Relative Hydrophobicity of Triphenylmethane Dyes as Revealed by Interaction with Tetraarylborate Anions

Relative Hydrophobicity of Triphenylmethane Dyes as Revealed by Interaction with Tetraarylborate Anions

The ion aggregates formed between cationic triphenylmethane dyes and tetraphenylborate(TPB) or tetrakis(4-fluorophenyl) borate (TFB) anions have been investigated spectroscopically. The photometric sensitivities of the dyes are found to be increasing in the order pararosaniline < malachite green < methyl violet 2B < crystal violet < ethyl violet. Cetyltrimethylammonium bromide(CTAB) and Triton X-100(TX-100) destroy the ion aggregates. By comparing the concentration of surfactant beyond which dye-borate mixed solutions behave identically with the dye blank, the order of hydrophobicity appears to be parallel with that of photometric sensitivity.