Dichromophoric hemicyanine dyes. Synthesis and spectroscopic investigation

The new dyes, xylene-1,4-bis[4-(p-aminostyryl)-pyridinium bromide] derivatives, have been synthesized and their spectroscopic properties were investigated. These dyes are stilbene-type pyridinium salts that possess in their structure different electron donor groups. We compile here the electronic absorption and the emission spectra properties as well the fluorescence quantum yields measured in organic solvents of varying polarity. The UV–vis and steady-state fluorescence spectroscopic investigations show the solvent-sensitive absorption and emission, which result from the intramolecular charge transfer (ICT) nature of the chromophores present in the dendritic structure.