- Email: [email protected]
Photoreduction of PQ2+ by visible light via an organic charge transfer complex
79 Photoreduction of PQ’* by visible lit
via au organic charge transfer complex
A. DERONZIER
DRF-G / Laboratoires
de Chimie - EOA (Equipe de Recherche associke au CNRS 6751, Cem?e
d’Etudes Nucl6aires de Grenoble,
85 X, 38041 Grenoble
Ckdex (France)
Non-aqueous solutions of paraquat PQ3+ in the presence of a large excess of the dithiophosphate anion dtp- (dtp- = (CzH50)2PSz, (CH,O),PSs-) exhibit an absorption band in the visible region. The origin of this band (Amax = 400 nm) is a charge transfer (CT) transition between the two redox sites of the complex: PQ2+ + 2dtp- G= (PQ2+,2dtp-) Flash photolysis experiments duces an electron transfer (pQ2+,2dtp-)
hv (’ ‘400
of the CT complex
show that photoexcitation
in-
nm) + PQ*+ + dtp.
PQ*+ remains in solution after the flash because the dimerization of dtp’ into the corresponding disulphide (dtp)* is more rapid than back electron transfer between dtp* and PQ*+. With continuous irradiation the amount of PQ-+ builds up. However, its concentration reaches a maximum with time as a consequence of the slow reduction of the disulphide (dtp)z by PQ-+ which competes with the photoproduction of PQ*+. Electrochemical measurements support this hypothesis.
Photolysis and spectroscopy of adsorbed chlorinated pollutants: polychlorobiphenyls
G. OCCHLUCCI
and A. PATACCHIOLA
lstitu to di Chimicu Nucleare de2 Consiglio Nazionale delle Richerche, 00016 Monterotondo Stazione (Italy)
C. P. IO,
Results are reported on the photolysis of polychlorobiphenyls (PCBs) adsorbed on montmorillonite and silica gel. The UV absorption spectra and the fluorescence emission spectra of some adsorbed PCBs are shown for comparison with those of dissolved PCBs. The adsorption makes the photodegradation of the polychlorobiphenyls more difficult, although still evident. A remarkable increase in the photolysis yield is effected by adding triethylamine as a sensitizer, as is also experienced in solution experiments.
via au organic charge transfer complex
A. DERONZIER
DRF-G / Laboratoires
de Chimie - EOA (Equipe de Recherche associke au CNRS 6751, Cem?e
d’Etudes Nucl6aires de Grenoble,
85 X, 38041 Grenoble
Ckdex (France)
Non-aqueous solutions of paraquat PQ3+ in the presence of a large excess of the dithiophosphate anion dtp- (dtp- = (CzH50)2PSz, (CH,O),PSs-) exhibit an absorption band in the visible region. The origin of this band (Amax = 400 nm) is a charge transfer (CT) transition between the two redox sites of the complex: PQ2+ + 2dtp- G= (PQ2+,2dtp-) Flash photolysis experiments duces an electron transfer (pQ2+,2dtp-)
hv (’ ‘400
of the CT complex
show that photoexcitation
in-
nm) + PQ*+ + dtp.
PQ*+ remains in solution after the flash because the dimerization of dtp’ into the corresponding disulphide (dtp)* is more rapid than back electron transfer between dtp* and PQ*+. With continuous irradiation the amount of PQ-+ builds up. However, its concentration reaches a maximum with time as a consequence of the slow reduction of the disulphide (dtp)z by PQ-+ which competes with the photoproduction of PQ*+. Electrochemical measurements support this hypothesis.
Photolysis and spectroscopy of adsorbed chlorinated pollutants: polychlorobiphenyls
G. OCCHLUCCI
and A. PATACCHIOLA
lstitu to di Chimicu Nucleare de2 Consiglio Nazionale delle Richerche, 00016 Monterotondo Stazione (Italy)
C. P. IO,
Results are reported on the photolysis of polychlorobiphenyls (PCBs) adsorbed on montmorillonite and silica gel. The UV absorption spectra and the fluorescence emission spectra of some adsorbed PCBs are shown for comparison with those of dissolved PCBs. The adsorption makes the photodegradation of the polychlorobiphenyls more difficult, although still evident. A remarkable increase in the photolysis yield is effected by adding triethylamine as a sensitizer, as is also experienced in solution experiments.