N. A. Makarova

Investigation of tetramethylenesulfonated calix[4]resorcinarene interactions with azo dyes in aqueous solution.

The interaction of a macrocycles 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.

Effect of Structure of Tetramethyl Sulfonated Calix[4]resorcinarene Aggregates on Paraquat Redox Reactions

The influence of amphiphilic tetramethyl sulfonated calix[4]resorcinarenes with different lengths of hydrophobic tails (R = CH3, C5H11) and trihydroxymethyl amide macrocycle on the behavior of a paraquat in the electrochemical redox process in aqueous solutions is studied. It is revealed that the aggregation of molecules with pentyl substituents makes it possible to partially or completely block the reduction of the paraquat and to resume the redox process depending on the concentration and ratio of components.

Binding of polar organic substrates by amphiphilic calixresorcin[4]arenes in the solution bulk and on the surface of anion-exchange resin

A comparative study is performed on the binding properties of free and immobilized water-soluble calixresorcin[4]arenes with respect to neutral organic molecules, one of which is capable of forming inclusion complexes, while the other possesses a fairly high potential of many-point hydrogen binding with the groups of the upper rim of macrocycle (parent substances of drugs Xymedon® and Dimephosphon®). It is revealed that macrocycle tetraanions present in aqueous solutions can be electrostatically immobilized on anion-exchange resin Amberlite IRA-900 Cl. The immobilization leads to changes in the binding mechanism of studied substrates due to the formation of calixresorcinarene aggregates on the surface of ion-exchange resin. The sorption of individual substrates and their mixtures is considered and models of the structure of immobilized aggregates of macrocycles and the mechanism of the binding of neutral guest molecules by the aggregates are proposed.

Aggregation and complexation in a series of tetramethylenesulfonate-substituted calix[4]resorcinarenes

NMR methods are employed to study the effects of inorganic salts, solvents, and guest molecules of methylviologen (MV2+) and choline (Ch+) on the aggregation properties of water-soluble tetramethylene-sulfonate-substituted calix[4]resorcinarenes containing methyl (1), amyl (2), and heptyl (3) substituents in the lower rim. It is established that, in aqueous solutions at concentrations of 1–10 mM, compound 1 exists in the monomeric form; the size of aggregates of amphiphilic compound 2 gradually increases (aggregation number varies from 1 to 20); and hydrophobic compound 3 dissolves only in slightly alkaline aqueous solutions to form large micellar aggregates. For macrocycles 2 and 3, which are inclined to aggregation, the aggregate sizes depend on the concentration, pH, and ionic strength of solutions, as well as on the presence of organic solvents. Macrocycle 1 binds guest molecules Ch+ and MV2+ to yield inclusion complexes. In the presence of aggregates of substance 2, the binding of guest molecules is more efficient and they are encapsulated between the rim of one molecule and the tail of another molecule of compound 2. The presence of guest molecules enhances the aggregation of macrocycle 2. In the case of compound 3 solutions, guest Ch+ molecules are predominantly localized in the hydrophobic environment of alkyl substituents of the host.

Monolayers and Langmuir–Blodgett films of amphiphilic tetramethylsulphonatocalix[4]resorcinarene and their interactions with polyethyleneimine and caeruloplasmin

The paper deals with the surface films of amphiphilic tetramethylsulphonatocalixresorcinarene (R = C11H23) 1 insoluble in water but forms rigid stable non-collapsing films at the water–air interface. Compression isotherms were used to investigate the interactions of the macrocycle films with two polymers fed to the aqueous subphases: synthetic – polyethyleneimine (PEI) and natural – an oxidase enzyme caeruloplasmin (CP). The interactions of the surface films of 1 with these substrates are predominantly dictated by the nature of the macromolecules and not by macrocycle interactions with their individual fragments. CP having retained its globular structure was extracted in the layer of 1 and became the dominating component of the film. The synthetic macromolecule of PEI, six times lower in its weight than CP, did not affect the morphology of the interfacial film, involved in the interactions only with its hydrophilic part directed inside the water.

Supramolecular Complexes of Diglycidyl Methylphosphonate with Calix[4]resorcinolarene

Various-composition supramolecular complexes of calix[4]resorcinolarene with diglycidyl methylphosphonate were synthesized in organic solvents. The products have well-defined melting points, they are cleaved by acetylation, but remain unchanged on treatment with triethylamine.