End Group Effect on Aggregation in Oriented Bisazomethine Dye Films on Aligned Poly(tetrafluoroethylene) Layers

Anisotropic molecular thin films have been prepared by depositing several bisazomethine dyes under vacuum through evaporation on aligned poly(tetrafluoroethylene) (PTFE) layers. Their anisotropy and spectra significantly depend on the double-end groups of dye molecules. Oriented J-aggregates, previously reported for diethylamino ends, also have been obtained for pyrrolidinyl and butoxy ends, whereas they have not been obtained for dimethylamino, dibutylamino, butyl, and methoxy ends. The aggregates from butoxy ends are remarkable for a substrate effect: they grow well on the layers by PTFE evaporation and rubbing whereas they do neither on friction transferred PTFE layers nor on glass.