Synthesis and crystalline state photochromism of 3,3′-diaryl biindenylidenedione derivatives

A new series of 3,3′-diaryl biindenylidenedione derivatives were synthesized through Grignard reaction. Some of their stereoisomers were obtained by photochemical transformation upon heating and a plausible reaction mechanism was proposed. Most of these compounds exhibited photochromism in crystalline states as well as generation of stable organic radicals. The absolute configurations of the stereoisomers were determined by single crystal X-ray crystallography. The results showed that the position of substituent could dramatically affect molecular structure and photochemical properties of the biindenylidenedione derivatives.