Supramolecular detection of metal ion binding: Ligand conformational control of cholesteric induction in nematic liquid crystalline phases

Tripodal tetradentate ligands may act as chemosensor molecules. Their abili ty to torque a nematic into a cholesteric phase increases upon complexation with copper ion. Moreover, changes in overall shape of the complexes induc ed by different metals and counter ions were transferred sensitively to the supramolecular level, observed by proportionate changes in the degree of t wisting. Modification of the oxidation state of the metal center also gave large changes in twisting power; this suggests potential application in ele ctrochemical molecular switches, The handedness of the induced cholesteric phase is related to the stereochemistry of the ligand: The small amount of chiral dopant needed for the LC technique (less than 2 nmol) suggests the p ossible determination of the absolute configuration of the parent primary a mines of the ligands.