Ruthenium methyl viologen

Later, an improved system for C02 photofixation was reported by the same authors.164 The new system consisted of 6.5 x 1(T5 M tris(2,2 -bipyridine)ruthenium(II), Ru(bpy)3, as the photosensitive electron donor, methyl viologen (MV2+, 20 mM) as the electron acceptor, and triethanolamine (TEOA, 0.6 M) as a sacrificial electron donor in a C02-saturated aqueous solution (Fig. 18). Under irradiation with a 300-W high-pressure Hg lamp with a CuS04 chemical filter (A > 320 nm), formic acid, which was detected by isotachophoresis, was produced in quantum yields of ca. 0.01%. Recently, however, Kase et al.165 have repeated this experiment using a 13C02 tracer and have claimed that the formic acid obtained was produced not by C02 reduction but rather by oxidative cleavage of TEOA. 

Figure 5.30 Molecular structure of the disulfide-linked ruthenium polypyridyl methyl viologen dyad, [RuC7VC6S]2 [65]...

Model systems that couple H2 oxidation with the reduction of a cofactor have been reported. The complex Cp L2RuH catalyzes the reduction of NAD [77] or methyl viologen [78] under dihydrogen. This system demonstrates that a ruthenium model system can catalyze the activation of hydrogen without the benefit of the protein scaffold. 

Figure 16.7 PCET reaction in a model fortyrosine oxidation in photosystem II. Inthe first step of the experiment, the ruthenium-tris-bipyridine portion absorbs light, and the excited electron is transferred to an external methyl viologen acceptor. In the second step, which is shown here, the tyrosine portion transfers an electron to the ruthenium and is deprotonated. Reproduced from Ref. [63].

The probe ruthenium(ll) frA-(l, 10-phenanthroline) and the electron donors 4-benzoyl-A-methylpyridinium and A-benzyl-A -methyl viologen were employed by Leventis et al. [12]. A base-catalyzed TMOS precursor recipe was used to prepare silica sol-gel monoliths. The wet gels were then soaked in methanol baths containing one of the dyads, or the mthenium complex, each of which is a cationic species that was taken up by the sol-gels to such an extent that no color was observed in the remaining bath solution. The doped gels... 

In several cases, this has shown to be true. For exanple, the photoelectron transfer between the tris(2,2 -bipyridine)ruthenium(lt) dication, [Ru(bipy)3l and methyl viologen 1,1 -... 

The photoreduction of viologens in surfactant systems has also been described by Massini and Voorn [70]. An amphipathic derivative of methyl viologen (Ci4MV ) (XII) has been employed as an electron acceptor in reactions involving the charge-transfer excited state of the ruthenium complex Ru(bpy) the reaction products MV and Ru(bpy)3 of the reaction between and... 

Photoreduction of Methyl Viologen on Cellulose Sensitized by Tris(2,2 -bipyridyl)ruthenium Complex [104]... 

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