Film Dichroism. VI. Linearly-polarized Absorption Spectra of Neutral and Divalent 3,6-Diaminoacridine Dyes in the Stretched Poly(vinyl alcohol) Film

Abstract

Abstract The linear dichroic spectra of the neutral (uncharged) and divalent (doubly charged) Acridine Orange, Acridine Yellow, and Proflavine were measured at 25 °C in the visible and UV wavelength regions by the film dichroism method. These 3,6-disubstituted symmetric acridine dyes were molecularly dispersed in the heattreated poly(vinyl alcohol) film by the staining method. The neutral and divalent dye species were prepared by adding a sufficient amount of sodium hydroxide or sulfuric acid to the staining dye solutions. The wavelength dependence of the reduced dichroism, ΔA/A, of the neutral species at a given stretch ratio was very similar to that of the monovalent species previously reported [Bull. Chem. Soc. Jpn., 52, 3163 (1979)]. Values of ΔA/A for the divalent species were nearly constant over the entire wavelength region 550–220 nm. The long-axis and short-axis polarized component (Az and Ay) spectra were computed for the neutral dye species from the observed parallel- and perpendicular-polarized dichroic spectra by using a reduction procedure. The broad, principal band of each dye species in the visible region was deduced to be a composite of two orthogonal (a strong Az and a weak Ay) electronic transitions.