A turn-on mode fluorescent diarylethene having an azacrown ether receptor: Metal-ion-gated enhancement of the photoreactivity and fluorescence

We report the metal-ion-gated enhancement of the photoreaction and fluorescence of a newly synthesized photoswitchable fluorescent diarylethene derivative having an azacrown ether receptor. In the absence of metal ions, the diarylethene molecule underwent the photoisomerization and turn-on mode switching of fluorescence, but the photoreactivity and fluorescing ability were suppressed by intramolecular photoinduced electron transfer (PET) from the azacrown ether moiety to the diarylethene unit. Upon binding of a metal ion to the azacrown ether, the PET process was blocked, and the photoreactivity and fluorescence were significantly enhanced. Such photoswitchable fluorescent molecules that change their photoresponsive properties upon recognizing metal ions have the potential to function as metal-ion chemosensors and molecular probes in metal-ion-sensitive super-resolution fluorescence microscopy.