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.
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