Multi-step redox systems with NIR-fluorescence based on 4H-imidazoles

Molecules. 2007 Apr 5;12(4):723-34. doi: 10.3390/12040723.


A new class of 4H-imidazoles was synthesized starting from fused-ring aromatic dinitriles. Strong bathochromic shifts of the longest wavelength absorptions were observed in the corresponding UV/vis spectra due to a conversion of the merocyanine chromophores into cyanines/(aza)oxonoles upon protonation/deprotonation of the 4H-imidazoles. Novel boratetraazapentalenes were synthesized via a cyclization reaction with boron trifluoride. These mesoionic species bearing a cyanine chromophore not only show NIR-fluorescence, they also participate as part of a quasi-reversible multi-step redox system. Large calculated semiquinone formation constants K(SEM) (3x10(10) to 5x10(11)) indicate a high thermodynamic stability of the corresponding radical anions (SEM).

MeSH terms

  • Anions
  • Boranes / chemistry
  • Electrochemistry / methods
  • Imidazoles / chemistry*
  • Ions
  • Kinetics
  • Magnetic Resonance Spectroscopy / methods
  • Models, Chemical
  • Oxidation-Reduction*
  • Spectrometry, Fluorescence / methods
  • Spectrophotometry, Ultraviolet / methods
  • Spectroscopy, Near-Infrared / methods*
  • Thermodynamics
  • Ultraviolet Rays


  • Anions
  • Boranes
  • Imidazoles
  • Ions
  • imidazole
  • boron trifluoride