Europium halides

The effusate which condensed on liquid nitrogen cooled copper collection targets was assayed by X-ray fluorescence. The Eu La radiation was determined at the peak maximum (26 = 36.84°, graphite analyzing crystal) by an external standard technique. Previous data (15, 19) have indicated the sticking coefficient of gaseous europium halide on chilled copper is approximately unity. 

The thermochemistry of rare-earth trifluorides was summarized in Gmelin Hand-buch (1976) and the thermochemistry of rare-earth tribromides and triiodides was summarized in Gmelin Handbuch (1978). The thermochemistry of trivalent rare-earth trichlorides was critically assessed by Morss (1976). Enthalpies of formation of most of the lanthanide tribromides were determined by Hurtgen et al. (1980). Thermodynamic properties for europium halides were assessed by Rard (1985). Only enthalpies of formation of Sc, Y, Dy and Tm triiodides have been redetermined since the classical work of Hohmann and Bommer (Morss and Spence 1992). A recent set of literature values of enthalpies of formation of rare-earth solid and gaseous trihalides has been published, accompanied by Born-Haber cycle estimated values for all trihalides (Struck and Baglio 1992). 

Ion-exchange reactions were used for the accumulation of europium(III) [158] and iron(III) [159] ions on the surface of GCE coated with Nafion , and chromium(VI) ions on the surface of GCE covered by a pyridine-functionalized sol-gel film [160], which were combined with the stripping SWV Furthermore, a cathodic stripping SWV was used for the determination of sulfide [161,162], thiols [163-166], selenium(lV) [167-170], halides [171-173] and arsenic [174] accumulated on the snrface of mercury electrode. 

Solutions of alkali metals in ammonia have been the best studied, but other metals and other solvents give similar results. The alkaline earth metals except- beryllium form similar solutions readily, but upon evaporation a solid ammoniste. M(NHJ)jr, is formed. Lanthanide elements with stable +2 oxidation states (europium, ytterbium) also form solutions. Cathodic reduction of solutions of aluminum iodide, beryllium chloride, and teUraalkybmmonium halides yields blue solutions, presumably containing AP+, 3e Be2, 2e and R4N, e respectively. Other solvents such as various amines, ethers, and hexameihytphosphoramide have been investigated and show some propensity to form this type of solution. Although none does so as readily as ammonia, stabilization of the cation by complexation results in typical blue solutions... 

In 1939 Klemm and Doll [276] prepared all the halides of divalent europium and studied the magnetic characteristics of these compounds. The magnetic susceptibilities (X g) and effective moments of the fluoride, chloride, bromide and iodide are tabulated in Table 15. Except for the... 

Parker, D., Senanayake, P. K., Williams, J. A. G., Luminescent sensors for pH, p0(2), halide and hydroxide ions using phenanthridine as a photosensitiser in macrocyclic europium and terbium complexes. J. Chem. Soc., Perkin Trans. 21998, 2129-2139. 

This work was undertaken as a part of a study of divalent lanthanide halides in an effort to obtain more accurate thermal data on EuC12 and to determine if the close similarity of the high-temperature thermodynamic properties of divalent europium and alkaline earth compounds emphasized earlier (13-16) could be extended. 

In halides lower oxidation states are more stable than in oxides. In most oxide lattices europium and ytterbium are the only lanthanide ions which, because of... 

Halides can form colour centres with absorption bands in the visible range. Doped with europium whose decay time of the allowed 5d —< 4f transition is of the order of 1 fis, they are the most appropriate materials. Because of the presence of fluorine, only BaCIF Eu and BaBrF Eu have a high enough chemical stability for screens fabrication. The highest efficiencies of photostimulated luminescence have been obtained with the fluorobromide (Amax = 390 nm). 

Figure 21 Crystal structures of various ternary phosphide halides. Europium (cadmium, mercmy), phosphorus, and halogeu atoms are drawn as large light grey, filled, and open circles, respectively. Some relevant coordination polyhedra aroimd the phosphorus atoms and the P-P bonds are shown. The HgBr4 tetrahedra in the (Hg2P)2HgBr4 strucmre fill the channels of the three-dimensional [Hg2P] network...

Divalent lanthanide chemistry has been dominated by the most readily accessible divalent lanthanide metals samarium(II), europium(II), and ytterbium(II) (classical ) for decades, and a large number of divalent lanthanide compounds have been prepared [92], There are three routes to generate divalent organolanthanide complexes oxidative reaction of lanthanide metal, metathesis reaction of a divalent lanthanide halide, and reductive reaction of a trivalent lanthanide complex. 

Compounds of divalent samarium, europium, and ytterbium are well-known. In recent years, lower halides of other lanthanides, such as neodymium 48), praseodymium 45, 49, 90), and thulium 4) have been obtained by reducing the trihalide with the metal. The corresponding reaction of thorium tetraiodide with thorium metal has led to the identification of two crystalline forms of Thl2 41, 91) it is unlikely that the Th ", or even Th ", ion is present in Thl2, but like Prl2, which is formulated as Pr " (r)2( ) (2), the compound is probably of the type Th " (r)2(2 ) 41). Certainly one crystal form is diamagnetic 41), suggesting the latter formulation. 

Luminescence spectra of a series of Ce(III) compounds containing halide, alkyl, aryl, ether, nitrile, and cyclic aromatic hydrocarbon ligands have been recorded under a range of conditions auid a matrix isolation UV study of the direct synthesis of (C2H4>f Eu using europium atoms has been reported. ... 

The luminescence of terbium (42) and europium macrocyclic complexes have been studied and found to depend upon pH. The phenanthridine sidechain acts as a photosensitizer and (42) exhibits luminescence quenched by molecular oxygen corresponding Eu compounds exhibit halide-quenched emisssion. ... 

Europium, samarium and ytterbium also give Grignard-like reagents, RMgl, when the metal reacts with alkyl halides in THF.370... 

Solid Europium Compounds. Solid europium oxide, chalcogenides, halides, carbonate, phosphate, etc., may be obtained by reduction of the corresponding Eu3 + compounds or, metathetically, from EuC12. The metal reacts with liquid ammonia at 50° to give the orange amide, Eu(NH2)2, which gives EuN when heated.54 The compounds are usually isostructural with the Sr2 + or Ba2+ analogs. However, definite lower fluorides and chlorides appear to exist except for La, Ce, Pr, Gd, Tb and Er.57... 

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