HYPERICIN DERIVED TRIPLET-STATES AND TRANSIENTS IN ALCOHOLS AND WATER

Direct pulse photoexcitation of an antivirally active compound, hypericin sodium salt in ethanol, results in a short-lived transient, attributed to a triplet state. In the presence of reducing agents, a long-lived transient is observed, which indicates a radical anion species. In isopropanol solution, an identical triplet state is formed, accompanied by a long-lived intermediate that consists of a semiquinone-type radical. Laser excitation of hypericin sodium salt aggregates dispersed in water produces a very short-lived transient, also assigned to a triplet state, which decays, leaving an absorption spectrum, indicating a radical anion species. The latter reacts with oxygen with a rate constant of k is similar to 6 x 10(7) M-1 s-1, suggesting the formation of superoxide.