Helical twisting power of chiral mono- and bis-aminoanthraquinones. Intramolecular and intermolecular chirality transfer in liquid-crystal phases

Abstract

The helical twisting power (HTP) of mono- and bis-aminoanthraquinones with chiral substituents depends strongly on the position of substitution. It is shown that the Intramolecular chirality transfer yields, for each compound, several conformers which are different for the 1-cyclohexylethyl, 1-phenylethyl and 1-naphthalen-1-ylethyl substituents. Each conformer contributes differently to the HIP of a compound. Furthermore, the HIP of a bis-substituted compound is approximately the sum of the HIP values of the corresponding mono-substituted compounds if the orientation of the substituents with respect to the orientation axis (principal axis of the order tensor belonging to the largest eigenvalue) is the same in each case. This means that the contribution of a ‘chiral area’, induced around an asymmetric carbon atom by Intramolecular chirality transfer, to the HTP depends on its orientation with respect to the orientation axis. A variation of this orientation can cause even a change of sign of the HIP in spite of the fact that the dependence of the HIP on the order parameters, S* and D*, is small.