OBSERVATION OF GAS-PHASE MOLECULAR DICATIONS FORMED FROM NEUTRAL ORGANICS IN SOLUTION VIA CHEMICAL ELECTRON-TRANSFER REACTIONS BY USING ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

The first observation of organic dications formed by multiple electron loss in electrospray mass spectra is reported. The dications of beta- carotene, canthaxanthine, cobalt(II) octaethylporphyrin, and nickel(II ) octaethylporphyrin were created in solution via chemical electrontra nsfer reactions and detected in the gas phase by electrospray ionizati on mass spectrometry (ES-MS) using a flow-injection experiment. The an alytes were injected into a flowing solvent-oxidant stream (10 muL/min ) composed of dried methylene chloride containing approximately 0.1% b y volume trifluoroacetic acid and 0.1% by volume antimony pentafluorid e (SbF5). The dications created in this oxidizing solvent system were preserved for detection by rapidly transferring them from the reactive solvent-oxidant system to the gas phase, where, in the absence of the solvent system, they were ''long-lived'' and amenable to mass analysi s. This work demonstrates means to produce ions novel to ES-MS and mea ns to detect and study by ES-MS species that are short-lived in soluti on. In addition, this work shows that electrospray ionization can pote ntially be used to generate gas-phase dications for mass spectrometric study that are difficult to produce directly from gas-phase neutrals by other ionization techniques (e.g., M2+ from beta-carotene).