TRIPLET, RADICAL ANION AND RADICAL CATION SPECTRA OF FUROCOUMARINS |
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| Authors: | R V BENSASSON † O CHALVET† E J LAND§ J C RONFARD-HARET |
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| Institution: | *Laboratoire de Biophysique, Inserm U.201, CNRS ERA 951, Muséum National d'Histoire Naturelle, 61, Rue Buffon, 75005 Paris;†Centre de Mécanique Ondulatoire Appliquée 23, Rue du Maroc, 75019 Paris, France;§Paterson Laboratories, Christie Hospital and Holt Radium Institute, Manchester M20 9BX, England, UK |
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| Abstract: | Abstract— Absorption spectra of triplets, radical anions and radical cations of four furocoumarins, psoralen (Ps), 8-methoxypsoralen (8MOP), 5-methoxypsoralen (5MOP) and 3-carbethoxypsoralen (3CPs), have been determined by laser flash photolysis and pulse radiolysis. The triplet spectra of 8MOP, 5MOP and 3CPs are strongly modified when going from an H-bonding solvent such as water to a non H-bonding solvent as benzene or acetonitrile while the triplet spectrum of Ps is solvent independent. Theoretical considerations using a CNDO/S method are able to explain the existence of these two different triplets. For 8MOP, 5MOP and 3CPs in water the triplets might be considered as triplet exciplexes 3(FCδ-. H2Oδ+) consistent with these triplet spectra being similar to the spectra of the corresponding radical anions. |
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