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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.

Paclitaxel (PTX), a widely used anticancer agent, is found in the inner bark of several Taxus species, although at such low levels that its extraction is ecologically unsustainable. Biotechnological platforms based on Taxus sp. cell cultures offer an eco-friendlier approach to PTX production, with yields that can be improved by elicitation. However, the also limited excretion of target compounds from the producer cells to the medium hampers their extraction and purification. In this context, we studied the effect of treating T. media cell cultures with the elicitor coronatine (COR) and calix[8]arenes (CAL), nanoparticles that can host lipophilic compounds within their macrocyclic scaffold. The highest taxane production (103.5 mg.L−1), achieved after treatment with COR (1 μM) and CAL (10 mg.L−1), was 15-fold greater than in the control, and PTX represented 82% of the total taxanes analyzed. Expression levels of the flux-limiting PTX biosynthetic genes, BAPT and DBTNBT, increased after the addition of COR, confirming its elicitor action, but not CAL. The CAL treatment significantly enhanced taxane excretion, especially when production levels were increased by COR; 98% of the total taxanes were found in the culture medium after COR + CAL treatment. By forming complexes with PTX, the nanoparticles facilitated its excretion to the medium, and by protecting cells from PTX toxicity, its intra-and extra-cellular degradation may have been avoided. The addition of COR and CAL to T. media cell cultures is therefore a bio-sustainable and economically viable system to improve the yield of this important anticancer compound. [Display omitted] • Calix[8]arenes (CAL) can host paclitaxel (PTX) within their macrocyclic scaffold. • Coronatine (COR) is an inducer of taxane production in biotechnological systems. • PTX production was increased by adding COR + CAL to Taxus media cell cultures. • CAL did not affect biomass formation and promoted PTX excretion to the medium. • COR + CAL treatment is an eco-friendly strategy for increasing taxane production. [ABSTRACT FROM AUTHOR]

This review refers to recent advances on the receptors involved in the field of host-guest recognition from the last five years. The most used receptors in this field were calixarenes, pillararenes, and cyclodextrins. First, a series of electrochemical sensors used to detect dopamine are described, then the electrochemical chiral detection of the tyrosine and tryptophan enantiomers is discussed. © 2021 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited. [ABSTRACT FROM AUTHOR]

This paper reviews the achievements in the field of synthesis of new thermally resistant explosive compounds in the years 2009 through 2019. The performance characteristics of these compounds (sensitivity, thermal decomposition parameters, and detonation parameters) were compared with those of 1,3,5-triamino-2,4,6-trinitrobenzene, which still seems to be an unrivalled model of a thermally resistant and generally low-sensitivity explosive material. New thermally stable explosives (TSEs) were found among macromolecular compounds with tri- and dinitrophenyl groups, nitro and amine-nitro derivatives of azoles, and polynitro derivatives of calixarenes. Some of them match TATB in terms of thermal resistance and additionally have higher detonation parameters. [ABSTRACT FROM AUTHOR]

The IR spectra of p-(3-carboxy-1-adamantyl)thiacalix[4]arene (1-AdCOOHTC4A) have been studied. IR spectra of crystalline 1-AdCOOHTC4A obtained at room temperature or upon heating to 250 °C or its dilute solutions lack bands of free hydroxyl groups. The frequency of hydroxyl groups at 3377 cm−1 indicates the formation of an intramolecular H-bond along the lower rim of the 1-AdCOOHTC4A molecule. On the top edge of thiacalixarene, the carboxyl groups form dimeric or cyclic tetrameric complexes via intermolecular H-bonds. The conformation of the cone persists, but there is a mutual influence of H-bonds along the upper and lower rims of the thiacalix[4]arene molecule. The structure with dimer H-bonds between carboxyl groups is 31.9 KJ/mol less preferable than the conformation with tetramer cyclic H-bonds for 1-AdCOOHTC4A. Comparison of the absorption band of νOH alcohol hydroxyl groups in the IR spectra of 1-AdCOOHTC4A at 3377 cm−1, with the corresponding band of 1-AdTC4A at 3372 cm−1, suggests that the presence of the second system of H-bonds of carboxyl groups in the first molecule does not affect the H-bond of alcohol hydroxyl groups. [ABSTRACT FROM AUTHOR]

Since the dawn of supramolecular chemistry, calixarenes have been employed as platforms onto which functional groups and binding sites can be loaded in a regio‐ and stereocontrolled manner for the recognition of charged and neutral species. Despite their wider annulus, potentially suitable to bind larger guests, the larger members of the calixarene series have been relatively less employed, mainly because of the synthetic difficulties to control their conformational flexibility and their regioselective functionalization. In this account, we will present the achievements gained during the last two decades on the use of the calix[6]arene as a platform to build‐up structures in which the macrocycle acts as a wheel for the synthesis of oriented (pseudo)rotaxanes. We also account on how these calix[6]arene hosts affect the reactivity or spectroscopic properties of their bound 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]

The chemical separation of zirconium from lanthanides by liquid–liquid extraction is challenging but critical for medical and technological applications. Using the example of 89Zr, we optimize the liquid–liquid-extraction process by means of the radiotracer technique. We produced 89Zr by proton irradiation of a metallic yttrium target at a cyclotron. The purification of the radionuclide was performed by a UTEVA resin. 89Zr was separated in no-carrier-added form in a sulfuric acid solution. 89Zr was successfully used in solvent extraction tests with calixarenes for the separation of zirconium from lanthanides. This reaction is suitable for the efficient extraction and purification of lanthanides. [ABSTRACT FROM AUTHOR]

Excessive inflammatory reaction aggravates brain injury and hinders the recovery of neural function in nervous system diseases. Microglia, as the major players of neuroinflammation, control the progress of the disease. There is an urgent need for effective non-invasive therapy to treat neuroinflammation mediated by microglia. However, the lack of specificity of anti-inflammatory agents and insufficient drug dose penetrating into the brain lesion area are the main problems. Here, we evaluated a series of calixarenes and found that among them the self-assembling architecture of amphiphilic sulfonatocalix[8]arene (SC8A12C) had the most potent ability to suppress neuroinflammation in vitro and in vivo. Moreover, SC8A12C assemblies were internalized into microglia through macropinocytosis. In addition, after applying the SC8A12C assemblies to the exposed brain tissue, we observed that SC8A12C assemblies penetrated into the brain parenchyma and eliminated the inflammatory factor storm, thereby restoring neurobiological functions in a mouse model of traumatic brain injury.

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]

Calixarenes (CAs), representing the third generation of supramolecular hosts and one of the most widely studied macrocyclic scaffolds, offer (almost) unlimited structure and application possibilities due to their ease of modification, which allows one to establish a large molecular library as a material basis for diverse biomedical applications. Moreover, CAs and their derivatives engage in various noncovalent interactions for the facile recognition of guests including bioactive molecules and are also important building blocks for the fabrication of supramolecular architectures. In view of their molecular recognition and self‐assembly properties, CAs are extensively applied in biosensing, bioimaging, and drug/gene delivery. Additionally, some CA derivatives exhibit biological activities and can therefore be used as new therapeutic agents. Herein, we summarize the diverse biomedical applications of CAs including in vitro diagnosis (biosensing), in vivo diagnosis (bioimaging), and therapy. [ABSTRACT FROM AUTHOR]

In this study, it has been reported the host–guest complex properties of calix[4]arene compounds (the 3rd generation supramolecule) against the 5-fluorouracil (5-FU) anticancer drug by density functional theory calculations at room temperature. The B3LYP hybrid method was used to determine the optimized structures of the host and guest molecules and their complexes. The adsorption energy changes of the complexes formed between calix[4]arene compounds and 5-FU drug were calculated to be negative values. The strongest interaction was determined for the water-soluble calix[4]arene compound with sulfonyl (–SO3H) groups (ΔE = − 98 kJ/mol and ΔH = − 100.5 kJ/mol). Moreover, it was determined that HOMO–LUMO gaps of all calix[4]arene compounds decreased. The charge transfer has occurred between the four calix[4]arene compounds and the drug molecule. The work function values of calix[4]arene compounds have been changed. These results indicate that calix[4]arene derivatives can be used as well-suited 5-FU sensor at room temperature. Solvent effect calculations have stated that the interaction of 5-FU molecule with the calix[4]arene compound with sulfonyl (–SO3H) groups weakens and the ΔE becomes less negative value (− 71.6 kJ/mol). [ABSTRACT FROM AUTHOR]

Lysine (K) is an important target residue for protein and peptide delivery across membranes. K is the most frequently exposed residue in proteins, leading to high demand for the development of K‐compatible transport activators. However, designing activators for K‐rich peptides and proteins is more challenging than for arginine‐rich species because of the kosmotropic nature of K and its recognition difficulty. In this study, we designed a new amphiphilic sulfonatocalix[5]arene (sCx5‐6C) as a K‐compatible transport activator. sCx5‐6C was tailored with two key elements, recognition of K and the ability to embed into membranes. We measured the membrane transport efficiencies of α‐poly‐l‐lysine, heptalysine, and histones across artificial membranes and of α‐poly‐l‐lysine into live cells, activated by sCx5‐6C. The results demonstrate that sCx5‐6C acts as an efficient activator for translocating K‐rich peptides and proteins, which cannot be achieved by known arginine‐compatible activators. [ABSTRACT FROM AUTHOR]

In the field of direct production of hydrogen from solar energy and water, photocatalytic methods hold great potential especially when metal‐free molecular components are preferred. In this work, we have developed a new class of calix[4]arene‐based molecular photosensitizers to be used as antenna systems in the photocatalytic production of hydrogen. The structure of the dyes has a typical donor‐π‐acceptor molecular architecture where a calix[4]arene scaffold is used as an embedded donor. The new materials have been fully characterized in their optical, electrochemical, and photocatalytic properties. The properties conferred by the calix[4]arene donor afforded twice larger performances compared to the corresponding linear system though showing similar quantitative optical properties. The new molecular design paves the way to a new strategy for photocatalytic hydrogen production where the calix[4]arene scaffold can afford more efficient systems and can offer the potential for host‐guest supramolecular effects. [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]

We report the synthesis of a series of amphiphilic p-sulfonatocalix[4]arenes with varying alkyl chain lengths (CX4-Cn) and their application as efficient counterion activators for membrane transport of cell-penetrating peptides (CPPs). The enhanced membrane activity is confirmed with the carboxyfluorescein (CF) assay in vesicles and by the direct cytosolic delivery of CPPs into CHO-K1, HCT 116, and KTC-1 cells enabling excellent cellular uptake of the CPPs into two cancer cell lines. Intracellular delivery was confirmed by fluorescence microscopy after CPP entry into live cells mediated by CX4-Cn, which was also quantified after cell lysis by fluorescence spectroscopy. The results present the first systematic exploration of structure-activity relationships for calixarene-based counterion activators and show that CX4-Cn are exceptionally effective in cellular delivery of CPPs. The dodecyl derivative, CX4-C12, serves as best activator. A first mechanistic insight is provided by efficient CPP uptake at 4 °C and in the presence of the endocytosis inhibitor dynasore, which indicates a direct translocation of the CPP-counterion complexes into the cytosol and highlights the potential benefits of CX4-Cn for efficient and direct translocation of CPPs and CPP-conjugated cargo molecules into the cytosol of live cells., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The highly strained, phenylene-derived organic cages are typically regarded as very rigid entities, yet their deformation potential and supramolecular properties remain underexplored. Herein, we report a pliable conjugated phenylene nanocage by synergistically merging rigid and flexible building blocks. The anisotropic cage molecule contains branched phenylene chains capped by a calix[6]arene moiety, the delicate conformational changes of which endow the cage with a remarkably deformable cavity. When complexing with fullerene guests, the cage showcases excellent guest-adaptivity, with its cavity volume capable of swelling by as much as 85 %., (© 2024 Wiley-VCH GmbH.)

Remediating soil contaminated with polycyclic aromatic hydrocarbons (PAHs) presents a significant environmental challenge due to their toxic and carcinogenic properties. Traditional PAHs remediation methods-chemical, thermal, and bioremediation-along with conventional soil-washing agents like surfactants and cyclodextrins face challenges of cost, ecological harm, and inefficiency. Here we show an effective and environmentally friendly calixarene derivative for PAHs removal through soil washing. Thiacalix[4]arene tetrasulfonate (TCAS) has a unique molecular structure of a sulfonate group and a sulfur atom, which enhances its solubility and facilitates selective binding with PAHs. It forms host-guest complexes with PAHs through π-π stacking, OH-π interactions, hydrogen bonding, van der Waals forces, and electrostatic interactions. These interactions enable partial encapsulation of PAH molecules, aiding their desorption from the soil matrix. Our results show that a 0.7% solution of TCAS can extract approximately 50% of PAHs from contaminated soil while preserving soil nutrients and minimizing adverse environmental effects. This research unveils the pioneering application of TCAS in removing PAHs from contaminated soil, marking a transformative advancement in resource-efficient and sustainable soil remediation strategies., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Photodynamic therapy as a burgeoning and non-invasive theranostic technique has drawn great attention in the field of antibacterial treatment but often encounters undesired phototoxicity of photosensitizers during systemic circulation. Herein, a supramolecular substitution strategy is proposed for phototherapy of drug-resistant bacteria and skin flap repair by using macrocyclic p-sulfonatocalix(4)arene (SC4A) as a host, and two cationic aggregation-induced emission luminogens (AIEgens), namely TPE-QAS and TPE-2QAS, bearing quaternary ammonium group(s) as guests. Through host-guest assembly, the obtained complex exhibits obvious blue fluorescence in the solution due to the restriction of free motion of AIEgens and drastically inhibits efficient type I ROS generation. Then, upon the addition of another guest 4,4'-benzidine dihydrochloride, TPE-QAS can be competitively replaced from the cavity of SC4A to restore its pristine ROS efficiency and photoactivity in aqueous solution. The dissociative TPE-QAS shows a high bacterial binding ability with an efficient treatment for methicillin-resistant Staphylococcus aureus (MRSA) in dark and light irradiation. Meanwhile, it also exhibits an improved survival rate for MRSA-infected skin flap transplantation and largely accelerates the healing process. Thus, such cascaded host-guest assembly is an ideal platform for phototheranostics research., (© 2024 Wiley‐VCH GmbH.)

P-tert-butyldihomooxacalix[4]arene is a well-known calix[4]arene analog in which one CH2 bridge is replaced by one -CH2OCH2- group. Thus, dihomooxacalix[4]arene has a slightly larger cavity than that of calix[4]arene and usually possesses a more flexible cone conformation, and the bridged oxygen atom might provide additional binding sites. Here, we synthesized a new functional p-tert-butyldihomooxacalix[4]arene 1 through Ugi reaction with good yield (70%), starting from condensed p-tert-butyldihomooxacalix[4]arene O-alkoxy–substituted benzaldehydes, benzoic acid, benzylamine, and cyclohexyl isocyanide. Proton nuclear magnetic resonance spectroscopy (1H NMR), 13C NMR, IR, and diffusion-ordered 1H NMR spectroscopy (DOSY) methods were used to characterize the structure of 1. Then soft gel was prepared by adding 1 into cyclohexane directly. It shows remarkable thermoreversibility and can be demonstrated for several cycles. As is revealed by scanning electron microscopy (SEM) images, xerogel showed highly interconnected and homogeneous porous network structures, and hence, the gel is suitable for storage and controlled release.

Two sets of functionalised calix[4]arenes, either with a 1,3-crown ether bridge or with an open-chain oligo ether moiety in 1,3-position were prepared and further equipped with additional deprotonisable sulfonamide groups to establish chelating systems for selected cations Sr2+, Ba2+, and Pb2+ ions. To improve the complexation behaviour towards these cations, calix[4]arenes with oligo ether groups and modified crowns of different sizes were synthesized. Association constants were determined by UV/Vis titration in acetonitrile using the respective perchlorate salts and logK values between 3.2 and 8.0 were obtained. These findings were supported by the calculation of the binding energies exemplarily for selected complexes with Ba2+.

Some of the least studied calixarenes are those that consist of azulene rings bridged by -CH2- groups. Since Lash and Colby’s discovery of a simple and convenient method for producing the parent all-hydrocarbon calix[4]azulene, there have been two other all-hydrocarbon calix[4]azulenes which have been synthesized in good yields by their method. This allowed studying their supramolecular properties. This report is of our latest work on the solution-state supramolecular complexation of one of these calix[4]azulenes, namely tetrakis(5,7-diphenyl)calix[4]azulene or “OPC4A”, with several electron-deficient tetraalkyammonium salts. As a result of more recent methods developed by us and others employing Suzuki–Miyaura cross-coupling reactions to produce additional functionalized azulenes, the promise of further greater functionalized calixazulenes lies in store to be investigated.

New calixarene-based nanosponges (CaNSs), i.e., hyper-reticulated polymers constituted by calixarene monomer units joined by means of bis(1,2,3-trialzolyl)alkyl linkers, were synthesized, characterized and subjected to preliminary tests to assess their supramolecular absorption abilities towards a set of suitable organic guests, selected as pollutant models. The synthesis was accomplished by means of a CuAAC reaction between a tetrakis(propargyloxy)calix[4]arene and an alkyl diazide. The formation of the polymeric network was assessed by means of FTIR and 13C{1H} CP-MAS solid-state NMR techniques, whereas morphological characterization was provided by SEM microghaphy. The materials were proved to possess pH-dependent sequestration abilities, due to the presence of the weakly basic triazole linkers. Sequestration efficiency indeed depends on the effective occurrence of both electrostatic and hydrophobic interactions between the guest and the polymer lattice. Thus, our CaNS nanosponges can be considered as a new class of purely synthetic smart absorbent materials.

This perspective focuses on the crucial role that energy decomposition schemes play in elucidating the physical nature of non-covalent interactions in supramolecular systems, particularly from the point of view of host–guest systems stabilized by non-covalent interactions, which are fundamental to molecular recognition. The findings reported here reveal the robustness and practical application of methods such as EDA-NOCV in rationalizing molecular recognition situations in systems such as calixarenes, cyclophanes and other box-shaped hosts, capable of incorporating different chemical species as anions and PAHs. We expect that the discussed cases in this perspective can be viewed as an initial assessment for the multidimensional nature of the weak interactions underlying supramolecular aggregations, which can be recognized in a plethora of different structures constantly synthesized and characterized by chemists around the world. [ABSTRACT FROM AUTHOR]

Calixarenes with their three-dimensional structural architecture and ease of functionalization at the upper and/or lower rim are well-known for their plethora of applications in chemical, physical, biological and other disciplines. Herein, CuAAC click inspired p-tert-butylcalix[4]arene tethered benzotriazolyl dendrimers, for example, N-1, N-2 type 2-fold compound 6 and 7 'G(0)' and 6-fold compound 16 and 17 'G(1)' generation benzotriazolyl dendrimer, were devised and also evaluated for their therapeutic potential both in vitro and in vivo. The developed calix[4]arene tethered benzotriazolyl dendrimers have been characterized by standard spectroscopic analysis including NMR (1H and 13C), MS, and SEC. Among all the benzotriazolyl dendrimers developed, compound 7 was identified as the effective one which provided potential anti-bacterial and anti-biofilm activities against drug-resistant and slime producing organisms without imparting cytotoxicity to the eukaryotic systems. [ABSTRACT FROM AUTHOR]

Calixarene is a vase-like supramolecule structure with many useful characteristics. For several decades, many studies have been conducted about the characteristics of calixarene that can be applied in fields such as material science, biotechnology and nanosensors. The Langmuir-Blodgett (LB) technique is a powerful method in obtaining a homogenous monolayer or several layers of thin film by controlling the molecular orientation on the air-water surface. Novel characteristics of calixarene have been discovered in applications such as sensing material, water treatment and catalysts. Calixarene also has the ability to form a stable complex with biomolecules, making it able to be developed as a biosensor. The discussion in this review paper focuses on the characteristics of calixarene thin films made using the LB method that are suitable for nanosensor applications. [ABSTRACT FROM AUTHOR]

Our interest in the potential of chiral tetramethoxy‐resorcinarene as agents for chiral recognition has led us to synthesise twelve distally‐bridged chiral resorcinarene crowns. The fascinating architecture of these partially‐enclosed chiral basket molecules is evident in the solid‐state structures which have been determined by single‐crystal X‐ray crystallography. Moreover, the enantiomers of these chiral resorcinarene crowns have been resolved via diastereomeric resolution, with the absolute configuration of the diastereomers being determined by X‐ray crystallography. This work enables further exploration of these enantio‐pure chiral baskets as possible chiral resolving agents. [ABSTRACT FROM AUTHOR]

The dialkylation of 2,14-dithiacalix[4]arene was studied employing various synthetic procedures known for the parent macrocycles (thiacalixarenes and/or classical calixarenes). The best results for distal dialkylation were achieved using the Mitsunobu reaction with the corresponding alcohols. Interestingly, due to the lower symmetry of the starting compound, the dialkylated derivatives represent inherently chiral systems. The introduction of chiral substituents thus leads to mixtures of diastereomers potentially useful for the separation of individual stereoisomers as demonstrated by chiral HPLC. The conformational behavior of the novel compounds was studied both in solution (NMR) and in the solid state (X-ray). [ABSTRACT FROM AUTHOR]

bis-Methoxycarbonylmethoxy derivatives capable of reacting with the surface of aminopropylated silica gel with the formation of chemically and thermally stable amide bonds were obtained by regioselective distal dialkylation of hydroxyl groups of phosphorylated tetrahydroxycalix[4]arenes in high yields. It was found that phosphine oxide and phosphonate P=O groups localized on the upper rim cooperatively bind Eu3+ cations and effectively sorb them from nitric acid solutions. [ABSTRACT FROM AUTHOR]

The key features of calixarene derivatives as multivalent ligands for biomacromolecules and as multifunctional catalysts are reviewed herein. The ease of functionalization and the possibility to control the regio‐ and stereochemical disposition of multiple ligating units around a central core allow to obtain ligands with high affinity and selectivity especially for proteins and nucleic acids. The hydrophilic/lipophilic character can also be finely tuned, allowing to obtain monomeric hybrid derivatives or amphiphiles able to self‐assemble alone or in co‐formulation with lipids to give nanoparticles and liposomes that incorporate calixarenes. The knowledge acquired up to now sheds light on the future applications of calixarenes in bionanotechnology and nanomedicine. [ABSTRACT FROM AUTHOR]

Calix[4]arenes have the ability to encapsulate biomimetic guests, offering interesting opportunities to explore their molecular recognition, very close to biological scenarios. In this study, p‐sulfonatocalix[4]arene (C4 A) anions and hydrated alkali cations have been used for the in situ recognition of cationic 1,ω‐diammonium‐alkanes and 1,ω‐amino‐acids of variable lengths. NMR spectroscopy illustrates that these systems are stable in aqueous solution and the interaction process involves several binding states or stabilized conformations within the C4 A anion, depending of the nature of the guest. DOSY experiments showed that monomeric 1 : 1 host–guest species are present, while the cation does not influence their self‐assembly in solution. The folded conformations observed in the solid‐state X‐ray single‐crystal structures shed light on the constitutional adaptivity of flexible chains to environmental factors. Futhermore, a comprehensive screening of 30 single crystal structures helped to understand the in situ conformational fixation and accurate determination of the folded structures of the confined guest molecules, with a compression up to 40 % compared with their linear conformations. [ABSTRACT FROM AUTHOR]

In this study, a new photoelectrochemical cell based on overall splitting of water into oxygen and hydrogen is constructed to obtain an improved photocurrent under a visible range of light. The photoanode was obtained by a gold electrode (GE) modified with carboxylic acid functionalized SH-Calix-4-arene-COOH and IrO 2 nanoparticles attached light absorbing cyanine dye via polymeric oligoaniline linkages. The conductive polymer, 4- (4H-Dithieno [3,2-b: 2 ′, 3′-d] pyrrol-4-yl)aniline, was coated on GE using electropolymerization and used as a photocathode after platinum nanoparticles (Pt) were attached on the surface. The system was illuminated under the visible light, and the water was oxidized via IrO 2 catalyst to produce hydrogen on the photocathode side while oxygen on the photoanode. A photocurrent density of 182.03 μA cm−2 was obtained by direct transfer of electrons without using a mediator. The bilirubin oxidase (BOx) enzyme was successfully used to remove excess oxygen from the reaction chamber and a further increase in photocurrent was reached up to 272.44 μA cm−2. Hydrogen production in the reaction chamber was measured by gas chromatography at different time intervals and a maximum of 1.25 × 10−8 mol cm−2 was obtained. Image 1 • A photoelectrochemical cell generating photocurrent via water splitting was constructed. • Calix[n]arene/Cyanin Dye/IrO 2 structure was used transfer electrons in high efficiency. • Electrocatalytic reduction of O2 into water is achieved by Bilirubin Oxidase. • The maximum power of 15.6 mW m−2 was reached at a current density of 39.6 mA m−2. [ABSTRACT FROM AUTHOR]

After thiophene and furan were treated with n‐BuLi, respectively, the mixtures were reacted with various ketones and then dehydrated under acidic conditions. This reaction sequence led to the formation of 1‐(2‐heteroaryl)cycloalkenes and (2‐heteroaryl)alkenes. When the alkenes were treated with 10 mol % NIS, calix[4]arenes were produced as the major products, with minor amounts of calix[6]arenes sometimes being produced. Reducing the loading of NIS to 1 mol % and increasing its overall concentration to 6 M resulted in a substantial increase in the yield of hexaspirocyclohexyl calix[6]thiophene (from 2 to 66 %). [ABSTRACT FROM AUTHOR]

The oxidation of antioxidants by oxidizers imposes great challenges to both living organisms and the food industry. Here we show that the host–guest complexation of the carefully designed, positively charged, amphiphilic guanidinocalix[5]arene pentadodecyl ether (GC5A‐12C) and negatively charged oleic acid (OA), a well‐known cell membrane antioxidant, prevents the oxidation of the complex monolayers at the air–water interface from two potent oxidizers hydroxyl radicals (OH) and singlet delta oxygen (SDO). OH is generated from the gas phase and attacks from the top of the monolayer, while SDO is generated inside the monolayer and attacks amphiphiles from a lateral direction. Field‐induced droplet ionization mass spectrometry results have demonstrated that the host–guest complexation achieves steric shielding and prevents both types of oxidation as a result of the tight and "sleeved in" physical arrangement, rather than the chemical reactivity, of the complexes. [ABSTRACT FROM AUTHOR]

The reaction between MnCl2·4H2O, 2,2′-bis-p-tBu-calix[4]arene (H8L1) and 2-(hydroxymethyl)pyridine (hmpH) in a basic dmf/MeOH solution results in the formation of the complex [Mn III10 Mn II4 (L1)3(hmp)4(μ3-O)4(μ3-OH)2(MeOH)4(dmf)6](dmf)4 (6) upon vapour diffusion of petroleum ether into the mother liquor. The crystals are in the monoclinic space group C2/c, with the asymmetric unit (ASU) comprising one half of the molecule. The structure describes a large S-shaped cluster (∼40 Å top to tail) where the unusual syn and anti conformations of the calixarene ligands results in two binding pockets each containing a [Mn III5 Mn II2 ] moiety comprised of two perpendicular, vertex-sharing [Mn4] butterflies. One butterfly possesses a [Mn III4 O4] core and the second a [Mn III2 Mn II2 O3] unit with the MnII ions in the central body positions. Magnetic susceptibility and magnetisation measurements reveal weak exchange interactions between the metal centres. [ABSTRACT FROM AUTHOR]

A calix[4]arene, in which two of the phenol functions are replaced by pyrazole units, [H2(bpzCal)], was investigated as a ligand for Cu+, Ag+ and Au+ ions. Using [Cu(MeCN)4]BF4 and AgSbF6 as the precursors, complexes [MH2(bpzCal)]X (M = Cu, X = BF4; M = Ag, X = SbF6) were formed, where the calixarene ligands adopt a 1,3‐alternate structure and the metal ions are coordinated linearly by the two pyrazolyl donors. [CuH2(bpzCal)]BF4 displayed a – for copper(I) complexes – unusual stability towards O2, which is due to the steric protection of the CuI center. By contrast a dinuclear copper(I) complex [Cu2(bpzCal)] that was obtained through treatment of [H2(bpzCal)] with two equivalents of Cu(HMDS) is rather sensitive towards O2. The preparation of a gold complex required the employment of a gold precursor, which contains one labile and one stabilizing neutral ligand, namely [(PPh3)Au(NCMe)]SbF6, which led to the formation of [(PPh3)AuH2(bpzCal)]SbF6. In this complex [H2(bpzCal)] acts only as a monodentate ligand for the gold center. Taken together, the results demonstrate the potential of [H2(bpzCal)] in providing rather different coordination spheres for metal ions. [ABSTRACT FROM AUTHOR]

A topological-chemical reactivity studies (using electronegativity, chemical hardness, chemical power, electrophilicity indices and topological indices like Wiener indice) has been applied on calixare-based rotaxane complexes containing tris(N-phenylureido)- calix[6]arene as wheel and a 4,4'-bipyridinium dication's units as axle. The results indicate that the formation of this type of rotaxanic complex needs a preorganisational modifications undertaken by the calixarene to match with its molecular surface the shape of the guest molecule (axle of rotaxane). The obtained chemical binding scenario suggests that we are dealing with a system that remains open until the delayed maximization of the HOMO-LUMO interval, fact that allows the continuous transfer of charge between the components of the rotaxane. [ABSTRACT FROM AUTHOR]

The IR spectra of p-(3-carboxy-1-adamantyl)-calix[4]arene (AdC4A) were studied. Using IR spectroscopy, it has been shown that in calixarene in dilute solution in CCl4, there was no free hydroxyl absorption band. The hydroxyl group band was characterized by a very low frequency, which indicates a strong intramolecular hydrogen bond on the lower rim of the calixarene molecules. On the upper rim of the calixarene, the carboxyl groups form cyclic dimer or tetramer complexes via intermolecular hydrogen bonds. The cone conformation persists, but there is a mutual influence of the hydrogen bonds along the top and bottom rims of the calixarene molecule. The structure with dimeric hydrogen bonds between the carboxyl groups is 16.5 KJ/mol more preferable than the structure with tetrameric cyclic hydrogen bonds for AdC4A. The reactivity depends on the type of association on the upper rim, whether these are hydrogen-bonded dimers or cyclic tetrameric association. [ABSTRACT FROM AUTHOR]

One of the most common phenol‐formaldehyde cyclic oligomers from hydroxyalkylation reactions that exhibit supramolecular chemistry are calixarenes. These macrocyclic compounds are qualified to act as synthetic catalysts due to their specific features including being able to form host‐guest complexes, having unique structural scaffolds and their relative ease of chemical modifications with a variety of functions on their upper rim and lower rim. Here, a functional magnetic nanocatalyst was designed and synthesized by using a synthetic amino‐functionalized calix[4]arene. Its catalytic activity was evaluated in a one‐pot synthesis of 2‐amino‐4H‐chromene derivatives. Besides, this novel magnetic nanocatalyst was characterized by spectroscopic and analytical techniques such as FT‐IR, EDX, FE‐SEM, TEM VSM, XRD analysis. [ABSTRACT FROM AUTHOR]

Calixarenes are supramolecular compounds with a unique three-dimensional structure, the biological activity of which is determined by the chemical groups on the upper or lower rim. As shown in the previous works, using isolated mitochondria and digitonin-permeabilized myometrium cells, the calix[4]arene chalcone amides modulated the levels of both mitochondria-membrane polarization and Ca2+ concentration in the myometrial mitochondria matrix. As shown, the incubation of the mitochondria with calix[4]arene chalcone amides is accompanied by changes of the average hydrodynamic diameter of mitochondria. The aims of this study are as follow: to investigate the kinetics of the mitochondria diameter changes under the effects of calix[4]arenes with two and four chalcone amide groups; find out whether or not calix[4]arene chalcone amides penetrate into the cell and whether the polarization of the mitochondria membranes undergoes alterations at the incubation of the primary myometrium-cells’ culture with these compounds. Experiments are conducted on two biochemical models: isolated myometrial mitochondria and primary myometrium-cells’ culture. The hydrodynamic diameter of mitochondria is investigated using the dynamic light-scattering method with the use of a laser correlation spectrometer Malvern Instruments ‘ZetaSizer-3’ (United Kingdom). Polarization of mitochondria membranes is investigated using confocal laser scanning microscope LSM 510 META Carl Zeiss. The calix[4]arene chalcone amide C-1070 fluorescence spectrum is studied using the QuantaMasterTM40 spectrofluorimeter (Photon Technology International). As shown: the hydrodynamic diameter of the mitochondria depends on the composition of the incubation medium, and in the presence of ATP, it is smaller than in its absence; the hydrodynamic diameter of the mitochondria increases in time at the incu-bation of mitochondria with calix[4]arene chalcone amides; calix[4]arene chalcone amides’ effect on the hydrodynamic diameter of the mitochondria increases with an increase in the number of chalcone amide groups in the structure of calix[4]arenes; calix[4]arene chalcone amides’ effect on the hydrodynamic diameter of the mitochondria depends on the composition of the incubation medium, and at the presence of ATP, it is smaller than at its absence. Using calix[4]arene chalcone amide C-1070 (as fluorescent equivalent of C-1011), it is proved that these compounds penetrate the myometrial cells. The modulatory effects of calix[4]arene chalcone amide with two chalcone amide groups on the polarization of the mitochondria membranes is shown using primary myometrium-cell culture and potential-sensitive probe JC-1. Medical statistics indicate that uterine fibroids are widespread pathology. The search for compounds, which can reduce the volume of the tumour, is extremely important. The results allow suggest that calix[4]arene chalcone amides are promising compounds in the further study of their effect on the viability of the undesirable cells due to the launch of apoptosis of mitochondrial pathway. [ABSTRACT FROM AUTHOR]