Organic Ion-Radicals in Frozen Solutions

7 ORGANIC ION-RADICALS IN SOLID PHASES 2.7.1 Organic Ion-Radicals in Frozen Solutions 

Let us first discuss relations between the nature of the matrix and the fate of the ion-radicals generated. Photoionization in rare gas matrix (when no electron acceptor is added) transforms aromatic 

In experiments where ion-radicals are generated by radiolytic reduction or oxidation in solid matrices, the concentration of solute molecules must be at least 10 M to ensure efficient scavenging of the initially generated electrons or holes. At the same time, the upper limit of the solute concentration should not exceed 10 -10 M. It is necessary that the direct effect of radiation on the solute molecule should be ignored. This is one of the major requirements for successful use of radiolytic methods for generating ion-radicals. 

If P is a substance of electron affinity lower than that of the solvent (e.g., AlkHal in SFg), the process leads to the formation of the cation-radical. If P is a substance of electron affinity higher than that of a solvent (e.g., AlkHal in CH3OH), the process leads to the formation of the anion-radical. These possibilities are depicted in the following equations, based on alkyl halides  

A simple method for the production and cryogenic trapping of ion-radicals is mentioned. The technique, cold window radical discharge (CWRD), enables the isolation of short-lived species in rare gas matrices, such as p-dichlorobenzene cation-radical. These species are formed within discharge plasmas, close to the trapping surface (Kolos 1995). 

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