Synthesis and Characterization of Electron Deficient Asymmetrically Substituted Diarylindenotetracenes

Purvis, L. J.; Gu, X.; Ghosh, S.; Zhang, Z.; Cramer, C. J.; Douglas, C. J.
J. Org. Chem. 2018, 83, 1828 (doi:10.1021/acs.joc.7b02756).

Electron deficient asymmetrically substituted diarylindenotetracenes (ASIs) were prepared via a series of Friedel-Crafts acylations, aryl-aryl cross-couplings, and an intramolecular oxidative cyclization to form the indene ring. Single crystal X-ray experiments showed good π–π overlap with π–π distances ranging from 3.26 to 3.76 Å. Both thermogravimetric analysis and differential scanning calorimetry indicated that ASIs are stable at elevated temperatures. From cyclic voltammetry experiments, HOMO/LUMO energy levels of ASI derivatives were determined to be near -5.4/-4.0 eV. UV/visible absorption spectra showed strong absorption of light between 400-650 nm with molar attenuation coefficients from 10^-4 to 10^-5 M^-1 cm^-1. ASIs were also found to have very low fluorescence quantum yields, less than 4%. Using the solid-state packing determined from the single crystal X-ray experiments, computational modeling indicated that ASI molecules should favor electron transport.