Due to the AIE property of the TPE units, UV–vis and fluorescence spectra of
2 and
5 showed different absorption, emission intensities, and fluorescent colors in different solvent systems with various polarities and solubilities (Figs. S21-S24 in Supporting information). For example, when the CHCl
3 was gradually added to a solution of
2 in MeCN, the fluorescent intensity was gently increased (Fig. S21). And the fluorescent intensities of
3–
5 were also increased when poor solvents (
e.g., CHCl
3, H
2O and CH
2Cl
2) were added (Figs. S22-S24). When compared with
1 (Φ
F = 13.8%), the fluorescence spectra of
2–5 in H
2O displayed red-shifted (Δ
λ = 21-30 nm) with Φ
F value of 10.4%, 18.3%, < 0.1%, and < 0.1%, respectively (Fig. S19 and Table S4 in Supporting information), which were attributed to the aggregation in poor solvent. And the fluorescence lifetimes of
2–5 are longer than
1 in MeCN (Table S2 and Fig. S20). Furthermore, the fluorescent intensities of
2 also increased with the increase of water content in MeCN-H
2O mixture and the emission wavelengths have a slight blue shift due to solvent effects (
Fig. 1b and Fig. S25 in Supporting information), while the fluorescent intensity of
5 remains almost constant (Fig. S27 in Supporting information). Besides, temperature-dependent fluorescence experiments implied that the fluorescence intensities of
2–5 decreased linearly as temperature gradually increased from 5 ℃ to 60 ℃, indicating the aggregation of AIE-active
2–5 were achieved at lower temperature (Figs. S28-S31 in Supporting information). Finally, concentration-dependent fluorescence experiments (2.0 ~ 100 µmol/L) showed
2–4 in MeCN have low critical aggregation concentration of 25.8 µmol/L, 32.1 µmol/L and 26.7 µmol/L, respectively (Figs. S32-S34 in Supporting information). And
5 showed linear increase as the concentration increases (Fig. S35 in Supporting information). These results confirm that
2–
5 have classic AIE property.