How much can an electric dipole stabilize a nematic phase? Polar and non-polar isosteric derivatives of [closo-1-CB9H10]− and [closo-1,10-C2B8H10]

Abstract

Replacement of a C–C fragment with an N⁺–B⁻ fragment leads to pairs of isosteric non-polar/polar nematics with a difference in the calculated molecular dipole moment of about 12 D. Contrary to the expectations, the uniform increase of the dipole moment does not affect phase stability equally, and a strong dependence on the substituent structure is observed. For one of the polar derivatives (5b, µ = 20 D) a record high dielectric anisotropy (Δε = 113) was measured in dilute nematic solutions.