Photochromism of Diarylethenes with Two Nitronyl Nitroxides:Photoswitching of an Intramolecular Magnetic Interaction

摘要

Photochromic diarylethenes that have P-phenyleve-substituted benzothiophene aryl groups with and without nitronyl nitroxide radicals at both ends of the molecules were synthesized.The abworption maxima of the closedring isomers showed a hypsochromic shift with the increase in the #pi#-conjugated chain length.The unique behavior was attributed to the stabilization by the resonant quinoid structures.Both photocyclization and photocycloreversion quantum yields of the diarylethene with nitronyl nitroxide radicals were found to increase with the increase in the #pi#-conjugated chain length.Photoswitching of the magnetic interaction between two nitronyl nitroxide radicals was studied by means of ESR spectroscopy.The change in exchange interaction between open- and closed-ring isomers of 1,2-bis{6-{4-[4-(1-oxyl-3-oxide-4,4,5,5-tetramethylimidazolin-2-y1)phenyl]phenyl}-2-methyl-1-benxothiophen-3-yl}hexafluorocyclopehtene was determined to be more than 30-fold.