Ya. V. Shalaeva

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.

Novel thermoresponsive water-soluble oligomers based on amphiphilic calixresorcinarenes

Abstract Novel water-soluble thermoresponsive oligomers TO1 and TO2 were obtained by reaction of amidoamine tetramethylcalixresorcinarenes (C1) and tetrapentylcalixresorcinarenes (C5) with ethylene glycol diglycidyl ether. The compounds were characterised by 1H and FT-PGSE NMR, FTIR, static light scattering and elemental analysis. The thermoresponsive properties of oligomers were investigated by spectrophotometry, DLS, FT-PGSE NMR and TEM. The cloud points of oligomers (43 °C for TO1 (5 mg/ml) and 41 °C for TO2 (1.2 mg/ml), respectively) were determined. The influence of salts effect on TO2 cloud points was investigated. The binding of anti-inflammatory drug naproxen (Nap) at 20 °C by TO1 and TO2 and its partial release at cloud points of oligomers in aqueous solution are observed using fluorescence and FT-PGSE NMR methods. New example of creating of thermoresponsive macrocyclic systems on the basis of amidoamine calixresorcinarenes with possibility of substrate binding and release under the influence of termo-stimuli in an aqueous solution was shown.