Yu. E. Morozova

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.

Protolytic properties and reactivity of aminomethylated calix[4]resorcarenes in reactions with esters of phosphorus acids

The acid-base properties and the kinetics of reactions of aminomethylated calix[4]resorcarenes (AMC) withp-nitrophenyl esters of phosphorus acids in aqueous solutions of propan-2-ol (80 vol.% PriOH) were studied by potentiometry, UV spectrophotometry, and31P NMR spectroscopy. The effect of the length of the hydrocarbon radical and substituents at the nitrogen atom on the protolytic properties and reactivity of AMC was studied. The reactions studied occur in two stages. At the first stage, phosphorylated AMC are formed, which are hydrolyzed to the corresponding acids at the second stage.

Dialkylaminomethylated calix[4]resorcinarenes. Reaction with carboxylic acids

Abstract5,11,17,23-Tetrakis(N,N-dimethylaminomethyl)-2,8,14,20-tetranonylcalix[4]resorcinolarene was found to form in solutions host-guest complexes with tartaric, phthalic, and succinic acids; the stability of the complexes depends on the degree of protonation of the host in the complex and the structure of the guest.

Protolytic Properties and Molecular Structure of 2,8,14,20-Tetramethyl-5,11,17,23-tetrakis(N-morpholino)- methylcalix[4]resorcinolarene

The protolytic properties of 2,8,14,20-tetramethyl-5,11,17,23-tetrakis(N-morpholino)methylcalix[4]resorcinolarene were studied by pH-potentiometric titration. Its crystal and molecular structure was determined by single crystal X-ray diffraction and UV spectroscopy. In solution the macrocycle exists as a zwitter-ion. In the crystal, the calixresorcinolarene molecule is in the cone conformation; two pairs of the opposite morpholine substituents are oriented inside and outside the macrocycle cavity and therefore show different acid properties.