PHOTOELECTRIC EFFECTS FROM CHLOROPHYLL a IN BILAYER MEMBRANES |
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| Authors: | Rodolfo T Arrieta † Iris C Arrieta † Pappi M Pachori Ann E Popp Jay S Huebner |
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| Institution: | Laboratoire de Physico-Chimie de l';Adaptation Biologique, CNRS UA 481, Museum National d'Histoire Naturelle, 43 rue Cuvier, 75231 Paris Cedex 05, France;Department of Chemistry, University of Illinois at Chicago, Box 4348, Chicago, Illinois 60680, U.S.A.;Hopital Henri Mondor, Laboratoire de Recherches Dermatologiques, 94010 Creteil, France |
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| Abstract: | Abstract— The photophysical and photochemical properties of thiophene derivatives have been studied by fluorescence and by 353 nm laser flash spectroscopy. α-Terthienyl and its derivatives show a moderate fluorescence quantum yield (less than 0.1) in cyclohexane, ethanol, or TritonX–100 micelles. An additional thiophene ring increases this value to 0.2 in ethanol or micelles. The transient triplet state of the six thiophenes is characterized by strong absorptions (ε⋍ 50000 M -1 cm-1) in the visible region. These triplet states are very long lived. They react with oxygen, producing singlet oxygen very efficiently because of their high quantum yield of triplet formation (0.1 to 0.3). They do not react with excellent hydrogen or electron donors such as indole, N-acetyl tryptophanamide or cysteine. The hydrophobic thiophenes investigated are, therefore, Type II photodynamic agents almost exclusively. |
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