Influence of the Structure of Nonionic Surfactants and the Length of Alkyl Substituents of Calix[4]resorcinarenes on Their Solubility, Acid–Base, and Complexation Properties

Regularities of solubilization of calix[4]resorcinarenes (H₈L) with the variable length of hydrophobic radicals (R = CH₃, C₃H₇, C₅H₁₁, C₇H₁₅, C₈H₁₇, C₉H₁₉, C₁₁H₂₃) by the micelles of nonionic surfactants Triton X-100 and Triton X-405 in aqueous solutions were studied using solubility measurements. It was found that the solubilization capacity of surfactant micelles with respect to H₈L and [H₄L]^4– depends on the extension (thickness) of their polar layers. It was shown by means of potentiometric titration that, in solutions of nonionic surfactants, the constants of the interaction between tetraanions [H₄L]^4– and tetrametylammonium ions depend on the structure and concentration of nonionic surfactants and the hydrophobicity of H₈L molecules. A change in the affinity of the [H₄L]^4– anions for protons and tetramethylammonium cations in nonionic surfactant solutions was revealed in relation to the length of substituents R and reagent concentrations.     

Synthesis and magnetic properties of the complex of 3-acetylquinoxalin-2(1<Emphasis Type="Italic">H</Emphasis>)-one with Cu(II)

The complex CuHL(NO₃)₂ · H₂O, where HL = 3-acetylquinoxalin-2(1H)-one was synthesized and studied. Elemental analysis, magnetochemistry, and ESR, electronic, and IR spectroscopy were used to show that this complex is a polymer with the copper ion having a distorted octahedral surrounding. Each ligand bidentately coordinates to one copper ion and monodentately coordinates to the second.     

Receptor properties of calix[4]resorcinarenes toward tetramethylammonium and choline cations in micellar solutions of sodium dodecyl sulfate

Concentration range of solubilization of calix[4]resorcinarene (H₈L) in sodium dodecyl sulfate (SDS) micelles was found. The interaction of the deprotonated form of H8L (tetraanions [H₄L]⁴⁻) with tetramethylammonium (TMA) and choline cations in micellar solutions of SDS was studied by pH-metry and NMR spectroscopy. The concentration dependences of the change in the cloud point in a multicomponent system TMA (choline)-[H₄L]⁴-SDS-tetrabutylammonium bromide were determined. A correlation of these dependences with host-guest binding processes was found. The sharp change in the cloud points of the corresponding micellar solutions in concentration regions of TMA (0-5·10⁻⁴ mol L⁻¹) and choline (0–1.1· 10⁻³ mol L⁻¹) is caused by the formation of inclusion complexes TMA (choline)-[H₄L]⁴⁻ at the interface of the aqueous and micellar pseudophases. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1366–1371, August, 2006.     

Aminomethylphosphonate Derivatives of Tetramethylcalix[4]resorcinolarene. Synthesis and Some Extraction Properties in Relation to the Lantane Ions

O,O-Dibutyl-N-benzylamino- and O,O-dibutyl-N-phenylaminomethylphosphonate derivatives of tetramethylcalix[4]resorcinolarenes were prepared and characterized. Their effectiveness in the extraction of lanthanum(III) ions from water to chloroform in the presence of picrate ions is demonstrated. This extraction is accompanied by the formation of a complex of the composition La(Pic)₃(L)₂.     

Photophysical and electrochemical properties of the outer-sphere associate of [Ru(bipy)<Subscript>3</Subscript>]<Superscript>2+</Superscript> with <Emphasis Type="Italic">p</Emphasis>-sulfonatothiacalix[4]arene

¹H NMR titration and X-ray diffraction analysis revealed that [Ru(bipy)₃]²⁺ forms an outer-sphere inclusion complex with p-sulfonatothiacalix[4]arene in a ratio of 1: 1 in both aqueous solutions and the solid state. According to cyclic voltammograms and fluorimetric data, the outer-sphere association of [Ru(bipy)₃]²⁺ with p-sulfonatothiacalix[4]arene changes the reversible character of the electrochemical oxidation of [Ru(bipy)₃]²⁺ and lowers its emission intensity. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1863–1870, September, 2008.     

Aggregation and counter ion binding ability of sulfonatomethylcalix[4]resorcinarenes in aqueous solutions

¹H NMR spectroscopy, ¹H NMR spin-lattice relaxation, conductivity and pH-metric titration data have been used to study the aggregation and counter-ion binding of tetrasulfonatomethylcalix[4]resorcinarenes with methyl (H₈XNa₄) and amyl (H₈YNa₄) substituents. The data obtained reveal the self-aggregation of H₈YNa₄ driven by hydrophobic interactions. The NMR relaxation data indicate that Gd³⁺ is bound by both H₈XNa₄ and H₈YNa₄. The Gd³⁺ ions were found to induce the aggregation of H₈YNa₄ with critical association concentration (CAC) value less than in case of its self-aggregation. Using Gd³⁺ as a probe of counter-ion binding with the aggregate interface it was found out that binding of quaternary ammonium cations (QUATSs) with H₈YNa₄ aggregates and SDS aggregates is quite different, while binding of inorganic ions by both types of aggregates is similar. The most outstanding peculiarity of QUATSs binding with H₈YNa₄ aggregates is selective recognition of QUATSs, possessing trimethylammonium group, detected by NMR relaxation method.     

Solubilization and acidic and receptor properties of calix[4]resorcinarenes in aqueous solutions of oxyethylated dodecanol Brij-35

Solubilization of calix [4]resorcinarenes (Cn) with a varied length of hydrophobic substituents (R =Me, Pr, C₅H₁₁, C₇H₁₅, C₉H₁₉, and C₁₁H₂₃) in aqueous solutions of oxyethylated dodecanol Brij-35 was studied by the solubility method and 1D and 2D ¹H NMR spectroscopy. The solubilization of Cn in micellar solutions of Brij-35 is caused by the formation of mixed Cn-Brij-35 aggregates and is weakened substantially with the elongation of R. It was shown by pH-metry and 1D ¹H NMR spectroscopy that the receptor properties of the Cn anions toward the tetramethylammonium cations in the mixed aggregates differ substantially from those for the monomeric molecules in aqueous-organic and aqueous solutions. In particular, the binding of the tetramethylammonium cations does not result in screening of their N-Me fragments with the cyclophane cavity of the receptor.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 376–382, February, 2005.     

Sodium picrate effect on extraction of lanthanum and lutetium by aminophosphonate calix[4]resorcinarenes

Aminophosphonate calix[4]resorcinarene derivatives extract lanthanum and lutetium ions from aqueous solutions to chloroform much more efficiently than O,O-diethyl[(4-nitrophenyl)aminobenzyl] phosphonate does. In an excess of the metal ion in the aqueous phase with respect to the amounts of the extracting agent and sodium picrate, extraction occurs at the 1 : 1 molar ratio of the metal ion to extracting agent. In a twofold excess of the extracting agent and a considerable excess of sodium picrate over the metal ion, the composition of the extracted complex depends substantially on both the length of the alkyl substituent in the (AlkO)₂P(O) group in the extracting agent and the number of lanthanide.     

Basicity of a Novel Macrocycle Containing Thiopyrimidine and Uracil Moieties in Various Water–Organic Mixtures

The acid–base behavior of the novel macrocycle, containing thiopyrimidine and uracil moieties 32-trimethyl-23,36-dioxo-15,19-dithio-2,9,13,20,24,31,34,35-octaazatatracyclo [28,3,1^10,14,1^20,24]hexatriacontaheptaen-1(34),10(35),11,13,21,30,32 (1) and the acyclic 1,6-bis[4-(N,N-dimethylamino)-6-methylpyrimidinile-2-thio]hexane (2) were studied by potentiometric, UV-Vis, ¹H, NMR spectroscopic methods in water–dimethyl sulfoxide (methanol, 1,4-dioxane) solutions and at the interface between water and chloroform phases. The data obtained indicate, that thiopyrimidine nitrogens are the protonation sites of both 1 and 2. The protonation of 2 occurs in one step, while 1 is protonated stepwise in the pH range 9–2.5. The NMR data indicate that the intramolecular interaction between protonated pyrimidine and uracil moieties is the main reason for the stabilization of protonated forms of 1. The protonation constants of 1 were found to be different in various water–organic mixtures, which is in accord with the different ¹H NMR spectra of 1 in various solvents. The protonation of 1 at the water–organic phase boundary is effected by the extraction of [1·2H]²⁺ into the aqueous phase, which can be regarded as a way of obtaining its water -soluble form.     

The outer-sphere association of p-sulfonatothiacalix[4]arene with some Co(III) complexes: the effect on their redox activity in aqueous solutions

The effect of the ion-pairing of Co(III) complexes with p-sulfonatothiacalix[4]arene (STCA) on Fe(II)–Co(III) electron transfer rate was evaluated from the analysis and comparison of kinetic data in double Co(III)–Fe(II) and triple Co(III)–Fe(II)—STCA systems at various concentration conditions. Complexes [Co(en)₃]³⁺(1), [Co(en)₂ox]⁺(2), [Co(dipy)₃]³⁺ (3), [Co(His)₂]⁺(4) and [Fe(CN)₆]⁴⁻ were chosen as Co(III) and Fe(II) compounds. The effect of STCA was found to correlate with the association mode. The outer-sphere association with STCA was found to exhibit the insignificant effect on Fe(II)–Co(III) electron transfer k _et constants for complexes 3 and 4 with bulky and rigid chelate rings, while more sufficient inclusion of flexible ethylendiaminate rings of 1 and 2 into the cavity of STCA results in the unusual increase of k _et.