Substitution of a carboxyl group onto the 9 position of anthracene, as in 9-methyl anthroate (9-COOMe), results in some significant differences in the spectral properties of the ester relative to those of the anthracene parent molecule. For example, the fluorescence quantum yield (øf) and fluorescence maximum (υmax) of 9-COOMe become quite solvent dependent due to an excited state geometry change in which the excited singlet takes on significant charge transfer character (1,2).