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AbstractThe emergence of calixarenes as versatile compounds in recent years marks a significant advancement in scientific research. In the area of analytical chemistry, calixarenes have garnered attention for their utility as selective chemosensors, enabling the sensitive and specific detection of metal ions through colorimetric and fluorimetric methods. Moreover, calixarenes have found applications in bioimaging, where they serve as effective probes for visualizing biological structures and processes with high resolution and sensitivity. Additionally, recent studies have explored the anticancer properties of calixarenes, unveiling their potential as therapeutic agents for cancer treatment. This comprehensive review explores recent advancements in calixarenes chemistry, emphasizing their significance in the colorimetric and fluorimetric detection of metal ions. Additionally, it highlights the mechanisms involved in chemosensor design, providing insights into the underlying principles driving their efficacy. Furthermore, the application of calixarenes in bioimaging, particularly for visualizing cellular structures and processes, is discussed, showing their potential in biomedical research and diagnostics. The anticancer activity of calixarenes and their derivatives is also explored, shedding light on their promising role as therapeutic agents. Through an extensive examination of recent literature, this review provides valuable insights into the multifaceted applications of calixarenes and offers perspectives for future research directions. [ABSTRACT FROM AUTHOR]

One pot sequential reactions of silica gel with tetrachlorosilane/triethylamine mixture and after with the conical upper rim tetraphosphorylated tetrahydroxy(thia)calixarenes yielded porous organo-inorganic sorbents modified by spatially ordered phosphonate, phosphinate or phosphine oxide groups capable of co-operative binding of metal cations. The grafting improves efficacy of europium(III) sorption by the silica gels. DFT calculations of the calixarene-Eu3+ complexes predict a calixarene flattened cone conformation with the coordination of Eu3+ cation to three of four P = O oxygen atoms and one of the aromatic systems. Adding three water molecules excludes completely cation–π interactions. [ABSTRACT FROM AUTHOR]

Nucleotides and their derivatives are vital biomarkers that play essential roles in biochemical reactions and influence processes of metabolism and anabolism. However, discriminating between various structurally similar nucleotides and their phosphate derivatives using convenient means still poses a challenge. Here, we designed a supramolecular fluorescence sensor array constructed with four different calixarenes loaded with dyes to discriminate between nucleotides and their phosphate derivatives. Based on the differences in the ability of calixarenes to recognise various nucleotides and nucleotide phosphates, a unique fluorescence response pattern is generated for each analyte. With the assistance of linear discriminant analysis, the discrimination of target analytes is effectively achieved. Subsequent assays involving various concentrations of nucleoside triphosphates and mixtures of nucleotide phosphates have also verified the potential of this sensor array based on calixarenes in the investigation of nucleotides. [ABSTRACT FROM AUTHOR]

Sequential treatment of silica gel with tetrachlorosilane and cone-shaped tetraphosphorylated tetrahydroxy(thia)calixarenes yielded porous organo-inorganic sorbents, the surface of which is covered by spatially ordered phosphonate, phosphinate and phosphine oxide groups capable of co-operative binding of metal cations. Sorption of europium(III) by the modified silica gels was studied. [ABSTRACT FROM AUTHOR]

Understanding the factors that have influence on the compactness of calixarene assemblies is important for choosing or designing molecules for specific function. In this paper, we comparatively investigated the packing performances of a series of amphiphilic calixarene assemblies by fluorescence anisotropy. Calixarene frameworks, the upper-rim decoration of head groups and the length of lower-rim alkyl chains of amphiphilic calixarenes all affect their packing compactness. This work has guiding significance for further application studies. [ABSTRACT FROM AUTHOR]

This study explores the impact of a small structural modification on a biomimetic receptor. The hosting structure is a calix[6]arene capped by a tetraaza core. Two receptors are compared: one (1) presents three anisole units while the other (2) has three phenols. The latter was obtained with an excellent yield by selective demethylation thanks to a supramolecular strategy. Complexation studies showed that [2.H]+ displays strong affinities for Cl−, NO3−, HSO4−, whereas [1.H]+ is non-responsive. The anions are embedded at the level of the small rim, hydrogen-bonded to the protonated cap and the phenol groups. Ternary complexes are obtained in the presence of ammoniums. Finally, [2.H]+ shows high affinity for small zwitterions presenting a carboxylate and an ammonium groups separated by one or two carbon atom(s), not three, due to multi-point recognition. These results open routes to the design of new receptors for a variety of anionic and zwitterionic guests. [ABSTRACT FROM AUTHOR]

Four multi-component complexes based on p-sulfonatocalix[4]arene anion, the methyltriphenylphosphonium cation, lanthanide ions (Gd(III)) and different ionic liquid-based cations (1-methyl-3-butylimidazolium, 1-methyl-3-octylimidazolium and 1,4-bis((3-methylimidazolidinyl)methyl)benzene) were synthesised and structurally characterised. Common bilayer arrangements are formed in the extended structures of all four complexes, though the bilayer thicknesses varies depending on the components involved. Molecular capsule formation is facilitated by the inclusion of methyltriphenylphosphonium, 1-methyl-3-butylimidazolium and 1,4-bis((3-methylimidazolidinyl)methyl)benzene cations, but not in the case of the 1-methyl-3-octylimidazolium cation. Molecular capsule size depends on the nature of the included guest cation, and methyltriphenylphosphonium cations fill compact spaces between calixarenes in these new bilayer arrays. [ABSTRACT FROM AUTHOR]

Two new derivatives of calix[4]arene bearing on the upper rim 2-thiopenyl (Thicalix) or 2-pyridyl (Pycalix) Schiff-base substituents have been synthesised and characterised by IR, NMR, MS, and single crystal X-ray diffraction techniques. It was shown that the interaction of Thicalix with the copper(II) and palladium(II) ions is accompanied by hydrolysis of the azomethine bonds with subsequent oxidation of the aminophenolic fragment to diquinone Diquin, while the reaction of potassium tetrachloropalladate(II) with Pycalix results in the formation of metallocompex with 1:2 calix[4]arene/Pd(II) ratio. The single crystal X-ray diffraction analysis of Thicalix (1), the complex [(PdCl2)2(Pycalix)] (2) and Diquin (3) revealed that all compounds form molecular crystals as a result of numerous supramolecular interactions involving C − H···O, C − H···Cl, and C − H···π contacts. For 1 and 3 such interactions result in formation of dimers, while in 2 the dodecanuclear palladium aggregates composed of six calix[4]arene moieties are formed. [ABSTRACT FROM AUTHOR]

Water soluble calixarenes are versatile mediators of protein assembly, including the fabrication of crystalline frameworks. Here, we report the X-ray crystal structure of cytochrome c (cytc) co-crystallised with two different calixarenes: phosphonato-calix[6]arene (pclx6) and sulfonato-calix[8]arene (sclx8). Each calixarene type acts as an independent molecular glue that mediates cytc dimers within the crystal. The calixarene-mediated dimers combine to yield chains of cytc-sclx8-cytc-pclx6-pclx6 repeating units. These supramolecular copolymer units pack together, via a protein-protein interface, to yield a porous dendrite-like assembly. Interestingly, the tri-component framework has features in common with previously reported structures of cytc in complex with pclx6 or sclx8. Known protein-calixarene 'building blocks' combine in novel ways to yield the tri-component assembly, highlighting the versatility of calixarene molecular glues in protein crystal engineering. [ABSTRACT FROM AUTHOR]

We present the synthesis and structure-activity relationships of sulfonatocalix[4]arene hosts bearing novel substitutions. The calix[4]arenes are modified on the upper rim at either one or two of the phenolic units, where the dual modifications are introduced regioselectively on neighbouring or opposing phenols. The calix[4]arenes are mono- or di-functionalised with nitro or formyl groups, with the remaining upper-rim sites in all cases occupied by sulphonates. Equilibrium association constants were determined between each host and the guests nicotine, nornicotine, and cotinine. Indicator displacement-based binding studies show that nicotine binds most strongly to the different members of the library followed by nornicotine, whereas cotinine displays weak to no binding. NMR titrations were carried out with nicotine and show different host-guest interaction geometries for the formyl-calix[4]arenes versus the nitro-calix[4]arenes. [ABSTRACT FROM AUTHOR]

Interaction of the ready available monoformyl or diformyltetrahydroxycalixarenes with excess of diisopropylphosphite sodium salt gives isopropyl esters of tetrahydroxycalixarene methylenebisphosphonic acid or dimethylenebisphosphonic acid respectively with preparative yields. α-Hydroxymethylenephosphonates and phosphonyl quinon methids are formed as intermediates in the reaction. The obtained esters converts with quantitative yields into corresponding free acids by sequential treatment with trimethylbromosilane and methanol. The tetrahydroxycalixarene methylenebisphosphonic acids exist in the cone-shaped conformation and selectively form stable host-guest supramolecular complexes with aminoacids. [ABSTRACT FROM AUTHOR]

Two multi-component crystal structures comprising a carboxylic acid-functionalized imidazolium zwitterion, a p-sulfonatocalix[4]arene anion and aquated metal ion (Na+ or Y3+) with or without an auxiliary component (the 3-methoxyphenyl-triphenylphosphonium cation) are reported. The carboxylic acid-functionalized imidazolium ion binds either as a monodentate or a bidentate ligand depending on the nature of the metal ions, and a bi-layer arrangement prevails in the extended structure regardless of the type of metal ion employed or presence/lack of auxiliary component. [ABSTRACT FROM AUTHOR]

Structural studies on p-sulfonatocalix[4]arene coordination compounds involving diverse metal ions with respect to their size and charge, caesium(I), copper(II) and neodymium(III) are reported. The metal coordination-driven self-assembly forms metallosupramolecules, either as a two-dimensional (2 D) or a three-dimensional (3D) network while retaining the commonly established bilayer array for p-sulfonatocalix[4]arene. The complex (Cs5-p-sulfonatocalix[4]arene-H+)·6H2O has five crystallographically independent caesium(I) ions with high coordination numbers. In the divalent complex {[Cu3(H2O)12-2(p-sulfonatocalix[4]arene)]2-}·2([Cu(H2O)5])2+·2NO3-·7H2O, two different copper(II) coordination environments are present, one with octahedral stereochemistry while bridging two opposing calixarenes with the other having a square pyramidal geometry involving one sulfonate group. Eight-coordinate neodymium(III) metal ions prevail in Nd0.25(H2O)1.25(p-sulfonatocalix[4]arene + H+)0.25, involving four sulfonate groups from four different calixarenes. [ABSTRACT FROM AUTHOR]

In this study, we first used water-soluble iron oxide nanoparticles for Candida rugosa lipase immobilisation. Moreover, two new complexation phenomena of the prepared water-soluble Fe3O4 nanoparticles with an enzyme might address interesting results in terms of enzyme activity and stability in typical enzymatic reactions. The catalytic activity on pH and temperature dependence, and reusability of the immobilised lipases (p-SCX4-NP-E and p-SCX8-NP-E) were also investigated with the hydrolysis reaction of p-nitrophenyl palmitate (p-NPP). The results show that the highest catalytic affinities for p-SCX4-NP-E and p-SCX8-NP-E were obtained at pH 5.0 and pH 7.0, respectively. [ABSTRACT FROM AUTHOR]

A new bimodal triazole-bridged pyrene-appended calix[4]arene 2g has been synthesised and characterised and complexation studies showed that the binding of Cd2+ and Zn2+ occurs as demonstrated by enhanced monomer and declining excimer emission fluorescence spectral changes. With several other metal ions, quenching of both monomer and excimer emissions occurred. The observed monomer formation in the fluorescence spectra seen with Zn2+ and Cd2+ is possibly linked not just to the diminished parallel orientations of the pyrene rings but with the magnitude of the resulting HOMO-LUMO gaps and other parameters measured by DFT calculations. [ABSTRACT FROM AUTHOR]

The spontaneous preparation of well-defined functional nanoscale systems is very important, since this formulation process requires additional resources, external supply of energy and time. One of the widely used methods of their spontaneous formation is the self-assembling process using of various calixarene building blocks. The relative simplicity of the synthesis of initial calixarene skeleton, the possibility of modifying both of its rims with a wide range of chemical groups, and the presence of a hydrophobic aromatic cavity allow the use of calixarenes to create both individual and mixed aggregates. This article summarises different types of self-assembled calixarene-based amphiphilic aggregates with useful properties. Potential applications of these aggregates in biological nanotechnology are also described. [ABSTRACT FROM AUTHOR]

Selective molecular recognition is of primary importance for applications such as sensing and separation of chemicals. This work describes the host-guest and crystallisation properties of a penta-carbamated calix[6]arene designed as a molecular container with a H-donating recognition group directed towards the heart of the cavity. As demonstrated by NMR spectroscopy and X-ray diffraction studies, this macrocyclic receptor can selectively recognise small H-bond acceptors through one or two hydrogen bonds, the guests nesting inside the polyaromatic cavity surrounded by eleven bulky tert-butyl groups. [ABSTRACT FROM AUTHOR]

This article is based on a review of the literature and our own experience with toxicological molecules. We explain the nature of calix[n]arenes and as their recognized properties are used to detect compounds of toxicological interest, mainly the most important pesticide families such as organophosphorated, organochlorine compounds, pyrethroid insecticides, carbamate fungicides, and herbicides, using different techniques. In addition, we show the role of the macrocycle and its interactions, and the advantage of using this type of compound for improving conventional techniques, where the phenomenon of recognition is very important, such as chromatography, solid-phased extraction, and the development of specific sensors, among others and Even we also show the use of this macrocycle for detoxication procedures in vivo. In this way, we display as the multiple possibilities of functionalization of the calix[n]arenes makes these versatile molecules in the phenomena of specific recognition. Finally, This review highlights the main analytical methods reported in the literature for determination of plaguicides by host–guest interaction with calixarenes. In this way, among the available analytical tools, chromatographic, and electrochemical-based methods are the most used techniques for the detection and to quantify plaguicides using calixarenes. [ABSTRACT FROM AUTHOR]

Heavy-metal pollution is a foremost concern, as excessive heavy metals produce environmental contamination, and the accumulative effects of heavy metals pose a major hazard to human health. There is an urgent need for a fast, sensitive and effective method for detecting heavy metal cations in the environment. In recent years, using Quartz Crystal Microbalance (QCM) technique, significant progress was achieved in quantitative analysis by providing a new approach for determination of chemical content analysis. The objective aim of this review is to assess the research development of QCM applications in detection of heavy metal cations in natural water (or aqueous solution) and reflect the challenges and forthcoming point of view for QCM-based sensors for heavy-metal ions. A brief outline about the basic measurement methodologies and analytical techniques is given. To illustrate applications of the QCM techniques, the influence of the structural transformation resulting from polymer, macrocyclic 'calixarenes' and nanostructural coating on sensation will be discussed. Lastly, we summarise fields of applications and future forecast for the utilisation of functionalised QCM surface as a chemical sensor to study the interaction of heavy metal ions with calixarenes. [ABSTRACT FROM AUTHOR]

Calixarenes are known to form host–guest complexes and supramolecular nanoassemblies with well-defined architectures. However, the use of these materials in conjunction with drug moieties is still under explored. One reason is the insufficient biocompatibility studies. Our present study represents a systematic in vitro investigation of the cytotoxicity associated with C-methylresorcin[4]arene, C-methylpyrogallol[4]arene, p-phosphonated calix[8]arene and a metal-seamed calixarene–copper(II) complex, using human HEK293 and rat C6G cell lines and two different cell viability assays (MTT and CellTiter-Glo) to avoid species-biased results. All compounds showed low to moderate toxicity. The trend in the CC50 values indicated that the suppression of the coordination ability and the presence of phosphonate groups decrease the overall cytotoxicity of the compounds. The results of this study not only establish calixarenes and their immediate families as potential drug carriers and drug modifiers, but also reveal a pathway for fine-tuning their toxicological behaviour by appropriate chemical modification. [ABSTRACT FROM AUTHOR]

Phosphorus-containing inherently chiral calix[4]arenes as well as calix[4]arenes substituted with phosphinoferrocene chiral groups at the lower rim are described. Stereoselective synthesis, structure, and catalytic properties of the chiral calixarenes are discussed. [ABSTRACT FROM AUTHOR]

The present work deals with the theoretical study of conformational equilibrium of calix[4]tetrolarenes (1,2,3 trimethoxy substituted calix[4]arene) in gaseous and solvation phases. A total of 64 calculations (four conformations at eight level of theories) were performed using Density Functional Theory (DFT) functionals viz. wB97XD, B97D, B3LYP, CAM-B3LYP with diffused (6-31 + G(d)) and non-diffused basis sets (6-31G(d)). It has been found that the conformational profile of calix[4]tetrolarene changes from cone to 1,3-Alternate upon incorporating - OMe group. The B97D and wB97XD functionals gave the most accurate result having rmsd value ~0.73Å followed by B3LYP and CAM-B3LYP > 0.78Å. Furthermore, NBO calculations demonstrated that reduction in charges at lower rim oxygens reduces the chances of hydrogen bonding. Moreover, global reactivity parameters and molecular dynamics also complement the observed trend. Owing to the methoxy substitutions, anion binding study of these new molecules indicates towards the promising capability to bind Cl− and F− ions. [ABSTRACT FROM AUTHOR]

Preferential crystallization from a mixture of C-methylresorcin[4]arene (RsC1) and calix[6]arene (Calix6) in the presence of different bases has been investigated. In the presence of pyridine, a boat conformer of RsC1 crystallizes, whereas in the presence of triethylamine, Calix6 crystallizes in a symmetrically distorted conformation. The packing arrangements of the macrocycles show discrete solvent pockets for calixarenes and channels for resorcinarenes. [ABSTRACT FROM AUTHOR]

Three novel calix[4]arene molecule-based 1,8 naphthalimide fluoroionophore for the selective determination of kesoxim-methyl were synthesized and used in pesticide binding studies. The possible interaction between pesticides and fluorescent calix[4]arene molecules was monitored by UV/Vis absorption and fluorescence spectroscopy. When compared the studied pesticides, kesoxim-methyl was strongly quenched the fluorescence intensity of upper rim-modified calix[4]arene. UV and fluorescence titration experiments were also studied to determine both the quenching mechanism and stoichiometric ratio consisted in complex formation. Furthermore, pesticide release experiments were also performed with a fertilizing agent as urea by using fluorescence spectroscopy technique. [ABSTRACT FROM AUTHOR]

Amphiphilic PEGylated calix[5]arenes 1 and 2 were obtained in one step from the parent p-tert-butylcalix[5]arene and p-methylcalix[5]arene. Very low critical micellar concentrations (0.5 and 4.5 μM for 1 and 2 respectively) were determined by the Rose Bengal micellization method. Aggregation features were studied by means of 1H and DOSY NMR as well as by AFM. Release of Rose Bengal from the micellar environment was accomplished by increasing the temperature. [ABSTRACT FROM AUTHOR]

25,27-(Dipropylmorpholinoacetamido)-26,28-dihydroxycalix[4]arene was used as a chemical sensor material in this work. The calix[4]arene LB thin films were prepared onto a gold-coated glass and quartz glass substrates to fabricate a thin film chemical sensor element. Atomic Force Microscopy (AFM) and Surface Plasmon Resonance (SPR) techniques were used to characterize all the calix[4]arene LB thin films. The film thickness and the refractive index of thin films can be evaluated with the fitted experimental SPR datas. The refractive index and the thickness per monolayer of LB films were determined as a 1.58 ± 0.04 and 1.27 ± 0.09 nm, respectively. The calix[4]arene LB thin film chemical sensor element was exposed to dichloromethane, chloroform, benzene and toluene vapors. The SPR kinetic measurements displayed that, the photodetector response change, ΔIrf for saturated dichloromethane vapor is much larger than the other vapors with the ΔIrf value of 48 au and the diffusion coefficient value of 5.1 × 10−16 cm2s−1. Swelling process was analyzed by well known Fick's Equations. In this approach diffusion coefficients () for swelling were conformed to the square root of time and were correlated with the volatile organic compounds. Our results showed that calix[4]arene thin film has a highly selective with a large response to dichloromethane vapor. [ABSTRACT FROM AUTHOR]

Stepwise recovery of silver(I), palladium(II) and platinum(IV) with suitable calix[4]arene extractants was carried out by investigating the extraction and stripping process using a droplet-based microreactor system. The highest percentages of silver, palladium (100%) and platinum ion (37.2%) were extracted from a real waste only within 4.00s using a microreactor system compared with 24 and 72 h to reach extraction equilibrium in a batch method. Fourier transform infrared spectroscopy studies revealed a very good relation in peak shifts on the metal complexation with calix[4]arene derivatives after extraction and stripping. The droplet-based microreactor system emerges as an effective tool to be applied in metal recovery. [ABSTRACT FROM AUTHOR]

Calix[4]arene dihydroxyphosphonic acid has been demonstrated to possess an interesting range of biological properties, including atypical anti-cancer activity. The robustness of calix[4]arene dihydroxyphosphonic acid and its ubiquitous dimeric motif offers perspectives for pre-defined solid state complexation with small molecules. In the current article we describe co-crystals (organic salts) of calix[4]arene dihydroxyphosphonic acid with four nucleic base cations: adeninium, cytosinium, guaninium and uracilium. A number of characteristic interactions between the components in the four co-crystals are pointed out also using the Hirshfeld surface analysis. All the four co-crystals are based on layers of calix[4]arene dimers, alternating with layers of nucleic acid molecules. Two of the reported crystal structures (cytosinium and guaninium) are 1D channel-type structures, while the two others (adeninium and uracilium) represent 2D channel-type structures. In three out of four reported structures, interactions between the cations of nucleic bases are present generating 1D chains of cations. A constant motif is that the nucleic base is present in a type of cavity formed by one aromatic ring and a phosphonic acid moiety. [ABSTRACT FROM AUTHOR]

An organic material, p-tert-butyltetrasulfonylcalix[4]arene, self-assembles via hydrogen bonding to form a diamondoid supramolecular network. Possessing discrete, zero-dimensional (0D) microcavities, the thiacalixarene derivative adsorbs CO2 at high pressures. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are extremely versatile ligands that are capable of supporting the formation of a wide variety of polymetallic clusters of paramagnetic metal ions. One can exert influence over cluster formation through alteration of the calix[4]arene framework and subsequent ‘expansion’ of the lower-rim polyphenolic binding site. The present contribution investigates cluster formation with calix[4]arenes substituted at all four methylene bridge positions with furan moieties. Two known cluster types have been isolated with this ligand, the structures of which lend insight into factors that may ultimately preclude the formation of mixed-metal species. [ABSTRACT FROM AUTHOR]

The solid state structure of the co-crystal between proximal p-tert-butylcalix[4]dihydroquinone, ethylacetate and 4,4’-bipyridine shows an interesting interplay of H-bond and van der Waals interactions that allow to rationalise the assembly possibilities of the calixarene compound under study. [ABSTRACT FROM AUTHOR]

The ‘one-pot’ reaction of 2-hydroxy-3,5-di-tert-butylsalicylaldehyde with in situ generated ‘amino calixarene’ (from {Mo[(2-NC6H4)2CH2CH2]Cl2(DME)}, KOtBu and p-tert-butylcalix[4]areneH4LH4) afforded, after work-up, the heterobimetallic salt K(NCMe)2[Mo(NCMe)(OEt)(2-C6H4CH2CH2C6H4NH2-2)L] (1∙2MeCN). By constrast, use of the ‘amino calixarene’ [Mo(NCMe)(2-C6H4CH2CH2C6H4NH2-2)L] afforded the potassium/ethoxide-free complex [Mo(NCMe)(2-C6H4CH2CH2C6H4N-2-CHC6H2-2′-(OH)-3′,5′-tBu)L] (2∙2MeCN). Reaction of the ‘amino calixarene’ (two equivalents) with the dialdehyde [1,3-(CHO)2-5-MeC6H3OH-2] led, following work-up, to the isolation of the cation-anion pair [C46H42N4O2]2+[Mo6O19]2−·C2H3N (3∙MeCN). The molecular structures of 1·2MeCN, 2·2MeCN and 3·MeCN are reported, for which it was necessary to use synchrotron radiation for data collection. Complex 1 contains an eliptical calixarene conformation as a result of π-interactions between the K+ and the arene groups and a distorted O5N octahedral geometry at the molybdenum centre, whereas in ‘K+/ethoxide-free’ 2, the calixarene retains the cone conformation and the metal possesses a distorted octahedral O4N2 coordination environment. In 3, a protonated macrocyclic cation, formed via hydrolysis, has weak intermolecular interactions with the polyoxomolybdate anion. [ABSTRACT FROM AUTHOR]

The dihydrazide calix[4]arene was immobilized onto sporopollenin in order to encapsulate Candida rugosa lipase (CRL) via sol-gel entrapment. The kinetic resolution of the new encapsulated lipase was investigated for enantioselective hydrolysis of racemic naproxen methyl ester and 2-phenoxypropionic acid methyl ester. The results demonstrated that the activity and enantioselectivity of the lipase were improved when the lipase was encapsulated in the presence of calix[4]arene-immobilized sporopollenin. The encapsulated lipase showed an excellent rate of enantioselectivity against the (R/S)-naproxen methyl and (R/S)-2-phenoxypropionic acid methyl esters, with E = 350 and 295, respectively, compared to the free enzyme. [ABSTRACT FROM AUTHOR]

An organic material, p-tert-butyltetrasulfonylcalix[4]arene, self-assembles via hydrogen bonding to form a diamondoid supramolecular network. Possessing discrete, zero-dimensional (0D) microcavities, the thiacalixarene derivative adsorbs CO2 at high pressures. [ABSTRACT FROM AUTHOR]

Calix[4]arenes are extremely versatile ligands that are capable of supporting the formation of a wide variety of polymetallic clusters of paramagnetic metal ions. One can exert influence over cluster formation through alteration of the calix[4]arene framework and subsequent ‘expansion’ of the lower-rim polyphenolic binding site. The present contribution investigates cluster formation with calix[4]arenes substituted at all four methylene bridge positions with furan moieties. Two known cluster types have been isolated with this ligand, the structures of which lend insight into factors that may ultimately preclude the formation of mixed-metal species. [ABSTRACT FROM AUTHOR]

The ‘one-pot’ reaction of 2-hydroxy-3,5-di-tert-butylsalicylaldehyde with in situ generated ‘amino calixarene’ (from {Mo[(2-NC6H4)2CH2CH2]Cl2(DME)}, KOtBu and p-tert-butylcalix[4]areneH4LH4) afforded, after work-up, the heterobimetallic salt K(NCMe)2[Mo(NCMe)(OEt)(2-C6H4CH2CH2C6H4NH2-2)L] (1∙2MeCN). By constrast, use of the ‘amino calixarene’ [Mo(NCMe)(2-C6H4CH2CH2C6H4NH2-2)L] afforded the potassium/ethoxide-free complex [Mo(NCMe)(2-C6H4CH2CH2C6H4N-2-CHC6H2-2′-(OH)-3′,5′-tBu)L] (2∙2MeCN). Reaction of the ‘amino calixarene’ (two equivalents) with the dialdehyde [1,3-(CHO)2-5-MeC6H3OH-2] led, following work-up, to the isolation of the cation-anion pair [C46H42N4O2]2+[Mo6O19]2−·C2H3N (3∙MeCN). The molecular structures of 1·2MeCN, 2·2MeCN and 3·MeCN are reported, for which it was necessary to use synchrotron radiation for data collection. Complex 1 contains an eliptical calixarene conformation as a result of π-interactions between the K+ and the arene groups and a distorted O5N octahedral geometry at the molybdenum centre, whereas in ‘K+/ethoxide-free’ 2, the calixarene retains the cone conformation and the metal possesses a distorted octahedral O4N2 coordination environment. In 3, a protonated macrocyclic cation, formed via hydrolysis, has weak intermolecular interactions with the polyoxomolybdate anion. [ABSTRACT FROM AUTHOR]

The solid state structure of the co-crystal between proximal p-tert-butylcalix[4]dihydroquinone, ethylacetate and 4,4’-bipyridine shows an interesting interplay of H-bond and van der Waals interactions that allow to rationalise the assembly possibilities of the calixarene compound under study. [ABSTRACT FROM AUTHOR]

This paper reports planar chromatographic behavior and multivariate characterization of three types of macrocyclic compounds: cyclodextrins, calixarenes and macrocyclic antibiotics. Additionally two non-macrocyclic chemicals (estriol and pyrene) were analyzed as the reference retention markers. Target compounds were chromatographed using normal and reversed-phase systems and involving mono as well as binary water-organic liquids mobile phases based on methanol, ethanol and acetonitrile. Non-forced flow TLC/HPTLC elution was performed under isothermal (elevated temperature = 303 K) and mobile phase vapor saturated conditions using 10 cm long glass plates positioned vertically inside temperature controlled Dewar type chambers. It is hoped that presented retention data, which were collected for the whole range of binary mobile phases compositions (0-100%) may be useful for designing of hybrid active layers for extraction, separation and detection systems involving host-guest interactions. Retention profiles were inspected using multivariate statistics (principal component analysis, PCA). Based on reported data various extraction and separation systems can be created where weak or strong interactions of macrocycles with chromatographic stationary phases or given micro device active supports should be expected. Particularly, studied macrocycles can be applied as selective additives for solid phase adsorption (SPE, SPME), microfluidic paper devices (μPAD) as well as micro-total analytical systems (μTAS), where bars formed active layers are fabricated. [ABSTRACT FROM AUTHOR]

New thermoresponsive star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx) and poly(2-ethyl-2-oxazoline) (PEtOx) with arm grafting to upper rim of calix [8]arene core were synthesized and studied in aqueous solutions by light scattering and turbidimetry methods. The solution behavior was compared with that for polyoxazoline stars with varying positions of arm grafting, i.e., to lower rim of calix[8]arene. The observed growth of the phase separation temperature for PiPrOx as compared to PEtOx is explained by different dehydration temperatures of ethyl- and isopropyloxazoline units. The phase separation temperatures decrease after the changeover from lower rim grafting to upper rim one due to varying configurations of calix[8]arene. [ABSTRACT FROM AUTHOR]

A novel calixarene-based diimine, 1,3-bis(pyren-1-yliminomethyl)calix[4]arene (5), serves as a turn-on-type fluorescent sensor, which selectively detects Hg2+in THF/H2O (99:1, v/v) in the presence of various other metal ions. Such selectivity is not seen with half salen1derived from salicylaldehyde and 1-aminopyrene.1H NMR analysis reveals that it is a chemodosimetric sensor based on its hydrolysis mediated by Hg2+to release 1-aminopyrene molecules as fluorescent chromophores. [ABSTRACT FROM PUBLISHER]

Triflate Ester of Calix[n]arene (n = 4, 6, 8) (TEC[n] (n = 4, 6, 8)) were synthesized based on a new synthetic route, then TEC[n] (n = 4, 6, 8) were further modified by reacting with low molecular weight Chitosan (CS) to get three kinds of new Calix[n]arene-Chitosan polymers (n = 4, 6, 8) (C[n]CSP (n = 4, 6, 8)) through Buchwald-Hartwig cross coupling reaction. The structures of the polymers were characterized by FT-IR, SEM, Elemental analyzer and 13C SSNMR. And the results found that Chitosan was successfully introduced to Calix[n]arene (n = 4, 6, 8) (C[n] (n = 4, 6, 8)) without any long-chain alkyl between Chitosan and Calixarene. These new polymers are partially substituted calixarene. The substitute degree of C[4]CSP, C[6]CSP and C[8]CSP is 17.75%, 21.08% and 54.53% respectively. And the optimal preparation conditions were discussed and the results were listed as following, molar ratio (1:2), catalyst (0.05 mmol), solvent ratio (1:1.5 (10 mL•1.0 mmol−1)) and reaction time (5h). [ABSTRACT FROM AUTHOR]

The complex characteristics ofp-sulfonated calix[n]arene and colchicine were examined using various techniques. Cyclic voltammetry indicated that the structural matching and electrostatic interactions were the dominant stabilizing factors for the host–guest complexes. The method showed a long linear voltammetric range forp-sulfonated calix[4]arene from 1 × 10−8to 1 × 10−6 mol L−1with a detection limit of 3 × 10−9 mol L−1. Ultraviolet absorption spectroscopy confirmed that a 1:1 ratio complex was formed. Molecular mechanics showed that the benzene ring of colchicine entered thep-sulfonated calix[4]arene cavity. The solubility of colchicine increased with thep-sulfonated calix[4]arene concentration 50-fold from 0.13 to 6.4 mol L−1. The simulation of cell membrane permeability indicated that colchicine was released from the colchicine-p-sulfonated calix[4]arene complex and entered the hydrophobic micelles. These results show thatp-sulfonated calix[4]arene is suitable as a drug carrier for colchicine. This work has expanded applications of drug loading, transport, and targeted release for the treatment of gout. [ABSTRACT FROM PUBLISHER]

In this study, a tetramine-substituted calix[4]arene derivative, which was synthesised from calix[4]arene by treatment with dimethylamine in one step via Mannich reaction, was used to fabricate a new calix[4]arene-embedded polysulphone membrane (calix@membrane). Its structure and surface morphology were determined using thermogravimetric analysis and scanning electron microscopy, and elemental analysis techniques. Moreover, a Donnan dialysis system was employed to investigate Cr(VI) transport efficacy of calix@membrane at different pH values. Results showed that calix@membrane represented a promising transport capability for HCr2O7−due to their efficient complexation behaviour. [ABSTRACT FROM PUBLISHER]

A novel bis-naphthalimidocalix[4]arene-Cu(II) supramolecular complex has been observed to provide an efficient recognition system for CN−ions in aqueous medium. The binding stoichiometry of bis-naphthalimidocalix[4]arene and copper ion has been found to be 1:1 while that for bis-naphthalimidocalix[4]arene-Cu(II) and cyanide ion it has been determined to be 1:2. [ABSTRACT FROM AUTHOR]

The dimeric assembly of 5,11,17,23-tetrabromo-25,26,27,28-tetrahydroxy thiacalix[4]arene (2) was constructed with several interesting noncovalent interactions such as halogen bonding, sulfur···sulfur (S···S), C=O···π, and hydrogen bonding which were also supported by DFT calculations. In addition, we studied the conformational preferences of2using variable temperature NMR experiments. The results revealed that the compound exists in various conformations in a solution state and in a partial cone conformation in a solid state. [ABSTRACT FROM PUBLISHER]

Calix[4]arene-based cation receptor 1 has been synthesised by following a multi-step synthetic procedure. The fluorescence properties of 1 upon the addition of various metal ions were investigated by fluorescence spectroscopy. As a result, it was revealed that 1 displayed dramatic quenching effect upon the exposure to Cs+. In contrast, no significant quenching effects were observed upon the addition of other metal ions such as Li+, Na+, K+, Mg2+, Ca2+, Sr2+, Ag+, Zn2+and Ni2+. Compound 1 was also found by Job plot to form a 1:1 complex with Cs+. In addition, we also prepared 1-embedded electrospun nanofibrous film (NF-1) as an adsorbent for Cs+. NF-1 is proved to adsorb Cs+effectively from an aqueous solution, indicating that it would be usefully utilised as an adsorbent to remove Cs+. [ABSTRACT FROM PUBLISHER]

Tetrathiafulvalenes (TTFs)1, redox-controllable electron-rich heterocycles, were employed as building blocks for the construction of molecular receptors and switchable macrocycles. Redox-active calixarene-based molecular receptors2with various substituents R1on the tetrathiafulvalene groups and rigid or flexible attachment of TTF units to the backbone have been prepared using modular construction approach. The addition of planar electron-deficient guests to receptor solutions leads to formation of deeply-colored charge-transfer complexes with high binding constants reaching 2.5 × 105 M−1. TTF substituents display the strong influence on the binding constants and charge transfer intensity. By the synthesis of macrocyclic tetrathiafulvalene-azobenzene (TTF-AB) conjugates3, we have shown the first example of photochemically controlled macrocyclization, in which the formation of smaller 1 + 1 and larger 2 + 2 cyclization products can be modulated by photoisomerization of one of the reactants. The oxidation potential of the small, structurally rigid, TTF-AB macrocycle is found to depend on the conformation of the AB moiety. [ABSTRACT FROM PUBLISHER]

Triple-negative breast cancer (TNBC) is a heterogeneous and clinically aggressive disease with no approved targeted therapy. Curcumin has shown therapeutic potential against TNBC, but it shows low bioavailability and low efficacy when administered as a free drug. Here we describe a novel vehicle forin vivodelivery of curcumin based on the phosphorylated calixarene POCA4C6. Curcumin-loaded POCA4C6 micelles (CPM) were prepared using the thin-film method and they showed a unilamellar structure with an average particle size of 3.86 nm. The micelles showed high curcumin encapsulation efficiency and loading was based on liquid chromatography-tandem mass spectrometry. Studies with cell cultures suggest that CPM can sustainably release curcumin in a pH-dependent manner. The micelles efficiently inhibited proliferation, invasion, migration and tumor spheroid formation by BT-549 human breast cancer cells. These effects involved increased apoptosis and reduced levels of nuclear β-catenin and androgen receptor. After injection into tumor xenografts, CPM persisted in the tumor tissue and efficiently inhibited tumor growth without causing obvious systemic toxicity. CPM also significantly reduced levels of CD44+/CD133+breast cancer stem cells. Our results highlight the potential of CPM as an effective therapy against TNBC. [ABSTRACT FROM AUTHOR]

The article reviews the literature on the possibility of application of the calixarene-based compounds for selective separation of toxic heavy metals from aqueous solutions by the solvent extraction and transport across liquid membranes. The specific three-dimensional structure of calixarenes and their derivatives, simple and low-cost synthesis, and ease of chemical transformation qualify these compounds for the role of selective chemical extractants of toxic heavy metal ions present in industrial wastewater. This article analyses the influence of various process factors, with the greatest emphasis on the structure of the extractants/carriers, on efficient separation of heavy metal ions, primarily those most commonly found in galvanic wastewater. [ABSTRACT FROM PUBLISHER]

This article demonstrates the synthesis of new water soluble calix[4]arenes (8) based catalyst and application in one-pot, three component Mannich reactions to catalyze reaction between aromatic ketones/aldehyde and amines to acquire β-Amino carbonyl compounds in appreciable yields at room temperature in aqueous media. [ABSTRACT FROM AUTHOR]