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Abstract:
[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)].
