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A polycyclic aromatic hydrocarbon diradical with pH-responsive magnetic properties.

Xiangyu Fu1, Han Han1, Di Zhang1

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A novel molecule, BCHF1, exhibits zwitterionic and diradical properties, enabling pH-controlled reversible magnetic switching. This discovery opens new avenues for smart materials and molecular electronics.

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Area of Science:

  • Organic Chemistry
  • Materials Science
  • Supramolecular Chemistry

Background:

  • Polycyclic aromatic hydrocarbons (PAHs) are versatile molecular building blocks.
  • Controlling molecular properties through external stimuli like pH is crucial for advanced materials.

Purpose of the Study:

  • To design and synthesize a novel non-alternant PAH, BCHF1, integrating azulene and a quinoid moiety.
  • To investigate the molecule's zwitterionic, quinoidal, and diradical behaviors.
  • To demonstrate pH-controlled reversible magnetic switching.

Main Methods:

  • Synthesis of the BCHF1 molecule.
  • Characterization using 1H-NMR and absorption spectroscopy to confirm zwitterionic behavior.
  • Electron Paramagnetic Resonance (EPR) spectroscopy to detect diradical properties and singlet-triplet energy gap.
  • pH-dependent studies in solution and thin films.

Main Results:

  • Successful synthesis of BCHF1, a novel non-alternant PAH.
  • Evidence of zwitterionic behavior through pH-dependent spectral changes.
  • Detection of room-temperature diradical character with a small singlet-triplet energy gap.
  • Demonstration of reversible magnetic switching controlled by pH via EPR signal modulation.

Conclusions:

  • BCHF1 exhibits unique manifold behaviors including zwitterionic and diradical characteristics.
  • The molecule displays pH-controlled reversible magnetic switching, a significant finding for smart materials.
  • This work provides a new platform for designing responsive organic materials.