- Structural characterization of methanol substituted lanthanum halides
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The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75·5.25(MeOH)]+0.25 [LaBr3.25·4.75(MeOH)]-0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(μ-Cl)]2 (6) and [La(MeOH)9](I)3·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4-6 were slightly higher in comparison to their hydrated counterparts.
- Boyle, Timothy J.,Ottley, Leigh Anna M.,Alam, Todd M.,Rodriguez, Mark A.,Yang, Pin,Mcintyre, Sarah K.
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p. 1784 - 1795
(2010/07/03)
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- Systematics and anomalies in rare earth/aluminum bromide vapor complexes: Thermodynamic properties of the vapor complexes LnAl3Br12 from Ln = Sc to Ln = Lu
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Systematics and anomalies in the rare earth/aluminum bromide vapor complexes have been investigated by the phase equilibrium-quenching experiments. The measurements suggest that the LnAl3Br12 complexes are the predominant vapor compl
- Wang, Zhi-Chang,Yu, Jin
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p. 4248 - 4255
(2008/10/09)
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- Light-emission and excited-state dynamics in Tm2+ doped CsCaCl3, CsCaBr3, and CsCaI3
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The light-emission and photophysical properties of CsCaCl 3:Tm2+ (1.04%), CsCaBr3:Tm2+ (0.48%), and CsCaI3:Tm2+ (0.76%) are presented. We find that Tm2+ is a multiple emitter under 21 834 cm-1 laser excitation at low temperatures in all three compounds. Several distinct types of emission are observed and characterized: sharp and long-lived 4f-4f emission in the infrared (IR) and up to four broad and fast decaying emission bands in the near-IR and visible, originating from the 4f-5d states of Tm2+. The optical spectroscopic properties of the samples are compared, and we find that the measured differences in the relative intensities and the shifts in the position of the emissions can be related to the chemical influence on the absorption and emission properties of Tm2+. Thus, it nicely illustrates the principle of chemical variation on the optical spectroscopic properties. An investigation of the temperature dependence of the luminescence yields important information about the dynamics of the excited states. The interplay and competition between radiative and nonradiative pathways is explained and modeled using a single configurational coordinate approach.
- Grimm, Judith,Suyver, J. Freek,Beurer, Eva,Carver, Graham,Guedel, Hans U.
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p. 2093 - 2101
(2008/10/09)
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- Synthesis and crystal structure of (NH4)3Cu4Ho2Br13. Further bromides of the (NH4)3Cu4M2Br13 Type (M = Dy-Lu, Y) and on Rb3Cu4Ho2Br13
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Single crystals of (NH4)3Cu4Ho2Br13 were obtained for the first time from the reaction of CuBr with HoBr3 which was contaminated with NH4Br: cubic, space group Pn3, Z = 2, a = 1101.71(5) pm. The crystal structure may be considered as a variant of the fluorite type according to [(HoBr6)4] [(NH4)6Cu4Br)2] ≡ Ca4F8. Pure products can be prepared from the binary halides in glass ampoules at 350°C. The bromides (NH4)3Cu4M2Br13 (M = Dy-Lu, Y) and Rb3Cu4Ho2Br13 are isotypic with (NH4)3Cu4Ho2Br13. Johann Ambrosius Barth 1996.
- Wickleder, Mathias S.,Bohnsack, Andreas,Meyer, Gerd
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p. 675 - 678
(2008/10/09)
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