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• Newly macrocyclic materials based on oxacalix[4]arene have been synthesized. • All four oxacalix[4]arene-based azo-ester derivatives shows LC properties. • All macrocyclic compounds exhibited enantiotropic columnar hexagonal phase. • The selected compound is further tested for the photo tuning properties. Oxacalix[4]arene is a unique type of macrocyclic compound closely related to calixarenes. It consists of four aromatic rings connected by oxygen bridges. This molecule exhibits a remarkable blend of rigidity and flexibility, making it adaptable to various molecular interactions. In present study, we present our findings on the synthesis and characterization of four new supramolecular bowl-shaped materials (FOC 1 -FOC 4) originating from the robust core structure of tetranitro oxacalix[4]arene. The thermal decomposition was analyzed through the thermogravimetric analysis. All four oxacalix[4]arene-based macrocycles adopted a 1,3-alternate (saddle-like) conformation and exhibited a columnar hexagonal phase with a behavior to self-assemble at room temperature. All four macrocycles (FOC 1 -FOC 4) displayed enantiotropic mesophases within a temperature range of 56.0 °C to 63.0 °C. Further, the relationship between the molecular structure, particularly the varying alkyl chains, and the mesomorphic properties of these compounds was also examined. It was found that the mesomorphic behavior of FOC 3 and FOC 4 was significantly influenced by cis and trans isomerization. These two compounds exhibited photoswitching behavior, transitioning between their cis and trans forms when exposed to 365 nm light. Notably, they displayed a prolonged stability in the cis form after UV exposure, which is valuable for applications requiring precise control over the switching process. [Display omitted] [ABSTRACT FROM AUTHOR]

Aromatic units bring special features to supramolecular receptors when the challenge of binding and release of CO2 is being addressed. Recent examples arising from calixarenes, pillararenes and cyclophanes are discussed in this review. The abilities of these systems to spatially organize metal coordination, hydrogen bonding or hydrophobic interactions for the purpose of CO2 binding are pointed out. Consequences for sensing and catalytic reactions are also highlighted.

[Display omitted] • Calix [4] arene-TPE and sulfonate copolymer were synthesized. • In comparison to CP-TPE, the modified CP-TPE-SO 3 H was hydrophilic. • CP-TPE-SO 3 H exhibits stronger electrostatic interaction than CP-TPE. • The pseudo-second-order rate constant of POP-TPE-SO 3 H toward TC is 0.0407 g mg−1 min−1. Removal of cationic pollutants, including dyes, herbicides, and antibiotics from water is significant owing to their persistence, bioaccumulation, carcinogenicity, mutagenicity, and reproductive risks. In this paper, a calixarene-tetraphenyl ethylene containing copolymer adsorbent, named CP-TPE, was synthesized using the Suzuki-Miyaura coupling reaction between the resorcinol calixarene and tetraphenyl ethylene boric acid esters. Subsequently, the phenolic groups on the CP-TPE were further reacted with chlorosulfonic acid, resulting in a sulfonated product named CP-TPE-SO 3 H. The introduction of the sulfonate groups not only significantly improved the hydrophilicity of CP-TPE-SO 3 H but also enhanced the electrostatic interaction between CP-TPE-SO 3 H and cationic molecules, achieving an outstanding maximum adsorption capacity for paraquat (representative herbicide, 300.06 mg g−1) and tetracycline hydrochloride (representative antibiotic, 888.74 mg g−1), which surpassed the majority of reported polymeric adsorbents. Moreover, the k 2 of CP-TPE-SO 3 H on TC (0.0407 g mg−1 min−1) reached the maximum value reported so far. This study demonstrated the significance and superiority of sulfonation modification in synthesizing POPs-based adsorbents, which can be potentially employed in real wastewater treatment. [ABSTRACT FROM AUTHOR]

The cover image shows amphiphilic calixarenes embedded in a phospholipid bilayer membrane. Anionic calixarenes facilitate counterion‐mediated transport of positively charged peptides across said membranes highlighting the utility of amphiphilic calixarenes for peptide transport into liposome and for direct cytosolic delivery of charged molecules into cells, which still is a significant problem in the fields of biology and medicine. [the image refers to the article "Anionic Calixarenes in Biomembrane Transport of Peptides" by Justin Neumann and Andreas Hennig.].. [Extracted from the article]

• Four new dinuclear lanthanide complexes derived from a mono-functionalized calix[4]arene ligand have been prepared and characterized. • The solid-state structures of [La 2 (mono-O-propargyl-calix[4]arene) 2 (MeOH) 4 ] and [La 2 (mono-O-propargyl-calix[4]arene) 2 (MeOH) 4 ] have been determined by X-ray diffraction analysis. • Their ability of the lanthanum complex to react with azides in a click reaction has been demonstrated. The ability of the propargylated calix[4]arene ligand H 3 L (= 25-(2-propynyloxy)-26,27,28-trihydroxy-calix[4]arene) to bind lanthanide ions has been studied. The triply deprotonated ligand was found to support dinuclear neutral complexes of composition [Ln 2 L 2 (MeOH) 4 ] (Ln= La (1), Gd (2), Tb (3), Tm (4)). Spectroscopic data for 1 – 4 as well as X-ray crystallographic analysis of single crystals of 1 ∙(MeOH) 2 and 2 ∙(MeOH) 2 reveal that two [Ln L ] entities dimerize via two phenolato groups to generate a centrosymmetric (MeOH) 2 O 3 Ln(μ-O) 2 LnO 3 (OHMe) 2 core structure. The Ln3+ ions reside in a distorted mono-capped octahedral coordination environment. Squid magnetic measurements for the Gd3+ and Tb3+ complexes agree with the formulation as dinuclear compounds, and reveal the presence of very weak antiferromagnetic exchange interactions (J < 0.1 cm−1). The ability of the La3+ complex to react with azides in a click reaction is also demonstrated. Dinuclear lanthanide complexes of a propargylated calix[4]arene ligand H 3 L (= 25-(2-propynyloxy)-26,27,28-trihydroxy-calix[4]arene) have been synthesized and characterized. Their ability to react with azides in a click reaction has been demonstrated. [Display omitted] [ABSTRACT FROM AUTHOR]

Cancer is one of the leading causes of death worldwide, and the limited success of currently used anticancer drugs is a driving force for the search for new compounds with anticancer potential. Calixarenes make up a fascinating class of macrocycles that find a wide range of biological applications in supramolecular chemistry. Especially in recent years, the anticancer activity of various calixarene derivatives has been reported by many researchers. The aim of this review article is to find relatively simple, efficient, and synthetic methods for the preparation of macrocyclic compounds containing various pharmacophoric groups to produce new and effective anticancer materials in cancer research and to investigate the usability of calixarene-based supramolecular in cancer research. [ABSTRACT FROM AUTHOR]

A small family of novel halogen-bonded crystalline supramolecular architectures of calixarenes was obtained by the co-crystallization of cone (1) and 1,3-alternate tetrakis(3-iodopropargyloxy)calix[4]arene (4) as tetradentate halogen donors with different multidentate acceptors. Particularly interesting is the interpenetrated diamondoid network of 4 with DABCO, which represents the first example of a 2D network of calixarene macrocycles where halogen bonding is the key interaction for self-organization. [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. [ABSTRACT FROM AUTHOR]

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

Two novel calix[ n ]arene-based immunogens were able to yield anti-cocaine antibodies and decrease the levels of [99mTc]TRODAT-1, a cocaine-based radionuclide, in the brain of the tested mice. [Display omitted] • The first total synthesis of the novel calix[n]arene-based immunogens V4N2 and V8N2 is reported. • V4N2 and V8N2 promoted the production of cocaine antibodies and also modulated the biodistribution of [99mTc]TRODAT-1, a radiolabeled analogue of cocaine. • V4N2 and/or V8N2 are potential candidates for the development of an immunogenic agent for the treatment of cocaine use disorder. 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. 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. 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. 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. The present results demonstrate the potential of V4N2 and V8N2 as immunogens for the treatment of cocaine use disorder. [ABSTRACT FROM AUTHOR]

Comparison of various calix[6]arene and calix[4]arene derivatives revealed that only analogues bearing a permanent positive charge non-covalently bind to ds-DNA and ds-RNA, by insertion into a DNA minor groove or RNA major groove. Also, these cationic analogues revealed strong and highly selective charge-dependent stabilization of AT-DNA against thermal denaturation, the calix[6]arene trication being an order of magnitude more efficient than its calix[4]arene dicationic analogue. At variance to DNA/RNA selectivity for only cationic calixarenes, both neutral and cationic calixarenes bind nucleoside monophosphates with similar efficiency, by forming tweezer-like supramolecular complexes, with nucleobases inserted between aromatic pendant arms grafted to calixarene rims. Such nucleotide-calixarene complexes were monitored by an emission change of calixarene as a function of nucleobase insertion, at variance to DNA/RNA complexes in which calixarene is inserted into the polynucleotide groove, which does not change calixarene emission – stressing the importance of the ligand insertion within a calix-basket for fluorimetric sensing. [ABSTRACT FROM AUTHOR]

The development of efficient, reliable, and easy‐to‐use biosensors allowing early cancer diagnosis is of paramount importance for patients. Herein, we report a biosensor based on silver nanoparticles functionalized by peptide aptamers for the detection of a cancer biomarker, i. e. the Mdm2 protein. Silver nanoparticles (AgNPs) were produced and stabilized with a thin PEGylated‐calix[4]arene layer that allows (i) the steric stabilization of the AgNPs and (ii) the covalent conjugation of the peptide aptamers via the formation of an amide bond. These peptide‐conjugated AgNPs were then used to detect Mdm2 via a dual trapping strategy that was previously reported with gold nanoparticles (AuNPs). Our results showed that replacing AuNPs by AgNPs improves the detection limit by nearly one order of magnitude, down to 5 nM, while the high selectivity of the system and the stability of the particles provided by the calixarene coating allow the detection of Mdm2 in human serum. [ABSTRACT FROM AUTHOR]

The recent discovery of calix[3]pyrrole, a porphyrinogen‐like tripyrrolic macrocycle, has provided an unprecedented strain‐induced ring expansion reaction into calix[6]pyrrole. Here, we synthesized calix[n]furan[3‐n]pyrrole (n=1∼3) macrocycles to investigate the reaction scope and mechanism of the ring expansion. Single crystal X‐ray analysis and theoretical calculations revealed that macrocyclic ring strain increases as the number of inner NH sites increases. While calix[1]furan[2]pyrrole exhibited almost quantitative conversion into calix[2]furan[4]pyrrole within 5 minutes, less‐strained calix[2]furan[1]pyrrole and calix[3]furan were inert. However, N‐methylation of calix[2]furan[1]pyrrole induced a ring‐expansion reaction that enabled the isolation of a linear reaction intermediate. The mechanism analysis revealed that the ring expansion consists of regioselective ring cleavage and subsequent cyclodimerization. This reaction was further utilized for synthesis of calix[6]‐type macrocycles. [ABSTRACT FROM AUTHOR]

Proximally single-atom-bridged calix[4]arenes possess a rigidified cavity and, thus, unusual complexation properties. Here, we report on the synthesis of the first such heteroatom-bridged compound: amine-bridged calix[4]arene. This compound, prepared by thermal decomposition of 4-azidocalix[4]arene, was obtained alongside very interesting rearranged, inherently chiral 10 H -azepino[1,2- a ]indole derivatives. NMR titration confirmed the suitability of the amine cavity for the complexation of methylammonium cations; moreover, the –NH– bridge function enables its further derivatization. [ABSTRACT FROM AUTHOR]

A rapid and scalable synthesis of supported NHC−Pd(II)‐pyridine complexes on a benzyloxycalix[8]arene macrocycle is reported. Their subsequent use in Suzuki‐Miyaura benchmark reactions led to the optimisation of the nature of the ligands around the metal centre, delivering two very active precatalysts. They both promote the cross‐coupling of challenging API precursors at low catalytic loadings, when used as insoluble species in EtOH as a green reaction solvent. Moreover, their activity has been shown to be comparable or even superior to that of more conventional homogeneous catalysts. Of main importance, a simple filtration of the insoluble supported catalysts after reaction afforded the lowest Pd contamination values in the target products, in some cases directly approaching the levels authorised by the industrial regulations. Offering furthermore the possibility of easy palladium recovery in the current context of its overconsumption, we are convinced that these calixarene‐supported NHC‐PEPPSI Pd complexes are valuable tools for the fine chemical industry, to prepare metal‐free functionalised biaryl compounds in high yields, ranging from 76 to 94%. [ABSTRACT FROM AUTHOR]

Kidney stones are an ailment that affects many people globally. While kidney stones can sometimes be treated with simple dietary changes this does not solve all cases. Most kidney stones are comprised predominantly of calcium oxalate and there are few very options in terms of accepted treatments for patients who suffer from this reoccurring condition. This research investigates the use of additives, resorcin[4]arenes and calix[4]arenes functionalised with three different amino acids (lysine, aspartic acid and proline) and their impact on the nucleation, morphology and zeta potential of calcium oxalate in a synthetic urine environment. The resorcin[4]arene functionalised with aspartic acid showed the stabilisation of calcium oxalate dihydrate rather than calcium oxalate monohydrate typically observed. The calix[4]arenes functionalised with proline and lysine showed large impacts on the morphology of the crystals formed. Additionally, the additives show significant impacts on the zeta potential of the crystals formed. It was also discovered that all three additives show evidence of incorporation to different extents through the crystal. These impacts were only observed when the macrocycles functionalised with amino acids were present, as the free amino acids showed minimal impact. [ABSTRACT FROM AUTHOR]

Cup‐shaped molecules are of great interest due to their appealing architectures and properties. Compared with widely studied calixarenes, polyoxometalate‐based cup‐shaped molecules currently remain a virgin land waiting for exploration. In this work, we report the first discovery of two giant cup‐shaped inorganic–organic hybrid polyoxoniobates (PONbs) of {Cu12Nb120} and {Cd16Nb128}. The former integrates three tricyclic Nb24 clusters and a hexacyclic Nb48 cluster into a cup‐shaped molecule via a Cu12 metallacalixarene, while the latter unifies two tricyclic Nb24 clusters and a brand‐new pentacyclic Nb40 cluster into another cup‐shaped molecule via a hybrid Cd16 unit. With 132 and 144 metal centers, {Cu12Nb120} and {Cd16Nb128} show the largest two inorganic–organic hybrid PONbs known to date. [ABSTRACT FROM AUTHOR]

This study focuses on the construction of two new inclusion complexes of quercetin with p-sulfonatocalix[4]arene-tetracarboxylic acid and/or p-sulfonatocalix[8]arene-octacarboxylic acid, so that the drug gets soluble in an aqueous media. The structures of the inclusion complexes have been analyzed through FT-IR, NMR and UV–Vis spectroscopy. Evidences indicate that the π–π interaction and hydrogen bonding involve in the inclusion complexes of water-soluble calixarenes (Clx4 and Clx8) with quercetin. The associating constants and stoichiometry of the inclusion complexes constructed between p-sulfonatocalix[n]arene-carboxylic acids (Clx4 and Clx8) and quercetin have been also estimated. In addition, the antioxidant behaviors of the inclusion complexes have been investigated. [ABSTRACT FROM AUTHOR]

Carbonic anhydrases (CAs) continue to represent a relevant pharmaceutical target. The need of selective inhibitors and the involvement of these metalloenzymes in many multifaceted diseases boost the search for new ligands able to distinguish among the different CA isoforms, and for multifunctional systems simultaneously able to inhibit CAs and to interfere with other pathological events by interacting with additional targets. In this work, we successfully explored the possibility of preparing new CAs ligands by combining calixarenes with benzensulfonamide units. Inhibition tests towards three human CA isoforms evidenced, for some of the ligands, Ki values in the nanomolar range and promising selectivity. X‐ray and molecular modeling studies provided information on the mode of binding of these calixarene derivatives. Thanks to the encouraging results and the structural features typical of the calixarene scaffold, it is then possible to plan for the future the design of multifunctional inhibitors for this class of widely spread enzymes. [ABSTRACT FROM AUTHOR]

We report on the synthesis of bivalent water‐soluble calix[4]arene and calix[5]arene hosts, Super‐sCx4 and Super‐sCx5 as new broad‐spectrum supramolecular binders of neuromuscular blocking agents (NMBAs). Synthesis was achieved using the target bisquaternary amine NMBAs as a template to link two highly anionic p‐sulfonatocalixarene building blocks in aqueous solution. Bivalent anionic hosts Super‐sCx4 and Super‐sCx5 bind by engaging both quaternary amines present on a variety of NMBAs. We report low μM binding to structurally diverse alkyl, steroidal, curarine and benzylisoquinoline NMBAs with high selectivity over the neurotransmitter acetylcholine and a variety of other hydrophobic amines. [ABSTRACT FROM AUTHOR]

In this era, explosives are easily available compared to the early days. Thus, more effective detection of explosives has become the main concern of homeland security. In the past decades, a large number of sensing materials have been developed for the detection of explosives in solid, vapor, and solution states through fluorescence methods. In recent years, great efforts have been devoted to developing new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. Modified calixarenes have high potentials to detect nitroaromatic compounds (NACs) due to their favorable structural properties. It summarizes the detection of NACs by the modified calixarene system formed by the complex. Various methodologies responsible for complex formation and binding mechanisms (PET, FRET, EE, etc.) are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed. [ABSTRACT FROM AUTHOR]

Aim. To study the effect of 5,11,17,23-tetrakis(diisopropoxyphosphonyl)-25,26,27,28-tetrapropoxycalix[4]arene and oсtаkis(diethoxyphosphoryloxy)-tert-butylcalix[8]аrene additives to the MeCN – H2O mobile phase (86:14) on the selectivity of the separation of aromatic compounds by the reversed-phase high performance liquid chromatography (RP HPLC) using a Separon SGX C18 support. Results and discussion. The process of complexation of phosphorylated calix[4,8]arenes with benzene derivatives in the mobile phase plays a key role in the RP HPLC separation of analytes. The stability constants of the inclusion complexes and the chromatographic separation coefficients of the analytes depend on the nature of the aromatic compounds and the cavity size of the calixarene macrocycle. Experimental part. The HPLC analysis was performed in acetonitrile – water (86:14) solution using a Separon SGX C18 column. The stability constants of the calixarene complexes were determined using the dependence of 1/k’ chromatographic parameters of benzene derivatives on the calixarene concentration in the mobile phase. Molecular modelling of the calixarene complexes was carried out using a Hyper Chem 8.0 program. Conclusions. The phosphorus-contained calixarenes due to their ability to form supramolecular complexes with aromatic molecules can be used as additives to the RP HPLC mobile phase and improve separation of benzene derivatives.

Abstract 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 Calixarenes are of interest as receptors for ions and small molecules and as organic materials. Exchanging the arene units through heteroaromatics allows changing their optoelectronic and host–guest properties. We herein present calix[n]phenothiazines (n = 3, 4) as novel macrocycles, accessible in two-step syntheses. The phenothiazine units show reversible redox events and emissive properties, and N-hexyl-substituted calix[3]phenothiazine binds to both ammonium ions and a bisimidazole as neutral guests.

The purpose of this study was to synthesize and structurally characterize ketocalixarenes (i.e., calixarenes where the bridging methylene bridges are replaced by carbonyl groups) derived from the largest "major" calixarene, namely p - tert -butylcalix[8]arene 3a . Ketocalix[8]arenes were synthesized by the oxidation of protected p - tert -butylcalix[8]arene derivatives. Octamethoxy-p-tert-butylketocalix[8]arene 6b was prepared by the photochemical reaction of the calixarene 3b with NBS in a CHCl 3 /H 2 O mixture. The oxidation of the methylene groups of octaacetoxy- p - tert -butylcalix[8]arene 3c was conducted by a reaction with CrO 3 in Ac 2 O/AcOH. The basic hydrolysis of the acetate groups of the oxidation product yielded octahydroxy- p - tert -butylketocalix[8]arene 6a . In the crystal, the molecule adopts a saddle-like conformation of crystallographic C 2 and idealized S 4 symmetry. Strikingly, the array of OH/OH intramolecular hydrogen bonds present in the parent 3a is completely disrupted in 6a .

Calixarenes are reportedly excellent activators that can remarkably improve the transport efficiencies of cell penetrating peptides. We employed eight calixarenes to systematically study the influence of structure on activation efficiency, which revealed that the scaffold, head group, and alkyl chain are all significant factors for activation efficiency by affecting affinities with the peptide and membrane. [ABSTRACT FROM AUTHOR]

This mini review summarizes Vicens' research on calixdendrimers since 2004. [ABSTRACT FROM AUTHOR]

Jacques Vicens perceived a special relationship between painting and chemistry, especially supramolecular chemistry based on calixarenes, and integrated both to construct sophisticated molecules with exceptional properties. In honor of his remarkable life, this article is a survey of his way of thinking and his approach to chemistry. [ABSTRACT FROM AUTHOR]

Heteroditopic calix[6]arenes are extensively exploited as synthetic receptors and as molecular components of supramolecular threaded and interlocked structures. We describe the synthesis of two novel calix[6]arene macrocycles, the upper rim of which is functionalized with either two or three phenylthioureido groups. These moieties are excellent hydrogen‐bond donors and largely affect the conformation of the macrocycle, both in solution and in the solid state. Alternate conformers are observed in solution, and they give rise to supramolecular chains in the solid state. Moreover, and because of this conformational freedom, also the recognition properties toward the formation of pseudorotaxanes with bipyridinium‐based axles are strongly affected. The number of phenylthioureido units of the macrocyclic host and the nature of the counterions of the bipyridinium guest determine the stability of the complexes. NMR, UV‐Vis and electrochemical measurements revealed that very stable 1 : 1 inclusion complexes are formed between the triphenylthioureido calix[6]arene and a bipyridinium guest with tosylate counterions, whereas no complex is observed between the diphenylthioureido macrocycle and a hexafluorophosphate bipyridinium salt. [ABSTRACT FROM AUTHOR]

Three cobalt-calixarene coordination frameworks, namely, {[Co4Cl(H4TC4AS)]4(HPO3)8}4− (CIAC-253), {[Co4Cl(H4TC4AS)]4(PO4)8}12− (CIAC-254) and {[Co4Cl(H4TC4AS)]3(Ph-PO3)6}3− (CIAC-255) were obtained by solvothermal reaction of a cobalt salt, sodium p-sulfonatothiacalix[4]arene (Na4H4TC4AS) and phosphate, phosphite and phosphonate ligands. In CIAC-253 and CIAC-254, the shuttlecock-like Co4Cl-(TC4AS) secondary building units (SBUs) are bridged by HPO32− or PO43− anions into two quadrilateral frameworks while in CIAC-255, the Co4Cl-(TC4AS) SBUs are linked into a triangular framework by phenylphosphonate anions. The supramolecular interactions between the phenyl groups of phosphonate and TC4AS play a crucial role in the formation of the triangle. Magnetic measurements revealed that all the cobalt(II) centers exhibit antiferromagnetic interactions. [ABSTRACT FROM AUTHOR]

The vibrational spectra of the p-tetrasulfonatothiacalix[4]arene pentasodium salt (TCAS) and tert-butylthiacalix[4]arene (BuTCA) were studied. Comparison of the TCAS and BuTCA IR spectra allows us to isolate the bands of tert-butyl and sulfonate groups. Geometry, IR and Raman spectra were calculated for conformation cone, partial cone, 1,2-, and 1,3-alternate. The most stable conformation of the TCAS is the cone. Characteristic bands were determined for each of the possible conformations. In the case of the TCAS molecule, four ions of sodium are coordinated with the oxygen atoms of sulfonate groups, and the fifth ion interacts with the oxygen and sulfur atoms of the macrocycle. Under the influence of sodium ions, the distribution of electron density in the TCAS molecule and its ability to supramolecular interactions change. [ABSTRACT FROM AUTHOR]

In this study, the ligand exchange mechanism at a biomimetic ZnII centre, embedded in a pocket mimicking the possible constrains induced by a proteic structure, is explored. The residence time of different guest ligands (dimethylformamide, acetonitrile and ethanol) inside the cavity of a calix[6]arene‐based tris(imidazole) tetrahedral zinc complex was probed using 1D EXchange SpectroscopY NMR experiments. A strong dependence of residence time on water content was observed with no exchange occurring under anhydrous conditions, even in the presence of a large excess of guest ligand. These results advocate for an associative exchange mechanism involving the transient exo‐coordination of a water molecule, giving rise to 5‐coordinate ZnII intermediates, and inversion of the pyramid at the ZnII centre. Theoretical modelling by DFT confirmed that the associative mechanism is at stake. These results are particularly relevant in the context of the understanding of kinetic stability/lability in Zn proteins and highlight the key role that a single water molecule can play in catalysing ligand exchange and controlling the lability of ZnII in proteins. [ABSTRACT FROM AUTHOR]

The surface coordination of p‐sulfonato‐ (C[4]), p‐sulfonatothia‐ (SC[4]) and p‐sulfonato‐sulfoxocalix[4]arene (SO2C[4]) on La0.9Tb0.1F3 nanoparticles (TbNP) was investigated by UV‐Vis absorption and luminescence spectroscopies. SO2C[4] displayed the strongest affinity towards the NPs and a significant antenna effect leading to observation of the characteristic Tb emission bands upon calixarene excitation. NPs decorated by a shell of SO2C[4] were prepared and the interaction with rhodamine 6G (R6G) was studied. The progressive addition of R6G resulted in a strong Tb to R6G energy transfer process, as revealed by a long lived emission of R6G upon SO2C[4] excitation. The FRET efficiency was almost quantitative (87–90 %), pointing to an average distance of 28 to 32 Å between the R6G and the Tb emitting centres of the NP. An association of one R6G per SO2C[4] was deduced with a very strong apparent affinity (K=2.5×107 M−1) in water. Similar interactions were observed with paraquat, resulting in TbNP luminescence quenching. In both cases, an unexpected increase of the association constant of the cation with SO2C[4] was observed when SO2C[4] is anchored at the surface of the NP. [ABSTRACT FROM AUTHOR]

The macrocyclic calix[4]arene ligand H2L comprises two non‐fluorescent 2,6‐bis‐(iminomethyl)phenolate chromophores, which show a chelation‐enhanced fluorescence enhancement upon Zn2+ ion complexation. Macrocyclic [ZnL] complexes aggregate in the absence of external coligands via intermolecular Zn−N bonds to give dimeric [ZnL]2 structures comprising two five‐coordinated Zn2+ ions. The absorption and emission wavelengths are bathochromically shifted upon going from the liquid (λmax,abs (CH2Cl2)=404 nm, λmax,em (CH2Cl2)=484 nm) to the solid state (λmax,abs=424 nm (4 wt%, BaSO4 pellet), λmax,em=524 nm (neat solid)). Insights into the electronic nature of the UV‐vis transitions were obtained with time‐dependent density functional theory (TD‐DFT) calculations for a truncated model complex. [ABSTRACT FROM AUTHOR]

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

Hexamethoxycalix[6]arene 3 forms a directional pseudorotaxane complex with the chiral axle (S)-(α-methyl-benzyl)benzylammonium 2+. Between the two (endo-chiral)-2+@3 and (exo-chiral)-2+@3 pseudorotaxane stereoisomers, the former is preferentially formed. This result confirms the validity of the "endo-α-methyl-benzyl rule", previously reported by us. DFT calculations suggest that C-H ... π interactions between the methyl group of 2+ and the calixarene aromatic rings, determine the stereoselectivity of the threading process toward the "endo-α-methyl-benzyl preference". An amplification of optical rotation is observed upon formation of the pseudorotaxane complex (endo-chiral)-2+@3 with respect to free axle 2+. Thus, the specifical rotation of the 1:1 mixture of chiral 2+·B(ArF)4− salt and achiral 3 was augmented upon formation of the pseudorotaxane and DFT calculations were used to rationalize this result. [ABSTRACT FROM AUTHOR]

An approach for the lower rim modification of the calix[4]arene‐based molecular tweezes with monopyrrolo‐tetrathiafulvalene (MPTTF) arms attached to the upper rim of calixarenes is described. First, calixarene‐MPTTF conjugates with free hydroxyl on the lower rim are synthesized using the Ullmann reaction, then hydroxyl groups are substituted by propargyl groups, which can be used for further modification by the click reaction. The new calixarene‐TTF derivatives displayed reversible redox processes, as well as demonstrated binding affinity for electron‐deficient molecular guests such as tetracyanoquinodimethane. The described synthetic approach will be used for the modular synthesis of molecular receptors tailored for specific applications. [ABSTRACT FROM AUTHOR]

Calix[4]pyrroles can be obtained from the efficient preprogrammed condensation between acetone and pyrrole. This reaction forms the attractive macrocycle resembling in its constitution, but not in its oxidation state, to the porphyrin structure, prominently present in the vital "pigments of life". Calix[2]pyrrolidine[2]pyrrole and calix[4]pyrrolidine, the partially and totally reduced version of the macrocycle, became accessible through the hydrogenation of calix[4]pyrrole, but only under strenuous reaction conditions. The only known hydrogenation, which could give clues for improving the process, was the reduction of the calix[4]furan. To shed light on the process, mixed calix[n]furan[4‐n]pyrroles were prepared, and their hydrogenation was studied. After a laborious optimization process, the best conditions were discovered improving the yield of the hydrogenation process from the level of a formation to the level of a complete conversion. The calix[4]pyrrolidine is now accessible in two high yielding synthetic steps. The efforts to understand and to optimize the factors involved in the hydrogenation process of this perazamacrocycle are here reviewed. [ABSTRACT FROM AUTHOR]

Sitagliptin, an oral antidiabetic drug, is an effective medication for lowering blood glucose level either as monotherapy or in combination with other antidiabetic drugs. This work aims for the fabrication of a potentiometric sensor for sitagliptin detection. The sensor was designed by doping the polyvinyl chloride polymeric ion-selective membrane with calix[4]arene as an ionophore which highly improved the linearity range (1 × 10−6—1 × 10−2 M), sensitivity, selectivity and limit of detection (6.3 × 10−7 M) compared to ionophore-free membrane. The method was then validated according to the International Council for Harmonization (ICH) guidelines. The sensor was successfully employed to determine sitagliptin in bulk and pharmaceutical dosage form without any pre-treatment steps. Moreover, to demonstrate the deployability of the proposed sensor; it has been applied for the dissolution testing of sitagliptin by in-line continuous monitoring of sitagliptin release as a function of time from the pharmaceutical dosage form into the dissolution medium. This in-line dissolution monitoring has many advantages such as there is no need for the frequent sampling followed by the complicated procedures of samples treatment. Finally, the proposed potentiometric method was evaluated using the analytical eco-scale and has proved to be excellent green analysis in which solvent consumption and pre-treatment of samples were not necessary for its application. [ABSTRACT FROM AUTHOR]

This paper shows that 25‐propyloxy‐26,27‐dibenzoyloxy‐calix[4]arene can be a convenient precursor for the formation of inherently chiral configuration on the calixarene platform. The methods for sequential regioselective debenzoylation and electrophilic substitution on the upper rim were developed. The inherently chiral calix[4]renes with two and three different functional groups on the upper rim were synthesized. [ABSTRACT FROM AUTHOR]

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

This review critically examines the effectiveness of ion-imprinted membranes (IIMs) in selectively recovering lithium (Li) from challenging sources such as seawater and brine. These membranes feature customized binding sites that specifically target Li ions, enabling selective separation from other ions, thanks to cavities shaped with crown ether or calixarene for improved selectivity. The review thoroughly investigates the application of IIMs in Li extraction, covering extensive sections on 12-crown-4 ether (a fundamental crown ether for Li), its modifications, calixarenes, and other materials for creating imprinting sites. It evaluates these systems against several criteria, including the source solution's complexity, Li+ concentration, operational pH, selectivity, and membrane's ability for regeneration and repeated use. This evaluation places IIMs as a leading-edge technology for Li extraction, surpassing traditional methods like ion-sieves, particularly in high Mg2+/Li+ ratio brines. It also highlights the developmental challenges of IIMs, focusing on optimizing adsorption, maintaining selectivity across varied ionic solutions, and enhancing permselectivity. The review reveals that while the bulk of research is still exploratory, only a limited portion has progressed to detailed lab verification, indicating that the application of IIMs in Li+ recovery is still at an embryonic stage, with no instances of pilot-scale trials reported. This thorough review elucidates the potential of IIMs in Li recovery, cataloging advancements, pinpointing challenges, and suggesting directions for forthcoming research endeavors. This informative synthesis serves as a valuable resource for both the scientific community and industry professionals navigating this evolving field. [Display omitted] • MST-based IIMs: Promising for scalable Li recovery. • Investigates maximum Li + adsorption of 157 mg g−1. • Calls for refining IIM synthesis for higher capacity. • Suggests bespoke monomers for targeted Li + capture. • Highlights IIMs' potential in heavy metal recovery. [ABSTRACT FROM AUTHOR]

Abstract Guanidinocalix[5]arene and fluorescein reporter pair has been chosen to set up a supramolecular tandem assay principle based on the differential recognition of pyridoxal‐5′‐phosphate (the substrate of alkaline phosphatase, ALP), pyridoxal (the product of ALP) and phosphate (the product of ALP). This supramolecular tandem assay system offers an opportunity to monitor the activity of ALP in a label‐free, continuous, and real‐time manner. More importantly, a calibration curve can be given for selective and quantitative detection of pyridoxal‐5′‐phosphate (biomarker for several diseases).

Aim. To develop the method for the synthesis of the conjugate of diaminocalix[4]arene with 2-(2,3-dimethylphenyl)aminobenzoic acid (mefenamic acid) – bis-mefenamidocalixarene, determine its structure and physicochemical properties and assess its anti-exudative activity (AeA). Results and discussion. The conjugate of diaminocalixarene with mefenamic acid – bis-mefenamidocalixarene was synthesized at one step by the reaction of reactants in equimolar amounts in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The structure of the compound obtained was determined by spectral methods. AeA of bis-mefenamidocalixarene was studied in rats using the model of formalin edema. The results of the experimental studies showed that bis-mefenamidocalixarene exhibited the anti-exudative activity, which was equal to the reference drug – sodium diclofenac. Experimental part. The reaction of diaminocalixaren with 2- (2,3-dimethylphenyl)aminobenzoic acid (mefenamic acid) led to bis-mefenamidocalixarene with 40 % yield. The screening of AeA was carried out using modern digital plethysmometer (IITC Life Science (USA)). Conclusions. The effective one-stage method for the synthesis of the conjugate of diaminocalix[4]arene with 2-(2,3-dimethylphenyl)aminobenzoic acid – bis-mefenamidocalixarene has been developed. Its structure has been proven, and AeA has been studied. AeA is equal to the reference drug. It has been found that bis-mefenamidokalixaren synthesized is a promising compound for further profound studies.

Two mixtures of polyaminoazides were synthesized by a nucleophilic displacement strategy providing no separation of the components. The mixtures were adequately characterized by means of combined HR-ESIMS, FTIR and NMR techniques and, despite their complexity, they were successfully used to accomplish the subsequent preparation of pH-sensitive calixarene hyper-reticulated nanosponge materials. The desired responsivity to pH variations of the nanosponges obtained was verified by means of absorption tests on a set of organic pollutant model molecules.