Investigation of Tetramethylenesulfonated Calix[4]resorcinarene Interactions with Azo Dyes in Aqueous Solution

• Published in: The journal of physical chemistry. B Vol. 114; no. 41; pp. 13152 - 13158
• Main Authors: Morozova, Julia E, Kazakova, Ella Kh, Mironova, Diana A, Shalaeva, Yana V, Syakaev, Victor V, Makarova, Nely A, Konovalov, Alexander I
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 21.10.2010
• Subjects: B: Surfactants, Membranes
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp106060p

The interaction of a macrocycle’s aggregates with a guest molecule has special interest due to the double role, both of macrocycle cavity and self-associates, in the binding of the guests. Here, we report on the interactions of nonaggregated methyl-substituted (SCA1) and aggregated penthyl-substituted (SCA2) tetramethylenesulfonated calix[4]resorcinarenes with pH indicators methyl yellow (MY) and methyl orange (MO) in aqueous solutions. It was found that the pH of aqueous solutions of SCA1 and SCA2 depends on their concentration; besides, variation of the concentration of SCA1 and SCA2 results in a shift of the absorption maxima and of pH-sensitive azo dyes. Association of the marocycles with azo dyes was demonstrated to follow a proton-transfer mechanism accompanied by protonation of the dyes; it was found that excess of the macrocycle in solution with the universal buffer background shifts the pK a values and stabilizes the protonated form of the dyes. Consideration of interactions of small dye molecules with large molecular associates, containing both individual and multimolecule binding sites, gives a closer approximation of synthetic biomimetics to their natural prototypes.