Quantum phenanthrene

Ridder, L. Rietjens, I.M. Vervoort, J.A. Mulholland, A., Quantum mechani-cal/molecular mechanical free energy simulations of the glutathione S-transferase (Ml-1) reaction with phenanthrene 9,10-oxide, J. Am. Chem. Soc. 2002,123, 9926-9936. 

As can be seen from Table 2, certain phenanthrene derivatives produce more chemiluminescence than luminol. The diphenyl derivative 33 diluminyl evidently has its benzene rings in a non-coplanar position this is apparent from the fact that this compound does not behave as a benzidine derivative under the oxidative conditions of chemiluminescence reactions. The chemiluminescence quantum yield is only about one third that of luminol 100>. 

The chemical sensitization effect was 0.006 (calculated from the quantum yield of the photochemical transformation of 130 to 131, the yield of 131 obtained with the oxalate/hydrogen peroxide reaction, and the moles of oxalate employed). Higher chemical sensitization efficiencies (about 0.04) were observed when the oxalate/hydrogen-peroxide system was used in the addition of ethyl vinyl ether onto phenanthrene quinone... 

L. Lewis-Bevan, S. B. Little, J. R. Rabinowitz, Quantum Mechanical Studies of the Structure and Reactivities of the Diol Epoxides of Benzo[c]phenanthrene , Chem. Res. Toxicol. 1995, 8, 499 - 505. 

Sensitized PET reactions are often very slow and have low quantum yields due to dominating back-electron transfer. In these cases, the addition of cosubtrates (e.g., biphenyl or phenanthrene to DCA- or DCN-sensitized reactions) is useful. The use of such an additive is called cosensitization. In these reactions, the substrate is not oxidized (or reduced) by the excited sensitizer but by the radical ion of the cosensitizer (ET, ). This is a thermal electron-transfer step without the problems of back-electron transfer. The key step is the primary PET process (ETJ in which the cosensitizer radical ion is formed. The main characteristic of cosensitization systems is the high quantum yield of the free-radical ion (e.g., overall quantum yield is high and the reaction is fast (Scheme 7). 

Fig. 27. Quantum efficiency of sensitized hole injection in organic crystals (injected holes per incident photon) versus applied field strength (ratio of voltage to crystal thickness) Pe = perylene. Ar = anthracene, Ch = chrysene, Phen = phenanthrene...

Fig. 31. Quantum yield (filled circles) of rhodamine sensitized hole generation at the surface of organic crystals relative to perylene W/Wpe versus the ionisation energies 7C of the organic crystals (lower abcissa). The range of the estimate for the value at phenanthrene is indicated by the wiggled arrow. The activation times for electron transfer and back electron transfer Tjg are also shown (compare Section IV 7)...

Although naphthalene, phenanthrene, and anthracene resemble benzene in many respects, they are more reactive than benzene in both substitution and addition reactions. This increased reactivity is expected on theoretical grounds because quantum-mechanical calculations show that the net loss in stabilization energy for the first step in electrophilic substitution or addition decreases progressively from benzene to anthracene therefore the reactivity in substitution and addition reactions should increase from benzene to anthracene. 

These methods, used in conjunction with suitable phosphoroscopes, can also be used to measure quantum yields of phosphorescence (process 14) (32). Data are very scanty, due to experimental difficulties, so that estimates of the relative importance of processes 2, 3, 4, 14, and 15 remain very imperfect (48,64). Emission from fluid solutions is only by process 2, although with thorough de-oxygenation to eliminate process 11 process 14 might be detectable (34). Otherwise, process 14 is observed only in rigid glassy solvents, as with naphthalene, phenanthrene, or coronene in boric acid glass at room temperatures. 

As has been mentioned earlier, it is often very difficult to distinguish between and identify the roles of exciplexes (and excimers) and biradicals in cycloaddition reactions. Caldwell and Creed (1978b) have studied the cycloaddition of dimethyl fumarate to phenanthrene and found that the quantum yield of the cyclobutane photoaddition product is increased in the presence of oxygen. It was suggested that oxygen enhances intersystem crossing in the triplet biradical formed between the two reactants. Nitroxide radicals have also been found to increase intersystem crossing (Sj -> Tj) in carbocyanines when nonpolar solvents are used (Kuzmin et al., 1978). When polar solvents are employed full electron transfer takes place. 

Physical details relating to the isomerization of the stilbenes (12) have been determined.A study of the photophysical properties of the styrylstiIbenes (13) has shown that quantum yields for trans-cis isomerism are low from the singlet but high from the triplet state. The photochemical isomerization of the alkene (14) in an ethanol glass affords the trans-isomer with high efficiency even at liquid helium temperatures. Photochemical cis-trans-isomerization of cis-1,2-di-l-naphthylethylene (14) has also been studied in the crystalline phase. A study of the photochemical isomerization of a series of styryl phenanthrenes has been reported. The mechanism of the reaction involved was discussed. ... 

SET Induced Reactions - Further studies on ring opening reactions of 1,2-diarylcyclopropanes have focused on compounds (83) bearing an acetyl functional group.All of the cyclopropane derivatives studied show efficient cis.trans isomerism with reasonable quantum efficiency. The isomerism reaction involves an acetophenone-like triplet state with lifetimes shorter than 1 ns. The formation of ring opened products also takes place but inefficiently to give a mixture of the two alkenes (84) and (85). A study of the electron-transfer-induced photochemical reactivity of the cyclopropane (86) has been reported in the co-sensitisation system (biphenyl/phenanthrene/DCA). ... 

The conversion of naphthalene to 2-naphthoic acids by irradiation with carbon dioxide and electron donors (e.g. amines or dimethoxybenzene) has been further investigated and the quantum yields of the reaction measured for different solvents and donors. Electron transfer also occurs in the photochemical phosphonation of naphthalene and phenanthrene achieved by irradiation with trialkyl-phosphites and electron acceptors such as 1,3-dicyanobenzene. The photonitration of phenol in aqueous solutions of nitrate ion has been reported and phenols have been prepared by irradiation of substituted benzenes with the aromatic N-oxide (132). ... 

The Fixation of Carbon Dioxide and Nitrogen.—As reduced carbon compounds are convenient fuels, the possibility of achieving the reductive fixation of COa in vitro is appealing, if remote. There are very few data on photochemical reactions involving carbon dioxide, for it has no low-lying excited states and has not historically been of much interest to the photochemist. However, what appears to be the first example of photofixation of COa in a non-biological system has been briefly reported.18 Photoirradiation (with a high-pressure mercury lamp) of phenanthrene in the presence of an amine and C02 in a polar solvent (MeaSO or HCONMea) yielded 9,10-dihydrophenanthrene-9-carboxylic acid, in unspecified quantum yield. The mechanism appears to involve formation of COaT by electron transfer from the photoexcited amine, followed by attack of COaT on position 9 of phenanthrene. Similar reductive carboxylation of anthracene, pyrene, naphthalene, and biphenyl was observed. 

In a reaction analogous to that of stilbene, protonated azobenzene iso-merizes at room temperature under irradiation with ( )e, z = 0.27 and = 0.25. Subsequently, the dehydro-photocyclization starts from the photo-stationary E/Z mixture to give protonated benzo[c]cinnoline with a yield of (j) = 0.02. This is parallel to the stilbene-to-phenanthrene reaction, and it proceeds not in concentrated sulfuric acid where the thermal Z -> E reisomerization is fast, but best in ca. 66% acid. Protonated benzo[c]cinnoline and hydrazobenzene are formed, and the latter undergoes the benzidine rearrangement. The complexation with metal ions in azobenzene crown ethers under participation of the n-electrons of the azo group leads to an increase of the E Z quantum yield from 0.25 of the metal free compound to 0.4 to 0.6 in the Ba and Ca "" complexes. The Z E yield decreases from 0.18 to 0.13 and 0.05. If the crown is larger, the values increase to 0.35 and (pz-iE = 0.45. " ... 

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