Formes Transitoires Des Carotenoides: Etat Triplet Et Radical‐cation

Reactions between toluidine blue (a thiazine dye) and carotenoids (β‐carotene and zeaxanthine) were studied by flash photolysis, in ethanolic solutions. Two types of reactions were evidenced: a triplet‐triplet energy transfer from the triplet state of monoprotonated toluidine blue to the carotenoid whose triplet state decays rapidly ( t 1/2 = 5μsec). an electron transfer from the carotenoid to the mono‐ and bi‐protonated triplet states of toluidine blue. This produces a radical‐cation of the carotenoid (Car + ) which decays slowly ( t 1/2 ˜ 200 μsec) and has a strong absorption band around 900 nm.