THE EFFECT OF TETRAALKYLAMMONIUM CHLORIDE ON THE AGGREGATION OF BASIC DYES (THIAZINE AND XANTHENE DYES)

Abstract

The aggregation of the basic dye is explained adequately in terms of van der Waals force and the hydrophobic bond. It is difficult, however, to estimate the contribution of the hydrophobic bond to the aggregation. The interaction between the dye and tetraalkylammonium chloride (R₄ NCl) was studied spectrophotometrically to estimate the contribution of the hydrophobic bond. Results obtained were as follows:
1) R₄NCl causes the aggregation or disaggregation of C. I. Basic Blue 9, C. I. Basic Violet 10, and C. I. Basic Red 1 depending on the given conditions. The effect of tetraalkylammonium cation is greater than that of the Cl anion.
2) C. I. Basic Blue 9 and Basic Red 1 aggregate in the dilute solution of R₄NCl, i.e. Me₄NCl, Et₄NCl, and n-Bu₄NCl. These dyes disaggregate in concentrated solution of R₄NCl. C. I. Basic Violet 10 disaggregate in the presence of R₄NCl. The effect was in the order; n-Bu₄NCl>Et₄NCl>Me₄NCl.
3) The effect of NH₄Cl on the aggregation of C. I. Basic Violet 10 becomes larger at lower temperatures. The effect of Me₄NCl, Et₄NCl, and n-Bu₄NCl on the disaggregation becomes larger at higher temperatures.
4) The intensity of the interaction between the dye and R₄N⁺ was in the order; C. I. Basic Violet 10>C. I. Basic Red 1>C. I. Basic Blue 9.
Results described above revealed facts that the aggregation of the dye cation is caused by the formation of the ionic atmosphere of the dye cation, and that the disaggregation is caused by the formation of the hydrophobic bond between the dye cation and R₄N⁺.