2.1.1. Synthesis of 2,7-bis(2-methylthiophenyl)-9-hexyl-9H-carbazole (2a)

2,7-Dibromo-9-hexyl-9H-carbazole 4a (1.15 g, 2.80 mmol), 2-methylthiophenylboronic acid (1.22 g, 7.28 mmol), Pd(PPh₃)₄ (0.161 g, 0.139 mmol) and K₂CO₃ (2.33 g, 16.8 mmol) were placed in a round-bottom flask. Then, the system was purged with nitrogen. A previously purged mixture of THF and water (6:1 v/v, 58 mL) was added to the flask and stirred at reflux overnight. The reaction mixture was extracted with CH₂Cl₂, dried over MgSO₄ and the solvent was removed under reduced pressure. The crude was purified by flash column chromatography using a mixture of hexane and dichloromethane (20:1 v/v) as eluent. Compound 2a was obtained as a white solid in a yield of 80% (1.11 g, 2.25 mmol). ¹H NMR (400 MHz, CDCl₃) δ (ppm): 8.14 (d, J = 8.0 Hz, 2H), 7.47 (d, J = 8.0 Hz, 2H), 7.40–7.31 (m, 6H), 7.29–7.23 (m, 4H), 4.30 (t, J = 7.3 Hz, 2H), 2.37 (s, 6H), 1.94–1.83 (m, 2H), 1.45–1.20 (m, 6H), 0.84 (t, J = 7.1 Hz, 3H). ¹³C NMR (100 MHz, CDCl₃) δ (ppm): 141.9, 140.8, 138.2, 137.7, 130.5, 127.9, 125.3, 124.8, 122.2, 120.5, 120.2, 109.9, 43.4, 31.8, 29.3, 27.2, 22.7, 16.1, 14.2.