Non-destructive all-optical readout through photoswitching of intramolecular excimer emission

We report the first intramolecular excimer photoswitching induced by molecular motion within a dithienylethene (DTE) molecule, without destructive readout. The photochromic compounds DTE 1 bears two pyrene chromophores, judiciously positioned to face each other in the DTE’s open form. The close proximity of the pyrenes in the open form is confirmed by NMR experiments and geometry optimization. Intense pyrene excimer luminescence is recorded, both upon one- and two-photon excitation (OPE and TPE). The photocyclization reaction of the DTE core induces a molecular motion of one pyrene moiety which thus prevents the possibility of formation of an excimer. Our DTE-based pyrene 1 is stable upon TPE irradiation and shows a high photo-cyclization quantum yield. Such properties specifications, allow us to report the original non-destructive readout fluorescence by alternative exposure to OPE and TPE.