Abstract: Exploratory and mechanistic studies have been conducted probing electron- transfer-induced fluorescence quenching and photochemical cyclization processes in olefin- N-heteroaromatic cation systems. The fluorescence of the quinolinium and isoquinolinium perchlorates 1-5 is efficiently quenched by electron-rich olefins at rates near to the diffusion- controlled limit. Plots of calculated free energies for electron transfer vs. the log of the ...