2.3. Synthesis of 2,3,4,5-Tetrabromothiophene (Th-Br4)

Br₂ (5.3 mL, 0.033 mmol) and Th (2.0 g, 0.023 mmol) were dissolved in CHCl₃ (30 mL) and then the mixture was refluxed for 24 hours at 0 ℃. After cooling, the solution mixture was added to cool, saturated sodium thiosulfate. The obtained solid was purified in hot ethanol to remove any impurities from the monomer to obtain Th-Br₄ as a white powder (Figure 1, 80%, T_m: 119 °C). FTIR (KBr, cm^–1, Figure 2a): 1636 (C=C), 852 (C–S). ¹H NMR (500 MHz, DMSO, δ, ppm, Figure S2): No peak was detected. ¹³C NMR (125 MHz, CDCl₃, δ, ppm, Figure 2b): 116.936, 110.284.