REVERSIBLE PHOTODIMERIZATION OF ANTHRACENE AND TETRACENE

Abstract— Dianthracene is efficiently photodissociated, forming anthracene with a quantum yield of about 0.63. Like anthracene, tetracene undergoes a reversible photochemical reaction, the product of which appears to be di‐tetracene. In dilute, deoxygenated solutions the of quantum yeild for the formation of di‐tetracene is directly proportional to the concentration of the monomer ødim = 2.2 (T̃). The quantum yield for the reverse reaction is approximately 0.74 When dilute deaerated solutions of anthracene are irradiated with the unfiltered radiation from a quartz‐mercury arc, a degradation product is formed. Unlike the dimer, this product cannot be converted into anthracene either by heating it to 200d̀C or by irradiating it in solution with light of 254 nm. This degradation product appears to be the compound or compounds which Birks et al. believed to be dianthracene. Irradiation of deaerated solutions of anthracene (or tetracene) with light of wavelenghts longer than 300 nm produces only the dimer, which has an absorption spectrum similar to that reported by Coulson et al.