Dimerization constants of some azo dyes from proton magnetic resonance spectra-II

ABSTRACT

The effect of aggregation upon proton magnetic resonance [PMR] spectra of GI acid Red 26 and CI acid Red 27 was observed in a series of aqueous solutions of different concentrations. An upfield shift by increasing the dye concentration has been attributed to the magnetic anisotropy of ring currents in neighboring molecules. The low-field shift which accompanies the disaggregation showed the vertical array stacking of the dye anions in the micelles at high concentrations. The dimerization constant Kd and limiting chemical shifts sigma M, sigma D are calculated and discussed. Addition of salt solution and decrease in temperature favor aggregation were taken place