PHOTOCHROMISM OF 1-(1-NAPHTHOXY)ANTHRAQUINONES

The photochromic behavior of 1-(1-naphthoxy)anthraquinone (1) has been newly investigated. Upon UV light irradiation, the color of a benzene solution of 1 turned from pale yellow to orange. The quantum yield of the coloration was 0.05. The excited singlet state was revealed to be responsible for the coloration. The decay of the colored species obey ed good first-order kinetics and consisted of two processes, i.e. the reversion to the starting substance and the change toward final format ion of 1-hydroxyanthraquinone. The activation enthalpy of the process of reversion to 1 was obtained as 83.6 kJ mol-1. That of the other pro cess was 38.9 kJ mol-1. The colored species has been assigned as a 9-n aphtoxy-1,10-anthraquinone.