Elucidation of the formation of cation–π complexes and their conformational behavior in solution by CD spectroscopy

Circular dichroic exciton Cotton effects were observed for some pyridinium salts and a quinolinium salt having a benzyl or a naphthylmethyl group, which revealed the existence of an intramolecular cation–π interaction. The sign of the Cotton effects deduced the relative position of the two chromophores.