Rubrene peroxide

On heating, rubrene peroxide gives up most of its oxygen to regenerate rubrene. 

The explanation for these diradical reactions can not be quite so simple as the one hinted at above however, since the quantum yield of rubrene peroxide does not appear to depend only on the concentration of photoactivated rubrene triplet molecules but also on the concentrations of rubrene itself and of oxygen.77... 

Cyclic peroxides may serve as a source of singlet oxygen. Wasserman et reacted 9,10-diphenylanthracene peroxide (238, conveniently prepared as in Nilsson and Kearns ) with 138 to give 140 rubrene peroxide proved to be considerably less efficient. Decomposition of anthracene peroxide alone takes another course. 32.396 jg treated with phthaloyl peroxide... 

The addition of O2 (whether or A ) to 138 or 4 has apparently not been studied theoretically although selection rules for singlet oxygen reactions/ interpretation of substituent effects and orbital correlations for homolytic fission and re-formation of the peroxide bond in 9,10-diphenyl-anthracene peroxide and rubrene peroxide have been published. 

The formation of acene peroxides was studied by Dufraisse et al.0,100 A classical example of this reaction is the formation of rubrene peroxide (164) from rubrene and oxygen.187... 

Rubrene peroxide (164) gives 189 with magnesium iodide which probably acts as a mild Lewis acid.230 Cyclic peroxides containing a hydrogen atom on the C atom carrying the 0—0 group are decomposed by bases in accordance with the Kornblum-de la Mare mechanism [Eq. (14)].231... 

The laser-excited fluorescence from dibenzofuran in a biphenyl host at 4.2 K and three different sites in the lattice have been identified. The two-photon excitation spectrum of single crystals of carbazole at 4.2 K has been analysed in detail. Very extensive vibrationally unrelaxed fluorescence is observed following dye-laser excitation of single vibronic levels of naphthazanine and the rates and pathways of relaxation are examined by picosecond emission spectroscopy. The photophysics of rubrene peroxide have been measured for the first time by Bayrakceken. Picosecond fluorescence has been used to study the spectra and kinetics for Sj— So and Si transitions for... 

Autoxidation of acenes has been studied in particular by Dufraisse and his co-workers.14 Irradiation without addition of a sensitizer converts them in solution (e.g., in CS2) rapidly into the corresponding peroxide an example is rubrene peroxide (5,12-epidioxy-5,12-dihydrorubrene) ... 

DPA) in dimethylphthalate at about 70°, yields a relatively strong blue Umax =435 nm) chemiluminescence the quantum yield is about 7% that of luminol 64>. The emission spectrum matches that of DPA fluorescence so that the available excitation energy is more than 70 kcal/mole. Energy transfer was observed on other fluorescers, e.g. rubrene and fluorescein. The mechansim of the phthaloyl peroxide/fluorescer chemiluminescence reaction very probably involves radicals. Luminol also chemiluminesces when heated with phthaloyl peroxide but only in the presence of base, which suggests another mechanism. The products of phthaloyl peroxide thermolysis are carbon dioxide, benzoic acid, phthalic anhydride, o-phenyl benzoic acid and some other compounds 65>66>. It is not yet known which of them is the key intermediate which transfers its excitation energy to the fluorescer. 

As mentioned in Section II. C., the concerted bond cleavage of 1.2-dioxetane derivatives has been proposed to be of general importance in respect of the excitation step of a large number of chemiluminescence reactions. The first experimental results concerning simple dioxetanes were obtained by M. M. Rauhut and coworkers in their work on activated oxalic ester chemiluminescence 24>. From experimental data on the reaction of e.g. bis (2.4-dinitrophenyl)oxalate with hydrogen peroxide in the presence of rubrene, they concluded that 1.2-dioxetanedione... 

Olas and Wachowicz (2002) investigated the effects of tranx-resveratrol and vitamin C on oxidative stress in blood platelets. The level of 02 in control blood platelets and platelets incubated with resveratrol or vitamin C was recorded using a chemiluminescence method. On the other hand, Oh and others (2006) reported the x02 quenching activities of various freshly squeezed fruit and vegetable juices by measuring their inhibitory effects on the rubrene oxidation induced by x02 from disproportionation of hydrogen peroxide by sodium molybdate in a microemulsion system. 

The main features of the chemiluminescence mechanism are exemplarily illustrated in Scheme 11 for the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of imidazole (IMI-H) as base catalyst and the chemiluminescent activators (ACT) anthracene, 9,10-diphenylanthracene, 2,5-diphenyloxazole, perylene and rubrene. In this mechanism, the replacement of the phenolic substituents in TCPO by IMI-H constitutes the slow step, whereas the nucleophilic attack of hydrogen peroxide on the intermediary l,l -oxalyl diimidazole (ODI) is fast. This rate difference is manifested by a two-exponential behavior of the chemiluminescence kinetics. The observed dependence of the chemiexcitation yield on the electrochemical characteristics of the activator has been rationalized in terms of the intermolecular CIEEL mechanism (Scheme 12), in which the free-energy balance for the electron back-transfer (BET) determines whether the singlet-excited activator, the species responsible for the light emission, is formed ... 

However, the most severe criticism of the CIEEL hypothesis relates to the chemiexcita-tion efficiency experimentally obtained for the standard CIEEL systems, diphenoyl peroxide (4) and 1,2-dioxetanone (2) . In a study on the electron transfer catalyzed decomposition of l,4-dimethoxy-9,10-diphenylanthracence peroxide (21), Catalan and Wilson obtained very low chemiexcitation quantum yields with various commonly utilized activators (4>s =2 10 EmoH ) and reinvestigated the CL of diphenoyl peroxide (4), determining quantum yields in the same order of magnitude (4>s = (2 1)10 Emol ) as those obtained by 21 (Table 1). We have more recently determined the quantum yields in the rubrene-catalyzed decomposition of dimethyl-1,2-dioxetanone (9) and also found a much lower value than the one initially reported (Table 1) °. Since the diphenoyl peroxide and the 1,2-dioxetanone systems are the two prototype CIEEL systems, the validity of this hypothesis itself might be questioned due to its low efficiency in excited-state formation. ... 

Mechanistic studies were started by Gaffron15-17 in 1926. At this time Moureu, Dufraisse, and Dean18 discovered the direct photooxygenation of rubrene and Windaus and Brunken19 discovered the photosensitized oxygenation of ergosterol. The structures of both the products formed were elucidated some years later and shown to be those of transannular peroxides (endoperoxides).20-23... 

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