Abstract
Abstract— 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∼ 6 × 107 M‐1 s‐1, suggesting the formation of superoxide.
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