Conjugated Metal-Organic Macrocycles: Synthesis, Characterization, and Electrical Conductivity

Area of Science:

• Materials Science
• Nanotechnology
• Chemistry

Background:

• Dimensional reduction of solids yields novel physical properties.
• Two-dimensional (2D) conductive metal-organic frameworks (MOFs) offer unique electronic characteristics.
• Understanding charge transport in reduced-dimension MOFs is crucial for advanced electronics.

Purpose of the Study:

• To synthesize and characterize copper-based macrocycles as fragments of 2D MOFs.
• To investigate the self-assembly and electronic properties of these macrocycles.
• To explore their potential for device applications.

Main Methods:

• Synthesis of copper-based macrocycles (CuTOTP-OR) from 2,3,6,7-tetraoxidotriphenylene.
• Characterization of self-assembled nanotubular structures via electron microscopy.
• Measurement of electrical conductivity and fabrication of thin-film field-effect transistors.

Main Results:

• CuTOTP-OR macrocycles self-assemble into nanotubes with ~2 nm internal diameters.
• Observed strong π-π stacking facilitating out-of-plane charge transport.
• Achieved pressed pellet conductivities up to 2(1) × 10^-3 S cm^-1.
• Demonstrated ambipolar charge transport in thin-film transistors.

Conclusions:

• CuTOTP-OR macrocycles provide a processable alternative to 2D MOFs.
• These materials enable facile device integration and study of charge transport mechanisms.
• The findings suggest similar charge transport behavior in parent 2D MOFs like Cu₃(HHTP)₂.