Directly obtaining kinetic and mechanistic data for the reactions of nitroxyl (HNO) with biomolecules (k≈10 -10 m s ) is not feasible for many systems because of slow HNO release from HNO donor molecules (t is typically minutes to hours). To address this limitation, we have developed a photoactivatable HNO donor incorporating the (3-hydroxy-2-naphthalenyl)methyl phototrigger, which rapidly releases HNO on demand. A "proof of concept" study is reported, which demonstrates that, upon continuous xenon light excitation, rapid decomposition of the HNO donor occurs within seconds. The amount of HNO generated is strongly dependent on solvent and the rate of the reaction is dependent on the light intensity.

The design and synthesis of a photoactivatable HNO donor incorporating the (6-hydroxynaphthalen-2-yl)­methyl (6,2-HNM) photocage coupled to the trifluoromethanesulfonamidoxy analogue of the well-established HNO generator Piloty’s acid is described. The photoactive HNO donor stoichiometrically generates HNO (∼98%) at neutral pH conditions, and evidence for concerted C–O and N–S bond cleavage was obtained. The methanesulfonamidoxy analogue primarily undergoes undesired N–O bond cleavage.

A new family of photoactivatable HNO donors of general structure RSO2NHO‐PT [where PT represents the (3‐hydroxy‐2‐naphthalenyl)methyl (3,2‐HMN) phototrigger] has been developed, which rapidly releases HNO. Photogeneration of HNO was demonstrated using the vitamin B12 derivative aquacobalamin as a trapping agent. The amount of sulfonate RSO2– produced was essentially the same as the amount of HNO released upon photolysis, providing a convenient method to indirectly quantify HNO release. Two competing pathways were also observed; a pathway involving O–N bond cleavage leading to release of a sulfonamide, and a pathway resulting in release of the parent Nhydroxysulfonamide RSO2NHOH (for HNO donors with Me‐ and Ph‐containing leaving groups only). Up to approximately 70 % of the HNO‐generating pathway was observed with the CF3‐containing leaving group, with HNO generation favored for small percentages of aqueous buffer in the acetonitrile/pH 7.00 phosphate buffer solvent mixture. Characterization of the photoproducts obtained from steady‐state irradiation by NMR spectroscopy showed that the desired HNO‐generating pathway was less favored for HNO donors with Me‐ and Ph‐containing leaving groups compared to the CF3‐containing leaving group, suggesting that the excellent CF3‐containing leaving group promotes HNO generation.