Induced Cholesteric Phases of Chiral Aminoanthraquinones

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Abstract
The temperature dependence of the HTP of 1, 4-bis-(S-1-(1-naphthyl)ethylamion)-9, 10-anthraquinone [S-5] or [R-5] and of 1, 8-bis-(S-1-(1-naphthyl)ethylamion)-9, 10-anthraquinone [S-6 in ZLI 1695 (Merck) is expounded to be a consequence of a shift of an equilibrium between at least two conformers A ⇄ B with an equilibrium constant K < 1, derived from the temperature dependence of a CD couplet. Conditional on this equilibrium, the HTP(T) is a linear function of the amplitude of the couplet. The sign of the CD of the isotropic solution is determined by the conformer A whereas the sign of the HTP is given by B. The helix inversion for [S-5] in ZLI 1132 (Merck) appears to be a result of a slightly increasing concentration of the conformer B.