Anisotropic reorientation of perylene and 3,9-dibromoperylene in glycerol: fluorescence anisotropy decay and quantum-mechanical study Original Research Article

The authors compare results of fluorescence anisotropy decay measurements for perylene and 3,9-dibromoperylene (3,9-DBP) in glycerol. The observed time-dependent fluorescence depolarization is interpreted in terms of the hydrodynamic model of molecular reorientation. A highly anisotropic reorientation of perylene is confirmed. Possible reasons of the deficit of the initial value of the fluorescence emission anisotropy (EA) of perylene in glycerol are discussed. The most plausible explanation appears to be the non-planarity of perylene in either the ground or the first excited state. Results of quantum-mechanical calculations support this view. The experimental data suggest that the symmetric rotor model usually applied to the case of perylene is oversimplified. The first observation of the anisotropy of rotational diffusion for 3,9-DBP is presented.