“…It is noteworthy that the corresponding neutral systems in methanol, ether, or cyclohexane, generate the same or similar radicals when irradiated through mechanisms which most likely involve hydrogen atom abstraction. Flash photolysis studies by Kosower(293) with l-ethyl-4-carboethoxypyridinium iodide 401 and by Cozzens(294) with I-methylpyridinium, I-methylcollidinium, and I-methylquinolinium io-dides have shown that these systems undergo intramolecular electron transfer generating iodine atoms and the corresponding heterocyclic radicals [e.g., 402, equation (49) (50) Charge transfer complexes which arise via single-electron transfer are also reported to be responsible for the fluorescence quenching of N-methylacridinium cation by various negatively charged counter ions. (295) Similarly, fluorescence quenching involving electron transfer in pyridinium salts has also been reported by McCall and Whitten.…”