Nitric Oxide Sensing through 1,2,3,4-Oxatriazole Formation from Acylhydrazide: A Kinetic Study

A simple molecular probe displays
highly selective turn-on response
toward NO by the unprecedented NO-induced formation of a 1,2,3,4-oxatriazole
ring exhibiting no interference from various endogenous biomolecules
including DHA, AA, etc. Kinetics of the reactions between NO and the
probe provide a mechanistic insight into the formation of 1,2,3,4-oxatriazole
which showed that, though initially 1,2,3,4-oxatriazole is formed
and extractable in solid form, it exists in equilibrium with the ring
opened azide form which ultimately hydrolyzed and converted to carboxylic
acid and nitrate. The reaction displays second-order dependence on
[NO] and first-order on [Probe]. The probe is water-soluble, cell
permeable, and noncytotoxic and appropriates for live cell imaging.
This constitutes the first report where there is a direct evidence
of NO-induced ring closing reaction of an acyl hydrazide moiety leading
to the formation of 1,2,3,4-oxatriazole.