PM3 STUDY OF THE ELECTRONIC-SPECTRA OF SOME SUBSTITUTED AMINOCOUMARINS

The photophysical properties of some 7-aminocoumarins have been invest igated by PM3/CI method. Solvent effects have been evaluated by the co ntinuum reaction field approach. The results show that all the molecul es emit from a planar internal charge transfer (ICT) state. Radiationl ess decay occurs via the twisted ICT state, no evidence of a deactivat ion path via pyramidalization of the amino group has been found. Compu ted potential energy barriers for the torsional motion of the amino gr oup are in line with the observed rate constants for nonradiative deca y. (C) 1998 Elsevier Science B.V.