than that of pyrene because the oxidation potentials of BDATP and pyrene in acetonitrile are 0.157 and 1.2011 V vs. SCE, respectively, and thus the electron ejected by multiphoton ionization has enough kinetic energy and the thermalization length can be similar to the one in radiation chemistry.
A general synthetic strategy for the preparation of disubstituted thionines is described. The Lauth hydrogen sulfide and the Bernthsen thiosulfate methods have been explored for the preparation of disulfonated thionines (DST's) with negative results for the former (less than 1% yield) and very modest results for the latter (5% yield). A new method based on the nucleophilic coupling of a p-phenylenediamine with the synthetic equivalent of an aniline has resulted in considerable improvement, regarding particularly the suppression of byproducts (15-20% yield). The relatively low yields obtained still with the new route are an indication that thionation and ring closure of diphenylamines are difficult when electron-withdrawing groups are present. The new route has enabled the unambiguous structural characterization of two isomeric DST's known as DST-1 and DST-2 to be 4,6-and 2,6-DST, respectively. The 470-MHz
The rotating optical disc-ring electrode consists of a transparent disc surrounded by a concentric ring electrode. Light is shone through the central disc to drive a photoredox system. The current from the photogenerated product is measured downstream on the ring electrode. The convective diffusion equation for this system is solved and analytical solutions are presented for the collection of a stable product. The theory takes into account the bleaching of the solution. Experiments performed on the iron-thionine system are found to be in good agreement with the theory.
Results are reported on the dark electrochemistry and photoelectrochemistry of thionine (TH) and two of its disulfonated derivatives (2,6-DST and 4,6-DST) on the title electrode (RODRE) that clearly indicate that coating of the electrode with a thin layer of polymeric thionine is crucial for measurement of sizable photoinduced ring currents. The parent TH does not require the polymeric coat since, due to its adsorption and aggregation properties, a One to two monolayer film of aggregated molecules spontaneously coats the electrode. The advantage of using, in addition to the lipophilic TH, the hydrophilic DST's rests in the lack of adsorption properties for the latter since, otherwise, their photophysical, photochemical, and electrochemical properties are quite similar, the presence of the sulfonates representing only a second-order effect. These findings are consistent and help to explain the recently published observation that the measured efficiency of the parent iron-thionine system drops by a factor of 19 or more when semitransparent gold electrodes coated with thick polythionine layers are utilized in experimental photogalvanic cells. The key to these results has been the application to this problem of an optical rotating electrode, the RODRE, which combines two different surfaces on the same electrode: the transparent disk surface, used to illuminate the photogalvanic solution, and the Pt metal ring surface, used to detect stable electroactive species photochemically generated in the disk zone. In the RODRE, the ring detector is effectively maintained in the dark and, thus, photocurrents arising from species in solution can be easily separated from photocurrents arising from species in the coat. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.255.6.125 Downloaded on 2015-06-06 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.255.6.125 Downloaded on 2015-06-06 to IP
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