Substituent-sensitive anisotropic rotations of 9-acetoxy-10-phenylanthracenes: fluorescence anisotropy decay and quantum-mechanical study

The ellipsoid-of-revolution hydrodynamic model of molecular reorientation was used to interpret the results of fluorescence anisotropy decay measurements for 9-acetoxy-10-phenylanthracene, 9-acetoxy-10-biphenylanthracene, 9-acetoxy-10-(4′-acetoxyphenyl) anthracene and 9-acetoxy-10-(2′-acetoxyphenyl)anthracene in liquid paraffin. The anisotropy of rotational diffusion was detected only for 9-acetoxy-10-(2′-acetoxyphenyl)anthracene but cannot be excluded for other derivatives as well. While no significant spectral changes were observed on changing the position and type of substituent (acetoxy or phenyl), the fluorescence anisotropy decay was found to be a sensitive indicator of such structural differences.