Metachromic interactions between azo and triphenylmethane dyes in aqueous solution

Abstract Interactions between dilute aqueous solutions of the triphenylmethane dye Crystal Violet and the disazo dyes Brilliant Orange or Brilliant Yellow at room temperature produce strong metachromic absorptions at 494 nm which are absent from the spectra of either component alone. The addition of acetone, ethanol or methanol to these solutions or raising their temperature reverses the interaction. It is suggested that these observations are consistent with a strong interaction occurring between adjacent molecules of crystal violet which are held together in a specific orientation by interacting with a stereoregular network of disazo dyes held together by hydrogen bonding.