Twisted 1- and 2-Azaperopyrenes: Synthesis, Structure, and Properties.

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Peropyrenes are polycyclic aromatic hydrocarbons with unique photophysical properties.
• Nitrogen doping can significantly alter the electronic and optical characteristics of organic molecules.
• Developing novel synthetic routes to functionalized peropyrenes is crucial for advanced materials.

Purpose of the Study:

• To report the synthesis of previously unknown 1- and 2-azaperopyrenes.
• To investigate the structural, photophysical, and electrochemical properties of these nitrogen-doped peropyrenes.
• To explore the influence of regioselective N-doping on the peropyrene framework.

Main Methods:

• Brønsted acid-mediated benzannulation of alkynes for azaperopyrene synthesis.
• Pd/C-catalyzed, copper- and amine-free Sonogashira-type coupling for alkyne intermediate synthesis.
• X-ray crystallography, UV-Vis absorption, fluorescence spectroscopy, cyclic voltammetry, and computational studies.

Main Results:

• Successful synthesis of 1- and 2-azaperopyrenes with twisted conformations (bay twist 10.0-19.9°, end-to-end twist 5.5-25.0°).
• Observation of unprecedented conformational isomorphism in the synthesized compounds.
• Demonstration of altered photophysical and electrochemical properties due to single N-doping compared to carbon congeners.

Conclusions:

• A novel synthetic strategy for accessing twisted, nitrogen-doped peropyrene frameworks has been established.
• The study elucidates the impact of regioselective nitrogen incorporation on the molecular conformation and electronic properties.
• These findings open avenues for designing new functional organic materials with tailored optoelectronic characteristics.