Analysis of Cyclization Reaction from Higher Excited States ofDiarylethene Derivatives Having a Substituted Azulene Ring

摘要

Diarylethene derivatives have excellent photochromic properties with high thermalstability and a high fatigue resistance.The open form cyclizes to the closed form via S1excited state by UV irradiation.Azulene,on the other hand,is known as a compound whichviolates Kasha's rule.Due to the slow internal conversion from S2 to S1 caused by therelatively large energy gap,it shows fluorescence from S2 state.It has been reported that adiarylethene having an azulene ring show photochromism from S8 excited state mainlycomposed of HOMO-1→LUMO+2 transition.We have also previously reported thesyntheses and properties of some diarylethene derivatives having an azulene ring substitutedby electron donating or electron withdrawing group at 1-or 3-position.Some compoundsunderwent cyclization reaction via higher excited states,while others did not.