Ella Kh. Kazakova

Novel water-soluble tetrasulfonatomethylcalix[4]resorcinarenes

Abstract Here we present a simple, high-yielding method of preparation of the novel water-soluble tetrasulfonatomethylcalix[4]resorcinarenes. Preliminary results of complex formation between the host 1 and several aminoacids are reported.

Phosphorus-containing calixarenes

Calixarenes are macro(hetero)cyclic compounds having three-dimensional molecular cavities and are ubiquitous as synthetic receptors in supramolecular chemistry. This paper provides an overview of studies on the phosphorus-containing calixarenes and thiacalixarenes, within the context of synthesis, metal cation binding, catalysis, molecular recognition and bioactivity.

Crystal violet dye in complexes with amphiphilic anionic calix[4]resorcinarenes: binding by aggregates and individual molecules.

Here, we report on a systematic study of six calix[4]resorcinarene macrocycles bearing eight carboxylic groups on the upper rim and four different lower rim substituents that are either aliphatic (2, 4, and 5) or alkylaromatic (1, 3, and 6). The macrocycles were studied in their individual aqueous solutions and in the presence of triphenylmethane dye crystal violet. It was found that binding of crystal violet with aggregated macrocycles shields it from the bulk of solution, preventing its discoloration under basic conditions and electrochemical reduction on the glassy carbon electrode. Most efficient shielding, reducing the rate of discoloration more than 173 times, as compared to solution with no macrocycle, was achieved with 6 forming aggregates of average 72 molecules in 0.1 mM solutions.

Influence of amidoammonium calix[4]resorcinarenes on methyl orange protolytic equilibrium: supramolecular indicator systems

Here, we report on the study of cationic amidoammonium calix[4]resorcinarenes 1–5 of various lipophilicity capable of binding acid–base indicator methyl orange (MO). We identified the contributions of macrocycle aggregation and conformational mobility in the binding of MO. The effective pKa values of bound MO systematically decrease as the size and the packing density of the aggregates increase with an increase in calixresorcinarene lipophilicity. Consideration of a series of macrocycles clearly shows that large aggregates form most stable complexes, binding guests not on individual level but as aggregates. It was found that the most stable MO complex with 5 is formed due to electrostatic binding with ammonium groups of the macrocycle and incapsulation of MO in a hydrophobic layer of the aggregates. We have shown that competitive binding of MO and cationic surfactants by aggregates of 5 is suitable for visual/spectrophotometric detection of colourless anionic substrates.

The Complexation Properties of the Water-Soluble Tetrasulfonatomethylcalix[4]resorcinarene toward α-Aminoacids

The flexible bowl-type water-soluble molecule1, consisting of a resorcinol core and fourconvergent tetrasulfonatomethylene groups, existingas a tetraanion in neutral water solution, was studiedas the host molecule for recognition ofα-aminoacids. Out of 12 examined guestmolecules only those possessing aromatic hydrophobicmoieties or a long hydrophobic chain with a second ionogenic groupform inclusion complexes with 1. The complex formationwas considered with the help of both 1H NMRand pH-metric titration in a broad range of pH.The role of host and guest geometric complementarity aswell as additional π–π and hydrophobic interactionsis discussed. The lack of these interactions inaqueous media provides domination of the guestsolvation by water over the 1 : 1 complexformation with 1.

Synthesis and structural peculiarities of homeomorphic phosphorus bridgehead macrobicyclic compounds and novel dioxaphospha[3.1.1.]p, m, p-cyclophanes

The double-capping reaction of p,m,p-trinuclear diphenol 4 with PCl3 affords the three homeomorphic isomers 5-7 of a phosphite macrobicyclic compound in low yields. X-ray structures of out, out-isomer 5 and in, in-isomer 6 show very flat macrobicyclic structures with P-P distances of 4.9 A and 4.5/5.3 A (two conformers), respectively. The main product of the reaction, however, appears to be diphosphite 8, which contains two dioxaphospha[3.1.1.]p,m,p-cyclophane subunits. The structural peculiarities of 8 were studied after subsequent oxidation to the corresponding phosphate 12. At room temperature the free rotation either of the para-phenylene rings and the meta-phenylene ring in the macrocyclic moieties are hindered as could be demonstrated by means of NOESY measurements. The latter occupies an angled position in respect to the macrocyclic plane. This leads to the existence of conformational isomers due to different relative positions of the meta-phenylene ring to the P-OR substituent (cis,trans). We could isolate the cis,cis-isomer of 12 and establish its structure by X-ray diffraction.

The Synergistic Extraction of Lanthanide Ions by a Mixture of Calix[4]resorcinarene or its Dimethylamino-, Piperidyl- or Trimethylammoniummethylated Derivatives and 1,10-Phenanthroline in n-Heptanol

The alkylaminomethylatedcalix[4]resorcinarene derivatives, modified bydimethylamino-, piperidyl- and trimethylammoniummoieties, have been synthesised to investigate theirextractability towards lanthanide ions and to comparewith the extractability of calix[4]resorcinarene. Both calix[4]resorcinarene and its derivatives have beenshown to synergistically affect lanthanide ionextraction from neutral aqueous solutions by1,10-phenanthroline through outer-sphere interactionof lanthanide bis-phenanthrolinate cations withdeprotonated forms of calix[4]resorcinarene. Thederivatives with dimethylamino- andpiperidylmethylated moieties are shown to be moreeffective extractants in comparison with theunsubstituted one.

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.

The Inclusion Properties of a New Watersoluble Sulfonated Calix[4]resorcinarene towards Alkylammonium and N-Methylpyridinium Cations

The inclusion behaviour of a new water-soluble sulfonated calix[4]resorcinarene towards alkylammonium and N-methylpyridinium cations has been investigated on the basis of 1H NMR spectroscopy and pH-potentiometry data. The inclusion of the N-methylpyridinium cation has been found to be dependent on pH with the preferable inclusion of the methyl substituent in alkaline and the aromatic ring in neutral aqueous media.

A Watersoluble Sulfonatomethylated Calix[4]resorcinarene as Artificial Receptor of Metal Complexes

The binding of different sized and shaped metal complexes [Co(His)2]ClO4(1), [Co(en)2C2O4]Cl (2) and [K18-crown-6]SCN (3)(en-ethylendiamine, His-L-histidynate-anion) with a new tetrasulfonatomethylcalix[4]resorcinarene([H8X]Na4) was investigated in neutral and alkaline aqueous media by NMR and pH-metrictitration methods and compared with those of recently studied NMe4Br (4). The resultsobtained indicate that the outer-sphere coordination of complexes 1–3 by[H8X]4- proceeds via the interaction of hydrophobic fragments of the guestswith both the negatively charged rim and the hydrophobic cavity as a π-base. Thenature of binding does not change for cations 1, 2 and 4 on going from[H8X]4- in neutral to [H4X]8- in alkaline media, while the inclusionof 3 decreases on going from [H8X]4- to [H4X]8-.