Porphyrin-Based Air-Stable Helical Radicals

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Stable helical radicals are of interest due to their magnetic and chiroptical properties.
• Previous research focused on extending diphenylmethyl-fused nickel(II) porphyrin radicals to helical systems.
• The development of air-stable organic neutral helical radicals remains a significant challenge.

Purpose of the Study:

• To synthesize and characterize novel air-stable organic neutral helical radicals.
• To investigate the chiroptical and magnetic properties of these helical radical systems.
• To explore the potential of these molecules as multi-functional materials.

Main Methods:

• Intramolecular palladium-catalyzed twofold C-H arylation of modified nickel(II) porphyrins.
• Oxidative fusion reactions of meso-(bis(1-naphthyl)methyl) nickel(II) porphyrins.
• Enantiomeric separation and characterization using circular dichroism (CD) spectroscopy.
• Solid-state magnetic property measurements.

Main Results:

• Successful synthesis of doubly fused nickel(II) porphyrin radicals.
• One helical radical was resolved into enantiomers displaying mirror-image circular dichroism spectra up to 1300 nm.
• The helical dinaphthylmethyl-fused radical exhibited monomeric radical-dominated solid-state magnetism, contrasting with the parent compound's antiferromagnetic coupling.

Conclusions:

• The study presents the first air-stable organic neutral helical radicals based on nickel(II) porphyrins.
• These helical radicals possess distinct chiroptical and magnetic characteristics.
• The findings open avenues for designing advanced functional materials with tailored magnetic and optical responses.