Photosensitized electron-transfer reaction in the first excited singlet state of a polymethine-cyanine dye

The electron transfer from the first excited singlet state of a polymethine-cyanine dye, 3,3'-diethyloxadicarbocyanine iodide (DODCI), to methylviologen leads to redox products, which have been fully characterized by using an electron acceptor, p-benzoquinone (p-BQ), and an electron donor, ascorbic acid. The quantum yields of the redox products have been measured by using the DODCI photoisomerization process as an internal actinometer. A complete reaction scheme is proposed and the various reaction rate constants have been determined. The photosystem DODCI-MVCl/sub 2/-p-BQ-ascorbic acid is presented as a new system for the modeling of solar energy conversion.