Fluorogenic Mechanophore Based on Dithiomaleimide with Dual Responsiveness

The maleimide scaffold is widely used for the preparation of fluorogenic probes owing to its good fluorescence quenching ability. Here, we demonstrate that it can be also employed to prepare fluorogenic mechanophores. A dithiomaleimide-based mechanophore with two dansyl fluorophores attached to the maleimide core via the thioether bond is synthesized and incorporated into polymer chains. Upon mechanochemical activation, the relatively weak C–S is cleaved hypothetically due to its low bond dissociation energy, resulting in the removal of the maleimide conjugation and turning on of the dansyl fluorophore with >5-fold increase in the fluorescence emission peak intensity at 510 nm. In addition, an excess of a thiol can also lead to the cleavage of the dansyl fluorophore from the maleimide via thiol-exchange reactions. This mechanophore with dual responsiveness may have potential applications in stress sensing as well as thiol sensing. Moreover, the design concept of the mechanophore may allow access to many other fluorogenic mechanophores, since a number of fluorophores covering a wide range of emission wavelengths have been reported to be quenched by maleimides.