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 w as used to interpret the results of fluorescence anisotropy decay measureme nts for 9-acetoxy-10-phenylanthracene, 9-acetoxy-10-biphenylanthracene, 9-a cetoxy-10-(4'-acetoxyphenyl) anthracene and 9-acetoxy-10-(2'-acetoxyphenyl) anthracene in liquid paraffin. The anisotropy of rotational diffusion was d etected only for 9-acetoxy-10-(2'-acetoxyphenyl)anthracene but cannot be ex cluded 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 ind icator of such structural differences. (C) 1999 Elsevier Science B.V. All r ights reserved.