meso-substituted aromatic 34pi core-modified octaphyrins: syntheses, characterization and anion binding properties

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Octaphyrins are macrocyclic compounds with potential applications in various fields.
• Understanding their structural diversity and electronic properties is crucial for developing new functional materials.

Purpose of the Study:

• To synthesize and characterize novel modified octaphyrins with 34pi electrons.
• To investigate the structural features, including ring inversion, and their dependence on meso substituents.
• To explore the electronic properties and supramolecular assembly of these octaphyrins.

Main Methods:

• Acid-catalyzed alpha,alpha coupling of tetrapyrranes.
• Nuclear Magnetic Resonance (NMR) spectroscopy (1D and 2D) for solution studies.
• Single-crystal X-ray diffraction for structural characterization.
• UV/Vis spectroscopy to determine electronic properties.

Main Results:

• Successful synthesis of modified octaphyrins in good yield.
• Identification of inverted heterocyclic rings (selenophene, furan, or pyrrole) dependent on meso substituents (mesityl or m-xylyl).
• Confirmation of aromatic character through UV/Vis and NMR spectroscopy.
• Protonated octaphyrins bind trifluoroacetate (TFA) anions in a 1:2 ratio via electrostatic and non-electrostatic interactions.
• Formation of 1D supramolecular arrays through intermolecular interactions.

Conclusions:

• A simple synthetic route to modified octaphyrins with tunable structures was established.
• The study reveals the influence of meso substituents on the specific ring inversion within the octaphyrin macrocycle.
• These octaphyrins exhibit porphyrinic character and aromaticity, with potential for self-assembly into supramolecular structures.