Synthesis and Characterization of Electron-Deficient Asymmetrically Substituted Diarylindenotetracenes

Abstract

Electron-deficient asymmetrically substituted diarylindenotetracenes 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 asymmetrically substituted indenotetracenes (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 and 650 nm with molar attenuation coefficients from 10 to 10 M cm. 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.

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…Under oxidative coupling conditions (FeCl 3 or DDQ), acenes bearing aryl groups attached to the central benzene rings generally cyclize to form new five‐membered rings . Scheme depicts an especially interesting example, where oxidation of symmetric tetracene 161 led to the unsymmetric product 162 containing two new rings of different sizes: five‐ and six‐membered …”

“…[139] As ar esult of the large steric hindrance,t he whole system is contorted and easily loses the two central tert-butyl substituents under acidic conditions. In addition to the structures shown in Figure 10, many other PA Hs have been synthesized using the oxidative coupling method [140][141][142][143][144][145][146][147] which, due to space limitations, cannot be included in this Review.…”

“…[153] Under oxidative coupling conditions (FeCl 3 or DDQ), acenes bearing aryl groups attached to the central benzene rings generally cyclize to form new five-membered rings. [142,144] Scheme 24 depicts an especially interesting example,w here oxidation of symmetric tetracene 161 led to the unsymmetric product 162 containing two new rings of different sizes:five-and six-membered. [154] Theb ottom-up synthesis of carbon nanoribbons is yet another impressive demonstration of the prowess of intramolecular oxidative coupling.Belonging to the nanographene class,c arbon nanoribbons are ribbon-or tape-like graphene fragments which are highly interesting because of their promising optoelectronic and semiconducting properties.…”

“…In addition to the structures shown in Figure , many other PAHs have been synthesized using the oxidative coupling method which, due to space limitations, cannot be included in this Review.…”

Synthesis of Sulfur‐Hybridized Pyracylene and the Unexpected Phenyl Shift Mediated Rearrangement of Scholl Reaction

“…With very few exceptions, most reported tetracene derivatives to date have been constructed by combining functional groups onto tetracene motif to tune their energy levels and solubility . Many innovative bottom‐up synthetic strategies have been developed to tetracene based PAHs . For example, the Scholl reaction, that is, oxidized dehydrogeneration cyclization reaction conducted with acidic oxidants such as FeCl 3 or DDQ/MeSO 3 H is usually preferred , .…”