Determination of Absolute Orientations of Hemicyanine Dyes Incorporated into the Channels of Silicalite-1 Films

Abstract

Hemicyanine dyes can be incorporated into silicalite-1 channels in uniform orientations.1 To find out the underlying mechanism, two different hemicyanine dyes having a long hydrophobic C18-alkyl chain on opposite ends of the dipolar nonlinear optical chromophore were adsorbed into the vertically oriented channels of silicalite-1 films supported on a glass plate. Second-harmonic phase measurement revealed that the above two molecules in the silicalite-1 channels were indeed oppositely oriented. A Langmuir monolayer of a hemicyanine was used as a reference sample to determine the absolute orientation of the dyes in the above samples, which allowed us to confirm that the hemicyanine dyes prefer to enter the zeolite channels with the hydrophobic tail part first.