Aromatic saddles containing two heptagons.

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Polycyclic arenes with non-planar structures are of interest for their unique electronic and optical properties.
• Saddle-shaped molecules offer distinct three-dimensional architectures compared to planar systems.
• The synthesis and characterization of novel polycyclic arenes are crucial for advancing organic electronics.

Purpose of the Study:

• To synthesize novel soluble saddle-shaped polycyclic arenes containing two heptagons.
• To investigate the structural and electronic properties of these new compounds.
• To explore their potential applications in organic electronics.

Main Methods:

• Synthesis of soluble derivatives of C70H26 (1a,b) and C70H30 (2a,b) from saddle-shaped diketones (3a,b).
• Crystal structure analysis to determine the molecular geometry and packing.
• Characterization of electronic properties using solution-processed thin film transistors.
• Analysis of local aromaticity and nonplanarity based on crystal structures.

Main Results:

• Successful synthesis of two new classes of saddle-shaped polycyclic arenes.
• Crystal structures revealed deep saddle shapes and distorted architectures due to helicene moieties.
• Analysis confirmed general adherence to Clar's rule for aromaticity.
• Compounds 1b and 3b demonstrated p-type semiconductor behavior in thin film transistors.
• Amorphous films of 2b exhibited insulating properties.

Conclusions:

• The carbonyl groups in diketones are key for extending the polycyclic π-framework.
• The synthesized saddle-shaped polycyclic arenes possess unique structural features influencing their electronic behavior.
• The distinct electronic properties (semiconducting vs. insulating) suggest tunable applications in organic electronics.