A charge-transfer complex of 10,10'-dihydroxy-9,9'-biphenanthryl and methylviologen as a visual inclusion host system.

A charge-transfer (CT) complex, composed of 10,10'-dihydroxy-9,9'-biphenanthryl as the electron donor and 1,1'-dimethyl-4,4'-bipyridinium dichloride as the electron acceptor, is formed only by the inclusion of guest molecules. The color of this inclusion CT complex is sensitive to the component guest molecules.