Scheibe‐Aggregate Monolayers of Cyanine Dyes without Long Alkyl Chains

Abstract

Abstract Scheibe‐aggregates of three cyanine dyes with methyl or ethyl groups instead of long alkyl substituents have been prepared at the air‐water interface by spreading a mixture of the cyanine dye and arachidic acid on a water surface and compressing the monolayer. The general features of the reflection spectra of the dye‐arachidic acid monolayers at the air‐water interface, in particular the presence of a distinct J‐band, are in accordance with absorption spectra of monolayers deposited on glass plates by the Langmuir‐Blodgett technique. The dichroism observed in polarized absorption spectra of the dye‐arachidic acid films indicates that the Scheibe‐aggregates of the dyes with a meso phenyl group have a preferential orientation of the long axis of the molecules in the layer plane parallel to the direction of motion in depositing the layer. The brick‐stone model of Scheibe‐aggregates is adequate for chromophore organization in these monolayers.