Synthesis and Studies of Pyrene-Embedded Stable Nonaromatic Dithiaheptaphyrin(1.0.0.1.1.2.1)s.

Area of Science:

• Organic Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Porphyrinoids are macrocyclic compounds with diverse applications.
• Pyrene-containing macrocycles offer unique photophysical properties.
• Previous pyreniporphyrinoids primarily used 1,3-linkages.

Purpose of the Study:

• To synthesize novel 1,4-pyrene-embedded heptaphyrins.
• To investigate the structural, spectral, and electrochemical properties of these new macrocycles.
• To explore the impact of exclusive 1,4-pyrene linkage on macrocyclic frameworks.

Main Methods:

• [5 + 2] condensation of 1,4-pyrene pentapyrrane with dipyrromethene diols.
• Oxidation using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).
• Characterization via MALDI-MS, NMR, UV-Vis spectroscopy, electrochemistry, and theoretical calculations.

Main Results:

• Successful synthesis of three novel 1,4-pyrene-embedded heptaphyrins in 5% yield.
• Spectroscopic analysis revealed characteristic absorption bands, including a pyrene-derived band at ~371 nm and macrocycle bands at 478 nm and 529-806 nm.
• Protonation induced a bathochromic shift into the near-infrared (NIR) region.
• Electrochemical studies indicated electron-rich macrocycles with specific oxidation and reduction potentials.
• Theoretical calculations and NICS(0) analysis confirmed nonaromatic character and distorted, non-coplanar geometries.

Conclusions:

• The study reports the first synthesis of expanded macrocycles featuring an exclusive 1,4-pyrene linkage.
• The synthesized heptaphyrins are stable and exhibit unique photophysical and electrochemical properties.
• The findings contribute to the understanding of structure-property relationships in pyrene-containing macrocycles.