Solvent and Substituent Effects on the Ultraviolet-Visible Absorption Spectra of Azo Dyes

Publisher Website
Google Scholar
Abstract
The effects of solvents, including polymeric substrates, and substituentson the absorption spectra of 4,4'-donor acceptor- substituted azo dyes were studied. The position of the intense, visible charge-transfer band was dependent on the di electric properties of the solvent ; a linear relationship was found between observed and calculated frequency shifts. Spec tral behavior obtained for the dyes in polymeric solvents was consistent with that obtained for the dyes in nonpolymeric solvents. The relationship between dye structure and solvent effects was also determined. Shifts in absorption maxima with substitution in positions insulated from the conjugated chromophoric system were consistent with Taft polar-substituent constants; the effects of such substituents were, therefore, primarily inductive in nature.