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Multi-step Redox Systems with NIR-Fluorescence Based on 4H-Imidazoles
Institute of Organic and Makromolecular Chemistry, Friedrich-Schiller University D-07743 Jena, Humboldtstr. 10, Germany
* Author to whom correspondence should be addressed.
Received: 22 March 2007; in revised form: 29 March 2007 / Accepted: 29 March 2007 / Published: 5 April 2007
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 KSEM (3x1010 to 5x1011) indicate a high thermodynamic stability of the corresponding radical anions (SEM).
Keywords: 4H-Imidazoles; boratetraazapentalenes; multi-step redoxsystems; NIR-fluorescence
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Matschke, M.; Beckert, R. Multi-step Redox Systems with NIR-Fluorescence Based on 4H-Imidazoles. Molecules 2007, 12, 723-734.
Matschke M, Beckert R. Multi-step Redox Systems with NIR-Fluorescence Based on 4H-Imidazoles. Molecules. 2007; 12(4):723-734.
Matschke, Martin; Beckert, Rainer. 2007. "Multi-step Redox Systems with NIR-Fluorescence Based on 4H-Imidazoles." Molecules 12, no. 4: 723-734.