Photosensitizers, chemical transformations

Alternatively, light is consumed and the reaction progress is possible only under continuous light absorption this option, called catalyzed photolysis, includes photoassisted generation of a reactive form of substrate or photocatalyst. In the former the process is called catalyzed photochemical reaction, whereas in the latter either catalyst activation may lead to formation of catalyst or photoinitiator, which initiates chemical transformations but is consumed within a reaction cycle, or the catalyst reacts with substrate in its excited state (photosensitization) in both cases... 

Synthetic routes to homoleptic and heteroleptic tris(diimine)ruthenium(II) complexes incorporating bidentate imine ligands and used, particularly, as photosensitizers in transformations of solar energy to chemical or electric energy 04CCR(248)1329. 

No general agreement exists on the definition of the term photocatalysis. Generally it implies that light and a catalyst are necessary to induce or accelerate a chemical transformation [1-9]. This definition includes photosensitization, a process by which a photochemical alteration occurs in one molecular entity as a result of initial absorption of radiation by another molecular entity called photosensitizer [10], but it excludes the photoacceleration of a stoichiometric thermal... 

For the gaseous-layer effects, such as entrainment and detrainment of species across the liquid interface, chemical transformations in the gas phase, the effects of solar radiation on photosensitive atmospheric reactions, and temperature effects on the gas phase, reaction kinetics are important. In the interface regime, the transfer of molecules into the liquid layer prior to their chemical interaction in the liquid layer is studied. Not only does the liquid regime receive species from the gas phase, but species from the liquid are also volatilized into the gas phase. Important variables in the liquid regime include the aqueous film thickness and its effect on the concentration of species, chemical transformations in the liquid, and reactions involving metal ions originating from the electrochemical corrosion reactions. 

In principle, the cytotoxic agent is generated without chemically transforming the sensitizer, which is thus available to absorb another photon and repeat the cycle. Therefore, if there is enough oxygen, a single photosensitizer molecule is capable of repeatedly sustaining its own concentration. 

Adam, W., Ahrweiler, M., and Sauter, M., Photosensitized oxygenation of a keto furan isolation of the first furan dioxetane by rearrangement of its endoperoxide and selected chemical transformations, Angew. Chem., 105, 104, 1993. 

Hollander s theory [41] of pair substitution, they concluded that an open chain or extended radical cation 28 + must precede a closed radical cation 291 + in which spin and charge are localized in an aromatic moiety with the reverse sequence of intermediates, which would perhaps appear more natural from the point of view of chemical intuition, the experimental polarization pattern could not be simulated. Based on their analysis, they obtained a rate constant of 4 x 10s s 1 for the transformation 28 + -> 29 +. Related cycloreversions of biological significance (photosensitized splitting of pyrimidine dimers) are dealt with in Section V.G.2. 

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