title: In-plume thermodynamics of the MALDI generation of fluorofullerene anions.
abstract: The mechanism of formation of fluorofullerene (FF) negative ions derived from the compounds C(60)F(18), C(60)F(36), and C(60)F(48) was studied by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (ToF) mass spectrometry (MS). A combined experimental/theoretical approach provides compelling evidence of nondissociative, thermodynamically controlled electron transfer from matrix-derived negative ions to the FF analyte as the main secondary-ionization process. Consistent with this thermochemical model, analyte parent molecular ion yield and degree of fragmentation for a particular MALDI experiment was found to depend on the 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, and 2,6-bis((thiophen-2-yl)methylene)cyclohexanone). For mixtures of C(60)F(n) compounds with different n values and therefore different electron affinitites, unwanted electron-transfer reactions, which can lead to the suppression of C(60)F(n)(-) ions with low n values, were successfully blocked for the first time by judicious choice of the matrix. Therefore, reliable qualitative MS analysis of FF mixtures with wide ranges of composition is now possible.
authors.affiliation: Chemistry Department, Moscow State University, Moscow 119992, Russia.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Streletskii
authors.forename: Ilya N
authors.initials: IN
authors.lastname: Ioffe
authors.forename: Sotirios G
authors.initials: SG
authors.lastname: Kotsiris
authors.forename: Mark P
authors.initials: MP
authors.lastname: Barrow
authors.forename: Thomas
authors.initials: T
authors.lastname: Drewello
authors.forename: Steven H
authors.initials: SH
authors.lastname: Strauss
authors.forename: Olga V
authors.initials: OV
authors.lastname: Boltalina