Skip to main content
OSTI.GOVU.S. Department of Energy Office of Scientific and Technical Information
U.S. Department of Energy
Office of Scientific and Technical Information
 

Kinetics and mechanism of porphyrin-photosensitized reduction of methylviologen

Journal Article · · J. Phys. Chem.; (United States)
DOI:https://doi.org/10.1021/j100219a027· OSTI ID:6472287
; ; ;

The electron transfer between cysteine (CysSH) and methylviologen (MV/sup 2 +/) is photosensitized by zinc tetrakis(p-sulfonatophenyl)porphyrin (ZnTPPTS) excited in its triplet state by visible light in aqueous solution at room temperature. Ground-state complexation of ZnTPPTS by MV/sup 2 +/ gives a 1:1 complex (K = 1.5 x 10/sup 3/ M/sup -1/) which does not yield any detectable transient upon excitation. The triplet state /sup 3/P of the free ZnTPPTS (phi/sub T/ = 0.9) is oxidized by MV/sup 2 +/ (k = 6.9 x 10/sup 9/ M/sup -1/s/sup -1/) yielding P/sup +/ and MV/sup +/ with a cage escape yield of approx. 0.5. Back-reaction of P/sup +/ and MV/sup +/ (k = 1.3 x 10/sup 9/ M/sup -1/s/sup -1/) can be prevented by reaction of P/sup +/ in the presence of a large concentration of CysSH (k = 1.7 x 10/sup 6/M/sup -1/s/sup -1/). CysS, the deprotonated form of the oxidized cysteine, reacts with CysS/sup -/ to give the radical CysS-SCys/sup -/ which reduces MV/sup 2 +/ (k = 8 x 10/sup 8/ M/sup -1/s/sup -1/), so that the initial yield of MV/sup +/ is twice the product of the quantum yield of triplet formation of the photosensitizer and the escape yield of P/sup +/ and MV/sup +/. A detailed mechanistic scheme of 11 reactions has been deduced from the results of flash - and continuous - photolysis experiments.

Research Organization:
Museum National d'Histoire Naturelle, Paris, France
OSTI ID:
6472287
Journal Information:
J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 86:22; ISSN JPCHA
Country of Publication:
United States
Language:
English

Similar Records

Photochemistry of compounds adsorbed into cellulose. 5. Solid-state reduction of methylviologen photosensitized by tris(2,2'-bipyridine)ruthenium(II)
Journal Article · Wed Apr 24 23:00:00 EST 1985 · J. Phys. Chem.; (United States) · OSTI ID:5262168
Redox reactions in micellar systems. communication 4. Eosin-photosensitized reduction of methylviologen
Journal Article · Mon Dec 09 23:00:00 EST 1985 · Bull. Acad. Sci. USSR, Div. Chem. Sci. (Engl. Transl.); (United States) · OSTI ID:5159490
Laser photolysis studies on the electron-transfer reaction from the photoexcited triplet state of chloroindium(III) tetraphenylporphyrin to methylviologen in methanol solutions
Journal Article · Wed Jan 30 23:00:00 EST 1985 · J. Phys. Chem.; (United States) · OSTI ID:5312014

Related Subjects

08 HYDROGEN
080106 -- Hydrogen-- Production-- Biosynthesis & Photochemical Processes
14 SOLAR ENERGY
140505* -- Solar Energy Conversion-- Photochemical
Photobiological
& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500 -- Photochemistry
AMINO ACIDS
AQUEOUS SOLUTIONS
AZINES
BIPYRIDINES
CARBOXYLIC ACIDS
CHEMICAL REACTION KINETICS
CHEMISTRY
COMPLEXES
CYSTEINE
DATA
DISPERSIONS
ELECTRON TRANSFER
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
KINETICS
MIXTURES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PHOTOCHEMISTRY
PORPHYRINS
PYRIDINES
REACTION KINETICS
SOLUTIONS
THIOLS
ZINC COMPLEXES