4,6-dinitrobenzene-1,3-diamine

4,6-Dinitrobenzene-1,3-Diamine Enables the Production of Benzodiimidazole-Thiophene Copolymers

Zhao, Yun, et al. Synthetic Metals 245 (2018): 175-181.

Researchers produced different cis/trans isomers of benzodiimidazole-thiophene copolymers (PBDIT) with varying alkyl chains to explore how isomer configurations affect conjugated polymer optoelectronic properties. The synthesis of BDIT monomers requires 4,6-dinitrobenzene-1,3-diamine as a fundamental precursor.
Synthesis of monomers cis/trans-benzidiimidazole-thiophene (BDITs)
Synthesis of 2,6-Bis(5-bromothiophen-2-yl)-1,5-dihydrobenzo[1,2-d:4,5-d'] diimidazole (1): The synthesis started by adding 5-bromothiophene-2-carbaldehyde (4.2 g, 22.0 mmol) to a DMF solution with 4,6-dinitrobenzene-1,3-diamine (1.98 g, 10.0 mmol) which was then heated to 120 °C for 4 hours. Following the mixture's reduction to room temperature, the chemist combined sodium dithionite (Na2S2O4, 2.7 g) with water (20 mL) and maintained stirring at 120 °C for 12 hours. Cooling the mixture followed by filtration and washing with water and vacuum drying resulted in a dark yellow solid (3.5 g, 72%) which had poor solubility and thus needed to be used directly in the next step without purification.
The next reaction began with the addition of 1-bromobutane (2.079 g, 15.4 mmol) to a mixture containing the previously obtained compound (3.4 g, 7 mmol) and sodium hydride (NaH, 0.56 g, 14 mmol) in DMF solvent (50 mL). The mixture was heated to 120 °C and stirred continuously for a duration of 12 hours. The cooled reaction mixture received 50 mL of chloroform (CHCl3) after which it was transferred into a container holding 200 mL of water. Then purified the solution by filtration and extraction followed by drying before applying column chromatography and recrystallization which resulted in a yellow powdery solid. The reaction produced cis-M1 with a yield of 19% while trans-M1 resulted in a 26% yield.