Dynamics of charge recombination processes in the singlet electron-transfer state of pyrene-pyromellitic dianhydride systems in various solvents. Picosecond laser photolysis studies

Journal Article · Thu Jan 15 04:00:00 EST 1987 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100286a016· OSTI ID:6948391

Mataga, N; Shioyama, H; Kanda, Y

In order to elucidate the underlying mechanisms showing that no dissociated ion radicals are produced even in acetonitrile solution when some complexes of the strong electron donors and acceptors with CT absorption bands in the visible region are photoexcited, the authors have made detailed time-resolved transient absorption spectral measurements and time-resolved fluorescence measurements upon the pyrene-pyromellitic dianhydride (PMDA) system in various solvents with picosecond laser spectroscopy. A weakly fluorescent electron-transfer (ET) state with 400-ps lifetime is formed by photoexcitation in benzene solution, while nonfluorescent geminate ion pairs with much shorter lifetimes due to the charge recombination (CR) deactivation are formed in more polar solvents. In all solutions examined, dissociation into free ions from the geminate pair cannot compete with the CR deactivation which becomes faster in more polar solvents due to the decrease of the energy gap between the ion pair and neutral ground state. Moreover, it has been demonstrated that ion pairs produced by encounter between excited pyrene and unexcited PMDA in acetonitrile have more loose structure and show a smaller CR rate constant than those produced by exciting the ground-state complex.

• Research Organization: Osaka Univ., Japan
• OSTI ID: 6948391
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 91:2; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
ACETATES
ACETONITRILE
ANHYDRIDES
AROMATICS
BENZENE
CARBOXYLIC ACID SALTS
CHEMICAL REACTIONS
CONDENSED AROMATICS
DATA
DECOMPOSITION
DYE LASERS
DYNAMICS
ELECTRON TRANSFER
ENERGY LEVELS
EXCIMER LASERS
EXPERIMENTAL DATA
GAS LASERS
HYDROCARBONS
INFORMATION
LASERS
LIQUID LASERS
MECHANICS
NEODYMIUM LASERS
NITRILES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PYRENE
S STATES
SOLID STATE LASERS
SPECTROSCOPY