Mechanism of excitation and emission of papaverine molecule : fluorescence polarization spectroscopy study and MO calculation of transition moments

The polarization of the fluorescence spectra of papaverine and isoquinoline was studied. The electronic structure of ground and excited states of papaverine, isoquinoline, and 5,6-dimethoxy-1-methylisoquinoline were studied by MNDO-PM3-CI and CNDO-CI methods. Results of spectral investigations, concerning the mechanism of excitation and emission of papaverine are presented along with theoretical considerations. The results strongly suggest the existence of coupling between the isoquinoline and benzene ring in the papaverine molecule.