Molecular layers of polymethine dyes on glass substrates have been investigated. As the surface concentration of molecules increases, the number of cis isomers of various structures decreases, and the relative concentration of all-trans isomers increases. The increased electron-donorability of the end groups and the lengthening of the conjugation chain increases the number of cis isomers of various structures. The equilibrium stereoisomer composition of the molecular layer is determined by the degree of asymmetry of the intramolecular electron-density distribution induced by its interaction with the substrate. A model is proposed for the reconstruction of the structure of the layer under the action of heating and photoexcitation. Reversible changes in the make-up of the layer are caused by stereoisomerization when a segment of a molecule rotates around the second bond of the conjugation chain; irreversible changes are caused by transformations in the asymmetry of the electron-density distribution in the molecule due to irreversible spatial reorientation of the components of the layer.
© 2011 OSAPDF Article