Self sensitization

NdOCI NdOCI+ Nd4++Ocl3 +e-(self-sensitization) pNd4++gNd3+ (Nd )m+ vis... 

Self-sensitization experiment of an aqueous Ag+ zeolite A suspension. 1 nAs corresponds to 3.94 nl of oxygen. 

Calzaferri, G., S. Hug, T. Hugentobler, and B. Sulzberger (1984), "Self-Sensitization of Photo-Oxygen Evolution in Ag+ Zeolites Computer-Controlled Experiments," J. Photochem. 26, 109-118. 

F. Regioselective Self-sensitized Oxygenation of Fullerene Adducts. 857... 

TABLE 15. Regioselectivity in the self-sensitized oxygenation of fullerene adducts"... 

Syntheses of Self-Sensitized Polymers by Cationic Copolymerizations. The cationic polymerizations of several vinyl ethers containing pendant ester groups such as cinnamic ester 12), methacrylic ester 16), acrylic ester (77), and crotonic ester 18) have been reported. Based on these reports, cationic copolymerizations of CEVE with photosensitizer monomers such as NPVE, NNVE, VNP and NPEVE were carried out using TFB as a catalyst in toluene at — 65 °C. Each copolymer was obtained with high yield except in the case of copolymerization of CEVE with VNP as summarized in Table I. 

Syntheses of Polymeric Photosensitizers and Self-sensitized Polymers by the Reactions of PCVE. Photosensitizer monomers such as NPVE, NNVE and NPEVE were synthesized by the reaction of excess CVE with potassium salts of the corresponding photosensitizing compounds using TBAB as a phase transfer catalyst as described in the experimental part. Substitution reactions of chloroethyl groups in PCVE with PNP and PNN were also carried out using TBAB as a phase transfer catalyst in DMF at 80 C for 24 h. 

The relationship between the thickness of polymer films containing about 10 mol-% of pendant photosensitizer groups and the conversions of the —C bonds after 10 min. irradiation is shown in Figure 5. The photochemical reactivity of PCEVE-NNVE decreased slightly with increasing thickness of the film. Interestingly, the reactivity of PCEVE-NPVE was not influenced by the thickness of the film in contrast to the self-sensitized polymers previously... 

In a related vein antenna chromophores have been developed for the self-sensitized photoreduction of ketones using isopropyl alcohol as a mild reducing agent189. One of the most effective chromophores for reduction of the model ketone 4-hydroxycyclohexanone was found to be the dimethylphenylsilyl group, as illustrated in equation 42. 

Table 13 Regioselectivity in the Self-Sensitized Oxygenation of Fullerene Adducts3...

Scheme 60 Self-sensitized photo-oxygenation of fullerenyl cyclobutenamine 136.

Table 13 Products of Self-Sensitized Photo-oxygenation of Cyclobuteneamines...

Scheme 61 Self-sensitized photo-oxygenation of N-(MEM)-substituted [5,6]-aza-fulleroid 151.

Wudl et al. [283] obtained the ring-opened TV-MEM-ketolactam 153 by self-sensitized photo-oxygenation of. V-methoxyethoxymethyl (MEM)-substituted [5,6]azafulleroid 151 (Scheme 61). The reaction is highly regioselective, most likely because the anti-Bredt carbon-carbon double bonds in 151 are more strained. 

Figure 6 Diastereomeric excess of 66E-68E produced upon self-sensitized diastereo i differentiating photoisomerization of (Z)-3-, 4-, and 5-benzoyloxycyclooctenes 66Z-68Z at different concentrations.

Scheme 1.8. Controlled opening of the fullerene cage by self-sensitized photooxygenation of an azahomo[60]fullerene derivative and subsequent add-induced formation of a dimeric aza[60]fullerene.

The analog photography community is well-versed with the fact that silver halides are tunable band gap semiconductors. Thus the photoactivity of AgCl can be tuned from the UV into the visible light region by a process known as self sensitization, which is due to the formation of Ag clusters during the photoreaction. The formation of these clusters introduces new levels within the forbidden gap that can now be populated by visible light (Fig. 7). 

Fig. 7. Energy level scheme for the photoassisted OER from water using AgCl layers after initial self-sensitization to generate Ag clusters.

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