where 𝐶𝐶 toluene and 𝐶𝐶 THF are the permittivity of toluene and THF, respectively. Figure plots the Stokes shift (cm -1 ) as a function of the solvent parameter (∆𝑓𝑓) for the bands assigned to q-eq. (red dots) and q-ax. (green dots). Both the plots were proportional to ∆𝑓𝑓 , indicating that the Mataga-Lippert equation is well applicable to this system. Thus, the dipole moments of the excited states are reasonably derived from the slopes of these plots. By the linear least squares fit (solid lines in Figure ), we determined the excited-state dipole moments of q-eq. and q-ax. to be 20.8 D and 23.2 D, respectively. This result means that the excited states of both the conformers have almost the same dipole moment though their conformations are largely different. To rationalize the little difference in the excited-state dipole moments between the two conformers, we performed TD-DFT calculations and calculated natural transition orbital (NTO) .