Photochromic benzo[g]quinoxalines

The photochromism of two 2,3-diarylbenzo[g]quinoxaline derivatives was explored. Irradiating 2,3-diphenylbenzo[g]quinoxaline with 350 nm light led to the formation of its photodimer, which could be reverted to its monomers either thermally or photochemically.The resulting photodimer absorbs at a longer wavelength than analogous dianthracene derivatives. 2,3-Dipyridylbenzo[g]quinoxaline was also observed to undergo photodimerization. The ability of these readily prepared benzoquinoxaline derivatives to undergo [4 + 4]-photocycloaddition reactions makes them attractive alternatives to anthracene derivatives.