Alexander I. Konovalov

Calix[4]arene based α-aminophosphonates: Novel carriers for zwitterionic amino acids transport

Abstract a series of calix[4]arene based α-aminophosphonates were synthesized by the Kabachnik-Fields reaction of the calixarene-diamine (either at lower or upper rim), diethyl phosphite and a carbonyl compound (acetone or cyclohexanone). These compounds exhibited remarkable selectivity as carriers for the membrane transport of the zwitterionic form of aromatic amino acids.

Cloud point extraction of lanthanide(III) ions via use of Triton X-100 without and with water-soluble calixarenes as added chelating agents

The use of water-soluble calixarenes: p-sulfonato thiacalixarene (ST), tetra-sulfonatomethylated calix[4]resorcinarene (SR), calix[4]resorcinarene phosphonic acid (PhR) as chelating agents in cloud point extraction (CPE) of La(III), Gd(III) and Yb(III) ions using Triton X-100 as non-ionic surfactant is introduced. The data obtained indicate that both complexation ability and structure of calixarenes govern the extraction efficiency of lanthanides. In particular ST and SR, forming 1:1 lanthanide complexes with similar stability in aqueous media, exhibit different extractability when used as chelating agents in CPE. First synthesized PhR was found to be the most efficient chelating agent exhibiting pH-dependent selectivity within La(III), Gd(III) and Yb(III) in CPE.

The synthesis of tetracarbonyl derivatives of thiacalix(4)arene in different conformations and their complexation properties towards alkali metal ions

Abstract The three conformations of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis[(benzoyl)methoxy]-2,8,14,20-tetrathiacalix[4]arene 1 : cone, partial cone and 1,3-alternate, were prepared by the treatment of 5,11,17,23-tetra-tert-butyl-2,8,14,20-tetrathiacalix[4]arene-25,26,27,28-tetraol (TCA) with α-bromo acetophenone in the presence of appropriate alkali carbonate M2CO3 (M=Na, K, Cs) as base catalyst in acetonitrile. Structure of the conformers were established by 1H NMR, 1H–1H COSY, 1D NOE, 2D ROESY and X-ray experiments. The alkali cation binding selectivity of the obtained macrocycles was investigated by the ion-pair extraction method.

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.

Self-assembling systems based on amphiphilic alkyltriphenylphosphonium bromides: Elucidation of the role of head group

A systematic study of the aggregation behavior of alkyltriphenylphosphonium bromides (TPPB-n; n=8, 10, 12, 14, 16, 18; here n is the number of carbon atoms in alkyl groups) in aqueous solutions has been carried out and compared with trimethyl ammonium bromides (TMAB-n). Critical micelle concentrations (cmcs) of TPPB-n and TMAB-n decrease with the number of carbon atoms with the slope parameter of ca.0.3. The low cmcs and effective solubilization power toward Orange OT indicate high micellization capacity of phosphonium surfactants. The low counterion binding parameter β is revealed for TPPB-10 and TPPB-12, while high counterion binding of ≥80% is observed for high TPPB-n homologs. Values of the surface potential ψ calculated on the basis of pK(a) shifts of p-nitrophenols is similar for both series and monotonously increase with alkyl chain length. Several points indicate non-monotonic changes within TPPB-n series. There are peculiarities of the tensiometry and solubilization plots for high homologs and above mentioned increases in counterion binding on transiting from low to high molecular weight surfactants. Differences in aggregation behavior between TPPB and TMAB series and between low and high homologs can be due to the specific structural character of the TPP(+) cation, which is supported by X-ray data.

Novel Highly Charged Silica-Coated Tb(III) Nanoparticles with Fluorescent Properties Sensitive to Ion Exchange and Energy Transfer Processes in Aqueous Dispersions

Novel silica-coated Tb(III) nanoparticles with high luminecsence were synthesized using the reverse microemulsion procedure. The quenching of luminescent properties of these nanoparticles can be achieved by ion exchange and energy transfer mechanisms. The quenching through the ion exchange of Tb(III) by H+ or La(III) is time dependent, indicating that the ion exchange is probably diffusion controlled. The quenching by Co(III) complex cations is achieved by the energy transfer mechanism and thus is not time dependent. The analysis of quenching data in Stern-Volmer cooordinates reveal the negative charge of the silica-coated Tb(III)-TCAS nanoparticles and several types of luminophoric species, located within the core and close to the surface of silica nanoparticles.

Compressibility of liquids. Rule of noncrossing V-P curvatures.

Weight analysis of the liquid introduced into the stainless steel bomb under pressures up to 1 kbar in the temperature range of 20-50 degrees C at the interval of 10 degrees C was performed for 1,4-dioxane, acetonitrile, toluene, ethyl acetate, chlorobenzene, and n-hexane. The coefficients of the Tait equation were determined for all of the solvents at each temperature. There was a clear linear relation between the tangent bulk modulus (1/beta T) at atmospheric pressure (1 bar) and the secant bulk modulus at 1 kbar; 1/betaT=0.9865 x (1000 V0/DeltaV(1kbar))-4559 was found at a wide range of temperatures for different liquids, including glycerol and even mercury. This represents the rule of noncrossing P-V curvatures for the liquids. Using the correlation, it is possible to predict the coefficients (C, B) of the Tait equation from the experimental data of betaT at 1 bar or, on the other hand, to calculate the value of betaT from experimental compression at high pressures.

Pressure effect on the rate and equilibrium constants of the Diels-Alder reaction 9-chloroanthracene with tetracyanoethylene

Abstract The pressure effect on the forward and backward rate constants and equilibrium constants of the Diels-Alder reaction of 9-chloroanthracene with tetracyanoethylene has been investigated in 1,2-dichloroethane up to 1000 kgcm−2 at 298.15 K. The reaction volume obtained from the pressure effect on equilibrium (−20.6 ±1.5 cm3mol−1) and as difference of activation volumes of forward (−28.5±1.5) and backward (−6.5 ± 0.5) reaction (−22.0±1.5 cm3mol−1) are in agreement with partial molar volume difference of adduct (255.5±1.5) diene (170.7±0.5) and dienophile (107.8±0.2) giving −23.0 ±2 cm3mol−1.

Supramolecular Systems Based on Novel Mono- and Dicationic Pyrimidinic Amphiphiles and Oligonucleotides: A Self-Organization and Complexation Study

Novel mono- and dicationic pyrimidinic surfactants are synthesized and their aggregation behavior is studied by methods of tensiometry and nuclear magnetic resonance (NMR) self-diffusion. To estimate their potentiality as gene delivery agents, the complexation with oligonucleotides (ONus) is explored by dynamic light scattering (DLS) and zeta-potential titration methods and ethidium bromide exclusion experiments. Bola-type pyrimidinic amphiphile (BPM) demonstrates rather a weak affinity to ONus. Although it induces mixed associations with ONus, only slight charge compensation changes occur at a large excess of bola, with no recharging reached. Similarly, the ethydium bromide exclusion study reveals a slow increase in the binding capacity toward an ONu with an increment in BPM concentration. The monocationic pyrimidinic surfactant (MPM) and its gemini analogue (GPM-1) are ranked as intermediates in both their aggregative activity and complexing properties toward ONus. They both form mixed associates with ONus well below the critical micelle concentrations (cmcs) of 2 and 15 mM respectively. However, GPM-1 has a much lower isoelectric point at the molar ratio surfactant/ONu r~1 compared to r~3 for MPM. This probably indicates a larger electrostatic contribution to the ONu complexation in the case of GPM-1. The most hydrophobic pyrimidinic surfactant (GPM-2), bearing three alkyl tails, demonstrates enhanced aggregative activity and binding capacity toward ONus as compared to former pyrimidinic surfactants. Due to effective aggregative (low cmc of 0.04 mM) plus binding properties (fraction of bound ONu β=0.76 at r=2.5), GPM-2 may be ranked as a promising agent for wider biological applications.

Solution behavior of mixed systems based on novel amphiphilic cyclophanes and Triton X100: Aggregation, cloud point phenomenon and cloud point extraction of lanthanide ions

Aggregation and cloud point (CP) behavior, as well as CP extraction of lanthanide ions have been studied for novel non-ionic cyclophanic surfactants with the varied length of polyoxyethylene and hydrophobic moieties (CnEm) based on calix[4]arene platform in their mixtures with Triton X100 (TX100). The dynamic light scattering data reveal the contribution of the large size lamellar or stack like mixed aggregates in CnEm-TX100 solutions. Aggregation and CP behavior of TX100-CnEm mixed solutions are quite different from those of conventional non-ionic surfactants. The effect of the hydrophobic substituents and polyoxyethylene chains length of CnEm on the CP extraction of La(III), Gd(III) and Lu(III) in the mixed TX100-CnEm micellar solutions is discussed in the correlation with their aggregation and cloud point behavior. The obtained data elucidate the cyclophanic structure of CnEm as the key reason of the formation of large lamellar-like aggregates with TX100, exhibiting the unusual CP behavior and CPE efficiency.