14456-47-4Relevant articles and documents
Switchable green and white luminescence in terbium-based ionic liquid crystals
Getsis, Anna,Mudring, Anja-Verena
, p. 3207 - 3213 (2011)
[C12mim]Br (C12mim = 1-dodecyl-3-methyl) and [C 12mpyr]Br (C12mpyr = N-dodecyl-N-methylpyrrolidinium), both doped with TbBr3, as well as the neat compounds [C 12mim]3[TbBr6] and [C12mpyr] 3[TbBr6] show mesomorphic behavior and are able to form smectic liquid crystalline phases. The thermal phase behavior of all compounds was investigated by hot-stage polarizing optical microscopy and differential scanning calorimetry. Whilst the doped compounds crystallize around room temperature, the neat compounds solidify as glasses around-5 °C and qualify also as ionic liquids. The crystal structure of the acetonitrile solvate of the imidazolium compound, [C12mim]3[TbBr6] ·2CH3CN, could be determined by single X-ray diffraction. The structure features alternating double layers of [C12mim]+ cations and [TbBr6]3- octahedra with hydrogen bonded acetonitrile. [C12mim]3[TbBr6]·2CH 3CN can serve as a structure model for the smectic mesophase of the solvate-free [C12mim]3[TbBr6]. All materials show strong green luminescence from the 5D4-level of Tb3+ after excitation into the 4f8→ 4f 75d1 transition. In case of the imidazolium compounds, the color of this emission can be switched between green and blue-white depending on the excitation energy. After excitation with λex = 254 nm, strong green emission mainly from the 5D4-level of Tb 3+ is observed. With λex = 366 nm, only the blue-white luminescence from the imidazolium cation itself is detected.
Lanthanide containing ionic liquid crystals: EuBr2, SmBr 3, TbBr3 and DyBr3 in C12mimBr
Getsis, Anna,Mudring, Anja-Verena
, p. 1726 - 1734 (2011/01/07)
Doping the ionic liquid crystal C12mimBr with various lanthanide halides yields interesting novel liquid crystalline and luminescent materials. The thermal phase behavior of all compounds was investigated by hot-stage polarizing optical microscopy and differential scanning calorimetry and the photophysical properties were determined by luminescence spectroscopy. C 12mimBr itself is an ionic liquid crystal that shows bluish-white emission upon excitation with UV light due to transitions in the imidazolium p-system. Doping lanthanide bromides into C12mimBr with concentrations of about 1 mol-% does not affect the liquid crystalline behavior of the host materials to a great extent and room temperature liquid crystals are obtained. All materials show an appreciable luminescence. EuBr2 in C12mimBr yields a material, which shows a blue emission originating from 4f-5d-transitions. SmBr3-doped samples show a red and TbBr 3 samples a green luminescence. Upon doping C12mimBr with DyBr3 an orange luminescent liquid crystalline material is obtained. Most interestingly the emission color for the TbBr3 and DyBr 3 containing materials can be tuned from bluish-white (mainly C 12mimBr emission) to green (for TbBr3) and orange-yellow (for DyBr3) depending on the wavelength of the excitation light used.
Lanthanide(III) halides: Thermodynamic properties and their correlation with crystal structure
Rycerz,Gaune-Escard
, p. 167 - 174 (2008/10/09)
Temperatures and enthalpies of phase transitions of 17 lanthanide(III) halides determined experimentally are reported. Correlations were made between temperature of fusion of lanthanide(III) halides, on the one hand, and enthalpy of fusion, on the other, versus atomic number of lanthanide. According to this classification, the lanthanide(III) halides split into groups, as also do the corresponding crystal structures. A correlation between the crystal structure of lanthanide(III) halides and their respective entropy of fusion (or entropy of fusion + entropy of solid-solid phase transition) was inferred from the aforementioned features. Fusion in those halides with hexagonal, UCl3-type and orthorhombic, PuBr3-type, structures entails an entropy of fusion change (or entropy of fusion + entropy of solid-solid phase transition change) by 50 ± 4 J mol-1 K-1. The homologous entropy change within the group of halides having the rhomboedric, FeCl3-type, structure, is smaller and equals 40 ± 4 J mol-1 K-1. Halides with monoclinic, AlCl3-type, crystal structure constitute a third group associated to an even smaller entropy change upon fusion, only 31 ± 4 J mol-1 K-1. The halides with lower entropies of fusion also have a lower S1300 K - S298 K indicating either a higher degree of order in the liquid or a higher entropy in the solid at room temperatures.
