Abstract
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 OSA
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