Visible-light photolysis

Benzo[c]cinnoline is reduced by visible-light photolysis in isopropanol to 5,6-dihydrobenzo[c]cinnoline irradiation of this at a shorter wavelenth converts it to carbazole. ... 

Triple-branching functionalization of complex 7 yielded nona-allyl derivative 8 which was demetallated by visible light photolysis in the presence of triphenyl-... 

The radical reactivity of Craq002+ has been especially well documented. This complex is ideal for mechanistic studies, not only because of the convenient combination of lifetime and reactivity, but also because it is nearly inert to visible-light photolysis. Photochemical generation of reactive partners in the presence of Craq002+ is thus possible, and rapid radical reactions can be observed and studied directly, as shown on the examples of acylperoxyl radicals, NO, and NO2. 

This problem is not so severe when acyl xanthates are used as precursors because these substrates absorb in the visible region, while the products do not (however, the products might still be recycled to the radical pool by radical addition-elimination). Visible light photolysis of benzoyl xanthane (42) and allyl acetate provides (43) in 60% yield. Standard (ionic) 3-elimination of the xanthane is a facile reaction that gives (44). When the tertiary acyl xanthane (45) is irradiated in the presence of W-benzylmaleimide... 

Figure 6. Hydrogen production at 25°C in deaerated solutions as a function of catalyst (rhodium) concentration during the first two hours of irradiation using 350 nm cut-off and water filters. Plotted are the amount of hydrogen produced in 25 ml DHP vesicle solution.and measured in the gas phase (16 ml) by GC s 2 x 10- J M DHP, 2 x 10 M CdS symmetrically distributed on both sides of the vesicles, and 10 J M PhSH as electron donor pH approximately 7 at sonication and during photolysis. Concentrations of the catalyst, reduced by uv irradiation prior to visible light photolysis ( - Dl 1 ° ...

Scheme 23. One-pot syntheses of the pheno l-tria I lyl iron complex and metal-free dendron by variation of the experimental conditions. The iron complex can be demetalated by visible-light photolysis the metal-free phenol-triallyl dendron can be obtained more rapidly direct from the p-ethoxytoluene-iron complex.

P. T. Buckley and J. W. Birks, Evaluation of visible-light photolysis of ozone-water cluster molecules as a source of atmospheric hydroxyl radical and hydrogen peroxide, Atmospheric Environment 29, 2409-2415 (1995). 

Visible light photolysis of diazo(3-thienyl)methane (25) (Scheme 9) in argon matrices generated a methylenecyclopropene as the s-Z conformer (27), which isomerized to the s-E form (28) on further photon absorption. The intermediate carbene (26) was not observed directly, but it could be trapped by oxygen in O2-doped matrices. A second intermediate in the reaction pathway, l. f-2-thiabicy-clo[3.1.0]hexa-3,5-diene, was also postulated, and a few weak absorptions in the matrix IR spectra may have belonged to this species. 

Eu2+/Ru(bpy)3+/Co° Me4[14] tetraene N4)41) and Ru(bpy)2+/Ti3+42). Visible light photolysis yield Co (Me4 [14] tetraene N4) and Ti2+ ions which spontaneously react with HzO to evolve H2. The following mechanisms have been proposed for the sustained... 

Fig. 8.6. Influence of irradiation time on the yield of hydrogen obtained from the visible light photolysis of Ru(bipy)2+ (10 4M/and MV2+ (5 x 10 3M), pH = 4.7 (adjusted with acetate buffer), Ti02 particles (500 mg r1) charged with 0.2% Ru02, 40 mg l"1 Pt (R = 16 A) codeposited on Ti02...

Here visible light photolysis, generates the reductant proflavine9 radical. Like the ketyl radical mentioned earlier, the proflavine anion radical is very reactive and disappears rapidly. Utilisation of a relay such as MV2+ leads to increase in photocurrent from 30 fiA to 180 fiA which remains stable over a few hours. 

Transformation of 945 into the thiohydroxamate ester 947 followed by visible-light photolysis in the presence of tributyltin hydride allows large scale preparation of the methylene cyclopentane 948. The overall yield of 948 from 945 after chromatographic purification on silica gel is 55—65%. Desilylation of 948 and subsequent epoxidation of the exocyclic olefin with freshly prepared dimethyldioxirane solution provides the epoxyalcohol 949 in high yield. A Dess—Martin oxidation to the epoxyketone followed by rearrangement on silica gel to the enone, a Luche reduction from the convex face, and a final isopropylidene ketal hydrolysis provides 950 as a single diastereomer [262] (Scheme 205). 

Figure 2. Difference infrared spectra before and after visible light photolysis of toluene and oxygen in zeolites BaX and BaY near room temperature with A > 400 nm. Toluene losses are indicated by asterisks. Also shown is an authentic spectrum of benzaldehyde adsorbed in BaYfor comparison with product spectra.

Seery MK, George R, Floris P, Pillai SC. Silver doped titanium dioxide nanomaterials for enhanced visible light photolysis. J Photochem Photobiol A 2007 189 258-63. 

In the case of allene + NO reaction in solid Ar during the visible-light photolysis (585 nm), 2-allylnitrite radical was detected by Fourier transform infrared (FT-IR) spectroscopy, whereas excitation of dimethylacetylene - NO systems (610 nm) gives the acetylmethyliminoxy radical and dimethylketene [75]. As a result of oxygen atom transfer from NO to the central carbon atom, 2-allenylidoxy transient biradical is generated in allene ... 

H observed, however, are fairly high (O.l - 0.8). Visible light photolysis of the CT bands in colored metal complexes of these ions, in few cases reported (e.g. Cu (phen) ) however failed to produce... 

Several light-induced electron transfer cycles using transition metal polypyridyl complexes that lead to catalytic fixation of CO2 or CO have been identified [69,70]. Visible light photolysis of C02-saturated aqueous acetonitrile solutions containing Ru(bpy)32+ (as photosensitizer), Co(II) ions (as the catalyst), 4,7-Me2-phenanthroline (as the ligand to complex the Co(II) in situ), triethanolamine (as donor) yields a mixture of CO and H2 (synthetic gas). The syn gas mixture is produced by simultaneous occurrence of two reduction reactions ... 

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