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A series of cationic p-tert-butylcalix[4]arenes, with side-arms that are functionalized with imidazolium groups, have been synthesized in good yields. The parent tetrahydroxy para-t-butyl-calix[4]arene was dialkylated at the phenolic hydrogen atoms using α,ω-dibromo-alkanes to yield bis(mono-brominated) alkoxy-chains of variable length. The brominated side-arms in these compounds were then further alkylated with substituted imidazoles (N-methylimidazole, N-(2,4,6-trimethyl-phenyl)imidazole, or N-(2,6-di-isopropylphenyl)imidazole) to yield a series of dicationic calixarenes with two imidazolium groups tethered, via different numbers of methylene spacers (n = 2–4), to the calixarene moiety. Related tetracationic compounds, which contain four imidazolium units linked to the calix[4]arene backbone, were also prepared. In all of these compounds, the NMR data show that the calixarenes adopted a cone configuration. All molecules were characterized by NMR spectroscopy and by MS studies. Single crystal X-ray diffraction studies were attempted on many mono-crystals of these cations, but significant disorder problems, partly caused by occluded solvent in the lattice, and lack of crystallinity resulting from partial solvent loss, precluded the good resolution of most X-ray structures. Eventually, good structural data were obtained from an unusually disordered single crystal of 5a, (1,3)-Cone-5,11,17,23-tetra-t-butyl-25,27-di-hydroxy-26,28-di-[2-(N-2,6-diisopropylphenyl-imidazolium)ethoxy]calix[4]arene dibromide and its presumed structure was confirmed. The structure revealed the presence of H-bonded interactions and some evidence of π-stacking. Some of these imidazolium salts were reacted with nickelocene to form the nickel N-heterocyclic carbene (NHC) complexes 7a–7d. A bis-carbene nickel complex 8 was also isolated and its structure was established by single crystal X-ray diffraction studies. The structure was disordered and not of high quality, but the structural data corroborated the spectroscopic data. [ABSTRACT FROM AUTHOR]

This study aims to investigate the adsorption characteristics of tetracycline from polluted waters using C-4- hydroxyphenylcalix[4]resorcinarene as an adsorbent. The adsorptive efficiency of C-4-hydroxyphenylcalix[4]resorcinarene is optimized by adjusting various operational parameters such as the adsorbent dosage, the pH, the contact time, the temperature, and the initial adsorbate concentration. The most efficient remediation is 96% at 10.0 mg/L tetracycline as the initial concentration, 0.05 mg/L C-4-hydroxyphenylcalix[4]resorcinarene, a contact time of 30 min, pH 5.6, and ambient temperature. The adsorption ability of C-4-hydroxyphenylcalix[4]resorcinarene toward tetracycline is also investigated in water with different characteristics, including solutions with and without the addition of background salts. The results show that C-4-hydroxyphenylcalix[4]resorcinarene can effectively remove tetracycline from aqueous solutions with an adsorption capacity of ca. 36.9 mg/g. The study also finds that the removal process followed pseudo-second order kinetics and Freundlich isotherm models. Moreover, the adsorption is spontaneous and exothermic, suggesting a thermodynamically favorable chemisorption process. In addition, the optimized method is successfully applied to remove tetracycline from various real natural water systems. [ABSTRACT FROM AUTHOR]

Controlled protein assembly and crystallization is necessary as a means of generating diffraction‐quality crystals as well as providing a basis for new types of biomaterials. Water‐soluble calixarenes are useful mediators of protein crystallization. Recently, it was demonstrated that Ralstonia solanacearum lectin (RSL) co‐crystallizes with anionic sulfonato‐calix[8]arene (sclx8) in three space groups. Two of these co‐crystals only grow at pH ≤ 4 where the protein is cationic, and the crystal packing is dominated by the calixarene. This paper describes a fourth RSL–sclx8 co‐crystal, which was discovered while working with a cation‐enriched mutant. Crystal form IV grows at high ionic strength in the pH range 5–6. While possessing some features in common with the previous forms, the new structure reveals alternative calixarene binding modes. The occurrence of C2‐symmetric assemblies, with the calixarene at special positions, appears to be an important result for framework fabrication. Questions arise regarding crystal screening and exhaustive searching for polymorphs. [ABSTRACT FROM AUTHOR]

The effect of the platinum content (3–10 wt %) in the Pt/SnO2(Sb)-based working-electrode material on the properties (sensitivity, high-speed performance, recovery time) of solid-state potentiometric gas sensors for hydrogen and carbon monoxide including their simultaneous presence in air is studied. Sensors with 5% Pt demonstrate the best characteristics: the efficient carbon-monoxide detection for its concentration from 0.01 to 1 vol %; no effect of hydrogen present in the CO + air mixture in concentrations comparable with the CO concentration; the shortest relaxation time (~30 s at 1% CO). [ABSTRACT FROM AUTHOR]

Macrocyclic arenes including calixarenes, resorcinarenes, cyclotriveratrylene, pillararenes and so on have emerged as highly attractive synthetic macrocyclic hosts due to their unique structures, facile functionalization, and broad range of applications. In recent years, there has been growing interest in the development of novel macrocyclic arenes composed of various aromatic building blocks bridged by methylene groups, which have found applications in various research areas. Consequently, the development of novel macrocyclic arenes has become a frontier and hot topic in supramolecular and macrocyclic chemistry. In this review, we feature the recent advances in the synthesis and applications of novel macrocyclic arenes that have emerged in the last decade. The general synthetic strategies employed for these macrocyclic arenes are systematically summarized, and their wide applications in molecular recognition and assemblies, molecular machines, biomedical science and functional materials are highlighted. [ABSTRACT FROM AUTHOR]

The present work focuses on the study of the aggregation and complexing properties of calixarenes as potential DNA condensation agents for gene delivery. In the current study, 1,4-triazole derivatives of calix[4]arenes 7 and 8 containing monoammonium fragments were synthesized. The synthesized compound's structure was characterized by using various spectroscopic techniques (FTIR, HRESI MS, ¹H NMR and ¹³C NMR). The interactions between a series of calix[4]arene-containing aminotriazole groups (triazole-containing macrocycles with diethylenetriammonium fragments (3 and 4) and triazole-containing macrocycles with monoammonium fragments (7 and 8)) and calf thymus DNA were carried out via UV absorption, fluorescence spectroscopy, dynamic light scattering and zeta potential measurements. The role of the binding forces of calixarene–DNA complexes was analyzed. Photophysical and morphological studies revealed the interaction of the calixarenes 3, 4 and 8 with ct-DNA, which transformed the fibrous structure of ct-DNA to completely condensed compact structures that are 50 nm in diameter. The cytotoxic properties of calixarenes 3, 4, 7 and 8 against cancerous cells (MCF7, PC-3) as well as a healthy cell line (HSF) were investigated. Compound 4 was found to have the highest toxic effect on MCF7 breast adenocarcinoma (IC50 3.3 μM). [ABSTRACT FROM AUTHOR]

We have developed a new strategy for the preparation of a light‐responsive ionic liquid crystal (LC) that shows photo‐switchable proton conduction. The ionic LC consists of a bowl‐shaped calix[4]arene core ionically functionalized with azobenzene moieties. The non‐covalent architectures were obtained by the formation of ionic salts between the carboxylic acid group of an azo‐derivative and the terminal amine groups of a calixarene core. The presence of ionic salts results in a hierarchical self‐assembly process that extends to the formation of a nanostructured lamellar LC arrangement (smectic A phase). In this LC phase, the ionic LC calixarene is able to display proton conductive properties, since the ionic nanosegregated areas (formed by the ionic pairs) generate the continuous channels that favor proton transport. The optical and photo‐responsive properties were studied by UV‐Vis spectroscopy, demonstrating that the azobenzene moieties of the ionic LC undergo reversible (E)‐to‐(Z) isomerization by irradiation with UV light. Interestingly, this (E)‐to‐(Z) photoisomerization results in a decrease of the proton conductivity values since the bent‐shaped (Z)‐isomer disrupts the lamellar LC phase. This isomerization process is totally reversible and leads to an ionic LC material with unique photo‐switchable proton conductive properties. [ABSTRACT FROM AUTHOR]

Chiral pyrrolic macrocycles continue to attract interest. However, their molecular design remains challenging. Here, we report a calixpyrrole‐based chiral macrocyclic system, calix[1]furan[1]pyrrole[1]thiophene (1), synthesized from an oligoketone. Macrocycle 1 adopts a partial cone conformation in the solid state, and undergoes racemization via ring inversion. Molecular dynamics simulations revealed that inversion of the thiophene is the rate determining step. Pyrrole N‐methylation suppressed racemization and permitted chiral resolution. Enantioselective N‐methylation also occurred in the presence of a chiral ammonium salt, although the stereoselectivity is modest. A unique feature of 1 is that it acts as a useful synthetic precursor to yield several calix[n]furan[n]pyrrole[n]thiophene products (n=2–4), including a calix[12]pyrrole analogue that to our knowledge constitutes the largest calix[n]pyrrole‐like species to be structurally characterized. [ABSTRACT FROM AUTHOR]

The extraction ability and selectivity of nonmacrocyclic (8-quinolinol and 2,3-dihydroxynaphthelene) and macrocyclic (sulfur-containing calixarene derivatives) ligands toward rare earth and transplutonium elements in carbonate media was studied. Both macrocyclic and nonmacrocyclic derivatives showed moderate selectivity to americium in the Am/Eu pair (separation factor SF from 1.6 to 14 at pH > 12), and sulfur-containing calixarenes showed also high selectivity to Am in the Am/Cm pair (SF 3–8 at pH > 13). The compounds studied show promise as extractants for group recovery and separation of actinides, and also for separation of rare earth and transplutonium elements in carbonate media. [ABSTRACT FROM AUTHOR]

The binding behaviour of two ureido-hexahomotrioxacalix[3]arene derivatives bearing naphthyl (1) and pyrenyl (2) fluorogenic units at the lower rim towards selected nitroaromatic compounds (NACs) was evaluated. Their affinity, or lack of it, was determined by UV-Vis absorption, fluorescence and NMR spectroscopy. Different computational methods were also used to further investigate any possible complexation between the calixarenes and the NACs. All the results show no significant interaction between calixarenes 1 and 2 and the NACs in either dichloromethane or acetonitrile solutions. Moreover, the fluorescence quenching observed is only apparent and merely results from the absorption of the NACs at the excitation wavelength (inner filter effect). This evidence is in stark contrast with reports in the literature for similar calixarenes. A naphthyl urea dihomooxacalix[4]arene (3) is also subject to the inner filter effect and is shown to form a stable complex with trinitrophenol; however, the equilibrium association constant is greatly overestimated if no correction is applied (9400 M−1 vs 3000 M−1), again stressing the importance of taking into account the inner filter effect in these systems. [ABSTRACT FROM AUTHOR]

Context: The molecular design of spatially preorganized molecules is one of the critical issues in organic chemistry. Molecular recognition and multipoint binding define them. They organize nanoscale assemblies and devices and stably form host–guest inclusion complexes. Not only is this kind of research important in theory but it also has applications. They are used to create the basic elements of sensory devices: elements of cellular electronics, functional nanofilms and coatings, molecular switches, etc. Thiacalix[4]arenes are a useful molecular platform for constructing a wide range of preorganized receptor structures. This research aims to examine the structure and spectra of distally substituted para-tert-butylthiacalix[4]arene aliphatic (C1) and aromatic (C2) esters. The comparison of the spectra of C1, C2, and C3 makes it possible to reveal the structures and H-bonds of these compounds. The structures and H-bonds of these compounds can be seen by analyzing the spectra of C1, C2, and C3. Calculations were made for the spectra of various C1 and C2 molecule conformations. The most stable conformation for C1 and C2 molecules is a distorted cone 2 (DC2) with the same ester group orientation. The pinched cone (PC) conformation is the most unstable. Thiacalixarene molecules' cavities shrink from 3.61 to 3.57 Å when aromatic ester groups take the place of aliphatic ester groups. Two OH groups are linked to an oxygen atom in the DC1 and DC2 conformations of the C1 and C2 molecules. H-bonds in C1 and C2 molecules affect the supramolecular characteristics of these molecules. A drop in ionization energy and increases in electron affinity, chemical potential, softness, electrophilicity index, and dipole moment occur when aliphatic esters are replaced with aromatic ones. Methods: Disubstituted aliphatic and aromatic esters' IR, Raman, and NMR spectra have been investigated. The DFT/B3LYP/6-311G(d,p) method and the GAUSSIAN 09W software were used to determine the vibrational spectra of molecules and optimize their geometry. A gauge-independent (GIAO) approach was used to determine chemical shifts in the NMR spectra with respect to tetramethylsilane. [ABSTRACT FROM AUTHOR]

To achieve reliable, effective, and rapid quality evaluation of complex traditional Chinese medicine (TCM) products, we proposed a supramolecular fluorescence sensing method based on pattern recognition. An azocalixarene-based sensor array was constructed to evaluate batch-to-batch consistency of Qufeng Zhitong Capsule (QZC). The molecular recognitions between azocalixarenes and the contents of QZC are transduced through the fluorescence signal output of the QZC itself or the applied indicator. Data simulations show that differences in composition and concentration between products can lead to altered fluorescence signals. Based on the constructed eight-element sensor array, a standard fluorescent fingerprint presented in a radar chart, was established by analyzing a large number of qualified samples, enabling the differentiation of qualified and unqualified QZC samples. The supramolecular fluorescence sensing method has the advantages of easy construction and fast response, which may provide a reference method and basis for establishing a new mode of quality evaluation of QZC and even other TCM.

A self-assembled tetrahedral cage results from two C3-symmetry building blocks, namely, homooxacalix[3]arene tricarboxylate and uranyl cation, as demonstrated by X-ray crystallography. In the cage, four metals coordinate at the lower rim with the phenolic and ether oxygen atoms to shape the macrocycle with appropriate dihedral angles for tetrahedron formation, whereas four additional uranyl cations further coordinate at the upper-rim carboxylates to finalize the assembly. Counterions dictate the filling and porosity of the aggregates, whereas potassium induces highly porous structures, and tetrabutylammonium yields compact, densely packed frameworks. The tetrahedron metallo-cage complements our previous report (Pasquale et al., Nat. Commun., 2012, 3, 785) on uranyl–organic frameworks (UOFs) from calix[4]arene and calix[5]arene carboxylates (octahedral/cubic and icosahedral/dodecahedral giant cages, respectively) and completes the assembly of all five Platonic solids from just two chemical components.

Four calixarene‐coordinated titanium‐oxo clusters, namely, [Ti4(C6A)2(μ3‐O)2(DMF)2] (CIAC‐258), [Ti8(H3C6A)4(C6H5PO3)8(μ2‐O)4]4− (CIAC‐259), [Ti6(TC4A)3(μ2‐O)3 (OiPr)6] (CIAC‐260) and [Ti6(H2TC4A)4(C6H5PO3)4(μ2‐O)5(DMF)2]2− (CIAC‐261) were obtained, which feature sandwich‐like, windmill‐like, triangular, and tetrahedral structures, respectively. The polarity of the solvent determines the involvement of the auxiliary ligand phenylphosphonic acid in the formation of the products and their structures. Compounds CIAC‐258 and CIAC‐261 exhibit good catalytic performance in the selective oxidation of sulfides to sulfoxides with H2O2 as the oxidant, which can be attributed to the Ti active sites coordinated by exchangeable DMF molecules. Moreover, density functional theory (DFT) calculations revealed that the Ti‐hydroperoxo species formed by the interaction of the Ti active site in CIAC‐258 or CIAC‐261 and H2O2 is the most likely catalytic active component during the catalytic sulfoxidation process. [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]

This study aims to examine the potential of p-tert-butylkalix[4]arene derivatives, namely 5,11,17,23-tetra-tertbutyl-25,26,27,28-tetrahydroxy-calix[4]arene (TBCA), and 5,11,17,23-tetra-tert-butyl-25-monohydroxy-26,27,28-tribenzoyloxycalix[4]arene (TBMTCA) as adsorbent for metal cations, such as Pb(II) and Fe(III). The synthesized compounds were characterized using FT-IR and 1H-NMR spectroscopy. The adsorption studies were then carried out with contact time as a parameter, while the kinetics were evaluated using the Lagergren and Ho-McKay equations. The isotherms were analyzed using the Langmuir and Freundlich equations. For the kinetics of TBCA adsorbents, Pb(II) cations followed the Ho-McKay model, while Fe(III) was based on Lagergren. Furthermore, for the TBMTCA adsorbent, Pb(II) followed the Lagergren kinetic model, while Fe(III) was based on the Ho-McKay. The cation adsorption isotherms of Pb(II)-TBCA, Pb(II)-TBMTCA, Fe(III)-TBCA, and Fe(III)-TBMTCA are more in line with the Langmuir model. These results indicate that they can be used as heavy metal adsorbents, and recycled to increase their economic value. [ABSTRACT FROM AUTHOR]

The calix[4]arene scaffold, blocked in the cone conformation through alkylation with long alkyl chains, and decorated at the upper rim with four guanidine or arginine units, effectively catalyzes the cleavage of the phosphodiester bond of DNA and RNA model compounds in water. An exhaustive kinetic investigation unequivocally points to the existence of spontaneous aggregation phenomena, driven by hydrophobic effect, occurring at different critical concentrations that depend on the identity of the compound. A pronounced superiority of the assembled structures compared with the monomers in solution was observed. Moreover, the catalytically active units, clustered on the macrocyclic tetrafunctional scaffold, were proved to efficiently cooperate in the catalytic mechanism and result in improved reaction rates compared to those of the monofunctional model compounds. The kinetic analysis is also integrated and corroborated with further experiments based on fluorescence spectroscopy and light scattering. The advantage of the supramolecular assemblies based on tetrafunctional calixarenes leads to believe that the active units can cooperate not only intramolecularly but also intermolecularly. The molecules in the aggregates can probably mold, flex and rearrange but, at the same time, keep an ordered structure that favors phosphodiester bond cleavage. This dynamic preorganization can allow the catalytic units to reach a better fitting with the substrates and perform a superior catalytic activity. [ABSTRACT FROM AUTHOR]

Functionalization of the phenolic rim of p‐tert‐butylcalix[8]arene with phenanthroline to create a cavity leads to formation of two regioisomers. Substitution of positions 1 and 5 produces the known C2v‐symmetric regioisomer 1,5‐(2,9‐dimethyl‐1,10‐phenanthroyl)‐p‐tert‐butylcalix[8]arene (L1,5), while substitution of positions 1 and 4 produces the Cs‐symmetric regioisomer 1,4‐(2,9‐dimethyl‐1,10‐phenanthroyl)‐p‐tert‐butylcalix[8]arene (L1,4) described herein. [Cu(L1,4)I] was synthesized from L1,4 and CuI in good yield and characterized spectroscopically. To evaluate the effect of its cavity on catalysis, Ullmann‐type C−S coupling was chosen as proof‐of‐concept. Selected aryl halides were used, and the results compared with the previously reported Cu(I)/L1,5 system. Only highly activated aryl halides generate the C−S coupling product in moderate yields with the Cu(I)/L1,4 system. To shed light on these observations, detailed computational investigations were carried out, revealing the influence of the calix[8]arene macrocyclic morphology on the accessible conformations. The L1,4 regioisomer undergoes a deformation that does not occur with L1,5, resulting in an exposed catalytic center, presumably the cause of the low activity of the former system. The 1,4‐connectivity was confirmed in the solid‐state structure of the byproduct [Cu(L1,4−H)(CH3CN)2] that features Cu(I) coordinated inside a cleft defined by the macrocyclic framework. [ABSTRACT FROM AUTHOR]

With the emergence of host-guest systems, a novel branch of complexation chemistry has found wide application in industries such as food, pharmacy, medicine, environmental protection and cosmetics. Along with the extensively studied cyclodextrins and calixarenes, the innovative cucurbiturils (CB) have enjoyed increased popularity among the scientific community as they possess even better qualities as cavitands as compared to the former molecules. Moreover, their complexation abilities could further be enhanced with the assistance of metal cations, which can interestingly exert a dual effect on the complexation process: either by competitively binding to the host entity or cooperatively associating with the CB@guest structures. In our previous work, two metal species (Mg2+ and Ga3+) have been found to bind to CB molecules in the strongest fashion upon the formation of host–guest complexes. The current study focuses on their role in the complex formation with three dye molecules: thiazole orange, neutral red, and thioflavin T. Various key factors influencing the process have been recognized, such as pH and the dielectric constant of the medium, the cavity size of the host, Mn+ charge, and the presence/absence of hydration shell around the metal cation. A well-calibrated DFT methodology, solidly based and validated and presented in the literature experimental data, is applied. The obtained results shed new light on several aspects of the cucurbituril complexation chemistry. [ABSTRACT FROM AUTHOR]

Calix[4]arene‐plumbylene complexes Pb[Calixt‐Bu(O)2(OR)2], where R=benzyl, 9‐fluorenyl, SitBuMe2, and SiiPr3, have been synthesized by the reaction of Lappert's plumbylene Pb[N(SiMe3)2]2 with the corresponding 1,3‐diethers of calix[4]arene. The products have been fully characterized by 1H, 13C{1H}, and 207Pb NMR spectroscopy, elemental analysis, and X‐ray diffraction analysis. The products adopt two different forms depending on the R groups: the alkyl derivatives were obtained as exo‐isomers in which the lead atom resides outside the cavity of the calix[4]arene, while the silyl derivatives were isolated as endo‐isomers where the lead atom is situated inside the cavity. X‐ray diffraction studies revealed that the lead(II) atoms in the exo‐ and endo‐isomers are coordinated by the ethereal oxygen atoms (OR) and the aromatic rings (ArOR), respectively, which are maintained in solution as evidenced by 207Pb NMR studies. [ABSTRACT FROM AUTHOR]

Over the past two decades, non‐covalent chemistry has introduced various promising artificial receptors and revolutionized the host‐guest chemistry. These versatile receptors have particularly been entertained in sensing and recognizing of diverse neutral molecules and/or ionic entities (e. g. anions, cations and ion‐pair) of particular interest. Notably, supramolecular chemistry had given birth to a plethora of important molecules, explored in the chemical, biological, environmental, and pharmacological world to resolve the critical issues related to the human health while keeping environmental concerns in mind. Amongst the various types of supramolecular monotopic receptors (anions, cations, and neutral molecules), heteroditopic receptors (ion‐pair receptors) consisting of distinct binding sites in one system for both cation and anion, have gained much interest from the scientific community in recent past because of their unique binding abilities. Interestingly, these promising artificial receptors have shown potential applications in sensing, recognition, transport and extraction processes besides their uses in salt/waste purification. Bearing the importance of these systems in mind, we intended to report the recent developments in ion‐pair chemistry. Herein, we divided the whole document into three main sections; first one describes the introduction and history of the ion‐pairs receptors. The second portion highlights the synthesis and applications of ion‐pair receptors in sensing, recognition, molecular machines, photoswitching behaviour, extraction and transport properties, whereas the last part of this manuscript provides concluding remarks as well as future prospects of ion‐pair receptors. We hope that this manuscript will be helpful to stimulating researchers around the globe to find out the hidden opportunities in this and related areas. [ABSTRACT FROM AUTHOR]

Core‐fluorescent cavitands based on 2‐(2′‐resorcinol)benzimidazole fluorophores (RBIs) merged with the resorcin[4]arene skeleton were designed and synthesized. The cavitands, due to the presence of intramolecular hydrogen bonds and increased acidity, show excited state intramolecular proton transfer (ESIPT) and readily undergo deprotonation to form dianionic cavitands, capable of strong binding to organic cations. The changes in fluorescence are induced by deprotonation and binding events and involve huge Stokes shifts (due to emission from anionic double keto tautomers) and cation‐selective enhancement of emission originating from the restriction of intramolecular motion (RIR) upon recognition in the cavity. Ab initio calculations indicate that the macrocyclic scaffold stabilizes the ground state tautomeric forms of the fluorophores that are not observed for non‐macrocyclic analogs. In the excited state, the emitting forms for both macrocyclic scaffolds and non‐macrocyclic analogs are anionic double keto tautomers, which are the result of excited state intramolecular proton transfer (ESIPT) or excited state double proton transfer (ESDPT). [ABSTRACT FROM AUTHOR]

Compared with organic solar cells (OSCs) adopting conventional architecture, inverted OSCs have offered generally better stability, where ZnO is the most widely used electron transporting layer (ETL) material. For ZnO-based inverted OSCs, a well-tuned interface of organic (active layer)-inorganic (ZnO film) with matched surface energy (γS) is critical for both high performance and high stability. In this work, two typical calixarenes, C4A and BuC4A, were employed as the tuning agents to adjust this organic-inorganic interface for ZnO-based inverted OSCs. As a result, with PM6:L8-BO as the active layer, significantly promoted power conversion efficiencies (PCEs) from 17.14% (for ZnO) to 18.25% (for ZnO/C4A) and 17.80% (for ZnO/BuC4A) were achieved. Photodynamic studies indicate that the enhanced performance is due to the faster charge extraction process, the suppressed recombination and more ideal internal electric field in ZnO/calixarene-based devices. In addition, well-matched interface energy and more ordered molecular aggregation in active layer effectively improved photostability and thermal stability for ZnO/calixarene-based devices. These results indicate that calixarenes could act as effective modifying agents of ZnO to improve inverted OSCs' performance and stability simultaneously, and likely also stimulate calixarenes' and other macromolecules' broader studies in other organic electronic devices. [ABSTRACT FROM AUTHOR]

Introduction: Cocaine use disorder is a significant public health issue without a current specific approved treatment. Among different approaches to this disorder, it is possible to highlight a promising immunologic strategy in which an immunogenic agent may reduce the reinforcing effects of the drug if they are able to yield sufficient specific antibodies capable to bind cocaine and/or its psychoactive metabolites before entering into the brain. Several carriers have been investigated in the anti-cocaine vaccine development; however, they generally present a very complex chemical structure, which potentially hampers the proper assessment of the coupling efficiency between the hapten units and the protein structure. Objectives: The present study reports the design, synthesis and preclinical evaluation of two novel calix[n]arene-based anti-cocaine immunogens (herein named as V4N2 and V8N2) by the tethering of the hydrolysis-tolerant hapten GNE (15) on calix[4]arene and calix[8]arene moieties. Methods: The preclinical assessment corresponded to the immunogenicity and dose–response evaluation of V4N2 and V8N2. The potential of the produced antibodies to reduce the passage of cocaine analogue through the blood–brain-barrier (BBB), modifying its biodistribution was also investigated. Results: Both calix[n]arene-based immunogens elicited high titers of cocaine antibodies that modified the biodistribution of a cocaine radiolabeled analogue (99mTc-TRODAT-1) and decreased cocaine-induced behavior, according to an animal model. Conclusion: The present results demonstrate the potential of V4N2 and V8N2 as immunogens for the treatment of cocaine use disorder.

A new type of calix[4]arene-bis-1,3-diketone derivatives, in which the chelate groups are directly conjugated through the carbonyl carbon atom to the aromatic moieties of calix[4]arene, demonstrates the dramatic effect of lower rim substituents on the coordination of Eu3+ ions with conjugated 1, 3-diketo groups. Eu3+ -luminescence is more enhanced in complexes with dipropoxy-calix[4]arene compared to complexes with the tetrapropoxy analogue due to the difference in the structure of the complex. [Display omitted] This work presents new type of bis-1,3-diketone calix[4]arene derivatives, in which the chelate groups are directly conjugated through the carbonyl carbon atom with aromatic fragments of calix[4]arene, and their lower rims bear four propoxy groups or pairs of hydroxy and propoxy groups. Tetrapropoxy-calix[4]arene is synthesized by acylation of magnesium enolates of a calix[4]arene ketone with 1-benzoylbenzotriazoles, and the dipropoxy analogue is obtained by bromination of bis(chalcone)-calix[4]arene, followed by methanolysis and hydrolysis. Significant conjugation of 1,3-diketo groups with the π-system of calix[4]arene is revealed for calixarenes of both types. Analysis of complexes formed by the ligands using the UV–Vis and NMR diffusion methods in combination with DFT calculations makes it possible to identify differences in the modes of complex formation of di- and tetrapropoxy- substituted ligands. It is demonstrated that a more enhanced sensibilization of Eu3+-luminescence in complexes with dipropoxy-calix[4]arene compared to that for complexes with tetrapropoxy-counterpart correlates with the formation of a tetrameric structure, in which the binding of Eu3+ ions does not disturb the conjugation of 1,3-diketonate moieties with aromatic calix[4]arene fragments. This is quite different from the significant disturbance of conjugation during intramolecular bis-chelation of Eu3+ ion by 1,3-diketo groups of tetraalkyl substituted ligand. [ABSTRACT FROM AUTHOR]

Since the discovery of polyphenolic resins 150 years ago, the study of polymeric compounds named calix[n]arene has continued to progress, and those skilled in the art perfectly know now how to modulate this phenolic ring. Consequently, calix[n]arenes are now used in a large range of applications and notably in therapeutic fields. In particular, the calix[4]arene exhibits multiple possibilities for regioselective polyfunctionalization on both of its rims and offers researchers the possibility of precisely tuning the geometry of their structures. Thus, in the crucial research of new antibacterial active ingredients, the design of calixarenes finds its place perfectly. This review provides an overview of the work carried out in this aim towards the development of intrinsically active prodrogues or metallic calixarene complexes. Out of all the work of the community, there are some excellent activities emerging that could potentially place these original structures in a very good position for the development of new active ingredients.

Calixarenes are host molecules that can form complexes with one or more guest molecules, and molecular recognition in calixarenes can be affected by many factors. With a view to establishing molecular recognition rules, the host p-tert-butylcalix[6]arene (TBC6) was crystallized with different guest molecules (cyclohexane, anisole, heptane, toluene, benzene, methyl acetate, ethyl acetate, dichloromethane, tetrahydrofuran and pyridine) and the obtained structures were characterized by X-ray diffraction. With most solvents, 1:1 and/or 1:3 host–guest complexes were formed, although other stoichiometries were also observed with small guest molecules, and crystallization from ethyl acetate produced the unsolvated form. The calculated fill percentage of the TBC6 cavity was ∼55% for apolar guests and significantly lower for polar solvents, indicating that polar molecules can bind to apolar cavities with significantly lower packing coefficients. The most stable crystals were formed by 1:1 host–guest inclusion complexes. The ratio between the apolar surface area and the volume was used to predict the formation of inclusion versus exclusion complexes, with inclusion complexes observed at ratios

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.

A receptor cone-1 based on a hexahomotrioxacalix[3]arene bearing three pyridyl groups was successfully synthesized, which has a C₃-symmetric conformation and is capable of binding alkylammonium and metal ions simultaneously in a cooperative fashion. It can bind alkylammonium ions through the -cavity formed by three aryl rings. This behaviour is consistent with the cone-in/cone-out conformational rearrangement needed to reorganize the cavity for endo-complexation. As a C₃-symmetrical pyridyl-substituted calixarene, receptor cone-1 can also bind an Ag⁺ ion, and the nitrogen atoms are turned towards the inside of the cavity and interact with Ag⁺. After complexation of tris(2-pyridylamide) derivative receptor cone-1 with Ag⁺, the original C₃-symmetry was retained and higher complexation selectivity for n-BuNH₃⁺ versus t-BuNH₃⁺ was observed. Thus, it is believed that this receptor will have a role to play in the sensing, detection, and recognition of Ag⁺ and n-BuNH₃+ ions.

Calixarenes are macrocyclic molecules with unique three-dimensional structures, shaped like a cup with a hydrophobic upper rim and a hydrophilic lower rim surrounding a hollow cavity. Calixarenes are frequently studied as the host system and used as nanosensors in drug carrier as well as drug delivery system application. This is due to the characteristics of calixarenes as well as their derivatives, which can interact and form composite nanomaterials with ions and neutral species, including metal and non-metal. The ease of calixarenes to be synthesized and functionalized at various sites is the main reason of their widely use in different applications. This review article focuses on the structures, properties of calixarenes and their host-guest interaction with guest molecules, according to previous experimental researches as well as review studies that had been carried out. The applications of calixarenes in cosmetic and medical fields for the recent ten years are discussed. Drugs can be loaded into calixarenes by encapsulation and host-guest interactions. This contributes to the different applications, including the medical and cosmetic fields with low cytotoxicity and no haemolytic activity, which are crucial for safety purposes. Their great potential and contributions in these fields have been shown, which may be utilized in the future studies of supramolecular chemistry. [ABSTRACT FROM AUTHOR]

Azo derivatives of calixarenes are mostly reported for the extraction of transition metal ions and as switchable receptors or sensors for Na+ and K+ ions to mimic the biological Na+/K+ ion pump. Only a few reports describe the drug-like potential of azo calixarenes. The current work is an attempt to explore the anticancer potential of three upper rims modified azo derivatives of calix[4]arene. Sulfaguanidine (SGC), sulfanilamide (SCM), and 4-amino-2-methylbenzoic acid (COX) groups were linked with calix[4]arene via azo linkage and their antiproliferative effect was evaluated against breast (MCF7 and MDA-MB-231), colon (HCT-116), and lung (A549) cancer cell lines using MTT assay. SGC showed antiproliferative effect on MCF7 and MDA-MB-231 breast cancer cells with IC50 values of 32.2 and 27.3 µM, respectively. SCM exerted an antiproliferative activity against MCF7, MDA-MB-231, and HCT-116 cells with IC50 values of 31.8, 50.1, and 28.03 µM, respectively, while COX did not show an antiproliferative effect against all the tested cell lines. The compounds were docked against Cyclin-Dependent Kinase-2 (CDK2) receptor (PDB ID 1FVT) for their possible interactions followed by in vitro analysis by MTT assay. CDK2 was selected as the target enzyme because of the structural similarities of the synthesized compounds with previously reported CDK2 potential inhibitors. The docking results supported the in vitro results for the two compounds. A proposed scheme for using the azo derivatives of calix[4]arene as prodrugs is suggested for further investigation. [ABSTRACT FROM AUTHOR]

[Display omitted] Shape-persistent macrocycles enable superior control on molecular self-assembly, allowing the preparation of well-defined nanostructures with new functions. Here, we report on anionic amphiphilic calixarenes of conic shape and their self-assembly behavior in aqueous media for application in intracellular delivery of peptides. Newly synthesized calixarenes bearing four phosphonate groups and two or four long alkyl chains were found to form micelles of ∼ 10 nm diameter, in contrast to an analogue with short alkyl chains. These amphiphilic calixarenes are able to complex model (oligo-lysine) and biologically relevant (HIV-1 nucleocapsid peptide) cationic peptides into small nanoparticles (20–40 nm). By contrast, a control anionic calixarene with short alkyl chains fails to form small nanoparticles with peptides, highlighting the importance of micellar assembly of amphiphilic calixarenes for peptide complexation. Cellular studies reveal that anionic amphiphilic calixarenes exhibit low cytotoxicity and enable internalization of fluorescently labelled peptides into live cells. These findings suggest anionic amphiphilic macrocycles as promising building blocks for the preparation of peptide delivery vehicles. [ABSTRACT FROM AUTHOR]

Developing hierarchical ordered systems is challenging. Using organo-macrocycles to construct metal–organic frameworks (MOFs) and porous coordination cages (PCCs) provides an efficient way to obtain hierarchical assemblies. Macrocycles, such as crown ethers, cyclodextrins, calixarenes, cucurbiturils, and pillararenes, can be incorporated within MOFs/PCCs and they also endow the resultant composites with enhanced properties and functionalities. This review summarizes recent developments of organo-macrocycle-containing hierarchical MOFs/PCCs, emphasizing applications and structure–property relationships of these hierarchically porous materials. This review provides insights for future research on hierarchical self-assembly using macrocycles as building blocks and functional ligands to extend the applications of the composites. [ABSTRACT FROM AUTHOR]

The contemporary state of the art has been considered in the field of colloidal solutions of complexes of synthetic and natural polyelectrolytes with some supramolecular macrocycles (calix[n]arenes, calix[4]resorcinols, pillar[n]arenes, and calix[4]pyridinium) bearing charged groups. Examples of the obtained polymer complexes have been presented, and their characteristics (sizes and electrokinetic potentials) and properties (sensitivity to stimuli, capability of encapsulation, and cytotoxicity), as well as the potential of their application, have been described. [ABSTRACT FROM AUTHOR]

This review presents the systems with derivatives of calix[n]arenes and the commonly available fluorescent dyes of the fluorene series, such as rhodamines B, 6G, 123 and the fluorone series, such as fluorescein and eosin N. The first part of this review concerns the systems with the covalent immobilization of dyes on a macrocyclic platform and the principles of their design and potential application as chemosensors are considered. The second part of this review deals with the systems synthesized through "guest–host" supramolecular interactions and their use as chemo- and biosensors, whose operation is based on the principles of fluorescent dye liberation due to competitive complexation. The third part of the review is devoted to colloid systems with xanthene dyes. The use of dye-saturated colloid systems as chemosensors is considered, and the possibility of using the dyes as model guest molecules capable of concentrating in the hydrophobic layer of aggregates is shown alongside with their potentiality as a fluorescent probe for studying the aggregation processes. [ABSTRACT FROM AUTHOR]

Slurry-phase hydrocracking utilizing metal-containing oil-soluble compounds as precursors of dispersed catalysts is an effective approach for heavy oil upgrading. We propose applying metal-based p-tert-butylcalix[6]arene (TBC[6]s) organic species as dispersed catalyst precursors to enhance catalytic hydrogenation reactions involved in the upgrading of vacuum gas oil (VGO). Co- and Ni-based TBC[6]s were synthesized and characterized by SEM-EDX, ICP, XRD, and FT-IR. The thermogravimetric and calorimetric behaviors of the synthesized complexes, which are key properties of dispersed hydrocracking catalysts, were also explored. The experimental evaluation of the synthesized catalyst precursors show that the synthesized metal-based TBC[6] catalyst precursors improved the catalytic hydrogenation reactions. A co-catalytic system was also investigated by adding a commercial, first-stage hydrocracking supported catalyst in addition to the dispersed catalysts. The naphtha yields increased from 10.7 wt.% for the supported catalyst to 11.7 wt.% and 12 wt.% after adding it along with Ni-TBC[6] and Co-TBC[6], respectively. Mixing the metal-based precursors resulted in elevated yields of liquid products due to the in situ generation of highly active Co–Ni bimetallic dispersed catalysts. [ABSTRACT FROM AUTHOR]

Pd-catalysed reactions are amongst the most important in current chemistry. Consequently, very reactive catalysts were developed during the last decades, allowing very high conversions at low catalytic rates. However, decreasing Pd leaching in final products without decreasing catalyst efficiency remains an unsolved issue, especially in the pharma industry. We recently showed that using calixarenes as platforms for Pd-based catalysts constitutes an efficient answer to this concern. In the present work, we show that using these calixarenic platforms in combination with suitably engineered ligands allows for an even more strongly decreased Pd leaching. It thus opens up interesting perspectives for the synthesis of new families of catalysts combining a very high reactivity and a very low Pd leaching in final products. [ABSTRACT FROM AUTHOR]

The work is devoted to a study of the detection sensitivity and selectivity of a series of simulants of gaseous poisonous substances (PS). Two different sensor types were used, namely: 1) a quartz crystal microbalance (QCM), exhibiting a shift of the resonant frequency of quartz plates coated with calixarene thin layers, and 2) chemoresistive electrodes coated with layers of nanocomposites of intrinsically conducting polymers (ICP) changing their conductance under the influence of adsorbed gas molecules. The concentration of the analyzed volatile compounds varied within the range of 10 to 1000 ppm. The detection threshold ranged from 10 to 100 ppm depending on the analyzed substance for both transducer types. The response time was from 10 to 20 s for the QCM sensors and up to 1 minute for the ICP based sensors. The possibility of qualitative identification of poisonous substances in a wide concentration range by means of statistical analysis of the sensor array data is demonstrated. [ABSTRACT FROM AUTHOR]

Resistance to paclitaxel poses a major obstacle in esophageal squamous cell carcinoma (ESCC) treatment. A better understanding of the mechanisms underlying paclitaxel resistance could help identify prognostic biomarkers and improved therapeutic strategies. In this study, we established a patient-derived xenograft model of acquired paclitaxel resistance and used RNA sequencing to identify galectin-1, encoded by LGALS1, as a key mediator of resistance. Integrative analysis of clinical data and physiological studies indicated that serum galectin-1 levels were elevated in resistant patients and correlated with treatment outcomes before and during taxane therapy. Importantly, exposing cells to serum from resistant patients resulted in increased paclitaxel resistance compared to serum from sensitive patients, which was closely associated with galectin-1 concentrations in the serum. The specific clearance of galectin-1 from resistant patient serum significantly restored paclitaxel sensitivity, and inhibiting galectin-1, through knockdown or the pharmacologic inhibitor OTX008, increased sensitivity to paclitaxel. Galectin-1 inhibition reduced the activity of β-catenin, thereby inhibiting stem cell properties induced by the Wnt/β-catenin pathway. Furthermore, galectin-1 regulated MDR1 transcription through increased nuclear accumulation of β-catenin, thus increasing resistance to paclitaxel. Combining OTX008 with clinical taxane formulations effectively reversed paclitaxel resistance in vitro and in vivo. Elevated galectin-1 levels thus serve as an indicator of response to paclitaxel therapy in ESCC, offering a therapeutic intervention strategy to overcome drug resistance. Significance: Galectin-1 is a key mediator of paclitaxel resistance in esophageal squamous cell carcinoma that can be targeted to improve taxane efficacy, suggesting broad therapeutic potential for treating various cancer types., (©2024 American Association for Cancer Research.)

Reactions that promote the formation of carbon–carbon bonds are of great importance in organic synthesis, since they transform available, relatively inexpensive, and small organic molecules into more complex ones. One of the main protocols used for these transformations are cross‐coupling reactions, and due to their versatility and applications, several efforts have been devoted recently to developing catalysts for such reactions. Supramolecular chemistry has become a major player in this field and encompasses approaches that range from the synthesis of intricate complex architectures that may mimic enzymes, the slight structural modification of commercially available scaffolds, or even repurposing highly available materials such as agarose. This Review discusses the development of supramolecular catalysts for cross‐coupling reactions, focusing mostly on the Suzuki, Heck and Sonogashira reactions promoted by such assemblies. [ABSTRACT FROM AUTHOR]

We have designed and synthesized electron-rich calixarene derivatives, which undergo reversible electrochemical oxidation in a well-accessible potential range that allows the ready preparation and isolation of the corresponding cation radicals. Preparation of mono- or tetra-radical cation can be achieved by using stable aromatic cation-radical salts such as MA+•, MB+•, and NAP+• as selective organic oxidants. The cation radicals of calixarenes are stable indefinitely at ambient temperatures and can be readily characterized by UV-vis-NIR spectroscopy. These cation radicals bind a single molecule of nitric oxide within its cavity with remarkable efficiency. [ABSTRACT FROM AUTHOR]

The iodination of calix[4]arene and one of its monofunctionalised derivatives by bis(pyridine)iodonium(I) triiodide, [I(py)2]I3·2I2 has been studied. The iodination reactions proceed in good yields at room temperature (r.t.) without any co-reagents affording the corresponding tetra- and tri-substituted calix[4]arenes. Only electron-rich phenol groups are iodinated by [I(py)2]I3·2I2. Phenolether or Schiff-base type arene rings remain unaffected. The crystal structure of the iodination reagent, first published in 1961, has been re-determined which a higher precision. The crystal structures of the two per-iodinated calix[4]arenes show that self-inclusion occurs in the solid state. [I(py)2]I3·2I2 selectively iodinates electron-rich phenol groups of calix[4]arenes. Less electron-rich aryl rings remain unaffected. Self-inclusion of iodinated calix[4]arenes occurs in the solid state. [ABSTRACT FROM AUTHOR]

The formation of supramolecular complexes of 3-methyl-sulfido-propoxycalix[4]arene-methylene-bis-phosphonic acid with seventeen amino acids in aqueous solutions has been studied and their stability coefficients have been determined by the method of high-performance liquid chromatography. The structures of the supramolecular complexes have been proposed by molecular modeling and the influence of structural factors (the stabilization of different conformations of the obtained complexes depending on amino acid nature: possibilities of the realization of hydrogen bonds and electrostatic interactions between different groups of the amino acids and calixarene) on the stability of the supramolecules has been shown. [ABSTRACT FROM AUTHOR]

The iodination of calix[4]arene and one of its monofunctionalised derivatives by bis(pyridine)iodonium(I) triiodide, [I(py)2]I3·2I2 has been studied. The iodination reactions proceed in good yields at room temperature (r.t.) without any co-reagents affording the corresponding tetra- and tri-substituted calix[4]arenes. Only electron-rich phenol groups are iodinated by [I(py)2]I3·2I2. Phenolether or Schiff-base type arene rings remain unaffected. The crystal structure of the iodination reagent, first published in 1961, has been re-determined which a higher precision. The crystal structures of the two per-iodinated calix[4]arenes show that self-inclusion occurs in the solid state. [I(py)2]I3·2I2 selectively iodinates electron-rich phenol groups of calix[4]arenes. Less electron-rich aryl rings remain unaffected. Self-inclusion of iodinated calix[4]arenes occurs in the solid state. [ABSTRACT FROM AUTHOR]

In the present review, works on the classes of chelating extractants for metals, compounds with several amide and carboxyl groups, azomethines, oximes, macrocyclic compounds (crown ethers and calixarenes), phenanthroline derivatives, and others are systematized. This review focuses on the efficiency and selectivity of the extractants in the recovery of metals from industrial wastewater, soil, spent raw materials, and the separation of metal mixtures. As a result of this study, it was found that over the past seven years, the largest number of works has been devoted to the extraction of heavy metals with amino acids (16 articles), azomethines and oximes (12 articles), lanthanids with amide compounds (15 articles), lanthanides and actinides with phenanthroline derivatives (7 articles), and noble metals with calixarenes (4 articles). Analysis of the literature showed that amino acids are especially effective for extracting heavy metals from the soil; thiodiglycolamides and aminocalixarenes for extracting noble metals from industrial waste; amide compounds, azomethines, oximes, and phenanthroline derivatives for extracting actinides; amide compounds for extracting lanthanides; crown ethers for extracting radioactive strontium, rhenium and technetium. The most studied parameters of extraction processes in the reviewed articles were the distribution ratios and separation factors. Based on the reviewed articles, it follows that chelate polydentate compounds are more efficient compounds for the extraction of metals from secondary resources compared to monodentate compounds. [ABSTRACT FROM AUTHOR]

This short review aims to introduce the uniqueness, advantages, and recent progress in using calixarenes for membrane modifications and separations. This type of unique nano-porous materials may provide great prospects for next-generation membrane modifications and development. • Introduction of uniqueness of calixarene incorporated membranes for water reuses. • Summary of recent progress of calixarene embedded membrane for gas separations. • Elucidation of infiltration process for calixarene incorporated membranes. • Perspectives of calixarene embedded membranes for molecular separations. [ABSTRACT FROM AUTHOR]

Gene therapy is a technique that is currently under expansion and development. Recent advances in genetic medicine have paved the way for a broader range of therapies and laid the groundwork for next-generation technologies. A terminally substituted difluorene-diester Schiff Base calix[4]arene has been studied in this work as possible nanovector to be used in gene therapy. Changes to luminescent behavior of the calixarene macrocycle are reported in the presence of ct-DNA. The calixarene macrocycle interacts with calf thymus DNA (ct-DNA), generating changes in its conformation. Partial double-strand denaturation is induced at low concentrations of the calixarene, resulting in compaction of the ct-DNA. However, interaction between calixarene molecules themselves takes place at high calixarene concentrations, favoring the decompaction of the polynucleotide. Based on cytotoxicity studies, the calixarene macrocycle investigated has the potential to be used as a nanovehicle and improve the therapeutic efficacy of pharmacological agents against tumors. [ABSTRACT FROM AUTHOR]