Excited-state Phenomena

The excimer fluorescence of pyrene and substituted pyrenes has been studied in naturaP and syntheticvesicles. The rate constant for electron transfer to pyrene absorbed in didodecyldimethylammonium chloride vesicles was studied by pulse radiolysis, and evaluation of these results suggests a vesicle diameter of 20 nm. Sonication gives rise to an aggregate of smaller dispersisity than does methanol injection. Irradiation of pyrene in dihexadecyl 

Schnecke, M. Gratzel, and A. Flenglein, Ber. Bunsenges. Phys. Chem., 1977, 81, 821. 

Micellar photochemistry, and the generation of transients in micellar media by other means, have attracted much effort in the last two or three years. This is because of its potential in energy conversion, where physical separation of the oxidative and reductive parts of the catalytic cycle may permit photochemical cleavage of water. Some very promising results have already been obtained. 

Radiolysis and Rdated Tedmiques.—Solvated electrons are the primary product of pulse radiolysis, and react with micellated pyrene with a rate constant of 10 s , the corresponding reaction with nitropyrene being twice as rapid. 

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This is an introduction to the techniques used for the calculation of electronic excited states of molecules (sometimes called eximers). Specifically, these are methods for obtaining wave functions for the excited states of a molecule from which energies and other molecular properties can be calculated. These calculations are an important tool for the analysis of spectroscopy, reaction mechanisms, and other excited-state phenomena. 

H. Bassler and L. J. Rothberg (eds.), Chemical Physics on Excited State Phenomena in Conjugated Polymers, Chem. Phys. 227 (1998)... 

R. Reisfeld and C.K. Jorgensen, Excited state phenomena in vitreous materials 1... 

Finally, it is evident that confrontation with excited-state phenomena will bring enrichment of the NBO-bonding con-... 

Reisfeld, R., and C.K. Jorgensen, 1987, Excited State Phenomena in Vitreous Materials, in ... 

Excited-state Phenomena.—Czarniecki and Breslow provide an experimental test for structure and organization in micelles and vesicles based on inter-molecular hydrogen-atom abstraction by benzophenone triplet-state. This leads to functionalization at a particular site in the chain, which may be identified by degradation and mass spectrometry. With didodecyl phosphate and (97) or (98), the specificity is as shown (Figure 9) for sonicated surfactant, presumed to be in vesicular form. This shows a much altered specificity from the corresponding reaction in micelles. When sonication is carried out in a sodium borate buffer, a technique considered to provide multilamellar layers (opaque dispersion ) then the terminal selectivity is completely lost and C(6) is the most favoured site for attack. 

It is useful to think of this situation as a donor-acceptor interaction. The high-lying filled orbital donates electrons to the low-lying empty orbital, producing a stabilizing interaction. However, this interaction is not electron transfer nor the kind of donor-acceptor interactions often discussed in excited-state phenomena (Section 3.2.4). It is simply orbital... 

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