Photosensitized Reduction

Kamat, RV. 1989. Photoelectrochemistry in particulate systems 9. Photosensitized reduction in a colloidal TiOj system using anthracene-9-carboxylic acid as the sensitizer. J Phys Chem 93 859-864. 

Figure 7. Plot of the quantum yield vs. the HC104 concentration for the [Ru(bpy)3]2 +-photosensitized reduction of phenacyl bromide (1.0 x 10 2 mol dm-3) by AcrH2 (1.0 x 10-2moldm-3) in MeCN under irradiation of the visible light X = 452 nm [86],...

The [Ru(bpy)3]2+ photosensitized reduction of methyl viologen (MV2+) proceeds rapidly in water-swollen iminodiacetic acid type chelate resin beads which adsorb both [Ru(bpy)3]2+ and MV2+ (RM resin). The reduction takes place with the aid of polymer-bound iminodiacetate as a donor 102). Photosensitized formation of hydrogen peroxide occurs in an aqueous solution containing RM resin and oxygen molecules (Fig. 8)102 The some reaction also occurs using a polystyrene-coated filter paper, onto which both [Ru(bpy)3]2 + and MV2+ were adsorbed 103). 

The quantum yield of the [Ru(bpy)3]2 + photosensitized reduction of Co(III)-Schiff base complex cation in aqueous solution is greately affected by the composition of the polymer-supported polyanionic donors such as vinylbenzylamine-iV,iV-diacetate-... 

We have examined the photosensitized reduction of a series of + 4,4 -bipyridinium salts, CnV2+, (2), (where n=l-16) with Ru(bpy)l as sensitizer and (NHi jEDTA as electron donor in a water-in-toluene microemulsion media. Under steady state illumination the quantum yield of CjjVt" formation strongly depends on the alkyl chain length of the electron acceptor (Figure 4). It improves as the hydro-... 

Table II. Charge separation yields and recombination rates in the photosensitized reduction of CnV2 in water-in-toluene microemulsions (6)...

Table III. Turnover Numbers (TN) of the components involved in the photosensitized reduction of 2-butanone.

Fig. 9. Control of the photosensitized reduction process of jV,AT-(3-propylsulfonato)-4,4 -bipyridinium, PVS, in a microheterogeneous system composed of a Si02 colloid...

Fig. 10. Control of the photosensitized reduction of AT,AT-dialkyl-4,4 -bipyridinium electron acceptors, C V2+, in a water-in-oil microemulsion system...

Fig. 16a, b. Examination of reduction and oxidation processes of artificial photosynthetic devices by means of sacrificial components a) application of sacrificial electron donor in a photosensitized reduction process b) application of a sacrificial electron acceptor in a photosensitized oxidation process... 

Other Co(II)-complexes that were applied in the photosensitized reduction of C02 to CO (and concomitant H2-evolution) include Co(II)-ethylene glycol dimethyl ether complexes [178], and different tetraaza-macrocyclic Co(II)-complexes such as 27,28. A closely related system, where Ni(II)-tetraaza macrocycle (29) substitutes the cobalt homogeneous complexes in the photosystem including Ru(bpy) + as photosensitizer and ascorbic acid as electron donor, has been reported by Tinnemans [181] and Calvin [182],... 

Selective carbon dioxide reduction to CO has been accomplished in a non-aqueous medium that includes tricarbonyl (2,2 -bipyridinium) rhenium , /ac-Re(bpy) (CO)3X (X=Cl, Br) as light-active component and homogeneous catalyst for C02 reduction [183-185]. In dimethylformamide solutions that include TEOA as sacrificial electron donor, photosensitized reduction of C02 to CO proceeds with a quantum efficiency of

Mechanistic investigations have revealed that reductive ET quenching of the rhenium complex (Eq. (54)) yields the catalytic intermediate active in deoxygenation of C02. It has been suggested that carbon... 

Figure 7 Photosensitized reduction of oxazine dye using humic acid as sensitizer. The transient absorption spectrum was recorded following 532-nm laser pulse excitation of humic acid containing the dye and 1102.

Willner I, Maidan R, Mandler D, Durr H, Dorr G, Zengerle K. Photosensitized reduction of C02 to CH4 and H2-evolution in the presence of Ru and Os-colloids strategies to design selectivity of products distribution. J Am Chem Soc 1987 109 6080-6. 

By designing a system that results in oppositely charged photoproducts, we can produce a retardation of recoinblnatlon by the charged Interface. The photosensitized reduction of a neutral acceptor, propylviologen sulfonate (PVS°) by positively charged sensitizers such as Ru(blpy) and Zn-tetra-methylpyrldlnlum porphyrin, Zii-TMPyP, is des-... 

The quantum yield for the photosensitized reduction of PVS (using Ru(blpy)2+ as sensitizer) has been correlated with the Interfaclal surface potential of the SIO2 colloid (controlled by varying the Ionic strength of the medium) (22). The correlation curve (Figure 11) shows that up to an Interfaclal potential of ca. -40 mV the quantum yield Is not affected. Increasing the potential above this apparent threshold value results In a sharp Increase In the quantum yield. A similar correlation curve was obtained when Zn-TMPyP was used as sensitizer Instead of Ru(bipy). ... 

Zinc tetraphenylporphine has been found to sensitize the photoredox reaction between N-phenylglycine and p-benzoquinone in polar solvents. In MeCN and at wavelengths above 500 nm, the ketone is reduced to hydro-quinone, and following decarboxylation of the glycine to PhN=CH2 and hydrolysis, aniline is formed. In ethanol solution, photosensitized reduction... 

By the second approach, the enzyme is immobilized in a redox polymer assembly (Figure 39B). Electron-transfer quenching of the photosensitizer by the polymer matrix generates an electron pool for the activation of the enzyme. Photoreduction of nitrate to nitrite was accomplished by the physical encapsulation of NitraR in a redox-functionalized 4,4 -bipyridinium acrylamide copolymer [234]. In this photosystem, Ru(bpy)3 + was used as a photosensitizer and EDTA as a sacrificial electron donor. Oxidation of the excited photosensitizer results in electron transfer to the redox polymer, and the redox sites on the polymer mediate further electron transfer to the enzyme redox center, where the biocatalyzed transformation occurs. The rate constant for the MET from the redox polymer functionalities to the enzyme active site is — (9 + 3) x 10 s. Similarly, the enzyme glutathione reductase was electrically wired by interacting the enzyme with a redox polymer composed of polylysine modified with A-methyl-A -carboxyalkyl-4,4 -bipyridinium. The photosensitized reduction of oxidized glutathione (GSSG) (Eq. 21) ... 

Figure . Proposed reaction scheme for BTD-photosensitized reduction of AQDS by MES in CTAB micelles (adapted from [73]). BTD is either BTDB or BTDE (see text for definitions).

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