NIR-Responsive Double Closed-Ring Isomer of a Diarylethene Fused Dimer Synthesized by Stepwise Photochemical and Oxidative Cyclization Reaction.

The double closed-ring isomer of a diarylethene fused dimer was synthesized by a combination of photochemical and oxidative cyclization reaction. The double closed-ring isomer of a diarylethene fused dimer has fixed π-conjugation in a rigid planar framework so that this compound has been long-desired. However, with respect to the photocyclization of a diarylethene dimer with strong electronic interaction, the second-step cyclization is known to be suppressed due to fast energy transfer into the closed-ring isomer generated in the first-step photocyclization.