Printed in Great Britain. Pergamon Press Ltd. ©984 IUPAC PHOTOCHEMICAL CHARGE TRANSFER PHENOMENA — PICOSECOND LASER

Abstract — Fundamental aspects of the photoinduced charge transfer and charge separation processes have been discussed on the basis of the pico— second laser photolysis studies of some typical intra — and intermolecular exciplex systems, excited singlet state of EDA complexes and monophotonic electron ejection of some low ionization potential diamines in polar solvents. Picosecond laser studies have been extended to the biologically important porphyrin—quinone systems. Short—lived porphyrin—quinone exciplex can be observed in nonpolar solvent, but solvation—induced ultra— fast deactivation of the electron transfer state takes place in strongly polar solvents. It has been demonstrated that such ultrafast deactivaiton can be avoided by constructing intramolecular exciplex systems of por— phyrin and quinone combined by methylene chains and that more efficient charge separation can be acieved by two step electron transfer along the redox potential gradient in the systems with two kinds of quinones combined in series. Moreover, some related reaction processes such as hydrogen transfer due to the charge transfer followed by proton transfer, charge transfer interaction in the excited hydrogen bonding systems and coupling of the trans--cis photoisomerization with the intramolecular charge transfer have been investigated with picosecond laser spectroscopy