Structural Characterization of l-proline and Morpholine Appended Chiral Calix[4]resorcinarene Molecules

Calix[4]resorcinarenes serve as host molecules for small guest molecules. Recently calixarenes have been appended to chiral molecules in an attempt to promote chiral recognition. To take advantage of both cavity host and chiral substituent properties the position of the chiral moiety is important. We report the synthesis and structural characterization of two calix[4]resorcinarene based molecules that have helical chirality in the solid state. The calix[4]resorcinarene 1 has chiral l-proline ethyl ester substituents positioned perpendicular to the cavity whereas the calix[4]resorcinarene 2 has morpholines positioned parallel to the cavity which extend the depth of the cavity. Compound 1 is one of the first compounds to show the position of chiral centers with respect to the calixarene cavity. 1H and 13C NMR spectroscopy indicate that the helical chirality of 2 is retained at low temperature in nonpolar solvents.     

杯[4]吡咯在不同溶液中的分子动力学模拟研究

运用分子动力学(MD)模拟方法对杯[4]吡咯与不同溶剂之间的相互作用能、杯[4]吡咯在不同溶液中的构象变化以及杯[4]吡咯与溶剂分子之间的氢键相互作用进行了计算研究.模拟发现,杯[4]吡咯与不同溶剂间的相互作用能受溶剂分子偶极矩和杯[4]吡咯-溶剂分子间氢键相互作用影响.杯[4]吡咯在不同溶液中的构象发生翻转的主导因素是杯[4]吡咯与溶剂分子间形成氢键相互作用,溶剂分子的偶极矩不是杯[4]吡咯发生构象转化的主要因素.     

Functional modification,self-assembly and application of calix[4]resorcinarenes

As a special subset of calix[4]arene, calix[4]resorcinarene is an excellent molecular platform which could be modified by introducing functional groups to multiple sites at the upper and lower rims. There are mainly three ways to build functionalized calix[4]resorcinarene derivatives: (1) modification on the C-2 sites of calix[4]resorcinarenes; (2) modification on the phenolic hydroxyl groups of calix[4]resorcinarenes; (3) modification on the bridging methylenes at lower rim of calix[4]resorcinarenes. Functionalized calix[4]resorcinarene derivatives play an important role in the development of self-assembly chemistry, among which hydrogen bonding and metal coordination are the two most common interactions to obtain multicomponent structures. Moreover, due to the excellent topological structures and various active substituents of functionalized calix[4]resorcinarene derivatives, their applications in various fields, such as nanoparticles, catalysts, fluorescent materials, and sensors, have been briefly presented in this paper.

     

Synthesis and mesomorphic properties of calix[4]resorcinarene–triphenylene oligomers

By controlling the mol ratios of reactants, novel calix[4]resorcinarene–triphenylene monomer, dimer and tetramer were designed and synthesised in yields of 50–60% via Click chemistry. Their structures were characterised by NMR and MS. Their liquid crystalline behaviours were studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction analysis. The more triphenylene units on calix[4]resorcinarene resulted in the wider temperature scopes of mesophase and higher phase transition temperatures. The monomer 6 and dimer 7 showed the mixed columnar mesophase with hexagonal columnar structure and disordered lamellar columnar structure, and compound 8 possessed only disordered lamellar columnar mesophase. These research results suggest that calix[4]resorcinarene was a good platform to construct columnar liquid crystal and the mesomorphic properties were greatly influenced by the substituted numbers of mesogen units on calix skeleton.     

Nanoencapsulation of calix[4]arene inclusion complexes

A hexameric resorcinarene nanocapsule in wet CDCl3 forms inclusion complexes of calix[4]arene with tetramethylammonium and trimethylsulfoxonium cations to give highly stable Russian-doll-type multicomponent assemblies. The 2D NOESY experiments revealed the size of the assembly, the close proximity of the encapsulated calix[4]arene molecule to the resorcinarene molecules of the capsule, and the inclusion of the tetramethylammonium cation in the calix[4]arene cavity.     

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.     

Monolayers of Chiral Calix[4]Resorcinarenes: Surface Pressure and Surface Potential Studies

Abstract

Chiral amphiphilic C-undecylcalix[4]resorcinarenes substituted with phenylethyl group or L(-)nore-phedrine were found to form well-organized mono-layers at the aqueous solution-air interface. The substituents, L(-)norephedrine and phenylethyl group, determined the area occupied by the molecule on the water subphase. Introduction of these substituents lead also to perpendicular dipole moments of the molecules in the monolayers ca. 6 times larger than those of the parent amphiphilic calixresorcinarene, CAL11. Interactions of the compounds with K⁺ were detected by the increase of the surface potential values measured at maximum packing of the monolayer. Addition of amino acids to the subphase lead to conformational changes in the monolayers evidenced by increased surface mean molecular area of the unmodified C-undecyl-calix[4]resorcinarene. These changes were explained by the formation of hydrogen bonds with the amino acids at the expense of hydrogen bonding between the calixarene molecules in the monolayer. In contrast to unsubstituted calixresorcinarenes, interactions of the L(-)norephedrine-and phenylethyl-substituted molecules with amino acids could be easily recognized by the decrease of surface potential and dipole moment in monolayers formed by these calixarenes on subphases containing amino acids. A significant drop in the surface potential and an increased area per molecule demonstrated more specific interactions with selected amino acids: L(-)norephedrine-substituted calixarene interacted with D-valine and the phenylethyl-substituted, with D-tryptophan.     

Formation of ionic associates from oppositely charged calix[4]resorcinarene host molecules in the presence of guest molecules

The conditions for the formation and existence of capsular dimeric associates in a solution were studied. The associates are formed by the oppositely charged resorcinarene derivatives (tetrakis(dimethylaminomethyl)calix[4]resorcinarene hydrochloride and tetrakis(sulfonato- methyl)calix[4]resorcinarene). Possibilities of formation of a capsule in the presence of the molecules giving inclusion complexes with one of the macrocycles were considered. Switching between two states “capsular associate—mixture of original macrocycless” is achieved by controlling the ionic strength of the solution. The interaction of the host—guest complexes with complementary resorcinarene leads to capsular associate closure with the synchronous displacement of the guest molecules into the aqueous solution bulk.     

丙醛间苯二酚杯[4]芳烃烷基化衍生物的合成

以间苯二酚和丙醛为原料合成了丙醛杯[4]芳烃(1),1经不同的烷基化反应合成了新的丙醛杯[4]芳烃烷基化衍生物,其结构经1H NMR和IR表征。     

Outer-sphere association of p-sulfonatothiacalix[4]arene and tetrasulfonatomethylated calix[4]resorcinarene with cobalt(III) tris(dipyridyl): the effect on the spectral and electrochemical properties of the latter

According to the 1H NMR and X-ray data, the outer-sphere association of [Co(dipy)3]3+ with cyclophanic anions p-sulfonatothiacalix[4]arene and tetrasulfonatomethylated calix[4]resorcinarene is accompanied by the inclusion of the dipyridyl moiety of the former into the cavities of the cyclophanic anions in aqueous and aqueous-DMSO solutions and in the solid state. The first-step dissociation of p-sulfonatothiacalix[4]arene does not change the inclusion mode, but the increase in DMSO content leads to a shallower inclusion of [Co(dipy)3]3+. The electrochemical property changes of [Co(dipy)3]3+ with both receptors undergoing ion pairing indicate the stabilization of the tris(dipyridyl) cobalt complexes in lower oxidation states. The effect of the cyclophanic anions on the cyclic voltammograms of [Co(dipy)3]3+ correlates with the efficiency of binding of the latter with tetrasulfonatomethylated calix[4]resorcinarene and p-sulfonatothiacalix[4]arene.     

Interaction of monolayers of calix[4]resorcinarene derivatives with copper ions in the aqueous subphase

Stable monolayers of novel amphiphilic calix[4]resorcinarene derivates at the air–water interface were prepared. Their interactions with copper ions from the aqueous subphase were investigated by measuring surface pressure–area and surface potential–area isotherms, as well as by Brewster angle microscopy. Theoretical aspects of interpreting the dependence of the surface pressure on the bulk copper ions concentration were discussed. The interaction of copper ions with calix[4]resorcinarene derivates was interpreted in terms of Gibbs–Shishkovsky adsorption equation.     

Study of gramicidin A--phospholipid interactions in Langmuir monolayers: analysis of their mechanical, thermodynamical, and electrical properties

The mechanisms of interactions between gramicidin A (gA) and dimyristoylphosphatidylcholine (DMPC) in monolayers formed at the air-water interface were studied by analyzing their mechanical, thermodynamical, and electrical properties evaluated from measurements of pressure-area isotherms and of Maxwell displacement currents (MDC). A contactless method of recording MDC enabled us to monitor changes in the charge state of the monolayer-constituting molecules and to find the relation between a phase state of the monolayer and structural transitions of gA. The peptide-lipid interactions were quantified in terms of the excess of Gibbs free energy, excess entropy, as well as the molecular dipole moments at various gA/DMPC molar ratios, at various temperatures (in the gel phase and also in the liquid-crystalline phase of DMPC molecule), and at various surface pressures. It was found that the strongest interactions between gA and DMPC took place at the gA/DMPC molar ratio at around 0.25. At this monolayer composition, the phospholipids, via their carbonyl moieties, dominantly interact with the single helical gA, which mostly stands upright on the surface and is anchored by its C-terminus to the water surface, and prevent the formation of the intertwined helical gA dimers. The optimum ratio was confirmed also by anomalous electrical behavior of electrical dipole moments derived from MDC measurements.     

新型正丁醛杯[4]芳烃醚衍生物的合成

以正丁醛间苯二酚杯[4]芳烃为原料,经酯化、水解、酰氯化后再与9-蒽甲醇反应,合成了蒽单取代的正丁醛间苯二酚型杯[4]芳烃醚衍生物。其结构经1H NMR和IR表征。     

A sulfonated calix[4]resorcinarene with l-pipecolinic acid groups as a water-soluble chiral NMR solvating agent

A water-soluble calix[4]resorcinarene containing l-pipecolinic acid groups is investigated as a chiral NMR solvating agent for aromatic-containing substrates. The substrates form complexes by insertion of the aromatic ring into the cavity of calix[4]resorcinarene. Compounds with phenyl, naphthyl, indole, indoline and pyridyl rings were investigated. The substrates also have ammonium or carboxylate functional groups. The effectiveness of the calix[4]resorcinarene with l-pipecolinic acid groups is compared to similar reagents with proline, hydroxyproline, and α-methylproline moieties that have previously been reported. The derivative with l-pipecolinic acid usually produces better enantiomeric discrimination compared to previous calix[4]resorcinarene reagents.     

Calix[4]resorcinarene Ionophore in the Ion-Selective Electrodes with Plasticized Poly(vinylchloride) Membranes

Synthetic ionophore calix[4]resorcinarene was incorporated into the poly(vinyl chloride) (PVC) plasticized membrane of an ion-selective electrode (ISE). Calixarene interactions with quaternary ammonium and alkaline metals cations in the organic and water-organic media were carefully investigated by various authors. We studied the effects of choline and Na⁺ cations present in the working solution on the ionophore which was incorporated into a membrane phase. Due to the pH sensitivity of the ionophore, a study was undertaken in a wide range of pH values. The different characteristics of calix[4]resorcinarene interactions with these cations were discovered by the ISE with the PVC plasticized membrane containing this ionophore, which respond to both the choline and Na⁺ cations due to the variation of working solution pH.     

Novel network polymers based on calixresorcinarenes

The novel network polymers 2a-2d based on calix[4]resorcinarene derivatives were obtained with yields 2a: 80%, 2b: 90%, 2c: 70%, 2d: 70%. Polymers 2a and 2b containing fragments of tetramethylcalix[4]resorcinarene or tetraphenylcalix[4]resorcinarene as a repeating units were synthesized by condensation cis-tetramethylcalix[4]resorcinarene or cis-tetraphenylcalix[4]resorcinarene with formaldehyde. Polymers 2c and 2d containing fragments of furylcalix[4]resorcinarene were obtained by condensation of formaldehyde with products of calix[4]resorcinarene and furfural interaction. The IR spectra and sorption properties of the polymers were researched. It is found out that 2a-2d can participate in the cation-exchange reaction.     

Structural and thermodynamic aspects of complexation of a calix[4]resorcinarene with diverse cations in water-organic media

Solvation of a calix[4]resorcinarene and its anions in water-organic media of varying composition was characterized by solubility measurements, acid-base titration and X-ray structural analysis. Methanol, 2-propanol, and DMSO capable of developing calix[4]resorcinarene solvated complexes of varying structure and stability were used as the organic component. It was revealed that the influence of the organic component of water-organic solvents on the stability of guest-host complexes formed by some organic and complex cations with calix[4]resorcinarene anions depended on the structure of the complexes.     

Complex Formation of Dimethylaminomethylcalix[4]resorcinarene and 2-Dimethylaminomethylphenol with Cu(II) Salicylaldiminates

Electronic and ESR spectroscopy was used to show that the reactions of dimethylaminomethylcalix[4]resorcinarene with Cu(II) salicylaldiminates bearing alkyl substituents at the salicylaldiminate nitrogen atom give 1 : 1 adducts with the dimethylamino group coordinated axially to the Cu(II) complex. The spatially organized calix[4]resorcinarene structure and the possibility of outer-sphere interactions favor a much higher stability of the adduct compared with the similar complex with 2-dimethylaminomethylphenol. In going from alkyl to aryl substituents, salicylaldiminates are replaced by the anion derived from dimethylaminomethylcalix[4]resocinarene. The same replacement takes place in the reaction with 2-dimethylaminomethylphenol.     

Separation of cis- and trans-isomers of thioxanthene and dibenz[b,e]oxepin derivatives on calixarene- and resorcinarene-bonded high-performance liquid chromatography stationary phases

The chromatographic behavior of six calix[n]arene phases (n=4, 6, 8) and one calix[4]resorcinarene phase is described for the separation of cis- and trans-isomers of three thioxanthene (flupentixol, clopenthixol, chlorprothixene) and one benz[b,e]oxepin derivative (doxepin). The influences of two different organic modifiers (MeOH, MeCN) for the separation of the isomers on every column are described. Different selectivities of the stationary phases exist as a function of the ring size of the calixarenes and their substitution at the "upper rim" with p-tert.-butyl groups. Furthermore, the influence of free phenol groups on the resorcinarene phase is discussed. Relations between structural elements of the analytes and the retention behavior on the stationary phases are found. The selectivity of the calixarene and resorcinarene stationary phases is compared with a RP-C18 phase containing the same base silica. Advantages of the resorcinarene as well as of the calixarene columns exist for the separation of cis- and trans-isomers of three compounds dependent from the substitution in position 2 of the thioxanthenes, respectively the kind of the basic side chain of all substances.     

Maxwell displacement current allows to study structural changes of gramicidin A in monolayers at the air-water interface

We applied methods of measurement Maxwell displacement current (MDC) pressure-area isotherms and dipole potential for analysis of the properties of gramicidin A (gA) and mixed gA/DMPC monolayers at an air-water interface. The MDC method allowed us to observe the kinetics of formation of secondary structure of gA in monolayers at an air-water interface. We showed, that secondary structure starts to form at rather low area per molecule at which gA monolayers are in gaseous state. Changes of the MDC during compression can be attributed to the reorientation of dipole moments in a gA double helix at area 7 nm(2)/molecule, followed by the formation of intertwined double helix of gA. The properties of gA in mixed monolayers depend on the molar fraction of gA/DMPC. At higher molar fractions of gA (around 0.5) the shape of the changes of dipole moment of mixed monolayer was similar to that for pure gA. The analysis of excess free energy in a gel (18( ) degrees C) and in a liquid-crystalline phase (28( ) degrees C) allowed us to show influence of the monolayer structural state on the interaction between gA and the phospholipids. In a gel state and at the gA/DMPC molar ratio below 0.17 the aggregates of gA were formed, while above this molar ratio gA interacts favorably with DMPC. In contrast, for DMPC in a liquid-crystalline state aggregation of gA was observed for all molar fractions studied. The effect of formation ordered structures between gA and DMPC is more pronounced at low temperatures.