PHOTOCHEMICAL-REACTION OF [6]-1,4-CYCLOPHANEANTHRAQUINONE

[6]-1,4-Cyclophaneanthraquinone (CHAQ) has been synthesized and its Ph otochemical reaction is studied. Nanosecond laser photolysis of CHAQ i n EPA at room temperature reveals that both the lowest excited singlet and triplet states of CHAQ cause the intramolecular hydrogen-atom abs traction yielding the 1,4-biradical, i.e, the hydrogen-atom abstractio n by the carbonyl oxygen from the benzylic methylene of the cyclophane bridge. Since steady-state photolysis of CHAQ in EPA at 77K reveals t he formation of cyclophane-9-hydroxy-1,10-anthraquinone-1-methide (2), the results obtained by steady-state photolysis at room temperature a re interpreted as follows: (1) In benzene, 2 changes to a naphthoquino ne derivative (6). (2) In EPA, 2 yields its ethanol adduct (3) and the re exists an equilibrium between 3 (major) and 6 (minor). (3) By a dar k reaction, 3 and/or 6 revert very slowly to CHAQ.