Photochromism and light-induced radical behaviours of biindenylidenedione derivatives in solid state

Reactions of 2,2′-biindanylidene-1,1′,3,3′-tetraone with arylmagnesium bromide gave 3,3′-diaryl-3,3′-dihydroxy biindenylidenedione derivatives. These compounds exhibited photochromism in solid state, in which the formation of the isomeric radical species was confirmed by the election spin resonance spectroscopy, and the structures of new compounds 1 and 4 were determined by X-ray crystallography. The relationship between structures and properties was also discussed.