Дослідження сорбції тетраалкільних похідних калікс[4]аренів і калікс[4]резорцинаренів з поверхнею LiChrosorb RP 18 методами ОФ ВЕРХ та молекулярного моделювання

Tetrahydroxycalix[4]arene, tetraalkoxycalix[4]arenes and tetraalkylcalix[4]resorcinarenes are capable to reversible adsorption on the surface of the hydrophobic support LiChrosorb RP 18 under conditions of the reversed-phase high performance liquid chromatography. The main chromatographic characteristics of tetrahydroxycalix[4]arene, a series of tetraalkoxycalix[4]arenes and tetraalkylcalix[4]resorcinarenes have been determined. It has been found that in the conditions selected (the mobile phase is acetonitrile/water, 86/14, v/v) the retention times of the compounds studied are in the wide range from 4.67 min to 88.0 min depending on the nature of the substituents in the macrocyclic skeleton of the molecule. Thus, the retention times increase with increase of the length of the alkyl substituents at the lower rim of the calixarene macrocycle. According to the molecular modelling data the most effective sorption is explained by the inclusion of LiChrosorb RP 18 octadecyl groups into the lipophilic cavity formed by the alkyl substituents at the lower rim of the macrocycle of calixarene/calixresorcinarene. Thus, the molecular cavity formed by the benzene rings remains opened for the Host-Guest complexation with the analyte molecules. This sorption of tetraalkoxycalix[4]arenes and tetraalkylcalix[4]arenes on the LiChrosorb RP 18 surface can significantly improve its resolution ability in RP HPLC analysis. The influence of replacement of tetrahydroxycalix[4]arene hydroxyl protons with the alkyl groups on the conformation of the macrocycle has been studied.Тетрагидроксикаликс[4]арен, тетраалкоксикаликс[4]арены и тетраалкилкаликс[4]резорцинарены обратимо сорбируются на поверхности гидрофобной насадки LiChrosorb RP 18 в условиях обращенно-фазной высокоэффективной жидкостной хроматографии. Определены основные хроматографические характеристики тетрагидроксикаликс[4]арена, серии тетраалкоксикаликс[4]аренов и тетраалкилкаликс[4]резорцинаренов. Установлено, что в выбранных условиях (подвижная фаза – ацетонитрил/вода в соотношении 86/14 по объему) времена удерживания исследуемых соединений находятся в широком диапазоне 4.67-88.0 мин в зависимости от природы заместителей в макроциклическом скелете молекулы. При этом время удерживания возрастает по мере увеличения длины алкильных заместителей на нижнем ободе каликсаренового макроцикла. Согласно данным молекулярного моделирования наиболее эффективная сорбция происходит за счет включения октадецильних групп насадки в липофильную полость, образованную алкильными заместителями нижнего обода макроцикла каликсарена/каликсрезорцинарена. При этом молекулярная полость, сформированная бензольными кольцами макроцикла, остается открытой для комплексообразования с молекулами аналитов. Такая сорбция тетраалкоксикаликс[4]аренов и тетраалкилкаликс[4]резорцинаренов на поверхности хроматографической насадки LiChrosorb RP 18 может существенно улучшить ее селективность по отношению к аналитам в условиях обращенно-фазной высокоэффективной жидкостной хроматографии. Исследовано влияние замены гидроксильных протонов тетрагидроксикаликс[4]арена алкильными группами на конформацию макроциклического скелета молекулы.Тетрагідроксикалікс[4]арен, тетраалкоксикалікс[4]арени та тетраалкілкалікс[4]резорцинарени здатні до оберненої сорбції на поверхні гідрофобної насадки LiChrosorb RP 18 в умовах обернено-фазної високоефективної рідинної хроматографії. Визначені основні хроматографічні характеристики тетрагідроксикалікс[4]арену, низки тетраалкоксикалікс[4]аренів та тетраалкілкалікс[4]резорцинаренів. Встановлено, що у вибраних умовах (рухома фаза – ацетонітрил/вода у співвідношенні 86/14 за об’ємом) час утримання досліджуваних сполук знаходиться в широкому діапазоні 4.67-88.0 хв в залежності від природи замісників у макроциклічному кістяку каліксарену. При цьому час утримання зростає по мірі збільшення довжини алкільних замісників на нижньому вінці каліксаренового макроциклу. Згідно з даними молекулярного моделювання найбільш ефективна сорбція відбувається за рахунок включення октадецильних груп насадки LiChrosorb RP 18 в ліпофільну порожнину, утворену алкільними замісниками нижнього вінця макроциклу каліксарену/каліксрезорцинарену. При цьому молекулярна порожнина, сформована бензеновими кільцями макроциклу, залишається відкритою для комплексоутворення з молекулами аналітів.Така сорбція тетраалкоксикалікс[4]аренів та тетраалкілкалікс[4]резорцинаренів на поверхні хроматографічної насадки типу LiChrosorb RP 18 може суттєво поліпшити її роздільну здатність по відношенню до аналітів в умовах обернено-фазної високоефективної рідинної хроматографії. Досліджено вплив заміни гідроксильних протонів тетрагідроксикалікс[4]арену алкільними групами на конформацію макроциклічного кістяка молекули

Synthesis of Macrocyclic Stereoisomers Substituted with Oligolactide Fragments

© 2018, Pleiades Publishing, Ltd. Acylation of cone and 1,3-alternate stereoisomers of hydrazides of p-tert-butylthaicalix[4]arene tetrasubstituted at the lower rim with S,S-lactide in dimethylsulfoxide has afforded the macrocyclic oligolactide derivatives containing 16 (cone) to 24 (1,3-alternate) lactide fragments. It has been shown that nanosized aggregates (80 nm) are formed with silver nitrate in the case of the cone stereoisomer containing the oligolactide fragments at one side of the macrocyclic rim, whereas submicron particles (400 nm) are formed in the case of the 1,3-alternate conformation when the substituents are at different sides of the macrocycle

The thermodynamics of molecular recognition in supramolecular systems based on calyxarenes

The publications of the authors concerned with seeking simple structure-property relations for the thermodynamic parameters of intermolecular interactions in solid guest-host inclusion compounds with the participation of three receptors, namely, tert-butylcalyx[4]arene, tert-butylthiocalyx[4]arene, and 2,2′-bis(9-hydroxy-9-fluorenyl)biphenyl, are briefly reviewed. Rules determining structure-property correlations can exist for guest-host inclusion compounds. Generally, the correlations obtained are nonlinear

Stabilization of silica nanoparticles dispersions by surface modification with silicon derivative of thiacalix[4]arene

© 2015, Springer Science+Business Media Dordrecht. For the first time, silica nanopowder functionalized with thiacalixarene derivatives was synthesized by ultrasonication of nanoparticles (diameter 23.7 ± 2.4 nm) with organosilicon derivative of thiacalixarene in glacial acetic acid. The protocol resulted in the formation of colloidal solution of low-disperse (polydispersity index of 0.11) submicron-sized (diameter 192.5 nm) clusters of nanoparticles according to the dynamic light scattering data. As defined by scanning electron microscopy (SEM), mean diameter of thiacalixarene-functionalized nanoparticles is equal to 25.5 ± 2.5 nm and the shape is close to spherical. SEM images confirm low aggregation of thiacalixarene-modified nanoparticle compared to initial silica nanopowder (mean diameter of aggregates 330 and 429 nm, correspondingly). According to the thermogravimetry/differential scanning calorimetry and elemental analysis of the nanoparticles obtained, 5 % of the powder mass was related to thiacalixarene units. The effect of thiacalixarene functionalization of silica nanoparticles on linear polydimethylsiloxane (PDMS)—silica dispersions was modeled to achieve high resistance toward liquid media required for similar sol–gel prepared PDMS-based materials applied for solid-phase microextraction. In such a manner, the influence of thiacalixarene-modified nanofiller on thermal stability and resistance against polar organic solvents was estimated. Similarity of decomposition temperature of both thiacalixarene-functionalized nanoparticles and non-functionalized silica nanoparticles was found. Swelling/solubility behavior observed was related to partial dissolution of PDMS/silica (10 % mixture) in alcohols. Thiacalixarene-functionalized silica particles exerted significantly higher resistance of PDMS/silica composites toward alcohol solvents

Particle Propagation on a Circle with a Point Interaction

We study a particle propagation on a circle in the presence of a point interaction. We show that the one-particle Feynman kernel can be written into the sum of reflected and transmitted trajectories which are weighted by the elements of the n-th power of the scattering matrix evaluated on a line with a point interaction. As a by-product we find three-parameter family of trace formulae as a generalization of the Poisson summation formula.Comment: 21 pages, 12 figure

Sorption of hydrocarbons by leached chernozem

The sorption of n-octane, n-nonane, n-decane, decalin, and p-xylene on oven-dried and differently wetted leached chemozem, zeolite-bearing rock, and limestone was studied using static headspace-gas chromatography. It was found that leached chernozem exhibits a high capacity for selective sorption of hydrocarbons and has significantly heterogeneous sorption sites. Thermodynamic parameters of sorption, specific surface of sorbents, and the fractal dimension of soil surface were determined. An increase in the soil moisture content significantly inhibited the sorption of the hydrocarbons studied. Copyright © 2003 by MAIK "Nauka/Interperiodica" (Russia)

Configuration effect of the tert-butylthiacalix[4]arene tetracarboxy derivative on its receptor properties toward vaporous organic compounds

The effect of carboxy groups and the stable conformation of tert-butylcalix[4]arenes containing four carboxymethoxy substituents at the lower rim on their receptor properties toward organic substances and water was studied for the systems with guest vapor and solid host. For this purpose, the compositions of clathrates formed in these systems, their thermal stability, and parameters of the host-guest affinity were determined by the quartz microbalance method, thermogravimetry, thermogravimetry combined with differential scanning calorimetry and mass spectrometry, and static headspace gas chromatography. The introduction of four carboxymethoxy groups into tert-butylthiacalix[4]arene enhances its receptor capacity and affinity to water and aliphatic alcohols and decreases the thermal stability of the most part of the studied clathrates with hydrophobic guests except benzene. The studied tert-butylthiacalix[4]arene derivatives can be promising receptors for use in mass-sensitive sensors of the quartz microbalance type to methanol and ethanol vapors. © 2009 Springer Science+Business Media, Inc

Non-Weyl asymptotics for quantum graphs with general coupling conditions

Inspired by a recent result of Davies and Pushnitski, we study resonance asymptotics of quantum graphs with general coupling conditions at the vertices. We derive a criterion for the asymptotics to be of a non-Weyl character. We show that for balanced vertices with permutation-invariant couplings the asymptotics is non-Weyl only in case of Kirchhoff or anti-Kirchhoff conditions, while for graphs without permutation numerous examples of non-Weyl behaviour can be constructed. Furthermore, we present an insight helping to understand what makes the Kirchhoff/anti-Kirchhoff coupling particular from the resonance point of view. Finally, we demonstrate a generalization to quantum graphs with nonequal edge weights.Comment: minor changes, to appear in Pierre Duclos memorial issue of J. Phys. A: Math. Theo

One-dimensional Dirac operators with zero-range interactions: Spectral, scattering, and topological results

17 pagesInternational audienceThe spectral and scattering theory for 1-dimensional Dirac operators with mass $m$ and with zero-range interactions are fully investigated. Explicit expressions for the wave operators and for the scattering operator are provided. These new formulae take place in a representation which links, in a suitable way, the energies $-\infty$ and $+\infty$, and which emphasizes the role of $\pm m$. Finally, a topological version of Levinson's theorem is deduced, with the threshold effects at $\pm m$ automatically taken into account

Effect of the Polarizability of Organic Compounds on Isotherms of Sorption of Their Vapors with Solid tert-Butylcalix[4]arene

The stoichiometry and free energy of formation of saturated solid host-guest complexes were determined from the sorption isotherms of the vapors of organic compounds of various classes with solid tert-butylcalix[4]arene and from their limiting activity coefficients in toluene at 298 K. The contribution of the supramolecular effect to the free energy of formation of these complexes was estimated. The complexation stoichiometry and the observed supramolecular effect decrease with increasing molar refraction of the guest compound. The complexation stoihiometry is a step function of the molar refraction of the guest molecule