Highlights
Controlling Chirality by Circularly Polarized Light Irradiation
(Published in Angew. Chem. Int. Ed. Takezoe/Ishikawa Lab. Watanabe Lab.)
‘Cricular-polarization-induced enantiomeric excess in an achiral bent-shaped liquid crystal’ S.-W. Choi, T. Izumi, Y. Hoshino, Y. Takanishi, K. Ishikawa, J. Watanabe and H. Takezoe, Angew. Chem. Int. Ed. 45 (2006) 1382-1385.
Generally chiral species are necessary to synthesize chiral molecules. Only the exception is the use of circularly polarized light. In this method, however, efficiency is low and only a few %ee has been obtained except for a few examples. It is known that there are some phases in which achiral molecules are spontaneously segregated into chiral domains in banana mesogens. We succeeded in obtaining almost 100%ee in a banana mesogen with azo linkages shown in Fig. 1. By irradiating the sample cell with right or left circularly polarized light, left or right chiral domains were nucleated over the whole irradiated area.
Fig. 1 Chemical structure of a banana mesogen used and
CD spectra after irradiation of circularly polarized light.