Formation mechanisms of equilibrium component composition of molecular layers of polymethine dyes

Influence of molecule-substrate interaction on component composition of cyanine thin films

“…The results of the separation are consistent with the results obtained in studying the spectra of fluorescence emission and excitation [17] and with the data on the reversible thermally stimulated stereo isomerization of layer monomers [18]. For the analogous components of different dyes, the frequency shift of the absorption band maximum with respect to the all-trans isomer band maximum in solution is the same, which confirms the correctness of the separation procedure [13].…”

“…1). The frequency shifts of their bands are close to the C3 and C4 band shifts of the symmetric molecules with <1>0> 45° [13]. Increasing �<1>0 further to 20° causes reverse effect (Fig.…”

“…It was established that the absorption spectra of the cyanine dye layers are considerably broader that spectra of their solutions [13]. The spectra of layers have several absorption maxima, which correspond to the molecular components of different structure.…”

“…The absorption of the symmetric dye in ethanol is mainly determined by all-trans-configuration, which is associated with the symmetry of the electron density distribution and the uniformity of bond orders in the conjugated chain of a symmetric molecule [13]. In solutions of chemically asymmetric dyes, the shorter-wave monomeric cis-isomers, which have the different structures corresponding to rotations of a molecular fragment around the different carbon bonds of the conjugated chain, are present in addition to all-trans isomer.…”

“…In our study, the effect exerted by electron density distribution in the cyanine dye molecules on glass on the formation of the equilibrium component composition of molecular layers was determined by the methods of absorption spectroscopy. The effect of electron-donor ability of the end groups of symmetric cyanines on the component composition has been studied previously [13]. It was found that the interaction of the molecule with the surface of a substrate and with the surrounding causes asymmetry in the intramolecular electron density distribution in chemically symmetric molecules.…”