The Visible Spectra of Some 1,4‐Diaminoanthraquinone Disperse Dyes in Solvents and on Polymer Substrates

Abstract

The visible spectra of a series of 1,4‐disubstituted aminoanthraquinone dyes dissolved in different solvents and polymer substrates have been measured. The position of the absorption maximum has been correlated with a weighted mean ionization potential of the substituent groups. Solvent shifts were found to be small but the dependence on polarity and hydrogen‐bonding ability was shown to act in opposite directions. A detailed examination of the characteristic double‐peak structure of the visible‐absorption band has shown that the splitting is due to vibrational effects. The variation in the absorbance ratio of the two peaks with substituent and solvent has been explained in terms of the relative disposition of the ground‐ and excited‐state potential‐ energy curves. The effect of concentration on the double‐peak ratio has been re‐examined and found to be negligible.