Arene Derivatives Research Articles

Enantioselective resolution of racemic flurbiprofen methyl ester by lipase encapsulated mercapto calix[4]arenes capped Fe3O4 nanoparticles.

This work presents the synthesis of new mercapto calix[4]arenes derivatives (4 and 5). These derivatives were capped on Fe3O4 magnetic nanoparticles and subsequently encapsulated with Candida rugosa through sol-gel method to furnish enc-4 and enc-5, respectively, to enhance catalytic activity and enantioselectivity of lipase for hydrolysis reaction of racemic flurbiprofen methyl ester. Catalytic activity and enantioselectivity of enc-4 and enc-5 were assayed at different pH and temperature conditions and it was found that the resultant encapsulated enzyme exhibited higher thermal and operational stabilities compared to the free lipasein which enc-5 showed the excellent rate of enantioselectivity (E=176) for S-flurbiprofen better than free lipase (E=137) at pH 7 and 35°C for 48h. The time study shows that enantioselectivity reached the maximumvalue of E=244 after 72h. Catalytic activity of these materials was hardly affected by 20 and 23% after five usages of enc-4 and enc-5, respectively.

Smart Polymorphism of Thiacalix[4]arene with Long-Chain Amide Containing Substituents

A problem of controlled (smart) formation of polymorphs was solved for a set of tert-butylthiacalix[4]arene derivatives with four N-(2-acetoxyethyl)carbamoylmethoxy substituents at the lower rim with 1,3-alternate, cone, and partial cone conformations. For this, an effective polymorph screening with a reproducible influence of preparation history was achieved using guest vapor inclusion and a standard state of host glass powder. By this procedure with consequent guest release and heating, the ability of the studied calixarenes for polymorphism was investigated and compared as a function of their macrocycle conformation. The data of simultaneous thermogravimetry and differential scanning calorimetry with mass spectrometry of evolved vapors were determined together with the data of powder X-ray diffraction for the initial host samples, intermediate clathrates, and final polymorphs. In addition, single crystal X-ray diffraction data were obtained for four crystalline forms of the studied calixarenes. The results yielded a structure–property relationship, where 1,3-alternate calixarene without an extended H-bonded supramolecular network at least in one crystalline form has a much higher ability for polymorphism than the other two conformations. Thus, 10 polymorphs with essentially different crystal packing were found for this calixarene including a unique tetramorphism with four consecutive melting points of guest-free polymorph and corresponding three crystallization ranges. This ability of 1,3-alternate calixarene is linked with its other smart property: selective crystallization of its compact glass in vapors of binary liquid mixtures, which can be used for visual detection of very small benzene impurities (0.5% (v/v)) in cyclohexane.

Glucose-Responsive Supramolecular Vesicles Based on Water-Soluble Pillar[5]arene and Pyridylboronic Acid Derivatives for Controlled Insulin Delivery.

The stimuli-responsive behavior of supramolecular nanocarriers is crucial for their potential applications as smart drug delivery systems. We hereby constructed a glucose-responsive supramolecular drug delivery system based on the host-guest interaction between a water-soluble pillar[5]arene (WP5) and a pyridylboronic acid derivative (G) for insulin delivery and controlled release under physiological conditions. The approach represents the ideal treatment of diabetes mellitus. The drug loading and in vitro drug release experiments demonstrated that large molecular weight insulin could be encapsulated into the vesicles with high loading efficiency, which, to our knowledge, is the first example of small-size supramolecular vesicles with excellent encapsulation capacity of a large protein molecule. Moreover, FITC-labeled insulin was used to evaluate the release behavior of insulin, and it was demonstrated that high glucose concentration could facilitate the quick release of insulin, suggesting a smart drug delivery system for potential application in controlled insulin release only under hyperglycemic conditions. Finally, we demonstrated that these supramolecular nanocarriers have good cytocompatibility, which is essential for their further biomedical applications. The present study provides a novel strategy for the construction of glucose-responsive smart supramolecular drug delivery systems, which has potential applications for the treatment of diabetes mellitus.

Highly selective separation and recovery of Pd(II) from the automotive catalyst residue with the thiocarbamoyl substituted azothiacalix[4]arene derivative

ABSTRACTNew ligand, namely, 5, 11, 17, 23-tetrakis-((p-chlorophenyl) azo)-25,26,27,28-tetrakis ((dimethylthio carbamoyl)oxy) thiacalix[4]arene (CADTTCA), has been investigated for separation and recovery of Pd(II) through solvent extraction technique. Experimental parameters such as contact time, diluents, effect of H+ and Cl− concentration, and acid durability have been thoroughly investigated. The loading capacity toward Pd(II) was determined to be 113 mg/L using 0.25 mM CADTTCA. The extractant showed high selectivity and extractability for Pd(II) than the other metal ions present in automotive catalyst residue (ACR) solution containing platinum group (PGMs) metal ions (i.e., Pd(II), Pt(IV), Rh(II), La(III), Al(III) and Ce(III)). The recovery percentage of Pd(II) was 98% after five extraction-scrubbing-stripping cycles. The probable extraction mechanisms were established through the FT-IR spectral analysis.

Sensing abilities of functionalized calix[4]arene coated QCM sensors towards volatile organic compounds in aqueous media

This study presents the sensing studies of QCM sensors which coated with calix[4]arene derivatives bearing different functional groups towards some selected Volatile Organic Compounds (VOCs). Initial experiments revealed that QCM sensor coated with calix-3 bearing bromopropyl functionalities was relatively more effective sensor for methylene chloride (MC) emissions than the other calix[4]arene coated QCM sensors, in aqueous media. In further experiments, this effective calix-3 coated QCM sensor were used in detailed sensing studies of selected VOCs. However, the results demonstrated that calix-3 coated QCM sensor was most useful sensor for toluene (TOL) emissions among all. Moreover, the sensing of TOLs with calix-3 coated QCM sensor was also evaluated in terms of sorption phenomena. Consequently, calix-3 coated QCM sensor was good sensor for TOL emissions, and thus it demonstrated that the coating of QCM sensor surface with calixarenes was good approach for sensing of the VOCs.

High selectivity and extractability of palladium from chloride leach liquors of an automotive catalyst residue by azothiacalix[4]arene derivative

Pd(II) is a noble metal in the platinum group metals (PGMs) and has been used extensively in automobile catalysts. However, its resources are strictly limited; thus, the recovery of Pd(II) from wastes or secondary sources currently has great importance. A new ligand, namely, 11,17,23-tetrakis-[(p-methoxyphenyl)azo]-25,26,27,28-tetrakis[(dimethyl thiocarbamoyl)oxy]thiacalix[4]arene (MADTTCA), was investigated for the extraction of Pd(II) from a hydrochloric acid medium using chloroform as a diluent. Extraction data indicate that the extraction efficiency depends on the concentration of HCl, from 0.1–5.0M. The equilibrium extraction time of MADTTCA was achieved with a short contact time (15min), which made MADTTCA a suitable candidate for industrial applications. Notably, the maximum uptake capacity of MADTTCA for Pd(II) was found to be 417mg/L using 1.0mM MADTTCA. On the basis of the obtained data, the stoichiometric ratio between Pd(II) and MADTTCA was found to be 1:1. MADTTCA was shown to be highly effective at extracting Pd(II) from simulated mixed metal and automotive catalyst residue (ACR) solutions composed of six metal ions (PGMs), such as Pd(II), Pt(IV), Rh(II), Al(III), La(III) and Ce(III). More than 99.9% of the extracted Pd(II) was stripped with 0.1M thiourea in a 1.0M HCl solution. The title extractant was able to be recycled and reused at least five times without a significant loss of its extraction features. All of the obtained results revealed that MADTTCA can be used for the selective recovery of Pd(II) from ACR solutions.

Visual Detection of Cesium Ions in Domestic Water Supply or Seawater using a Nano-optode

Abstract Cesium, in particular radioactive Cs 137 is currently a significant environmental problem in Japan following the incident at the Fukushima-Daiichi nuclear power plant caused by the Great East Japan earthquake. Although radioscopes and gamma ray cameras have been developing to visualize radioactive species or contamination, it is not necessarily a simple matter to locate sources of contamination under high levels of background radiation. However, supramolecular approaches for environmental sensing of analyses are useful in the design of high-resolution molecular sensors. Here, we have developed an optical imaging technique for cesium ions involving an optode system in environmental water. An optode membrane was prepared incorporating a calix[6]arene derivative, which showed excellent selectivity toward cesium ions in aqueous solutions, even in water supplied for domestic use or seawater. Furthermore, this membrane was fabricated using nanoparticles with a diameter of ca. 100 nm. The nano-optode also gave an excellent response to cesium ions. Therefore, this optode provides a higher spatial resolution than existing radioscopes and gamma ray cameras under high level radioactive environments.

Co-polymers of oligolactic acid and tetrasubstituted thiacalix[4]arenes as a new material for electrochemical sensor development

New derivatives of oligolactic acid (OLA) have been obtained by cross-esterification with carboxylated thiacalix[4]arene derivatives in cone, paco and 1,3-alternate configurations. The products of the reaction characterized by NMR 1H, FTIR-ATR spectroscopy, MALDI-TOF mass spectroscopy and elemental analysis have been applied for surface modification of glassy carbon electrode (GCE). Electrochemical characterization with redox probes (ferricyanide ion and Methylene blue (MB)) showed predominant influence of electrostatic interactions influencing the flux of the charge carriers over the diffusion control. The role of a macrocycle moiety on the surface morphology and sensitivity toward measurement conditions has been established. The electrodes covered with new materials were applied as transducers in sensing specific DNA interactions and acetylcholinesterase (AChE) based hydrolysis of acetylthiocholine. This made it possible to distinguish factors affecting the DNA structure (MB intercalation, oxidative DNA damage, thermal denaturing) whereas immobilization of the AChE on the silver dendrites deposited in the inner volume of the polymers allowed recording the signal of thiocholine oxidation at extremely low working potential (0mV vs. Ag/AgCl).

Axle length- and solvent-controlled construction of (pseudo)[1]rotaxanes from mono-thiourea-functionalised pillar[5]arene derivatives

A series of thiourea-functionalised pillar[5]arene derivatives 3nm were constructed from a series of mono-amide-functionalised pillar[5]arenes 2n. The formation of their free forms or (pseudo)[1]rotaxane structures were controlled by their axle lengths or solvents, which were investigated by 1H NMR spectroscopy. Some of (pseudo)[1]rotaxane structures were also supported by their single-crystal structures.

A General Nickel-Catalyzed Method for C-H Bond Alkynylation of Heteroarenes Through Chelation Assistance.

A general nickel-catalyzed method for the alkynylation of heteroarenes through monodentate chelation assistance is described. Many heterocycles, including indoles, pyrroles, imidazoles, and pyrazole, efficiently coupled with (triisopropylsilyl)alkynyl bromide, and synthetically important functional groups, such as halides, ether, nitrile, and nitro, are tolerated. Synthetic applicability of this Ni-catalyzed method is demonstrated by the removal of the triisopropylsilyl group and further functionalization to triazolyl, benzofuranyl, and alkynyl arene derivatives. Preliminary mechanistic investigations of the alkynylation of indole suggest that the reaction proceeds through kinetically relevant C-H activation and follows a two-electron redox pathway. A catalytically relevant Ni species, namely, [(Phen)3 Ni]NiBr4 (PheN=1,10-phenanthroline), was isolated and structurally characterized.

Liquid Crystal Organization of Calix[4]arene‐Appended Schiff Bases and Recognition towards Zn2+

AbstractThe synthesis and liquid crystalline behavior of new calixarene Schiff base derivatives are reported. The materials were obtained by reaction of a tetraaminocalix[4]arene derivative with three aldehydes as mesogenic promotor moieties: 4‐(4′‐decyloxybenzoyloxy)benzaldehyde (A), 4‐(4′‐decyloxybenzoyloxy)salicylaldehyde (B) and 4‐(3′,4′‐didecyloxybenzoyloxy)salicylaldehyde (C). All of the compounds exhibit liquid crystalline properties and these were studied by optical microscopy, DSC and X‐ray diffraction. The relationship between the structure and the mesomorphic behavior of the compounds is discussed. The binding recognition and selectivity towards cations have been studied by absorption and fluorescence spectroscopy

Plugging a Bipyridinium Axle into Multichromophoric Calix[6]arene Wheels Bearing Naphthyl Units at Different Rims.

Tris‐(N‐phenylureido)‐calix[6]arene derivatives are heteroditopic non‐symmetric molecular hosts that can form pseudorotaxane complexes with 4,4′‐bipyridinium‐type guests. Owing to the unique structural features and recognition properties of the calix[6]arene wheel, these systems are of interest for the design and synthesis of novel molecular devices and machines. We envisaged that the incorporation of photoactive units in the calixarene skeleton could lead to the development of systems the working modes of which can be governed and monitored by means of light‐activated processes. Here, we report on the synthesis, structural characterization, and spectroscopic, photophysical, and electrochemical investigation of two calix[6]arene wheels decorated with three naphthyl groups anchored to either the upper or lower rim of the phenylureido calixarene platform. We found that the naphthyl units interact mutually and with the calixarene skeleton in a different fashion in the two compounds, which thus exhibit a markedly distinct photophysical behavior. For both hosts, the inclusion of a 4,4′‐bipyridinium guest activates energy‐ and/or electron‐transfer processes that lead to non‐trivial luminescence changes.

Molecular recognition of sulfonatocalixarene with organic cations at the self-assembled interface: a thermodynamic investigation

A microcalorimetric study on molecular recognition of p-sulfonatocalix[4]arene derivatives at self-assembled interface in comparison with in bulk water was performed, inspired by the dramatic change in physicochemical characteristics from bulk water to interface. A total of six cationic molecules were screened as model guests, including ammonium (NH4+), guanidinium (Gdm+), N,N′-dimethyl-1,4-diazabicyclo[2.2.2]octane (DMDABCO2+), tropylium (Tpm+), N-methyl pyridinium (N-mPY+) and methyl viologen (MV2+). The complexation with NH4+, Gdm+ and DMDABCO2+ is pronouncedly enhanced when the recognition process moved from bulk water to interface, whereas the complexation stabilities with Tpm+, N-mPY+ and MV2+ increase slightly or even decrease to some extent. A more interesting phenomenon arises from the NH4+/Gdm+ pair that the thermodynamic origin at interface differs definitely from each other although with similar association constants. The results were discussed in terms of differential driving forces, electrostatic, hydrogen bond as well as π-stacking interactions, originating from the unique physicochemical features of interfaces, mainly the polarity and dielectric constant.

A calix[4]arene derivative and its selective interaction with drugs (clofibric acid, diclofenac and aspirin)

The synthesis and characterisation of a partially substituted calix[4]arene, namely, 5,11,17,23-tetra-tert-butyl,25,27-bis[aminoethoxy] 26,28-dihydroxycalix[4]arene are reported. Its interaction with commonly used pharmaceuticals (clofibric acid, diclofenac and aspirin) was investigated by spectroscopic (1H NMR and UV), electrochemical (conductance measurements) and thermal (titration calorimetry) techniques. It is concluded on the basis of the experimental work and molecular simulation studies that the receptor interacts selectively with these drugs. Preliminary studies on the selective extraction of these pharmaceuticals from water by the calix receptor are reported and the potential for a carrier mediated sensor based on this ligand for ‘on site’ monitoring of pharmaceuticals is discussed.

Synthesis of a water-soluble 2,6-helic[6]arene derivative and its strong binding abilities towards quaternary phosphonium salts: an acid/base controlled switchable complexation process.

A water-soluble 2,6-helic[6]arene derivative was conveniently synthesized, and it showed strong binding abilities towards quaternary phosphonium salts in aqueous solution. Moreover, an acid/base controlled switchable complexation process was also described.

Modification of Oligolactic Acid with Tetracarboxylic p-tert-Butylthiacalix[4]arene Derivatives: Effect of Macrocyclic Fragment Configuration on Aggregation and Thermal Properties of Copolyesters

Modification of Oligolactic Acid with Tetracarboxylic p-tert-Butylthiacalix[4]arene Derivatives: Effect of Macrocyclic Fragment Configuration on Aggregation and Thermal Properties of Copolyesters

Complexation of Alkali Metal Cations by a Tertiary Amide Calix[4]Arene Derivative in Strongly Cation Solvating Solvents

The complexation of alkali-metal cations with calix[4]arene tertiary amide derivative (L) was studied in N- methylformamide (NMF), N, N- dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) by means of microcalorimetric and UV spectrophotometric titrations. The Gibbs energies, enthalpies, and entropies for transfer of reactants and products from N- methylformamide to other solvents were determined. Favorable enthalpic contribution to overall stability was found to be the most important for all complexation reactions, especially in the case of NaL+ formation, resulting in an affinity peak of L for this cation. The complexation entropy changes were always unfavorable. The ligand dissolution was endothermic in all solvents, accompanied by positive solution entropy. The highest complex stability constants were determined in NMF, whereas in DMSO the affinity of L towards alkali metal cations was the lowest. An interesting interplay between the transfer enthalpies and entropies of the reactants and complexes was revealed and discussed in detail.

Synthesis of Fluorescent Diphenylantracene-Based Calix[4]arene Derivatives and their Complexation with Alkali Metal Cations

Synthesis of Fluorescent Diphenylantracene-Based Calix[4]arene Derivatives and their Complexation with Alkali Metal Cations

Hexameric assembly of 5,17-di-substituted calix[4]arene in the solid state

Chiral 5,17-difunctionalized-25,26,27,28-tetrapropyloxycalix[4]arene possessing (S)-mandelamide arms ((S,S)-1) afforded cocrystals (S,S)-1·(solvent) (solvent = MeOH, EtOH, 1-PrOH, 2-PrOH, and CH3CN). Four of the five cocrystals contain unusual hexameric assembly of the calix[4]arene host.

Effects of side chains of oxatub[4]arene on its conformational interconversion, molecular recognition and macroscopic self-assembly.

A series of oxatub[4]arenes with different alkyl side chains have been synthesized. The conformational interconversion, molecular recognition and macroscopic self-assembly behaviour of oxatub[4]arene derivatives were investigated. The difference in side chains slightly changes the binding affinities, but results in different self-assembly morphologies at the solid state.