Fig. 3. Emission properties of X2A with different organic solvents. (A) Scheme of tunable π–π distance with the aid of solvents. (B) Molecular configurations and intramolecular π–π distances in X2A crystals (left) and photographs of X2A in different solutions (middle) and crystals (right) taken under 365 nm excitation. (C) PL spectra of X2A in dichloromethane, dibromomethane, 1,2-dichloroethane, methyl iodide, and tetrahydrofuran solutions (left) and corresponding crystals (right). (D) Calculated CIE coordinates in CIE 1931 color space chromaticity diagram based on the PL spectra in different solutions: CH₂Cl₂ (0.19, 0.38), CH₂Br₂ (0.21, 0.48), ClCH₂CH₂Cl (0.21, 0.46), CH₃I (0.22, 0.48), and THF (0.20, 0.45). (E) Calculated CIE coordinates in CIE 1931 color space chromaticity diagram based on the PL spectra of corresponding crystals: X2A-B-CH₂Cl₂ (0.16, 0.08), X2A-B-CH₂Br₂ (0.19, 0.15), X2A-B-ClCH₂CH₂Cl (0.17, 0.15), X2A-B-CH₃I (0.20, 0.22), and X2A-G (0.16, 0.30).