The synthesis and spectroscopic investigation of dichromophoric hemicyanine dyes

Alkane α,γ-bis4-methylpyridinium] diiodide and alkane α,γ-bis4-methylquinolinium] diiodide were prepared and used as starting materials in the synthesis of dichromophoric cyanine dyes. Structural confirmation of the synthesized dyes was carried out by ¹H NMR, MS spectroscopy and elemental analysis. The electronic absorption and the emission spectra for all the hemicyanines were measured in four organic solvents of varying polarity. All derivatives absorb in the region of about 500 nm and have molar absorptivity of about 10⁴ M⁻¹ cm⁻¹. The absorption spectra of tested compounds are affected by their structure i.e. the structure of dialkyl(aryl)amino group, the electron acceptor part of the dye and the linker between two identical hemicyanine chromophores. The fluorescence bands' positions, in contrast to the absorption, are strongly affected by the solvent polarity.