Quenching of triplet states of aromatic ketones by sulfur-containing amino acids in solution. Evidence for electron transfer

Journal Article · Thu Nov 18 04:00:00 EST 1993 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100148a015· OSTI ID:5423657

Marciniak, B; Bobrowski, K; Hug, G L ^[1]

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1. Univ. of Notre Dame, IN (United States)

The mechanism for quenching triplet states of benzophenones by sulfur-containing amino acids in water/acetonitrile solution was investigated by laser flash photolysis. The amino acids in the study were methionine, S-methylcysteine, and S-carboxymethylcysteine, and the eight aromatic triplets were those of benzophenone and its derivatives possessing electron-withdrawing or electron-donating groups. The presence of radical ions in the transient spectra and correlations of the quenching rate constants with the free energy change for electron transfer are strong indications that the process involves an electron transfer. These correlations were displayed as Rehm-Weller plots (logarithm of quenching rate vs free energy). Classical theoretical formulations of the Rehm-Weller correlations were used to estimate the intrinsic barriers and the transmission coefficients for the electron-transfer processes. Applying both [open quotes]quadratic[close quotes] Marcus and [open quotes]asymptotic[close quotes] Agmon-Levine free energy relationships led to the values of intrinsic barriers lower than the solvent reorganization energy calculated within the framework of the dielectric continuum model. These relationships also led to low electronic transmission coefficients. The low values of the intrinsic barriers for electron transfer were also obtained using the recently developed Tachiya approach. 58 refs., 5 figs., 2 tabs.

• OSTI ID: 5423657
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 97:46; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400 -- Electrochemistry
400500* -- Photochemistry
ACETONITRILE
AMINO ACIDS
BENZOPHENONE
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
DECOMPOSITION
DISPERSIONS
ELECTRON TRANSFER
ENERGY
FREE ENERGY
HYDROGEN COMPOUNDS
KETONES
LASERS
MIXTURES
NITRILES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
PHYSICAL PROPERTIES
RADICALS
SOLUTIONS
THERMODYNAMIC PROPERTIES
VOLTAMETRY
WATER