Photoinduced electron transfer in ionic liquids: use of 2,4,6-triphenylthiapyrylium as a photosensitizer probe.

The photochemistry of 2,4,6-triphenylthiapyrylium, TPTP+, in an ionic liquid, bmim-PF6, and in zeolite Y has been investigated and compared. Fluorescence spectroscopy was used to characterize the singlet excited state and to demonstrate singlet quenching by dicyclopentadiene, DCP, as an electron donor. Time-resolved laser spectroscopy documents generation of the triplet excited state, 3TPTP+, and reduction by DCP, generating the corresponding radical, TPTP*, and radical ion, DCP+*. The highly polar media stabilize the organic intermediates, causing them to be long lived.