Sensitized photolysis sensitizing agents

The photolysis of [Cr(CN)6] has been studied in DMF solution, where [CrlCbOjDMF] " is the first reaction product, and in H2O containing sensitizing agents. The results of both studies agree that the photoactive state is not the Eg one but is probably the one. The reactions of [Cr(H20)s-CN]2 +, cis-[Cr(H20)4(CN)2] and/ac-[Cr(H20)3(CN)3] with Hg and Ag to form dinuclear and trinucleai adducts have been investigated and equilibrium... 

The yield of trans product (18) is decreased by the presence of a radical scavenger such as 1,1-diphenylethylene and increased by dilution of the reactants with methylene chloride or butane, indicating this product to result from the triplet carbene. A heavy-atom effect on the carbene intermediate was observed by photolysis of a-methylmercuridiazoacetonitrile. With c/s-2-butene as the trapping agent either direct photolysis or triplet benzophenone-sensitized decomposition results in formation of cyclopropanes (19) and (20) in a 1 1 ratio ... 

Flash photolysis techniques were unsuitable for measuring the slow off reactions for the iron(II) model complexes such as Fen(TPPS)(NO), since the experimental uncertainties in the extrapolated intercepts of kohs vs. [NO] plots were larger than the values of the intercepts themselves. When trapping methods were used to evaluate NO labilization from FeII(TPPS)(NO), k(,n values were found to be quite small but were sensitive to the nature of the trapping agents used. Lewis bases that could coordinate the metal center appeared to accelerate NO loss. More reliable estimates for the uncatalyzed off reaction were obtained by using Ru(edta)- as an NO scavenger, and the koS values listed in Table I were obtained in this manner (21c). The small kQ values found for Fe(II) models are consistent with the trend observed for the ferro-heme proteins discussed above. 

Both neutral and anionic species of DNOC show absorption shoulders at wavelengths >300 nm (Schwarzenbach et al. 1988). However, photolysis of DNOC in water involving nucleophilic displacement of the nitro group by the hydroxyl group does not seem likely (EPA 1979). The photochemical reduction of the nitro group in DNOC is possible in water in the presence of a reducing agent (e.g., ascorbic acid or ferrous ions) and a sensitizer, such as chlorophyll (EPA 1979). However, there is no experimental evidence of the photochemical reduction of DNOC in water. 

The direct photolysis of 2,4-DNP in water is too slow to be an important environmental fate process (Lipczynska-Kochany 1992). 2,4-DNP may be photoreduced to 2-amino-4-nitrophenol in the presence of ascorbic acid or ferrous ions, and the reaction is sensitized by chlorophyll (Massini and Voorn 1967). The possibility of such photoreduction exists in natural water in which the suspended reducing matter may act as a reducing agent and humic substances or algae may serve as a sensitizer. 

Although the Ru nitrosyl [Ru(PaPy3)(NO)](BF4)2 (3) did not exhibit much sensitivity toward visible light, it has been successfully employed to dehver NO to biologically relevant proteins such as cytochrome c oxidase (CcO) (38) and soluble guanylate cyclase (sGC) (39). Time-resolved flash photolysis studies have shown that NO reacts with CcO (r = 940 ps k= X 10 s ) and 3 can be used as the nitrosylating agent in fast... 

Crystalline vitamin B12 is stable to heating at 100°C. Aqueous solutions of vitamin B12 at pH 4 to 7 can be autoclaved with very little loss. Cyanocobalamin is the most stable form. Nevertheless, the cobalamins are very sensitive in the presence of reducing agents, as well as in light (especially adenosyl- and methylco-balamins) and alkaline conditions. Photolysis results in two compounds stable only under anaerobic conditions. 

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