RESUMO
Peri-acenes are valuable models for zigzag-edged graphene nanoribbons, but their synthesis poses significant challenges. In this study, stable derivatives of peri-pentacene (Peri-P) and peri-hexacene (Peri-H) were synthesized. Through kinetic blocking and a synergistic captodative effect, both compounds displayed remarkable stability under ambient air and light conditions. They show significant diradical character (y0), with y0 = 75.4% for Peri-P and y0 = 90.7% for Peri-H, alongside narrow singlet-triplet energy gaps of -1.68 ± 0.04 and -1.28 ± 0.02 kcal/mol, respectively. The structure of Peri-H was confirmed by X-ray crystallography, with bond-length analysis and theoretical calculations indicating a dominant structure featuring five aromatic sextet rings. Their optical and electrochemical properties were also studied and compared to those of smaller peri-acenes.
RESUMO
Graphene-like molecules with multiple zigzag edges are emerging as promising gain materials for organic lasers. Their emission wavelengths can vary widely, ranging from visible to near-infrared (NIR), as the molecular size increases. Specifically, rhombus-shaped molecular graphenes with two pairs of parallel zigzag edges, known as [n]rhombenes, are excellent candidates for NIR lasers due to their small energy gaps. However, synthesizing large-size rhombenes with emission beyond 800â nm in solution remains a significant challenge. In this study, we present a straightforward synthesis of an aryl-substituted [4]rhombene derivative, [4]RB-Ar, using a method that combines intramolecular radical-radical coupling with Bi(OTf)3-mediated cyclization of vinyl ethers. The structure of [4]RB-Ar was confirmed through X-ray crystallographic analysis. Bond length analysis and theoretical calculations indicate that aromatic sextets are predominantly localized along the molecule's long axis. Significantly, [4]RB-Ar demonstrates narrow amplified spontaneous emission at around 834â nm when dispersed in polystyrene thin films. Moreover, solution-processed distributed feedback lasers employing [4]RB-Ar as the active gain material display tunable narrow emissions in the range of 830 to 844â nm.
RESUMO
Polycyclic aromatic hydrocarbons (PAHs) with a one-dimensional (1D), ribbon-like structure have the potential to serve as both model compounds for corresponding graphene nanoribbons (GNRs) and as materials for optoelectronics applications. However, synthesizing molecules of this type with extended π-conjugation presents a significant challenge. In this study, we present a straightforward synthetic method for a series of bis-peri-dinaphtho-rylene molecules, wherein the peri-positions of perylene, quaterrylene, and hexarylene are fused with naphtho-units. These molecules were efficiently synthesized primarily through intramolecular or intermolecular radical coupling of in situ generated organic radical species. Their structures were confirmed using X-ray crystallographic analysis, which also revealed a slightly bent geometry due to the incorporation of a cyclopentadiene ring at the bay regions of the rylene backbones. Bond lengh analysis and theoretical calculations indicate that their electronic structures resemble pyrenacenes more than quinoidal rylenes. That is, the aromatic sextets are predominantly localized along the long axis of the skeletones. As the chain length increases, these molecules exhibit enhanced electronic absorption with a bathochromic shift, and multiple amphoteric redox waves. This study introduces a novel synthetic approach for generating 1D extended PAHs and GNRs, along with their structure-dependent electronic properties.