Solvent effect on the steady-state fluorescence anisotropy of two-photon absorbing fluorene derivatives

The effect of solvent polarity on the fluorescence properties of several two-photon absorbing fluorene derivatives was investigated. A strong solvatochromic effect was observed for symmetrical fluorene compound, which can be explained by large changes in the quadrupolar moment under excitation. Limiting values of excitation anisotropy of the investigated fluorenes exhibited a dependence on solvent polarity, and the angles between the absorption and emission transition dipole moments decrease in polar solvents by more than a factor of two.