Nitrogen-Containing Aromatic Radical Anions Perform Multiple Proton and Electron Transfers Near-Simultaneously with Multiply Protonated Cations.

Gas phase ion/ion reactions between singly charged radical reagent anions and multiply charged cation precursors primarily result in either proton or electron transfer. These ion/ion reactions have been extensively studied for bioanalysis, and many reagent anions have been tested and reported. Here, nitrogen-containing aromatic radical anions were tested for the ability to conduct proton or electron transfer by their reaction with the ubiquitin [M + 13H]+13 precursor. The singly charged anion of 2,2'-biquinoline was found to undergo charge inversion to singly protonated cations via near-simultaneous proton and electron transfers while reactants were bound in a single ion/ion reaction complex. Although the focus of this paper was 2,2'-biquinoline, all three nitrogen-containing aromatic compounds tested produced similar results.