Guest controlled aggregation of amphiphilic sulfonatomethylated calix[4]resorcinarenes in aqueous solutions

Complexes of tetramethylensulfonatocalix[4]resorcinarene aggregates with methyl orange: Interactions with guests and driving force of color response

“…In our earlier works, we have demonstrated that aggregation plays a crucial role in the binding properties of amphiphilic macrocycles [6][7][8][9][10]. Hydrophilic analog of H with four methyl substituents at the lower rim forms no aggregates in 0-10 mM solutions and shows only a moderate binding efficiency.…”

“…Hydrophilic analog of H with four methyl substituents at the lower rim forms no aggregates in 0-10 mM solutions and shows only a moderate binding efficiency. Amphiphilic H, on the other hand, exists in aqueous solutions as head-to-tail dimers or 3-4 nm large polydisperse aggregates [8,9]. Their 95-99% binding efficiency toward suitable guests is accomplished by substrate binding with both the individual macrocycles and their aggregates (Fig.…”

“…Their 95-99% binding efficiency toward suitable guests is accomplished by substrate binding with both the individual macrocycles and their aggregates (Fig. 7) [8,9]. Binding of organic cations with H often causes increase of the aggregate dimensions [9].…”

“…7) [8,9]. Binding of organic cations with H often causes increase of the aggregate dimensions [9]. For MO complex with H, repulsion of their CH 2 SO 3 − and SO 3 − -groups does not favor MO encapsulation in the layer of aggregated H and the binding is <35% even in the presence of a 4.5-fold excess of the macrocycle [10].…”

“…Tetramethylensulfonated tetrapentylcalix [4]resorcinarene (H), reported here, in aqueous solutions is always aggregated either in dimers or in polydisperse aggregates that show a high (>90%) efficiency of guest binding. Sulfonated calix [4]resorcinarene forms inclusion complexes with ammonium-substituted guests of a suitable size, where bound guests are localized in the cavities formed by head-to-tail oriented molecules of H [8,9]. Binding efficiency of H toward earlier mentioned MO dye does not exceed 30% since it is not encapsulated in the layer of aggregated macrocycles and is bound exclusively on the surface of the aggregates.…”