Radical Cationic Pathway for the Decay of Ionized Glyme Molecules in Liquid Solution

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• 作者：Konstantin S. Taletskiy ; Vsevolod I. Borovkov ; Lyudmila N. Schegoleva ; Irina V. Beregovaya ; Andrey I. Taratayko ; Yuriy N. Molin
• 刊名：Journal of Physical Chemistry B
• 出版年：2015
• 出版时间：November 12, 2015
• 年：2015
• 卷：119
• 期：45
• 页码：14472-14478
• 全文大小：358K
• ISSN：1520-5207

文摘

Chemical stability of primary radical cations (RCs) generated in irradiated matter determines substantially the radiation resistance of organic materials. Transformations of the RCs of the glyme molecules, R(鈭扥鈥揅H₂鈥揅H₂鈭?_nO鈥揜 (R = CH₃, n = 1鈥?) has been studied on the nanosecond time scale by measuring the magnetic field effects in the recombination fluorescence from irradiated liquid solutions of the glymes. In all cases, the RCs observed were different from that expected for the primary ones and revealed very similar hyperfine couplings independent of the poly(ethylene oxide) chain length and of the substitution of terminal methyl groups by C₂H₅ or CH₂CH₂Cl, as has been shown with diglyme as an example. Quantum chemical analysis of possible chemical transformations for the monoglyme RC as a model system allowed us to discover the reaction pathway yielding the methyl vinyl ether RC. The pathway involves intramolecular proton transfer followed by C鈥揙 bond cleavage. Only one (鈭扥鈥揅H₂鈥揅H₂鈥揙鈭? fragment is involved in this transformation, which is nearly barrierless due to the catalytic effect of adjacent glyme molecules. The rapid formation of the methyl vinyl ether RC in the irradiated monoglyme was confirmed by the numerical simulation of the experimental curves of the time-resolved magnetic field effect. These findings suggest that the R鈥测€揙鈥揅H鈺怌H₂^鈥? formation is a typical decay pathway for the primary RCs in irradiated liquid glymes.