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Microscopic Visualization of Porous Nanographenes Synthesized through a Combination of Solution and On-Surface Chemistry
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Saddle-shaped aza-nanographene with multiple odd-membered rings
Maciej Krzeszewski1, Łukasz Dobrzycki2, Andrzej L Sobolewski3
1Institute of Organic Chemistry, Polish Academy of Sciences Kasprzaka 44-52 01-224 Warsaw Poland dtgryko@icho.edu.pl.
Chemical Science
|March 6, 2023
Summary
Researchers synthesized a novel saddle-shaped aza-nanographene with a unique 7-7-5-5-7-7 topology. This nitrogen-embedded polycyclic aromatic hydrocarbon exhibits interesting electronic properties and a distorted, non-planar structure.
Area of Science:
- Organic Chemistry
- Materials Science
- Nanotechnology
Background:
- Polycyclic aromatic hydrocarbons (PAHs) are fundamental carbon structures with diverse electronic properties.
- Engineering non-alternant PAHs with specific topologies and curvatures presents synthetic challenges.
- Nitrogen incorporation into PAH frameworks can significantly tune their optoelectronic characteristics.
Purpose of the Study:
- To synthesize a novel saddle-shaped aza-nanographene with a unique topology.
- To investigate the structural, optical, and electrochemical properties of the synthesized molecule.
- To explore the impact of odd-membered ring defects and nitrogen heteroatoms on PAH properties.
Main Methods:
- A four-step synthetic strategy involving intramolecular direct arylation, Scholl reaction, and photo-induced radical cyclization.
- Characterization using UV-Vis absorption and fluorescence spectroscopy.
- Electrochemical analysis via cyclic voltammetry.
Main Results:
- Successful synthesis of a saddle-shaped aza-nanographene featuring a 1,4-dihydropyrrolo[3,2-b]pyrrole core and a 7-7-5-5-7-7 topology.
- The molecule exhibits significant non-planarity with a saddle height of approximately 4.3 Å, leading to negative Gaussian curvature.
- Absorption and fluorescence maxima were observed in the orange-red region, attributed to intramolecular charge transfer, and it displayed three reversible oxidation steps with a low first oxidation potential.
Conclusions:
- The developed synthetic route enables the construction of complex, non-planar nitrogen-embedded PAHs.
- The unique structural features of this aza-nanographene result in distinct optoelectronic properties.
- The compound demonstrates good stability and tunable redox behavior, making it a promising candidate for advanced materials.
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