## 3 Results
### Optical Properties
#### 3.2.2 Fluorescence Spectra
CH\({}_{3}\)CN, THF/H\({}_{2}\)O 1:1, and ethanol solutions exhibited blue emission at low concentration but cyan emission at high concentration. Coherently with the emission spectra, in acetonitrile and THF/H\({}_{2}\)O 1:1, the cyan emission of the concentrated solution was more intense than the blue emission of the diluted solutions. In the less polar ethanol, the cyan emission  
Figure 5: (**a**) Emission maxima frequencies vs. concentrations. (**b**) Emission intensity as ratio between area under the emission plot of solution and area under emission plot of phenothiazze \(10^{-6}\) M detected on the same instrument and under the same conditions vs. concentration. (**c**) Normalized fluorescence spectra with highest intensities. More intense fluorescence spectra in dichloromethane, concentration \(10^{-6}\) M, of all compounds. of the concentrated solution was less intense than the blue emission of the diluted solutions. In THF, we only observed blue emission from the 10\({}^{-5}\) M solution. In Table 2, the emission maxima ranges and intensities are correlated with the solvent polarities. It is important to observe that we observed emissions at all concentrations in the solvents of intermediate polarity CH3 CN and CH3 CH2 OH; we observed no emissions in diluted solutions with the highest polarities (THF/H2O 1:1); and we observed no emissions in concentrated solutions in the solvents with low polarities (THF, CH2 Cl2). Furthermore, the high polarity solvents tended to redshift the emission, the low polarity solvents tended to lower the emission frequency, and the intermediate polarity solvents allowed observation of a wide range of emission frequency maxima. Based on the emissions and absorption maxima in solvents of different polarity, we were able to calculate the dipolar moments of the energy ground and excited states by the method reported in the literature [55; 56; 57]. We performed the calculations, the results shown in Table 3, based on the data at concentrations of 10\({}^{-6}\) and 10\({}^{-5}\) M (for details of calculation, see Figure S40 in Supplementary Information). The table shows that the dipolar moment was highest in the excited state and that the difference between the excited and ground states increased with the concentration. We analyzed the emission of 10\({}^{-3}\) M solutions of **5 mT** in THF/H2O with ratios of 7:3, 4:6, and 1:9 to understand the effect of aggregation on emission (water is not solvent for **5 mT**, as shown in Figure S41). As shown in Figure 6, the addition of water generated a blue shift in the emission. The emission intensity increased when the THF/H2O fraction changed from 1 to 4:6. In the 1:9 solution, no increased intensity was detected, and the spectral width upon irradiation at 300 nm. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Solvent** & \(\mathbf{d^{1}}\) & \(\mathbf{n^{1}}\) & \(\mathbf{\lambda_{abs}\ nm^{2}}\) & \(\mathbf{\lambda_{em}\ nm^{3}}\) & **I \({}^{4}\)** \\ \hline CH2 Cl2 & 9.08 & 1.424 & 305 (30) & 435–437 & 0–31 \\  & & & 385 (10) & & \\ THF & 7.60 & 1.407 & 300 (25) & & \\  & & & 376 (10) & & \\ CH3 CH2 OH & 24.55 & 1.363 & 305 (23) & & \\  & & & 359 (10) & & \\ CH3 CN & 37.5 & 1.344 & 300 (20) & & \\ THF/H2O & & & 360 (7) & & \\
1:1 & 41.21 & 1.38 & 300 (25) & & \\  & & & 376 (10) & & \\ \hline \hline \end{tabular} \({}^{1}\)\(d\) and \(n\) refer to the dielectric constant and refraction index at 20 \({}^{\circ}\)C, respectively. In THF/H2O 1:1, the values reported are from the literature [54]. \({}^{2}\) Absorption wavelengths (nm) \(\lambda_{2}\) and \(\lambda_{3}\) measured at concentrations around 10\({}^{-6}\) M. The intensities are reported in brackets in units of M\({}^{-1}\)cm\({}^{-1}\times 10^{-3}\). \({}^{3}\) Emission maxima ranges measured at different concentrations. \({}^{4}\) Ranges of relative intensity of emission by measuring the area under the emission curve and dividing for the area of phenothiazze 10\({}^{-6}\) M emission measured in the same conditions (same instrument and environment).  
\end{table}