Quadruply Twisted Hückel-Aromatic Dodecaphyrin

Area of Science:

• Organic Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Molecular topology and π-conjugated systems are crucial for understanding aromaticity.
• Bridged macrocycles offer unique structural and electronic properties.

Purpose of the Study:

• To synthesize and characterize novel pentafluorophenyl-substituted phenylene-bridged dodecaphyrins.
• To investigate the metalation and subsequent structural and electronic properties of these macrocycles.
• To explore the aromaticity and topology of twisted macrocyclic systems.

Main Methods:

• Condensation reactions to form the dodecaphyrin core.
• Oxidation using DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) to generate different congeners.
• Metalation with bis(dibenzylideneacetone)palladium(0) (Pd₂(dba)₃) to form bis-palladium(II) complexes.
• Structural characterization of isomers (anti and syn).

Main Results:

• Synthesis of meso-pentafluorophenyl-substituted 5,35-(1,4-phenylene)bridged [56]dodecaphyrin and its [54]- and [52]congeners.
• Formation of two bis-palladium(II) complexes (anti and syn isomers) from the [52]dodecaphyrin.
• Oxidation of the anti-isomer to a quadruply twisted non-aromatic or weakly aromatic macrocycle.
• Identification of the syn-isomer as the first quadruply twisted Hückel aromatic molecule.

Conclusions:

• The study successfully synthesized and characterized novel twisted dodecaphyrin macrocycles.
• The syn-bis-palladium(II) complex is a groundbreaking example of a quadruply twisted Hückel aromatic system.
• These findings contribute significantly to the understanding of molecular topology and aromaticity in complex macrocyclic structures.