Exciton Theory of the Electronic States of Dye—Polymer Complexes. III. Configurationally Induced Optical Rotatory Dispersion of Dye Transitions in Helical Complexes

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Abstract
The exciton theory of dye—polymer complexes is applied to the phenomenon of optical rotation displayed by the electronic transitions of dyes bound to helical polymers. In the model examined one chromophoric ligand is bound to an infinite single stranded helical polymer. There are no symmetry restrictions on the ligand which can be optically active, e.g., an asymmetric dimer of dyes, or inactive as is the case with most dye molecules. Optical rotation arising from the coupling of electric transition dipoles and quadrupoles and magnetic dipoles of ligand and monomer units is considered. The transition moments of the ligand are resolved into three components each of which couples to particular members of the set of allowed helix transitions. Thus the helix moments enhance those of the ligand enabling it to rotate the plane of polarization of incident light if it is symmetric and changing the rotation if it is asymmetric. Expressions are developed for the optical rotation of linearly polarized light by complexes with random and certain fixed orientations.