qualitative study of the state of some dye aggregates by using 13C and 1H-NMR spectra-1

The 13C and 1H-NMR spectra of solid as well as solutions of GI acid Red 26 and GI acid Red 27 are recorded and discussed to illustrate the structure of the dyes. Useful information is obtained about the presence of isomers and intermolecular interactions between the dye molecules. The relative shifts of dye protons are interpreted in terms of inductive and resonance interactions of substituent groups with the ring protons and with the neighboring current effects upon dilution or increasing concentration. The results indicated the presence of different molecular species of the dyes. Consequently, the spectra of the dyes could be used as a qualitative measure to study the state of dye aggregates

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

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