EXCITED-STATE PROPERTIES OF 2-ACRYLATED ANTHRAQUINONES

The absorption, fluorescence and phosphorescence properties of 2-acrylamido and 2-acryloxyanthraquinones are examined in different solvents. The latter has an unusual marked blue-shifted absorption maximum compared with that of the acrylamido derivative. Also, unlike most 2-substituted anthraquinones these molecules exhibit negligible fluorescence. In the former case, weak phosphorescence in observed which is associated with rapid deactivation of the lowest excited 1pipi* state by intersystem crossing to the second excited 3npi* state followed by internal conversion to the lowest excited 3pipi* state and hence radiative emission to the ground-state. In the latter case, very strong phosphorescence is observed which appears to occur from the second excited 3npi* state and resembles that of anthraquinone. No evidence is found for a low lying excited 3pipi* state. This effect is associated with vibronic coupling of the excited 1npi* and 1pipi* states resulting in rapid intersystem crossing to the 3npi* state followed by emission to the ground-state. The data are discussed in the context of their activities for photocrosslinking polymers.