To date, Tanaka et al. reported that only q-eq. exhibits TADF and q-ax. undergoes a structural relaxation to q-eq. and Chou et al. reported that the time constant of the relaxation is arpprox. 1.8 ps (Figure ). Nevertheless, the previous studies carried out only in low-permittivity solvents although solvent dependence of the optical properties of CT excited states are critical to the microscopic understanding of CT excited states. To understand the mechanism of dual emission in the excited states, it is important to reveal experimentally the properties and dynamics of the CT excited states in the two conformers. In this study, since the solvation of the CT excited states are dependent on the permittivity of the solvent, we used two solvents with different permittivity (𝜀𝜀), toluene (𝜀𝜀 = 2.38) and tetrahydrofuran (THF, 𝜀𝜀 = 7.58), and investigated the properties and dynamics of the CT excited states using spectroscopic measurements. The steady-state photoluminescence (PL) spectra for the two solvents showed different relative emission intensities between the two conformers whereas their absorption spectra are almost the same. By analyzing the photoluminescence spectra in mixture solvents with different ratios between toluene and THF, we found that the dipole moments of the CT excited states of q-ax. and qeq. are almost identical. The time-resolved PL (TR-PL) spectra in toluene and in THF showed a different behavior: TADF from q-eq. is significantly suppressed in THF whereas the emission from qax. showed little change. From the transient absorption (TA) spectra, we found that the time constants of structural change from q-ax. to q-eq. are insensitive to the solvent. Based on these results, we proposed a new energy diagram and emission mechanism in CT excited states of PTZ-TRZ.