AM1 STUDY OF THE ELECTRONIC-STRUCTURE OF COUMARINS

We report our calculations on a series of coumarin molecules. Using se miempirical methods with an AMI parametrization, we have calculated th e ground-state, first excited triplet state, and first excited singlet state energies and dipole moments as well as their dependence on the geometries of different labile side groups. We find that for all of th e coumarins there are excited triplet states in close energetic proxim ity to the excited singlet states, and the relative ordering of these states depends on the substituents attached to the coumarin chromophor e.