Abstract: The fluorescence spectra and fluorescence quenching of some substituted pyrylium salts have been studied in this work. It was found that under liquid N₂ temperature the exciplex emission in the region of longer wave length can be observed from the excited molecule of pyrylium salts with some quenchers used as an electron donor. Obtained results also indicated that a ground state stable CT complex can be formed when the pyrylium salt mixed with the electron donor. Therefore, the emission of excited CT complex in the frozen condition may be observed evidently, due to the difficult dissociation of the excited CT complex of the diminution of some routes of radiationless decay.

Key words: pyrylium salt, fluorescence quenching, exciplex, ground state charge transfer complex