Synthesis and Characterization of Quinuclidinium Derivatives of the [closo-1-CB₁₁H₁₂]^- Anion as Potential Polar Components of Liquid Crystal Materials

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[5] was established using X-ray diffraction (XRD) methods: P1Ì..., 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[0] and 1[6], 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.