Annulated Azuleno[2,1,8-ija]azulenes: Synthesis and Properties

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Non-alternant, non-benzenoid hydrocarbons possess distinct optical and electronic properties compared to benzenoid compounds.
• Synthesizing these structures with extended conjugation remains a significant challenge in organic chemistry.

Purpose of the Study:

• To develop a synthetic route for novel azuleno[2,1,8-ija]azulene derivatives.
• To characterize the optical, electronic, and aromatic properties of these new compounds.
• To evaluate their performance as semiconductors in organic field-effect transistors (OFETs).

Main Methods:

• A two-step synthesis involving four-fold aldol condensation between aromatic dialdehydes and tetrahydropentalene-2,5-(1H,3H)-dione.
• Spectroscopic analysis including 1H NMR spectroscopy.
• Density Functional Theory (DFT) calculations.
• Fabrication and characterization of organic field-effect transistors (OFETs).

Main Results:

• Successful synthesis of azuleno[2,1,8-ija]azulene derivatives with tunable band gaps (1.69–2.14 eV).
• High molar extinction coefficients (up to 3×10^5 M⁻¹ cm⁻¹).
• Demonstrated significant diatropic ring currents, indicating aromaticity.
• Achieved charge carrier mobility up to 0.05 cm²/Vs in OFET devices.

Conclusions:

• The developed synthetic strategy provides access to novel non-benzenoid hydrocarbons with extended conjugation.
• Azuleno[2,1,8-ija]azulene derivatives exhibit promising optoelectronic properties and significant aromaticity.
• These compounds are viable candidates for semiconductor applications in organic electronics, particularly in OFETs.