4H-Imidazoles as functional dyes: synthesis of bichromophores and extension of the merocyanine system |
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Authors: | Martin Matschke |
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Institution: | Institute of Organic and Macromolecular Chemistry, Friedrich-Schiller-University, Humboldt street 10, D-07743 Jena, Germany |
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Abstract: | A series of bichromophores consisting of a ‘classical’ chromophore and 4H-imidazoles were synthesized starting from appropriate cyano and carboxy functionalized systems. In their UV-vis spectra, an additive absorption of both chromophores was detected making them wide range-absorbing dyes. In addition, new properties as redox activity, pH-switchability and metal-chelating substructures are newly introduced into the molecules. In order to achieve more bathochromic absorbing systems, the chromophore of 4H-imidazoles was extended. The 4H-imidazo-1,2-a]-pyridines, which are easily accessible by cyclization of 2-aminopyridines with bis-imidoylchlorides, show long wavelength absorptions up to 616 nm. Their reduction reversibly yields yellow, blue fluorescent 1-azaindolizines. In contrast to leuco-forms of 4H-imidazoles, these reduction products show a high stability towards oxygen and could only be reoxidized to their starting materials by oxidation agents, such as DDQ. |
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Keywords: | 4H-Imidazoles Merocyanines Bichromophores Functional dyes |
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