Lineshapes in phosphorescence spectra of diazaphenanthrenes and protonated analogues: Evidence of the Duschinsky mixing effect

Abstract The phosphorescence spectra of 1,5-, 2,5-, 3,5-, 2,4-, 1,9- and 1,10-diazaphenanthrene (DAP) and some of their protonated analogues are measured in rigid glasses at 84 K. The results are compared with theoretical calculations. Good agreement is obtained between the intensities derived from the measured spectra and those determined from theory based on three Duschinsky-mixed accepting modes and one non-totally symmetric intensity promoting mode which is responsible for the coupling of the lowest T 1 and the nearby T 2 state. The non-diagonal nature of the Duschinsky rotation matrix suggests that the three accepting modes are mixed with each other. Although non-diagonal elements of the rotation matrices are small it turns out that the spectral bandshapes are very sensitive to normal coordinate rotations. Finally, we present some basic features of the phosphorescence spectra and triplet state lifetimes of the DAP obtained after protonation.