Zwitterionic pyridinium derivatives of [closo-1-CB_9H_10]− and [closo-1-CB_11H_12]− as high Δε additives to a nematic host

Abstract

Substituted closo-carbaborate–pyridinium zwitterions were prepared in 35–50% yield by reacting 1-amino-closo-1-carbaborates with 4-alkoxypyrylium triflates. Two of the new materials, 1[6]d and 2[10]b, exhibit a high temperature SmA phase, whose stability is driven by dipolar interactions. Solution studies in a nematic host, ClEster, demonstrated high positive dielectric anisotropy of these new compounds (Δε ≈ +50) resulting from a longitudinal molecular dipole moment of about 20 D.