HELICAL TWISTING POWER AND CIRCULAR DICHROISM AS CHIRALITY OBSERVATIONS : THE INTRAMOLECULAR AND INTERMOLECULAR CHIRALITY TRANSFER

The helical twisting power (HTP) of a chiral guest in a chiral or achiral mesophase as host system is a chirality observation and, therefore, should be a suitable quantity for determination of the absolute configuration. Rules correlating the sign of the HTP and the absolute configuration of the guest are not known or, as sometimes proposed, do not exist at all. The sign and size of the HTP of compounds with one or more chiral centers are determined by the effects of an intramolecular and an intermolecular chirality transfer. The intramolecular chirality transfer is a well known phenomena in the development of sector or helicity rules for circular dichroism spectroscopy. Due to the strong omisotrophy of the intermolecular chirality transfer in a liquid crystal phase the development of rules for the determination of the absolute configuration from the sign of the HTP is called in question. By analysis of the HTP and the circular dichroism (CD) of mono- and bis-aminoanthraquinones we now show that the development of rules in comparison to CD measurements does seem to be possible if some specialities of the anisotropic mesophases are taken into account. Chirality 9:407–423, 1997. © 1997 Wiley-Liss, Inc.