Angewandte Chemie International Edition
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Cover Picture (Angew. Chem. Int. Ed. 3/2000)
The cover picture shows at the top left green and red solid films that are formed by spin coating the transparent solution (shown between the samples) of a nonpolymeric dicholesteryl ester (ball-and-stick model shown in the background). The iridescent colors of the solid films can be controlled by changing the temperature within a region in which the diester is crystalline. Transmission, circular dichroism, and optical rotation dispersion spectra reveal that the helical ordering of the molecules (shown on the right) is the origin of the iridescent colors of the solid films. This is the first observation of the occurrence of this phenomenon for nonpolymeric compounds and may provide a simple method for preparing reflecting films. Further details on the synthesis and properties of these colorful supramolecular aggregates are reported by N. Tamaoki et al. on p. 509 ff.