PHOTOPHYSICS AND PHOTOCHEMISTRY OF NITROANTHRACENES .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 pipi* 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 npi* 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.