The intensity ratio of the two emission bands also depends on the solvent, indicating that the excited states in the two conformers are differently affected by the solvent. In order to quantitively investigate the effect of solvent on the excited states in each conformer, we measured the steady-state PL spectra in the mixed solvents of toluene and THF with varying the mixing ratio. This allows us to continuously change the solvent permittivity between those of toluene (2.38) and THF (7.58) (Figure ). The intensities of the emission bands assigned to q-ax. with a peak ranging from 422 nm to 453 nm were almost independent of solvent permittivity. On the other hand, the intensities of the emission bands assigned to q-eq. with a peak ranging from 576 nm to 675 nm decreased significantly with increasing solvent permittivity.