Properties of 16,17-disubstituted dihydroviolanthrones formed by reaction of violanthrones with photogenerated radicals.
The photophysical and photochemical properties of violanthrone (V1) and two 16,17-R derivatives with R = OC(8)H(17) and OCOC(17)H(35) (V2 and V3, respectively) in solution were examined. The fluorescence quantum yield of V3 is Phi(f) = 0.2, while that of V1 is low (0.01) and V2 even lower. A radical-induced reduction takes place in the presence of a photosensitizer, such as acetone, acetophenone or benzophenone, and an alcohol as donor. The reduction quantum yield in an argon-saturated solution, e.g. in 1-phenylethanol and glycerol triacetate, is close to unity. The products are the corresponding dihydroquinones (VH(2)s), which fluoresce strongly at 560-600 nm, Phi(f) = 0.6-1, and undergo back-oxidation on the admission of oxygen. The flash photolysis of violanthrones in the presence of both sensitizer and donor reveals ketyl radicals after the pulse, the intermediacy of the semiquinone radicals (VH*) at 650-750 nm and the formation of VH(2)s in the 0-1 ms range.
Gruen
Henry
H
Max-Planck-Institut für Bioanorganische Chemie, D-45413, Mülheim an der Ruhr, Germany.
Görner
Helmut
H
D001128:Argon / Q000737:chemistry; D001580:Benzopyrenes / Q000737:chemistry* / Q000528:radiation effects; D005609:Free Radicals / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010782:Photolysis; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000528:radiation effects; D013050:Spectrometry, Fluorescence
D001580:Benzopyrenes; D005609:Free Radicals; D017319:Photosensitizing Agents; D001128:Argon; C005289:oxybenzone (dye); D010100:Oxygen