STUDIES ON MOLECULAR-ORIENTATION IN MULTILAYERS OF LONG-CHAIN ANTHRAQUINONE DERIVATIVES BY POLARIZED INFRARED-SPECTRA

With seven anthraquinone derivatives containing one or two stearylamino groups at different positions, orientation of the chromophore in the built-up multilayers has been investigated by angular dependence of the polarized infrared spectra. The multilayers were prepared by the horizontal lifting method and the polarized infrared spectra were measured as functions of the angles for the film samples inclined variously against the incident beam and also rotated with respect to the plane of polarization. In the results, it has been found that orientation of the anthraquinone nuclei depends markedly on the numbers and relative positions of the long substituents, in accordance with the previous conclusion from pressure-area characteristics of the monolayers and the film thickness. It should be noted that in some cases the chromophores with long alkyl chains have a tendency to orient depending not only on the vertical direction to the water surface but also on the direction of monolayer compression in the two-dimensional plane, in other words, these exhibit the double-axial orientation in the surface films. The multilayers with a well-defined orientation of chromophores seem to be useful for the study on electronic spectra of dye aggregates. © 1979.