Surface complex photolysis

An examination of the wavelength dependence of the photorearrcungements of CuCl complexes of cyclododeca-1,5,9-trienes has revealed no reason to assume that the two types of reaction, cis-trans-photoisomer iaation and rearrangement, occur on separate energy surfaces The photolysis of... 

Recent advances in measuring the kinetics of the various electron-transfer steps in this system have been achieved by use of flash photolysis of ruthenated derivatives of cytochrome c (Ru-Cc) (17-19). In these studies [Ru(bpy)3]2+ is covalently bound to a surface residue at a site that does not interfere with the docking of cytochrome c to cytochrome c oxidase. Solutions are then prepared containing both Ru-Cc and cytochrome c oxidase, and the two proteins associate to form a 1 1 complex. Flash photolysis of the solution leads directly to the excitation of the RuII(bpy)3 site, which then reduces heme c very rapidly. This method thus provides a convenient means to observe the subsequent intracomplex electron transfer from heme c to cytochrome c oxidase and further stages in the process. 

Direct Photolysis of Surface-Located Inner Coordination Sphere Complexes. In the presence of a strong metal binding ligand, the underlying central metal ion in the surface layer of a metal oxide can exchange its structural OH" ions for the ligand. Thus, the association of citrate with an iron oxyhydroxide surface may be represented ... 

As we have seen, a great deal is known about emission sources and strengths, ambient levels, and mutagenic/carcinogenic properties of the particle-phase PAHs in airborne POM. However, because of the tremendous physical and chemical complexity of the aerosol surfaces on which photolysis, photooxidations, and gas-particle interactions take place in real polluted ambient air, much less is known about the structures, yields, and absolute rates and mechanisms of formation of PAH and PAC reaction products, especially for the more polar PACs. This is one area in which there exists a major gap in our knowledge of their atmospheric chemistry and toxicology. 

FIGURE 6 Potential interactive pathways and processes of humic substances emanating from decomposition products of higher plant tissues with extracellular and surface-bound enzymes and photolytic reactions, particularly with UV irradiance. Humic acid-enzyme complexes can be stable for long periods (weeks and months) and subsequently reactivated upon exposure to weak UV light. Further photolysis can cleave simple compounds from the macromolecules for subsequent utilization by microbes. 

While the relative importance of direct and sensitized photolysis has to be assessed case by case, it is very likely that these two processes play a substantial role in phototransformation of most organic solutes in surface waters, together with the photolysis of species that can act as ligands for Fe(III) (e.g. carboxylates). Indeed, the photolysis of Fe(III)-carboxylate complexes plays a major role in natural DOM photomineralization [75-78],... 

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