Chiral Induction by Optically Active Aminoanthraquinones in Nematic Phases

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Abstract
The helical twisting power of chirally substituted mono- and bis- aminoanthraquinones in ZLI 1695 is only weakly temperature dependent. An exception are the naphthyl substituted compounds where the temperature dependence is correlated with the temperature dependent equilibrium between at least two conformers. The order of the chiral dopant in the cholesteric phase is described approximately by the order parameters S*, D* and the orientation of the principal axes (x*i) of the order tensor against the molecular skeleton. Whereas there is no significant dependence of the HTP on S* and D*, the HTP is very sensitive to the orientation of the x*i axes. Varying their direction by different types of substitution it can be shown that an approximate additivity rule of the HTP contributions from equal chiral structures holds only if the orientation axis (x*3) is the same for the molecules compared.