Highly Luminescent Salts Containing Well-Shielded Lanthanide-Centered Complex Anions and Bulky Imidazolium Countercations

In this paper, we report on the syntheses, structures, and characterization of four molten salts containing imidazolium cations and europium(III)- or terbium(III)-centered complex anions. In the complex anions, the lanthanide centers are wrapped by four pseudodiketonate anionic ligands, which prevent them from contacting with high-frequency oscillators and allow them to show intense characteristic europium(III) or terbium(III) emission, small line widths, high color purity, high quantum yields (30−49%), and long decay times (\u3e2 ms)

Dysprosium-Based Ionic Liquid Crystals: Thermal, Structural, Photo- and Magnetophysical Properties

[C(12)mim](3)[DyBr(6)] (C12mim = 1-dodecyl-3-methylimidazolium) represents a new material with interesting luminescent behavior as well as mesomorphic and magnetic properties. The compound was found to show thermotropic liquid crystalline behavior and forms smectic mesophases which were investigated by hot-stage polarizing optical microscopy and differential scanning calorimetry. The emission color Of [C(12)mim](3)[DyBr(6)] can be tuned from white to orange-yellow by the choice of the excitation wavelength. Sample excitation with lambda(ex) = 366 nm leads to the blue-whitish luminescence from the imidazolium, cation itself With),ex = 254 nm the common Dy(III) emission is observed which mainly arises from the (4)F(9/2) --> (6)H(13/2) transition and, in consequence, the sample appears orange. Magnetic measurements show for Dy(III) in [C(12)mim](3)[DyBr(6)] an effective magnetic moment of mu(eff)=9.6 mu(B) at room temperature. The sample shows superparamagnetism and can be manipulated by an external magnetic field. In addition, the crystal structure of the corresponding acetonitrile solvate [C(12)mim](3)[DyBr(6)]center dot 2CH(3)CN (orthorhombic, Pbca, No. 62, Z = 8, Pearson code oP1328, a = 14.888(4) angstrom, b = 18.240(7) angstrom, c = 49.411(13) angstrom, 5596 unique reflections with I(o) > 2 sigma(I(o)), R(1) = 0.1047, wR(2) 0.2442, GOF = 1.167, T = 298(2) K) has been elucidated. It is characterized by alternating double layers Of [C(12)mim](+) cations of opposite orientation and nearly ideal [DyBr(6)](3-) octahedra with hydrogen bonded acetonitrile. The structure Of [C(12)mim](3)[DyBr(6)]center dot 2CH(3)CN serves as a structure model for the solvate free [C(12)mim](3)[DyBr(6)]

Mesomorphic glass-forming ionic complex composed of a pair of cholesterol phthalate and 1-Cn-3-methylimidazolium: Phase transition and enthalpy relaxation behavior

Ionic complexes consisting of a mesogenic cholesterol derivative and 1-alkyl (Cn)-3-methylimidazolium (CnMim) (n = 6–18) were prepared from ethanol solutions containing an equimolar mixture of cholesterol hydrogen phthalate (CHP) and 1-Cn-3-methylimidazolium hydroxide; the imidazolium hydroxide was obtained by anion exchange of 1-Cn-3-methylimidazolium bromide. The complex samples, termed [CnMim][CHP], were examined to evaluate their thermal transition patterns. Excluding the two samples (n = 6, 8) that showed no definite ordered phase, the complexes with n ≥ 10 formed a cholesteric (n = 10, 12) or smectic (n = 14–18) mesophase in a considerably wide range of temperatures; this wide range reflects the additional thermotropic property of the salts of CnMim with longer alkyl chains. These fluid mesophases transformed into a mesomorphic vitreous solid without crystallization in a usual cooling process. For the glassy mesomorphic samples of selected complexes (n = 10, 18), the enthalpy relaxation behavior was followed as a function of the aging temperature and time, and the data were analyzed in terms of a Kohlrausch–Williams–Watts (KWW) type of stretched exponential equation. A very narrow distribution of relaxation times was observed for the “liquid crystalline glasses”, indicating the high uniformity of the relaxation mode