Flash photolysis of molecules implicated in 9-nitroanthracene photochemistry

Unimolecular photochemistry of anthracenes

“…184 Considerable efforts have been devoted to investigating the photochemistry of 9-nitroanthracene (41). [186][187][188][189][190][191][192][193][194] The virtual lack of 9-nitroanthracene fluorescence is indicative of efficient intersystem crossing from the lowest excited xx* singlet state to an upper nx* triplet state.187 '188 The weak luminescence with maxima around 685 and 760 nm observed at 77 K in a solid matrix has been attributed to 9-nitroanthracene phosphorescence.189190 However, luminescence observed in solid matrices also can arise from various photoproducts of 9-nitroanthracene, particularly 9,10anthraquinone, which may be formed from photoexcited 9-nitroanthracene with high quantum efficiency (0.7) due to the presence of oxygen.192 193 A holographic study has revealed that 9-nitroanthracene in a polymer matrix disappears upon irradiation at 458 nm to give 9-hydroxyanthracene (39) with a quantum yield of about 0.01. 194 Evidence for the photolytic decomposition of 9-nitroanthracene was obtained in an early investigation in which irradiation with light of wavelengths of 370-410 nm was found to give nitric oxide and 10,10'bianthronyl (44), while excitation at longer wavelengths (420-530 nm) yielded the 4x + 4x head-to-tail cyclodimer of 9 In a series of spectroscopic investigations on 9-nitroanthracene, 9-benzoyl-10-nitroanthracene, and 9-cyano-10-nitroanthracene, the photochemical formation of 9-anthryloxy radicals as primary products has been confirmed, including by electron-spin resonance spectra.…”