Proton-Induced Multiple Changes of the Absorption and Fluorescence Spectra of Amino-Aza-Oligo(phenylenevinylene)s

Polarity, pH and ion-sensing fluorescent probes based on quadrupolar substituted 1,4-distyrylbenzenes are investigated. The chromophores with nitrogen atoms in the chromophore and/or as auxochomic groups were prepared via aldol condensation or Horner olefinations. Whereas variations of the environment only slightly alter the electronic excitation spectra, the fluorescence spectra appear to be highly responsive. Besides a positive solvatochromism, the emission is very sensitive towards protonation. Quenching or appearance of new emitting species depends on the substitution pattern and is controlled by the concentration of the acid. The absorption and emission of compounds with a pyridazine or a 2,2′-bipyridine as central unit is highly responsive to iron-(III) ions.