Spectral characteristics of ketocyanine dyes: Polyene bis-ω,ω′-dimethylaminoketones

1. Interaction of chromophores influences the absorption spectra of bis-ω,ω′-dimethylaminoketones, and as a result, symmetrical dyes have a longer wavelength absorption spectrum than the corresponding unsymmetrical dyes. 2. These dyes exist in solution in two isomeric forms with similar absorption spectra. 3. The fluorescence spectra and fluorescence excitation spectra in a number of cases depend on the wavelength of the fluorescence excitation and registration, respectively; this also indicates the presence of different isomeric forms of the dye in solution. 4. For all of the dyes that were studied, strong thermochromism is observed, i.e., a long-wave shift of the absorption spectra when the solutions are cooled.