Larger π-extended anti-/syn-aroylenediimidazole polyaromatic compounds: Synthesis, physical properties, self-assembly, and quasi-linear conjugation effect

Four π-extended anti-/syn-aroylenediimidazole (ADI) polyaromatic compounds (1, 2, 3, and 4) with 11- or 13-fused rings have been successfully synthesized via a tandem cyclocondensation reaction between tetraamines and naphthalene dicarboxylic monoanhydride monoimide. The observed optical bandgaps for 1-4 are 2.70 (458 nm), 2.34 (529 nm), 2.31 (537 nm), and 2.21 eV (561 nm), respectively, which are in accordance with the calculated bandgaps from DFT calculations for 1-4, which are 2.77, 2.49, 2.29, and 2.21 eV, respectively. Our results indicate that there are obvious anti-/syn- and π-extended effects in these molecules. The cyclic voltammetry (CV) measurements show that all the compounds exhibit quasi-reversible reduction waves. The experimental LUMO levels from CV show an interesting zigzag-curved change (zigzag-shaped curve) in sequence, which matches well with those of the theoretical calculations. Furthermore, the fitted decay lifetimes of 1-4 in CHCl₃ are 1.86, 1.32, 1.55, and 1.42 ns, which have the same trend as the above-mentioned zigzag-shaped curve. These trends are believed to be related to the intrinsically effective quasi-linear conjugation (QLC) with a theoretically calculated quasi-linear length of 1.10 nm, 1.94 nm, 1.56 nm, and 2.40 nm, respectively. The successful synthesis and characterization of four soluble π-extended ADI polyaromatic compounds could provide us with more diverse candidates for air-stable organic electronic devices. This journal is