Characterization of the Radical Product Formed from the Reaction of Nitric Oxide with the Spin Trap 3,5-Dibromo-4-Nitrosobenzene Sulfonate

Abstract

Previously, 3,5-dibromo-4-nitrosobenzene sulfonate (DBNBS) has been used in combination with electron paramagnetic resonance (EPR) spectrometry to trap nitric oxide (NO•). The reaction between DBNBS and NO• yields a radical product which gives rise to an EPR signal consisting of three lines with an AN = 0.96 mT, but the structure of this product is unknown. A two-stage high-performance liquid chromatography fractionation was performed to isolate the radical product from the other components in the DBNBS/NO• reaction mixture. The fractions containing the radical product were identified by the presence of the three-line EPR signal, and then these fractions were analyzed by negative ion fast atom bombardment–mass spectrometry (FAB–MS). Collectively, the FAB–MS data suggested that the radical product is the monosodium electrostatic complex with the dianion, bis(2,6-dibromo-4-sulfophenyl) nitroxyl. Analysis of the Gaussian and Lorentzian linewidths of the EPR signal suggested that bis(2,6-dibromo-4-sulfophenyl) nitroxyl molecules may group together to form micelles. Further studies also indicated that significant amounts of nitrogen and nitrate were produced during the reaction between DBNBS and NO•. A reaction scheme consistent with these results is presented.