HELICAL TWISTING POWER OF CHIRAL MONO-AMINOANTHRAQUINONE AND BIS-AMINOANTHRAQUINONE - INTRAMOLECULAR AND INTERMOLECULAR CHIRALITY TRANSFER IN LIQUID-CRYSTAL PHASES

The helical twisting power (HTP) of mono- and bis-aminoanthraquinones with chiral substituents depends strongly on the position of substitut ion. It is shown that the intramolecular chirality transfer yields, fo r each compound, several conformers which are different for the 1-cycl ohexylethyl, 1-phenylethyl and 1-naphthalen-1-ylethyl substituents. Ea ch conformer contributes differently to the HTP of a compound. Further more, the HTP of a bis-substituted compound is approximately the sum o f the HTP values of the corresponding mono-substituted compounds if th e orientation of the substituents with respect to the orientation axis (principal axis of the order tensor belonging to the largest eigenval ue) is the same in each case. This means that the contribution of a 'c hiral area', induced around an asymmetric carbon atom by intramolecula r chirality transfer, to the HTP depends on its orientation with respe ct to the orientation axis. A variation of this orientation can cause even a change of sign of the HTP in spite of the fact that the depende nce of the HTP on the order parameters, S and D*, is small.