Accession Number : ADA136345

Title :   Electron Donor-Acceptor Quenching and Photoinduced Electron Transfer for Coumarin Dyes.

Descriptive Note : Technical rept. 1 Jan-31 Oct 82,


Personal Author(s) : Jones,G , II ; Griffin,S F ; Choi,C ; Bergmark,W R

PDF Url : ADA136345

Report Date : 31 Oct 1983

Pagination or Media Count : 21

Abstract : The fluorescence of 7-aminocoumarins is quenched by a variety of organic electron donors or acceptors in acetonitrile. In general, donors with half-wave oxidation potentials less positive than 1.0 V vs SCE and acceptors with reduction potentials less negative than -1.5 V vs SCE are candidates for diffusion limited quenching of coumarin singlet states. Profiles of quenching rates are consistent with calculated free energies for electron transfer between excited coumarins and donors or acceptors. In flash photolysis experiments electron transfer for several dyes and quenchers (e.g., methyl viologen) is demonstrated. Relatively low yields of net electron transfer are consistently obtained due to inefficient ionic photodissociation via singlet quenching or a low yield of more photoactive coumarin triplets. Electrochemical properties of the coumarins have been investigated by cyclic voltammetry with the indications of reversible oxidation and irreversible reduction as important processes. (Author)

Descriptors :   *Photochemical reactions, *Electron transfer, *Dyes, *Coumarins, *Lasers, Electron donors, Electron acceptors, Quenching, Fluorescence, Photolysis, Oxidation reduction reactions, Acetonitrile, Electrochemistry, Voltammetry, Absorption spectra

Subject Categories : Radiation and Nuclear Chemistry
      Lasers and Masers
      Coatings, Colorants and Finishes
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE