CHIRAL POLYMETHINE DYES: A REMARKABLE BUT FORGOTTEN CONJUGATED π SYSTEM

摘要

Chiral polymethine dyes constitute a particular class of conjugated π systems. Artificial chiral polymethine dyes were first synthesized by Koenig and Langbein in 1928 in order to clarify the electronic structure of cyanine dyes; some natural dyes such as musca-aurin Ⅰ (from the toadstool fly agaric) and betanin (from the vegetable red beets) are known to be chiral pentamethinium cyanine dyes, the chirality of which stems from L-α-amino acids as end-groups. The reasons why chiral polymethine dyes are not only of historical interest but once again the subject of research are explained.