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HYPERICIN DERIVED TRIPLET STATES and TRANSIENTS IN ALCOHOLS and WATER
Author(s) -
Malkin Jacob,
Mazur Yehuda
Publication year - 1993
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1993.tb02951.x
Subject(s) - hypericin , chemistry , photochemistry , photoexcitation , ultrafast laser spectroscopy , semiquinone , triplet state , superoxide , ion , reaction rate constant , excitation , inorganic chemistry , kinetics , organic chemistry , molecule , laser , redox , medicine , physics , optics , quantum mechanics , electrical engineering , pharmacology , enzyme , engineering
— 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 × 10 7 M ‐1 s ‐1 , suggesting the formation of superoxide.