Photophysics and photochemistry of nitroanthracenes. Part 2. Primary process in the photochemical reaction of 9-nitroanthracene studied by steady-state photolysis and laser photolysis

From measurements of phosphorescence and triplet–triplet absorption spectra of the lowest excited triplet ππ* state of 9-nitroanthracene (NA) together with the absorption spectrum of 9-anthryloxy radical, it is concluded that photolysis of 9-nitroanthracene gives rise to the nitro → nitrite rearrangement for a higher excited triplet state of nπ* character, followed by the cleavage of 9-anthryl nitrite to 9-anthryloxy radical and nitrogen(II) oxide, yielding 9-anthrol (and anthrone), 10,10′-bianthrone and 9-nitrosoanthrone in ethanol; and 10,10′-bianthrone and 9-nitrosoanthrone in benzene. Hence, the primary process in the photochemical reaction of NA is essentially identical with those of 9-benzoyl-10-nitroanthracene and 9-cyano-10-nitroanthracene except that no 10,10′-bianthrone derivatives are formed.