title: Multi-step redox systems with NIR-fluorescence based on 4H-imidazoles.
abstract: 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).
authors.affiliation: Institute of Organic and Makromolecular Chemistry, Friedrich-Schiller University D-07743 Jena, Humboldtstr. 10, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Matschke
authors.forename: Rainer
authors.initials: R
authors.lastname: Beckert
mesh_terms: D000838:Anions; D001880:Boranes / Q000737:chemistry; D004563:Electrochemistry / Q000379:methods; D007093:Imidazoles / Q000737:chemistry*; D007477:Ions; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013050:Spectrometry, Fluorescence / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013816:Thermodynamics; D014466:Ultraviolet Rays
chemical_list: D000838:Anions; D001880:Boranes; D007093:Imidazoles; D007477:Ions; C029899:imidazole; C021274:boron trifluoride