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Quinuclidinium zwitterions of the [closo-1-CB11H12]− anion are synthesized in 2−3 steps and their structural, thermal, and dielectric properties are evaluated. Surprisingly, a nonliquid crystalline zwitterion exhibits the most favorable dielectric properties in a nematic liquid crystal host. The analysis of the experimental data is augmented with density functional theory results.
Antipodal substitution of the [closo-1-CB11H12]− anion with a 4-pentylquinuclidinium fragment and alkyl groups in positions C(1) and B(12) gave polar zwitterions 1[n] and 2[n]. The molecular structure of 1 was established using X-ray diffraction (XRD) methods: P1̅, a = 15.162(2) Å, b = 16.546(3) Å, c = 19.794(3) Å; α = 84.871(2)°, β = 84.057(2)°, γ = 84.058(3)°; Z = 8. All compounds exhibit high temperature in-plane ordered smectic phases that are stabilized by dipolar interactions. The ordered phases were investigated by powder XRD methods. Thermal and dielectric parameters for two derivatives, 1 and 1, were evaluated in nematic hosts, ClEster and BPhF. The dielectric data were analyzed with the Maier-Meier formalism augmented with density functional theory methods, and the results were compared to those for similar zwitterions previously reported.
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