Unexpected Gas-Phase Reactivity of the CH3OH Adduct of Michler's Hydrol Blue: Proton-Shuttle Catalysis and Stepwise Radical Expulsions

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• 作者：Detlef Schr&ouml ; der ; Jana Roithová ; Philipp Gruene ; Helmut Schwarz ; Herbert Mayr ; Konrad Koszinowski
• 刊名：Journal of Physical Chemistry A
• 出版年：2007
• 出版时间：September 20, 2007
• 年：2007
• 卷：111
• 期：37
• 页码：Gruene, Helmut Schwa
• 全文大小：271K
• 年卷期：v.111,no.37(September 20, 2007)
• ISSN：1520-5215

文摘

Electrospray ionization of a methanolic solution of Michler's hydrol blue, bis(4-(N,N-dimethylamino)phenyl)methyl tetrafluoroborate, 1⁺BF₄^-, produces the formal methanol adduct [1⁺·CH₃OH], which shows an unusualgas-phase chemistry. Tandem mass-spectrometry experiments and complementary theoretical studies indicatethat this adduct corresponds to the methyl ether of Michler's hydrol protonated at one of the dimethylaminogroups, cation 3⁺. Collision-induced dissociation of mass-selected 3⁺ leads to two sequential expulsions ofopen-shell species, resulting in a formal loss of [C₂H₆O], whereas no expulsion of methanol is observed. Incontrast, interaction of gaseous 3⁺ with a single molecule of a suitable base triggers an exoergic loss ofmethanol via proton-shuttle catalysis within the collision complex. The occurrence of this exothermic protontransfer also prevents the application of the otherwise successful kinetic method for the determination of thegas-phase proton affinity of the methyl ether of Michler's hydrol.