Eosin Complexation

Overall number of viologen units present in the compound as confirmed by the eosin complexation experiments Process affected by adsorption From Ref. [18]... 

The fact that the number of reducible viologen units is smaller than expected cannot be attributed to lack of branches in the structures of the dendrimers because the results obtained for eosin complexation clearly show that the examined compounds do contain 9 (A9 and 89 " and 21 and 821" viologen... 

Testing is undertaken by several methods, including chloroform extraction and use of a sulfonphthalein dye (absorbance of yellow-colored complex using bromophenol blue and bromocresol green) or the use of eosin (sodium tetrabromofluorescein) solution in acetone and tetrachloroethane solvent. After shaking with a citric acid buffer and eosin addition, upon standing the lower layer turns pink if filmer is present. Subsequent titration with Manoxol OT (sodium dioctyl sulfosuccinate) quantifies the filmer, with loss of the pink color indicating the end point. 

However, some data have been more difficult to incorporate into the mechanism shown in Figs. 8 and 9. As reported 21) in Section II,B the Fe protein can be reduced by two electrons to the [Fe4S4]° redox state. In this state the protein is apparently capable of passing two electrons to the MoFe protein during turnover, although it is not clear whether dissociation was required between electron transfers. More critically, it has been shown that the natural reductant flavodoxin hydroquinone 107) and the artificial reductant photoexcited eosin with NADH 108) are both capable of passing electrons to the complex between the oxidized Fe protein and the reduced MoFe protein, that is, with these reductants there appears to be no necessity for the complex to dissociate. Since complex dissociation is the rate-limiting step in the Lowe-Thorneley scheme, these observations could indicate a major flaw in the scheme. 

Aliphatic amines have been determined by a number of methods. Batley et al. [290] extracted the amines into chloroform as ion-association complexes with chromate, then determined the chromium in the complex colorimetri-cally with diphenylcarbazide. The chromium might also be determined, with fewer steps, by atomic absorption. With the colorimetric method, the limit of detection of a commercial tertiary amine mixture was 15ppb. The sensitivity was extended to 0.2 ppb by extracting into organic solvent the complex formed by the amine and Eosin Yellow. The concentration of the complex was measured fluorometrically. Gas chromatography, with the separations taking place on a modified carbon black column, was used by Di Corcia and Samperi [291] to measure aliphatic amines. 

Other workers have employed different sensitiser systems, e.g. duel sensitisation by a zinc porphyrin and copper phthalocyanine on TiOj, Eosin Y or tetrabro-mophenol blue on ZnO, and a ZnO/SnOj mixture with a ruthenium bipyridyl complex, to produce good energy conversion factors. 

The determination of chlorpromazine after formation of a ternary complex with eosin and Pd(II) was reported [142]. The method employs excitation at 462 nm, and detection of the emission at 545 nm. 

Berube Complexation of a planar dye (rhodamine, eosin or fluorescein) with a metal salt (potassium dichromate, barium chromate, magnesium chloride, or calcium chloride)... 

Photooxidation of Eosin with periodate ion has been used to initiate the polymerization of acrylonitrile in aqueous solution [187]. Addition of acrylonitrile to a periodate solution shifts the absorption maximum from 220 to 280 nm. This spectral change is interpreted as being due to complex formation between the monomer and oxidizing agent. The rate of photopolymerization increases linearly with the absorbed light intensity and monomer concentration. The observed intensity dependence indicates the main chain terminator is not produced photochemically. Polymer is not formed when the concentration of periodate ion is lower than 0.5 mM and the rate of polymerization is independent of its concentration for higher values. 

Addition of MDEA to a solution containing Eosin and 02I + increases the fluorescence intensity and shifts the spectrum toward the blue. Similarly, the fluorescence quenching by 2I + is less efficient in the presence of the MDEA, indicating that the amine destroys the complex between Eosin and diphenyliodonium. 

Johansen et al. compared fluorescein, Eosin, Rose Bengal, and Rhodamine B. The system included the electron acceptor, methyl viologen, mv2 + which does not oxidize the dyes (nor are there dye-mv2+ complexes involved) but which reacts with the semireduced radicals formed by reduction of the dyes. The reaction scheme, in the presence of a platinum catalyst, is shown in Eqs. (32)—(35). 

The nanocrystalline solids are metal oxides, especially titanium dioxide [54-58], Various dyes are used. Transition metal complexes such as (65) and (66) have broad absorption bands and allow the harvesting of a large fraction of sunlight [54,58], Fluorescent dyes are also used, such as Eosin-Y (67) [57], Dye-sensitized nanocrystalline solar cells are now giving efficiencies in excess of 10% [54,58], compared to just 1 % ten years ago [3],... 

A third method was also developed based on formation of the ternary complex with eosin and Cu(II), with the colored product being quantified using its absorbance at 549 nm. A mean recovery of 99.46% was found, characterized by a relative standard deviation of 0.81%. 

Dyes such as erythrosin B [172], eosin [173-177], rose bengal [178,179], rhodamines [180-185], cresyl violet [186-191], thionine [192], chlorophyll a and b [193-198], chlorophyllin [197,199], anthracene-9-carboxylate [200,201], perylene [202,203] 8-hydroxyquinoline [204], porphyrins [205], phthalocyanines [206,207], transition metal cyanides [208,209], Ru(bpy)32+ and its analogs [83,170,210-218], cyanines [169,219-226], squaraines [55,227-230], and phe-nylfluorone [231] which have high extinction coefficients in the visible, are often employed to extend the photoresponse of the semiconductor in photoelectro-chemical systems. Visible light sensitization of platinized Ti02 photocatalyst by surface-coated polymers derivatized with ruthenium tris(bipyridyl) complex has also been attempted [232,233]. Because the singlet excited state of these dyes is short lived it becomes essential to adsorb them on the semiconductor surface with... 

The substitution of l-chloro-2-naphthoxide ion by sulfite ion in water can also be initiated by visible light (436 nm) with the complex [Ru(bipy)2]Cl as the sensitizer and the complex [Co(bipy)3](C104)2 as the intermediate electron carrier3315. Another possibility is a dye photoinitiated reaction. In the latter example, the excited triplet of the dye (fluorescein, eosine or erythrosine) receives an electron from S03 2 whose radical anion (S03) reacts with halonaphthoxides to give finally the substitution product33c. 

Functionalized organic dyes with polyaminocarboxylate have been widely utilized as feasible sensitizers to afford visible region excitation for sensitization of NIR lanthanide luminescence [36 5]. Verhoeven and coworkers [36, 37] first prepared a series of neodymium(III), erbium(III), and ytterbium(III) complexes with polyaminocarboxylate-functionalized fluorescein (21) and eosin (22) as sensitizing chromophores. These complexes show sensitized NIR... 

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