# Luminescence Tuning of Fluorinated Bistolanes via Electronic or Aggregated-Structure Control
## 3 Results and Discussion
### PL Behavior in the Crystal Phase  
To our delight, we found that **1 aB-D** and **1 bB-D** crystals prepared by recrystallization via a slow evaporation technique exhibited PL. Figure 7 shows the obtained PL spectra acquired, and the photophysical data are listed in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Solvent (\(\varepsilon\)) 1** & **Toluene (2.38)** & **THF (7.58)** & **CH\({}_{2}\)Cl\({}_{2}\) (8.93)** & **MeCN (35.9)** & **DMF (36.7)** \\ \hline \(\lambda_{\mathrm{PL}}\) (nm) 2 ** & 409 & 482 & 451 & 518 & 523 \\ \(\Phi_{\mathrm{PL}}\) 3  & 0.79 & 0.55 & 0.95 & 0.58 & 0.40 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Photophysical properties of **1 bC** in various solvents.  
Figure 6: **(a)** PL spectra of **1 bC** in various solvents (concentration: \(1.0\times 10^{-6}\) mol L\({}^{-1}\)); **(b)** photographs under UV irradiation (\(\lambda_{\mathrm{ex}}\) = 365 nm) and CIE chromaticity diagram for the PL in various solvents.  
As shown in Figure 7a,b, \(\lambda_{\text{PL}}\) changed dramatically depending on the electron-withdrawing substituent, even in crystals: 414-420 nm (deep-blue PL) for AcO-substituted **1 aB** and **1 bB**, 459-479 nm (blue to light-blue PL) for CF\({}_{3}\)-substituted **1 aC** and **1 bC**, and 500-526 nm (yellowish-green PL) for CN-substituted **1 aD** and **1 bD**. Compared with the \(\lambda_{\text{PL}}\) values in CH\({}_{2}\)Cl\({}_{2}\) solution, those observed for the crystals were slightly shifted towards longer wavelengths, which may be due to quick deactivation via nonradiative processes owing to intermolecular interactions in the condensed phases. As discussed above, exchanging the CH\({}_{3}\)O group for a longer C\({}_{6}\)H\({}_{13}\)O moiety did not have a significant effect on the electronic structure; however, an intriguing band shift of 0.113 eV for **1 aC** vs. **1 bC** and 0.123 eV for **1 aD** vs. **1 bD** was observed. According to our previous reports [21, 23], this change in the PL behavior likely originates from a dramatic change in the aggregated structure induced by the difference in alkoxy chain length. Similar to the trend observed for the PL in CH\({}_{2}\)Cl\({}_{2}\) solution, a relatively strong correlation was observed between \(\mu_{\parallel}\) and \(\lambda_{\text{PL}}\) in the crystals. These results demonstrate that the PL behavior of the  
\begin{table}
\begin{tabular}{c c c} \hline
**Compound** & \(\lambda_{\text{PL}}\) **(nm)**1  \\ \hline
**1 aB** & 420 & 0.48 \\
**1 aC** & 459 & 0.80 \\
**1 aD** & 500 & 0.36 \\
**1 bB** & 414 (418) & 0.17 \\
**1 bC** & 479 (443) & 0.73 \\
**1 bD** & 526 (527) & 0.31 \\ \hline \end{tabular}
\end{table}
Table 3: Photophysical properties of **1 aB–D** and **1 bB–D** crystals.  
Figure 7: PL spectra of **(a) 1 aB–D** and **(b) 1 bB–D** crystals; **(c)** CIE chromaticity diagram calculated from the corresponding PL spectra.  
fluorinated bistolanes can also be modulated in crystal by controlling \(\mu_{\parallel}\) via the electron-withdrawing character of the terminal substituent.