Perylene conditioning

Pitts JN Jr, B Zielinska, JA Sweetman, R Atkinson, AM Winer (1985b) Reactions of adsorbed pyrene and perylene with gaseous N2O5 under simulated atmospheric conditions. Atmos Environ 19 911-915. 

Figure 8.2a-c shows optical transmission images of organic microcrystals of perylene, anthracene, and pyrene, excited at a laser power of 1.7 nj pulse under similar excitation conditions as in Figure 8.1c. The bright spots <2 pm in diameter at the center of each microcrystal were areas irradiated with the NIR laser pulse.

Chemiluminescence also occurs during electrolysis of mixtures of DPACI2 99 and rubrene or perylene In the case of rubrene the chemiluminescence matches the fluorescence of the latter at the reduction potential of rubrene radical anion formation ( — 1.4 V) at —1.9 V, the reduction potential of DPA radical anion, a mixed emission is observed consisting of rubrene and DPA fluorescence. Similar results were obtained with the dibromide 100 and DPA and/or rubrene. An energy-transfer mechanism from excited DPA to rubrene could not be detected under the reaction conditions (see also 154>). There seems to be no explanation yet as to why, in mixtures of halides like DPACI2 and aromatic hydrocarbons, electrogenerated chemiluminescence always stems from that hydrocarbon which is most easily reduced. A great number of aryl and alkyl halides is reported to exhibit this type of rather efficient chemiluminescence 155>. 

For example, under low flow conditions and at a temperature of 18 °C, the SPMD residence time for phenanthrene is 45.4 d and ke values for benzo[, /f,/]perylene are too small to measure, which suggests a residence time of > 10 d. 

It is important that both the twisted and chair forms of the cylclohexane cation-radical react with a solute, for example, with perylene. Therefore, generation of the perylene cation-radical is characterized with bimodal kinetics under these conditions. 

Lee and coworkers postulated the involvement of 50 and 51 (Ar = 2,4-dinitrophenyl) as two HEIs formed in parallel in the uncatalyzed reaction of DNPO and hydrogen peroxide in the presence of perylene. Due to the experimental observations of light emission from the reaction of DNPO and TCPO also in the absence of hydrogen peroxide, Lee and coworkers postulated the involvement of a nonperoxidic HEI (additionally to 51 and 3, 48 or 52) under these conditions. However, neither chemiluminescence quantum yields nor even relative emission intensities have been reported. Furthermore, it was shown " that the intensities and the chemiluminescence quantum yields in the absence of hydrogen peroxide are five orders of magnitude lower than in the presence of 10 M H2O2, indicating that the proposed additional pathway is of extremely low efficiency for excited-state... 

The generality of this reaction of N02 with particle-associated PAHs was demonstrated when, under similar laboratory conditions, perylene (a weak promutagen) was converted to 3-nitroperylene, and pyrene (a nonmutagen), at a slower rate, to 1-nitropyrene both nitro-PAHs are direct-acting frameshift mutagens. In a similar experiment, chrysene was not nitrated this is consistent with its low reactivity in the Nielsen reactivity scale (Table 10.30). 

Pitts, J. N., Jr., B. Zielinska, J. A. Sweetman, R. Atkinson, and A. M. Winer, Reactions of Adsorbed Pyrene and Perylene with Gaseous N205 under Simulated Atmospheric Conditions, Atmos. Environ., 19, 9II-9I5 (I985d). 

Determination of the Number of Electron-Acceptor Sites. This determination was done in a few cases using perylene and phenothiazine as reactants. The catalysts were reduced for 2 hours at 400°C under H2. Since we presume that silica-alumina may be modified by the reaction medium during palladium exchange, we used as our blank a support treated under conditions similar to that of the catalysts. The results (Table V) show a clear decrease of the number of oxidizing sites after palladium deposition. 

The compounds with the highest electron mobility are currently fullerene C60 [81, 82] and N,N4-dialkyl-3,4,9,10-perylene tetracarboxylic diimide derivatives [83, 84], with values up to 0.5 cm2 V 1 s 1. A major problem with these compounds is their high sensitivity to ambient conditions, especially oxygen and moisture. A small number of air-stable n-type compounds have been reported [85-88]. All are perfluorinated and their mobility does not exceed a few tenths of 1 cm2 V 1 s 1. 

Our previous results on hypericin indicate that excited-state H-atom transfer occurs even when one of the carbonyls is prohibited from accepting a hydrogen. The presence of such a transfer is apparent under very acidic conditions in AOT reverse micelles and cannot be excluded upon chelation of Tb3+ [76]. There is thus no evidence for a concerted H-atom-transfer mechanism in hypericin. In the present study, contrary to our initial expectations, we are not even able to demonstrate that hypomycin B executes an excited-state H-atom transfer hence our investigation sheds no light on the general question of how many H atoms are transferred in the perylene quinones and whether the transfer is concerted or stepwise. On the other hand, if further investigation reveals that H-atom transfer does not occur in hypomycin B, the result would have considerable implications for an understanding of the reaction coordinate for the H-atom transfer. 

Bernstein et al. have used IR spectroscopy and mass spectrometry to study the products formed from photochemical transformation of naphthalene, anthracene, chrysene, phenanthrene, pyrene, tetracene, pentacene, perylene, benzo(e)pyrene, benzo(ghi)perylene, and coronene in water ices using ultraviolet radiation under astrophysical conditions [27]. The results of their investigation have revealed that peripheral carbon atoms can be oxidized to produce aromatic alcohols, ketones, ethers (when bay region is present,... 

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