Search

The development of a microcantilever (MCL) sensing device capable of simultaneously detecting several metal ionic species in aqueous media with low limits of detection requires a variety of sensing layers that are ion specific. Calix[4]arenes are robust molecules that can be easily modified and have been extensively studied for their ion binding properties. They are also capable of forming self-assembled monolayers (SAMs) on the gold layers of MCLs and are capable of detecting various metal ions with different anionic counterions in aqueous solutions. In this paper, we report on the effect of the alkoxy group in the narrow rim [O-(alkoxycarbonyl)methoxy] substituents of bimodal calix[4]arenes, which have been used as metal ion MCL sensing layers, using classical solution state experimental studies. A DFT computational study to compare the experimental results with several metal ions is also reported herein.

Two pyrene-based MCLs with sensitive and reversible mechanochromic properties and different optical phenomena were prepared. One displays ACQ properties, while the other shows obvious AEE properties with a >10-fold increased ΦFL amplitude.

Alcohol-based hand sanitizers (ABHSs) containing ethanol (EtOH) or isopropyl alcohol (IPA) to inactivate microorganisms help to prevent the spread of respiratory diseases. These products have become very popular during the COVID-19 pandemic. Apart from vaccines or other preventative antiseptic measures, the majority of consumers have relied on different types of ABHSs to disinfect their hands. As a result, there has been a global rush in the demand for these ABHSs and other antiseptic hygiene products. This has resulted in the formation of many new commercial sanitizer producers. There are around fifty companies of varying sizes that have been marketing their ABHSs in Bangladesh, most of which have only been manufacturing their products for the first time since the COVID-19 pandemic. To monitor the quality and components of these products, the Bangladesh Council of Scientific and Industrial Research (BCSIR) analyzed approximately 200 different hand sanitizer samples using GC–FID mass spectrometry. All samples were alcohol-based except for 3 which were alcohol-free aqueous hand sanitizers. Of the supplied formulated ABHSs, 80 samples were found to contain only IPA and 54 contained only EtOH. However, 28 samples were found to be contaminated with methanol (MeOH), 7 samples contained only MeOH and 18 samples contained both EtOH and IPA. This is the first study to explore the analysis of alcohol content in formulated ABHSs and their marketing status in Bangladesh, but the findings could be of use in other jurisdictions as similar issues have been raised in many parts of the world.

Schiff-base derivatives are widely used organic compounds and their metal complexes have been drawing much attention to chemists due to interesting structural features and unique properties. The presence of nitrogen containing imine groups (−C=N−) in Schiff-bases as well as in their metallic complexes and the chelating properties of these compounds are responsible for their many unique biological properties. In this review, we have summarized various acyclic Schiff-base ligands and their different metallic complexes which have been reported in the last one decade. Schiff-bases and their metal complexes have shown a broad range of biological activities, including antifungal, antibacterial, antimalarial, antiproliferative, anti-inflammatory, antiviral, and antipyretic properties. We have reviewed and arranged the reported Schiff-base derivatives according to their diverse biological applications, especially their anti-bacterial and anti-fungal activities, anti-tumor and anti-cancer activities, anti-oxidant activities, anti-inflammatory activities and other therapeutic and medicinal properties. The other component of this work as a review of the molecular structures of various Schiff-bases since their molecular structures play a primary role in the biological properties. The presence of heteroatoms such as nitrogen, sulfur and oxygen with free electron pairs and aromatic rings in the structure of the Schiff-bases play significant roles in determining their properties.

A new bimodal triazole-bridged pyrene-appended calix[4]arene 2g has been synthesised and characterised and complexation studies showed that the binding of Cd2+ and Zn2+ occurs as demonstrated by en...

An unexpected formation of carbamothioates by a sodium hydride-mediated reaction of arylmethyl isocyanides with xanthate esters in DMF is reported. The products thus obtained were compared with the carbamothioates obtained by the sodium hydride-mediated condensation of the corresponding benzylamines and xanthate esters in DMF. To account for these unexpected reactions, a mechanism is proposed in which the key steps are supported by quantum chemical calculations.

Hepatitis C virus (HCV) can cause acute and chronic infection that is associated with considerable liver-related morbidity and mortality. In recent years, there has been a shift in the treatment paradigm with the discovery and approval of agents that target specific proteins vital for viral replication. We employed a cell culture-adapted strain of HCV and human hepatoma-derived cells lines to test the effects of our novel small-molecule compound (AO13) on HCV. Virus inhibition was tested by analyzing RNA replication, protein expression, and virus production in virus-infected cells treated with AO13. Treatment with AO13 inhibited virus spread in cell culture and showed a 100-fold reduction in the levels of infectious virus production. AO13 significantly reduced the level of viral RNA contained within cell culture fluids and reduced the cellular levels of HCV core protein, suggesting that the compound might act on a late step in the viral life cycle. Finally, we observed that AO13 did not affect the release of infectious virus from infected cells. Docking studies and molecular dynamics analyses suggested that AO13 might target the NS5B RNA polymerase, however, real-time RT-PCR analyses of cellular levels of HCV RNA showed only an ∼2-fold reduction in viral RNA levels in the presence of AO13. Taken together, this study revealed that AO13 showed consistent, but low-level antiviral effect against HCV, although the mechanism of action remains unclear. IMPORTANCE The discovery of curative antiviral drugs for a chronic disease such as HCV infection has encouraged drug discovery in the context of other viruses for which no curative drugs currently exist. Since we currently face a novel virus that has caused a pandemic, the need for new antiviral agents is more apparent than ever. We describe here a novel compound that shows a modest antiviral effect against HCV that could serve as a lead compound for future drug development against other important viruses such as SARS-CoV-2.

Methyl substituted 8‐methoxy[2.2]MPCPs 8 a–b were obtained via thiacyclophane and its oxidized products. Lewis acid‐catalyzed (AlCl3‐MeNO2) reactions of 5‐tert‐butyl‐8‐methoxy‐12,13,15,16‐tetramethyl[2.2]MPCP 8 b under various conditions led to transannular cyclization and isomerization reactions, affording the considerably less‐strained 5‐tert‐butyl‐8‐methoxy[2.2]MPCP 9, 5‐tert‐butyl‐8‐hydroxy‐14,16,17,18‐tetramethyl[2.2]metacyclophane 10 and pyrene derivatives 11 and 12. However,on prolonging the reaction time to 3 h for 8 b, the major product is 5‐tert‐butyl‐8‐hydroxy[2.2]MPCP 10. These reactions are strongly affected by the size and properties of the C‐8 substitutents as well as the methyl substitutents on the para‐linked benzene rings, which increase the strain in the molecules. The 1H NMR spectra and X‐ray crystallographic analysis of 8 b revealed that it adopts a syn‐conformation both in solution and in the solid state.

STAT3 signaling is known to be associated with tumorigenesis and further cancer cell-intrinsic activation of STAT3 leads to altered regulation of several oncogenic processes. Given the importance of STAT3 in cancer development and progression particularly breast cancer, it is crucial to discover new chemical entities of STAT3 inhibitor to develop anti-breast cancer drug candidates. Herein, 4-benzyl-2-benzylthio-5-methyl-1H-imidazole (2a) and 4-benzyl-5-methyl-2-[(2,6-difluorobenzyl)thio]-1H-imidazole (2d) from a group of thirty imidazole-bearing compounds showed greater STAT3 inhibition than their lead compounds VS1 and the oxadiazole derivative MD77. Within all tested compounds, ten derivatives effectively inhibited the growth of the two tested breast cancer cells with IC50 values ranging from 6.66 to 26.02 µM. In addition, the most potent derivatives 2a and 2d inhibited the oncogenic function of STAT3 as seen in the inhibition of colony formation and IL-6 production of breast cancer cell lines. Modeling studies provided evidence for the possible interactions of the synthesized compounds with the key residues of the STAT3-SH2 domain. Collectively, our present study suggests 2-substituted-4-benzyl-5-methylimidazoles are a new class of anti-cancer drug candidates to inhibit oncogenic STAT3 function.

Calixarene-analogous metacyclophanes (CAMs) are a special class of cyclophanes that are cyclic polyaromatic hydrocarbons containing three or more aromatic rings linked by one or more methylene bridging groups. They can be considered to be analogues of calixarenes, since, in both types of molecules, the component aromatic rings are linked by methylene groups, which are meta to each other. Since the prototype or classical calix[4]arene consists of four benzene rings each linked by methylene bridges, which are also meta to each other, it can be considered to be an example of a functionalized [1.1.1.1]metacyclophane. A metacyclophane (MCP) that consists of three individual hydroxyl-group functionalized aromatic rings linked by methylene groups, e.g., a trihydroxy[1.1.1]MCP may therefore, by analogy, be termed in the broadest sense as a “calix[3]arene” or a “calix[3]arene-analogous metacyclophane”. Most of the CAMs reported have been synthesized by fragment coupling approaches. The design, synthesis and development of functionalized CAMs, MCPs, calixarenes and calixarene analogues has been an area of great activity in the past few decades, due their potential applications as molecular receptors, sensors and ligands for metal binding, and for theoretical studies, etc. In this review article, we focus mainly on the synthesis, structure and conformational properties of [1.1.1]CAMs, i.e., “calix[3]arenes” and their analogues, which contain three functionalized aromatic rings and which provide new scaffolds for further explorations in supramolecular and sensor chemistry.

RATIONALE We report the unsolved molecular structure of the complex biopolymer sporopollenin exine extracted from Lycopodium clavatum pollen grains. METHODS TOF-SIMS and CID-MS/MS, MALDI-TOF-MS and CID-TOF/TOF-MS/MS were used for the analysis of this complex biopolymer sporopollenin exine extracted from Lycopodium clavatum pollen grains. Solid-state 1 H- and 13 C-NMR, 2D 1 H-1 H NOESY, Rotor-synchronized 13 C{1 H} HSQC, and 13 C{1 H} multi CP-MAS NMR experiments were used to confirm the structural assigments revealed by MS and MS/MS studies. Finally, high-resolution XPS was used to check for the presence of aromatic components in sporopollenin. RESULTS The combined MS and NMR analyses showed that sporopollenin contained poly(hydroxy acid) dendrimer-like networks with glycerol as a core unit, which accounted for the sporopollenin empirical formula. In addition, these analyses showed that the hydroxy acid monomers forming this network contained a β-diketone moiety. Moreover, MALDI-TOF-MS and MS/MS allowed us to identify a unique macrocyclic oligomeric unit composed of polyhydroxylated tetraketide-like monomers. Lastly, high-resolution X-ray photoelectron spectroscopy (HR-XPS) showed the absence of aromaticity in sporopollenin. CONCLUSIONS We report for the first time the two main building units that form the Lycopodium clavatum sporopollenin exine. The first building unit is a macrocyclic oligomer and/or polymer composed of polyhydroxylated tetraketide-like monomeric units, which represents the main rigid backbone of the sporopollenin biopolymer. The second building unit is the poly(hydroxy acid) network in which the hydroxyl end groups can be covalently attached by ether links to the hydroxylated macrocyclic backbone to form the sporopollenin biopolymer, a spherical dendrimer. Such spherical dendrimers are a typical type of microcapsule that have been used for drug delivery applications. Finally, HR-XPS indicated the total absence of aromaticity in the sporopollenin exine.

Phenyl‐ and thien‐2‐yl‐[2, 2′‐bithiophen]‐5‐yl)(thiophen‐2‐yl)methanones were synthesized by the condensation of 2‐thienyldithioester with the corresponding methyl ketones followed by cyclization with 2‐bromoacetylthiophene. Also, condensation of 2‐thienyldithioester with methyl ketones followed by treatment with methyl iodide gave β‐thien‐2‐yl‐β‐methylthio‐α,β‐unsaturated ketones, which reacted with the Simmons‐Smith reagent to give corresponding 4‐phenyl‐ and thien‐2‐yl‐2,2′‐bithiophenes. The optoelectronic properties of these bithiophene derivatives were studied by UV‐Vis absorption, fluorescence spectroscopy and cyclic voltammetry. The lowest‐energy conformations of these new compounds in the ground and first excited states, the electronic origins of their UV‐Vis absorption and fluorescence emission bands, and related frontier molecular orbital (FMO) properties were elucidated by density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) calculations. Furthermore, these aryl‐substituted bithiophenes were treated with anhydrous ferric chloride to undergo oxidative polymerization, and the fluorescence properties of the resulting polymeric products are also reported herein.

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.

A series of new 2‐arylbenzimidazole‐N‐1 acetamido conjugates have been synthesized and characterized. Their antifungal activities were evaluated against fluconazole‐resistant C. albicans and A. fumigatus by the inhibition zone technique and were compared with the standard amphotericin B. Minimum inhibitory concentrations were determined for the most potent compounds, after preliminary structure‐activity analysis. Based upon these results a sub‐set of twelve ethylglycinyl ester conjugates bearing fluoro, chloro or bromo substituents on the 2‐phenyl moiety were examined for structure‐activity relationships using an agarose diffusion method employing a hypersensitive Sacharomyces cerevisiae strain. None of these compounds however showed significant activity at the concentrations tested. Single‐crystal X‐ray determinations were conducted on two of the newly synthesized compounds and were compared with DFT computational analysis.

The synthesis of 6-tert-butyl-9-methoxy-14,15,17,18-tetramethyl[3.3]MPCP 11, via the TosMIC cyclo-condensation reaction followed by Wolff-Kishner reduction is described. Lewis acid (AlCl3-MeNO2) catalyzed reactions of 11 led only to de-tertbutylation and demethylation of the C(9)-methoxy group. A DFT analysis of the conformations of all of the synthesized [3.3]MPCPs products is also presented and a study of their Lewis acid-mediated properties. The contrast between the reactions of 11 with those of the corresponding [2.2]MPCPs is presented as is a DFT computational analysis of the various conformers of the molecules described herein.

7- tert -Butylpyrene-1-azine-salicylaldehyde, L1 has been synthesized as a dual fluorescent chemosensor based on an excited state intramolecular proton transfer (ESIPT) mechanism. Ligand L1 undergoes AcO − /F − triggered sharp fluorescence enhancement towards Zn 2+ in a co-operative fashion to form a complex with 2:1 stoichiometry. In order to investigate the influence of the 7- tert -butyl group, pyrene-1-azine-salicylaldehyde, L2 was also prepared. With ligand L1 , fluorescence enhancement in acetonitrile solution is found to be twice as large than with ligand L2 . The association constants of L1( O − ) 2 ⊃ Zn 2+ in the presence of AcO − and F − were determined to be K a2 = 9.2 × 10 8 M −1 and 1.5 × 10 6 M −1 , respectively using a 2:1 binding model. The results of a DFT interaction study were consistent with the experimental results.

Polymethyl substituted [3.3]metacyclophanes (MCPs) 4 a–d, were synthesized by the TosMIC coupling method followed by Wolff–Kishner reduction of the corresponding polymethyl-substituted [3.3]MCP-2,11-diones (3 a–d). 1H NMR spectroscopy reveals that both 5,6,7,14,16-pentamethyl[3.3]MCP-2,11-diones (3 a and 3 b) undergo conformational changes relative to the NMR time scale in solution at room temperature but that the anti conformer is preferred. Reduced 5,6,7,14,16-pentamethyl[3.3]MCP (4 a and 4 b) adopt fixed syn–conformations in solution at room temperature. X-ray analysis showed that in the solid state, 5,6,7,14,15,16-hexamethyl[3.3]MCP-2,11-dione 3 a adopts the anti-conformation and reduced 5,6,7,14,16-pentamethyl[3.3]MCP-2,11-diones 4 b adopts a syn-(chair-chair) conformation. A series of electrophilic substitution reactions such as formylation, acetylation and nitration were carried out with 5,6,7,14,16-pentamethyl[3.3]MCP 4 b to study their conformational isomers. The formyl, acetyl and nitro derivatives of 5,6,7,14,16-pentamethyl[3.3]MCP are fixed to adopt syn-conformations in solution at room temperature. The conformational isomers of the metacyclophanes and derivatives obtained from density functional theory (DFT) methods were used to estimate the total energies and energy minimized structures of the different conformations.

We report on a new 16 microcantilever sensor system for performing sensing experiments in liquid or gas. The system uses two 8-microcantilever arrays that are held in a sensor cell. The microcantilever deflections are monitored by oscillating two focused optical beams over the microcantilevers such that only one microcantilever is illuminated at one time and each microcantilever is illuminated approximately once per second. The optical beams are moved using a motorized translation stage. The reflected optical beams are detected by a two-axis photo-sensitive detector (PSD) producing a series of two eight peak shaped patterns. The raw data from both the PSD and the translation stage are used to fold the peak shaped patterns from each array one on top of the other so that the deflection of the cantilevers can be obtained from the change in height of each peak. The stability of the data was found to be highly dependent on the speed of the translation stage. When the translation stage was operated between 0.5 and 1 mm/s, the deflection of each microcantilever in units of surface stress was found to be highly reproducible and consistent between arrays. As a proof-of-purpose application, the system was used to detect Ca 2+ , Sr 2+ and Cs + ions using different calix[4]arene-based sensing layers. The results obtained were found to be reproducible and completely consistent with results obtained using a typical two single microcantilever sensor set-up.

An unexpected formation of carbamothioates by the reaction of arylmethyl isocyanides with xanthate esters in the presence of sodium hydride is reported. The products thus obtained were compared with carbamothioates obtained by the condensation of the corresponding benzylamines with xanthate esters in the presence of sodium hydride in DMF. A mechanism which is substantiated by DFT calculations to account for the unexpected reactions is proposed.

International audience; A series of 1,2‐dimethyl[2.10]metacyclophan‐1‐enes (MCP‐1‐enes) containing different substituent groups has been synthesized to illustrate their conformational behavior. 4,22‐dimethoxy‐1,2‐dimethyl[2.10]MCP‐1‐ene 3 was synthesized by a Grignard coupling reaction, Friedel‐Crafts acylation reactions and McMurry coupling reaction from 1,10‐dibromodecane. The formation of 4,22‐dihydroxy‐1,2‐dimethyl[2.10]MCP‐1‐ene 4 was carried out by demethylation of compound 3 with boron tribromide at room temperature. The syn type conformation of 4 was characterized by X‐ray diffraction and was found to form both intramolecular and intermolecular hydrogen bonds between the two hydroxyl groups. From this reaction an interesting compound [10]tetrahydrobenzofuranophane 5 was afforded on prolonging the reaction time. 5,21‐diformyl‐4,22‐dihydroxy‐1,2‐dimethyl[2.10]MCP‐1‐ene 6 has been prepared from 4,22‐dihydroxy‐1,2‐dimethyl[2.10]MCP‐1‐ene 4 by using the Duff method in the presence of hexamethylenetetramine. Structural analysis by 1H NMR spectroscopy and X‐ray diffraction confirmed that both the solution and the crystalline state of compound 6 adopts an anti‐conformation which forms an intramolecular hydrogen bond between the formyl group and the hydroxyl group, which is an interesting finding for long carbon chain MCP compounds.

A new fluorescent chemosensor L1 , a pyrene containing a long chain Schiff base derivative at the 1-position has been synthesized. Similarly, the receptors L2 and L3 are also designed in order to compare the binding ability for detection of Cu 2+ . The receptors exhibit very weak fluorescence ( Φ =0.01) due to the photoinduced electron transfer (PET). Upon addition of 10 equiv of Cu 2+ , the emission intensity of ligands L1 and L2 are increased 65-fold ( Φ =0.31) and 25-fold ( Φ =0.08) in CH 3 CN/CH 2 Cl 2 solvents system, respectively. NMR titration experiments, spectroscopic and DFT computational studies confirmed the binding phenomena and sensitivity of Cu 2+ .

Two novel receptors 5,11,17,23-tetra-tert-butyl-25,27-bis[(ethoxycarbonyl)methoxy]-26,28-bis-[1-methyl-(imidazole)meth-oxy]-2,8,14,20-tetra-thiacalix[4]arene (L1) and 5,11,17,23-tetra-tert-butyl-25,27-bis-[(benzyl)methoxy]-26,28-bis-[1-methyl-(imidazole)-methoxy]-2,8,14,20-tetrathiacalix[4]arene (L2) possessing imidazole moieties based on thiacalix[4]arene in the 1,3-alternate conformation have been synthesized and characterized. The crystal structures of L1 and L2 have been determined. The binding behaviour towards Li+, Na+, K+ and Ag+ ions has been examined by 1H NMR titration experiments in (CDCl3/CD3CN; 10:1, v/v) solution. The exclusive formation of mononuclear complexes of L1 with metal cations is of particular interest revealing a negative allosteric effect in the thiacalix[4]arene family. Liquid-liquid extraction experiments indicate that synthesized L2 can be utilized as an efficient reusable extractant for dichromate anion by controlling the pH of the aqueous solution.

A bimodal calix[4]arene functionalized with triazolyl-linked anthracenyl and 3-propylthioacetate groups is described.

Three novel thiacalix[4]arene receptors 4a–c each with a 1,3-alternate conformation and possessing two urea moieties linking various phenyl groups substituted with either para electron-donating or -withdrawing groups have been synthesized. The binding properties of these receptors were investigated by means of 1H NMR spectroscopy and UV-vis absorption titration experiments using various anions. The structures and complexation energies were also studied by density functional theory (DFT) methods. The results suggested that receptor 4c, which possesses two p-(trifluoromethyl)phenyl ureido moieties, can complex most efficiently in the urea cavity and exhibits high selectivity towards F− and AcO− ions.

Calix[3]benzofurans have been synthesized by a modified TosMIC coupling reaction, followed by acid treatment and an intramolecular cyclization reaction with TMSI (trimethylsilyl iodide); X-ray analysis established the structures of two samples, both showing a cone conformation. 1H NMR spectroscopic analyses of the calix[3]benzofurans reveal that they can adopt drastically different conformations in solution and undergo very fast conformational changes relative to the NMR time scale. Calix[3]benzofuran 4a exists as two conformers, namely the cone and saddle forms, in a ratio of 83 : 17 at −50 °C. A series of calix[3]benzofuran derivatives was synthesized by electrophilic aromatic substitutions, such as bromination, formylation and acylation, to investigate the influence of the substituents on the conformations of the calix[3]benzofurans. 1H NMR spectral analyses of the acyl derivatives at room temperature indicated that these macrocycles exist as a mixture of two isomers that are slowly interconverted on the 1H NMR timescale. The conformational isomers of the calix[3]benzofurans and their derivatives obtained from DFT methods (based on the crystal structure analysis results) were used to estimate the total energies of the different conformations.

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.

A new thiacalix[4]arene based fluorescent chemosensor L bearing two pyrenyl groups in a 1,3-alternate conformation has been synthesized, and its metal ion-binding and fluorescence-sensing properties were investigated in ethanol. The designed chemosensor L exhibited high selectivity toward Cu²⁺ ions versus the other tested metal ions with a detection limit of up to 1.44 × 10⁻⁷ M. The chemosensor L was capable of acting an efficient ratiometric fluorescent chemosensor at low ion concentration or as a fluorescence quenching type chemosensor due to the PET and heavy atom effects operating in high ionic strength solution. Further studies revealed that chemosensor L acted as a reversible sensor in the presence of Cu²⁺ and ethylenediamine.

Calix[4]azulene 1 is shown to be an effective molecular receptor for tetraalkylammonium halide and BF4− salts. The respective binding constants were determined using global-fit analyses of the spectral data from UV-vis absorption titration studies. A DFT study of the putative complexes formed with 1, and the X-ray structure of 1 itself is also reported.

Three organic ionophores (2-4) based on the p-tert-butylthiacalix[4]arene backbone, blocked in the 1,3-alternate conformation, bearing two pyridyl coordinating moieties (ortho for 2, meta for 3 and para for 4), have been synthesized and characterized in the solid state. The solvent extraction experiments with the metal ions showed that the ability of these derivatives to complex with Ag(+) appeared to be largely dependent on the position of the nitrogen atoms of the pyridyl ring. Two different complexation modes have been confirmed by 1H NMR titration. Ionophore 2 armed with two pyridyl moieties, complexed with Ag(+) cation through N···Ag(+)···S interactions; however, ionophore 3 and ionophore 4 complexed with Ag(+) through metal-nitrogen (N···Ag(+)) interactions. The DFT computational studies were consistent with the experimental findings. These findings will provide us with an important rule to design an appropriate thiacalix[4]arene ionophore in the future. Another study on the possibility for application of ionophores 2-4 for the treatment of waste water containing Cr(VI) and Cr(III), showed that ionophore 3 was useful in the application of the solvent extraction method in selective treatment of waste water containing Cr(VI) and Cr(III) prior to discharge.