Europium -2-thenoyltrifluoroacetone

A broad range of metal centers have been used for the complexation of functional ligands, including beryllium [37], zinc, transition metals such as iridium [38], and the lanthanide metals introduced by Kido [39], especially europium and terbium. Common ligands are phenanthroline (phen), bathophenanthrolin (bath), 2-phenylpyridine (ppy), acetylacetonate (acac), dibenzoylmethanate (dbm), and 11 thenoyltrifluoroacetonate (TTFA). A frequently used complex is the volatile Eu(TTFA)3(phen), 66 [40]. 

The fluorescent decay data of europium tris-thenoyltrifluoroacetonate (EuTTA)3 as given in Table XI suggests that both mechanisms are operative. This may be inferred from the fact that not only is the lifetime longest in tri-iV-butyl phosphate (TBP), but the quantum efficiency of energy transfer to the emitting level is also greater. The quantum efficiency is found to increase by a factor greater than the lifetime. 

Freeman, Crosby, Lawson (13), Kropp, and Windsor 17, 18) had reported that hydrated europium chloride crystals and aqueous solutions of europium salts, respectively, showed considerable enhancement of ion fluorescence and lifetimes upon substitution of H2O by D2O, the latter workers have reported (37) that wet hydrocarbon solutions of the thenoyltrifluoroacetone chelate of europium showed no enhancement of quantum yield and lifetime upon replacing the H2O present by D2O. They suggested that whereas deuteration enhanced the fluorescent properties of the free ions by inhibiting nonradiative deactivation of the Do level, the quantum efficiency of Do luminescence obtained upon direct excitation of this level (JO, 11) is already so high in the fluorinated diketone chelates e.g. thenoyltrifluoroacetone) that deuteration of the environment should have little further enhancing effect. 

Windsor and his co-workers 10, 11) have shown, by direct excitation of the levels in a number of europium compounds, that the quantum yield of fluorescence decreases progressively as one successively excites Do, Di, and Do. While the yield on direct excitation of Do is quite dependent on the particular compound and medium (the value is 0.82 for the thenoyltrifluoroacetone chelate in acetone solution), the proportion of the energy lost between e.g. - Do and - Do within a given compound is rather insensitive to changes in the environment. These nonradiative processes from " D and Di, whose nature is not understood, would appear to be responsible for most of the ca. 40% energy loss in these materials. 

M. Aihara, M. Arai, and T. Taketatsu, Flow Injection Spectrofluorimetric Determination of Europium(III) Based on Solubilizing Its Ternary Complex with Thenoyltrifluoroacetone and Trioctylphosphine Oxide in Micellar Solution. Analyst, 111 (1986) 641. 

Thiophen Derivatives of Analytical Interest.—2-Thenoyltrifluoroacetone has maintained its position as a chelating agent in analytical chemistry. Papers describing its use in the extraction or determination of thorium, copper, europium, thallium, niobium, and molybdenum have appeared. The effect of copper(n) on the formation of monothenoyltri-fluoroacetonatoiron(iii) has been studied. The stability constants of some bivalent metal chelates of di-(2-thenoyl)methane have been determined. 3-Thianaphthenoyltrifluoroacetone has been proposed as a reagent for the spectrophotometric determination of iron(iii) and cerium(iv). The stabilities of metal chelates formed from derivatives of thiophen-2-aldehyde and of rare-earth carboxylates of thiophen-2-carboxylate have been studied. 

The mass spectra of the lanthanide complexes of thenoyltrifluoroacetone, [R(CF3C0CHC0C4H3S)3], have been obtained for samarium, europium, gadolinium, and terbium (Das and Livingstone, 1975). The spectra are similar and fluorine migration to the metal ion with concomitant loss of CF2 occurs. The species RFJ was observed for samarium, gadolinium, and terbium and RF was observed for the easily reduced ions samarium and europium. No oxidation of terbium to terbium(IV) occurred. A mechanism for the fragmentation has been presented. 

Rare-earth jS-diketonate complexes can be synthesized by extraction methods. Halverson et al. (1964a, 1964b) obtained Lewis base adducts of europium(III) j8-diketonates by equih-bration of an aqueous solution of europium(lll) nitrate with a solution of the -diketone (or its ammonium salt) and of the Lewis base in diethyl ether. As the Lewis base, trioctylphosphine oxide (topo), tributylphosphate (tbp) or dihexylsulfoxide (dhso) were used. The molar ratios Eu + diketone Lewisbase were 1 3 2. The complexes are formed in the ether layer, and could be obtained as viscous oils from the ether solution. Richardson and Sievers (1971) prepared tris complexes of 1,1, l,5,5,6,6,7,7,7-decafluoro-2,4-heptanedione by extraction of an aqueous solution of the decafluoroheptanedione in diethyl ether. The rare-earth chlorides were used in 10 to 50% excess in order to prevent the formation of the corresponding tetrakis complexes. [Eu(tla)3(phen)] was prepared by extraction of an aqueous solution of europium(III) chloride, 2-thenoyltrifluoroacetone and 1,10-phenanthroline with benzene (Melent eva et al., 1966). After separation of the benzene layer from the aqueous layer, the [Eu(tta)3(phen)] complex was precipitated by addition of petroleum ether to the benzene layer. 

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