Reductive cleavage of C[double bond, length as m-dash]C bonds as a new strategy for turn-on dual fluorescence in effective sensing of HS.

Reductive cleavage of alkenes is rarely reported in synthetic chemistry. Here we report a unique HS-mediated reductive cleavage of C[double bond, length as m-dash]C bonds under mild conditions, which is a successful new strategy for the design of probes for effective sensing of HS with turn-on dual-color fluorescence. A short series of phenothiazine ethylidene malononitrile derivatives were shown to react with HS, reductive cleavage of C[double bond, length as m-dash]C bonds with intramolecular cyclization reactions to form thiophene rings. Enlightened by this new reaction mechanism, four effective probes with turn-off to turn-on fluorescence switches were successfully applied for sensing HS, an important gaseous signalling molecule in living systems, among which PTZ-P4 exhibited two fluorescent colors after reductive cleavage. The dual-color probe was applied for imaging endogenous HS and showed distinct differences in brightness in living for wild type N2, () mutants (higher levels of endogenous HS), and () mutants (lower levels of endogenous HS). The discovery of HS-mediated reductive cleavage of C[double bond, length as m-dash]C bonds is expected to be valuable for chemical synthesis, theoretical studies, and the design of new fluorescent HS probes.