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Area of Science:

  • Organic Chemistry
  • Supramolecular Chemistry
  • Materials Science

Background:

  • Expanded porphyrinoids are macrocyclic compounds with tunable electronic and photophysical properties.
  • Thiophene incorporation influences the conformational flexibility and electronic structure of these macrocycles.

Purpose of the Study:

  • To investigate the conformational changes in thiophene-based expanded porphyrinoids with increasing numbers of thiophene units.
  • To characterize the electronic properties and redox behavior of larger thiophene-based porphyrinoids.

Main Methods:

  • Synthesis and characterization of thiophene-based expanded porphyrinoids.
  • Variable temperature NMR spectroscopy to study conformational dynamics.
  • Spectro-electrochemical measurements to probe redox properties.

Main Results:

  • A transition from planar to twisted conformations was observed with increasing thiophene units.
  • Octaphyrin (40π electrons) exhibited temperature-dependent conformational interconversion in solution, unlike its rigid solid-state structure.
  • 60π-dodecaphyrin and 70π-tetradecaphyrin showed facile, reversible two-electron oxidation with unstable radical cation intermediates.

Conclusions:

  • Conformational flexibility is a key feature of thiophene-based expanded porphyrinoids, influenced by π-electron count and conjugation.
  • These systems offer potential for applications requiring dynamic molecular architectures and tunable redox properties.