Anthracene‐Fused Dibenzo[def,mno]chrysenes with a Helical Structure

Abstract

Scholl-type oxidative cyclodehydrogenation reactions were conducted for an anthryl-substituted dibenzo [def,mno]chrysene (DBC) precursor with the intention to prepare anthracene-fused DBCs with extended conjugation. The compound ADBC-1 with one cyclized ring and its two chloro-and oxy-derivatives (ADBC-Cl and ADBC-O) with good stability were successfully isolated and characterized. They showed largely red-shifted absorption spectra and amphoteric redox behavior. XRD analysis revealed that they can be regarded as large polycyclic aromatic hydrocarbons (PAHs) containing [5]helicene substructures with large twist angles of 67.8°-73.7°owing to steric congestion. Further cyclization to form newer CÀ C bonds failed, which can be explained by an open-shell diradical character and high HOMO energy levels of the products according to spinunrestricted DFT calculations. Results and Discussion SynthesisThe synthesis of the key intermediate ADBC was based on a Suzuki coupling-nucleophilic addition-Friedel-Crafts alkylationoxidative dehydrogenation strategy (Scheme 1). Compound 3 (9-bromo-10-mesityl-2,3,6,7-tetramethoxy-anthracene) was facilely synthesized in 49 % yield by Suzuki coupling reaction between excess of 9,10-dibromo-2,3,6,7-tetramethoxyanthra-[a] Q. ADBC-1 and Compound ADBC-Cl. 100 mg (0.0905 mmol) of ADBC was dissolved in 200 mL of anhydrous DCM in a dry reaction flask. Argon gas was purged into the reaction mixture throughout the reaction. A solution of 234.9 mg (1.4487 mmol) of anhydrous ferric chloride in 2 mL of nitromethane was charged into the reaction mixture through a syringe and stirred for 6 hrs at room temperature. Reaction was later quenched by 5 mL of water. Reaction mixture was later washed with 3 × 100 mL of water and the dichloromethane layer was collected and evaporated. The residue was purified by column chromatography (silica gel, DCM/Hexanes = 8 : 1, ADBC-Cl has larger polarity than ADBC-1) and preparative thin-layer chromatography (TLC) to afford ADBC-1 and ADBC-Cl as dark green solids (58.9 mg, 59 % for ADBC-1, and 26.8 mg, 26 % for ADBC-Cl). ADBC-1: 1 H NMR (400 MHz, CD 2 Cl 2 , ppm): δ = 9.66 (d, J = 8.1 Hz, 1H), 8.35 (d, J = 8.2 Hz 1H), 8.13 (d, J = 7.2 Hz, 1H), 8.02-7.96 (m, 2H), 7.81 (t, J = 7.8 Hz, 1H), 7.76 (d, J = 9.3 Hz, 1H), 7.67 (d, J = 8.4 Hz, 1H), 7.56 (d, J = 9.1 Hz, 1H), 7.20-4 5 6 7 8

Polycyclic Aromatic Hydrocarbons as Potential Building Blocks for Organic Solar Cells

“…The anthanthrene core has also been annulated at the 1 and 12 positions using the Scholl reaction of an anthracene‐modified anthanthrene derivatives (compound 11 , Figure ), which absorption band is red‐shifted by 181 nm relative to the non‐annulated precursor (E g =1.85 eV from the solution) . All attempts to obtain the all‐fused molecule failed due to the high HOMO energy level of the intermediates, leading to oxidation of the aromatic core.…”