| Abstract
| - The mechanism of formation of fluorofullerene (FF) negative ions derived from the compounds C60F18, C60F36,and C60F48 was studied by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (ToF) massspectrometry (MS). A combined experimental/theoretical approach provides compelling evidence ofnondissociative, thermodynamically controlled electron transfer from matrix-derived negative ions to the FFanalyte as the main secondary-ionization process. Consistent with this thermochemical model, analyte parentmolecular ion yield and degree of fragmentation for a particular MALDI experiment was found to depend onthe nature of the matrix material (the five matrices investigated were sulfur, trans-2-[3-{4-tert-butylphenyl}-2-methyl-2-propenylidene]malononitrile, 9-nitroanthracene, 2,6-bis((furan-2-yl)methylene)cyclohexanone, and2,6-bis((thiophen-2-yl)methylene)cyclohexanone). For mixtures of C60Fn compounds with different n valuesand therefore different electron affinitites, unwanted electron-transfer reactions, which can lead to thesuppression of C60Fn- ions with low n values, were successfully blocked for the first time by judicious choiceof the matrix. Therefore, reliable qualitative MS analysis of FF mixtures with wide ranges of composition isnow possible.
|
