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

[C(12)mim](3)[DyBr6] (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)[DyBr6] 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 F-4(9/2) --> H-6(13/2) transition and, in consequence, the sample appears orange. Magnetic measurements show for Dy(III) in [C(12)mim](3)[DyBr6] 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)[DyBr6]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 [DyBr6](3-) octahedra with hydrogen bonded acetonitrile. The structure Of [C(12)mim](3)[DyBr6]center dot 2CH(3)CN serves as a structure model for the solvate free [C(12)mim](3)[DyBr6].