Investigation of conformational and electron properties of biscyanine dyes

The spectral and luminescent characteristics of four biscyanine dyes and corresponding monomer dye in ethanol solutions and in polyvinyl butyral have been investigated. The influence of angle between chromophores of biscyanine molecules on splitting and intensity of absorption bands has been discussed. It has been shown that the splitting of the biscyanine excited electron level S₁ is caused both dipole and resonant chromophor interactions. It has been found that the fluorescence quantum yields of the biscyanines in ethanol at room temperature are 0.005-0.02. The introduction of biscyanines in a polymer matrix, which provides rigidity of a polymethine chain, results in reduction of molecules trans-cis isomerization and consequently increase of fluorescence quantum yields.