium benzoylacetonate (EuB3) dissolved in a mixture of ethyl and methyl alcohol. The ratio was 3 to 1 and the concentration of EuB3 was 5.2 x 1018 molecules/cm3. These solutions can be frozen into a glass uniformly at temperatures between —120° and — 170°C. In this range they report a fluorescent lifetime of about 5 x 10-4 sec. Additional information on laser action, fluorescent lifetimes, and spectral studies in chelates may be found in Ref. (138). 

In 1962, it was pointed out that europium complexes dissolved in organic solvents or in a polymer matrix have optical properties that make them potential candidates for laser materials. At the same time. Whan and Crosby and Filipescu and coworkers have also suggested the potential application of rare-earth chelates in lasers. Lempicki and Samelson in 1963 were the first researchers to obtain stimulated emission at... 

A variety of lasers based on tetrakis p-diketonates of have been developed over the last few years. A summary of the chemistry and energy transfer in these laser systems is presented, with particular attention to the salts of tetrakis benzoyltrifluoroacetone chelates of europium. Chemical effects attributed to solvents, benzene ring substitutions in the ligand, differing cations, and deuteration are considered. These effects manifest themselves most markedly in the variability of laser thresholds from compound to compound and solvent to solvent. The thresholds reflect association-dissociation equilibria, as well as energy transfer processes in the ligand and throughout the manifold of Eu " states. 

We prepared a number of derivatives of benzoyltrifluoroacetone bearing substituents on the meta and para positions of the benzene ring and converted these to the corresponding europium tetrakis chelates. Schimitschek (33) has studied the nine BTFA derivatives obtained by substituting fluorine, chlorine, or bromine at the ortho, meta, or para position of the ring. Table I shows that substituents can have a considerable effect on the laser threshold of these compounds although the... 

In one case, a change of the cation has been observed to shift the frequency of the laser emission. Lempicki and co-workers (27) observed that adding sodium acetate to a solution of piperidinium tetrakis (ben-zoylacetono) europium in an alcoholic solution changed the laser frequency from 6131 to 6114A. and suggested that here, a new species, an adduct of the tetrakis chelate and the cation, is formed with a different symmetry. 

Additional evidence which shows that the deuterium enhancement of laser performance is not principally caused by an increased efficiency of the transfer of energy from ligand to europium ion is provided by the data in Table IV which show that the already short lifetime of the triplet state in the gadolinium chelate is not at all changed by deuteration of the ligand or solvent. 

Lasers. Chelates of europium with some aromatic nitro compounds with phenolic and aldehydic function can be used to produce laser beams [137]. 

---