Two Cationic Antiaromatic Free-Base Corroles

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Porphyrinoids are vital macrocyclic compounds with diverse applications.
• Synthesizing antiaromatic porphyrinoids, especially free-base variants, presents significant synthetic hurdles.
• Controlling the geometry and electronic properties of these systems is crucial for their function.

Purpose of the Study:

• To report the first successful synthesis of cationic free-base antiaromatic corroles.
• To introduce a novel synthetic strategy employing beta-annulated benzene rings to stabilize these reactive species.
• To characterize the structural and electronic properties of the synthesized compounds.

Main Methods:

• A strategy involving beta-annulated benzene rings was employed to direct the synthesis.
• Crystallographic analysis was used to determine the solid-state structures.
• Spectroscopic techniques (e.g., NMR, UV-Vis) were utilized for characterization.
• Theoretical calculations were performed to understand electronic properties and confirm antiaromaticity.

Main Results:

• Two novel cationic free-base antiaromatic corroles, BC(H2)+ and BC(H4)3+, were successfully synthesized.
• BC(H2)+ exhibits a slightly saddle-shaped geometry, while BC(H4)3+ shows a severely distorted saddle shape.
• Crystallographic, spectroscopic, and computational data robustly confirmed the antiaromatic nature of both compounds.
• The beta-annulation strategy effectively suppressed unwanted side reactions during synthesis.

Conclusions:

• The study presents the first examples of cationic free-base antiaromatic corroles.
• The developed synthetic approach provides a viable route to access challenging antiaromatic porphyrinoid systems.
• These findings expand the scope of known porphyrinoid structures and offer new platforms for exploring antiaromaticity in macrocyclic chemistry.