Formation or Cleavage of Rings via Sulfide-Mediated Reduction Offers Background-Free Detection of Sulfide

A set of three highly
selective probes for sulfide detection has
been developed. Two novel mechanistic strategies for the detection,
including (a) transformation of a pro-fluorophore into an active fluorophore
and (b) destruction of a fused ring to activate a fluorophore, have
been explored. The structural features of the probes including azido
groups (“active” and “latent”) and leaving
groups (with or without being attached to the fluorophore) have been
investigated. During the course of the mechanistic studies, the single-crystal
structures of all the probes and the products were obtained. One of
the probes proved to be superior in terms of its ability to detect
sulfide in pure water via an in situ formation of
a fluorophore from a nonfluorescent precursor. These cheap and easy-to-prepare
probes offer practical applications of sulfide recognition in environmental
water samples and in the ovaries of fruit flies. A detection and quantification
method using one of these probes and analysis with a smartphone enabled
nonspecialists to detect sulfide reliably.