# Luminescence Tuning of Fluorinated Bistolanes via Electronic or Aggregated-Structure Control
## 3 Results and Discussion
### PL Behavior in the Solution Phase  
Next, we examined the photophysical behavior of the fluorinated bistolanes. First, we investigated the absorption and PL behavior in CH\({}_{2}\)Cl\({}_{2}\) solution (\(\sim\)1.0 \(\times\) 10\({}^{-5}\) mol L\({}^{-1}\) for absorption and 1.0 \(\times\) 10\({}^{-6}\) mol L\({}^{-1}\) for PL). Figure 5a,b shows the absorption and PL spectra, respectively, of **1 aB-D** (solid lines) and **1 bB-D** (dashed lines). Figure 5c shows photographs of the PL colors and the corresponding Commission Internationale d'Eclairage (CIE) chromaticity diagram. The photophysical data are listed in Table 1.  
In CH\({}_{2}\)Cl\({}_{2}\) solution, CH\({}_{3}\)O-Substituted **1 aB-D** each exhibited a single absorption band and the maximum absorption wavelength (\(\lambda_{\rm abs}\)) varied significantly depending on the electron-withdrawing substituent: 333 nm (AcO-substituted **1 aB**), 341 nm (CF\({}_{3}\)-substituted **1 aC**), and 356 nm (CN-substituted **1 aD**) (Figure 5a), in which the \(\lambda_{\rm max}\) in the calculated UV-Vis spectra obtained from TD-DFT calculation \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Ground (S0) State 3**} & \multicolumn{2}{c}{**Excited (S1) State 6**} \\ \cline{3-6}  & \(\lambda_{\rm abs}\) (nm) 1 (c) 2  & **\(\mu_{\parallel}\) (D)** & **HOMO/LUMO (eV)** \\ \hline
**1 aB** & 333 (55.2) & 1.91 & \(-\)7.09/\(-\)1.30 & 410 (0.85) & 3.48 & \(-\)6.74/\(-\)1.66 \\
**1 aC** & 341 (48.1) & 7.22 & \(-\)7.13/\(-\)1.58 & 444 (0.99) & 9.63 & \(-\)6.83/\(-\)1.94 \\
**1 aD** & 356 (46.7) & 9.67 & \(-\)7.15/\(-\)1.87 & 488 (0.91) & 12.2 & \(-\)6.86/\(-\)2.19 \\
**1 bB** & 335 (54.5) & 2.27 & \(-\)7.07/\(-\)1.29 & 414 (0.86) & 3.93 & \(-\)6.72/\(-\)1.65 \\
**1 bC** & 343 (52.5) & 7.51 & \(-\)7.12/\(-\)1.58 & 451 (0.95) & 10.0 & \(-\)6.81/\(-\)1.94 \\
**1 bD** & 360 (44.8) & 9.95 & \(-\)7.13/\(-\)1.86 & 493 (0.87) & 12.6 & \(-\)6.84/\(-\)2.19 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Photophysical data for **1 aB–D** and **1 bB–D** in CH\({}_{2}\)Cl\({}_{2}\) solution. resulted in a similar tendency: 338 nm (AcO-substituted **1 aB**), 347 nm (CF\({}_{3}\)-substituted **1 aC**), and 360 nm (CN-substituted **1 aC**) (Figure S21). As listed in Table 1, the \(\mu_{\parallel}\) values in the S\({}_{0}\) state were calculated to be **1 aB** (1.91 D) \(<\)**1 aC** (7.22 D) \(<\)**1 aD** (9.67 D), indicating a strong correlation between the \(\lambda_{\rm abs}\) and \(\mu_{\parallel}\) values. Upon excitation at \(\lambda_{\rm abs}\), **1 aB-D** in CH\({}_{2}\)Cl\({}_{2}\) each displayed a single PL band at a maximum PL wavelength (\(\lambda_{\rm PL}\)) of 410-488 nm with a high PL efficiency (\(\Phi_{\rm PL}\) = 0.85-0.91) (Figure 5b). As shown in Figure 5c, **1 aB-D** emitted deep-blue, blue PL, light-green PL, respectively, and the PL colors can also be quantitatively evaluated using the CIE chromaticity diagram. Similar to \(\lambda_{\rm abs}\), \(\lambda_{\rm PL}\) also exhibited a shift towards longer wavelengths depending on the \(\mu_{\parallel}\) value. Replacing the CH\({}_{3}\)O substituent with the longer C\({}_{6}\)H\({}_{13}\)O unit did not change the absorption or PL spectra significantly owing to the similar \(\mu_{\parallel}\) values. These results clearly demonstrate that the electron-density distribution induced by the electron-withdrawing substituent is an important parameter for controlling the photophysical properties in the solution phase. TD-DFT calculations revealed that the HOMO\(\rightarrow\)LUMO transition corresponded with the lowest-energy excitation with a large oscillator strength.