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In this study, p-morpholinomethylcalix[4]arene (p-MC4) was synthesized using Mannich reaction and utilized for the fabrication of polyacrylonitrile nanofibers impregnated with p-morpholinomethylcalix[4]arene (PAN/p-MC4) using electrospinning. The nanofibers were prepared by blending 12% solution of PAN with 20% solution of p-MC4. The PAN/p-MC4 NFs were thoroughly evaluated for their removal efficiency of Cu2+ from the aqueous media. The selectivity of PAN/-p-MC4 nanofibers was also examined by adsorbing a set of metal ions with same charge and similar ionic radius. The results of distribution ratio showed that PAN/p-MC4 nanofibers have superior selectivity for Cu2+ as compared to other heavy metal ions. The relative selectivity coefficients of PAN/p-MC4 nanofibers were found to be 25.2, 14.1, 8.9, and 4.03 for Cu2+/Ni2+, Cu2+/Co2+, Cu2+/Cd2+ and Cu2+/Pb2+, respectively. This indicates that PAN/p-MC4 nanofibers have a higher selectivity for Cu2+ ions. Numerous parameters such as pH, time, adsorbent dosage and analyte concentration were optimized to evaluate the maximum adsorption capacity of nanofibers for Cu2+. Adsorption isotherm models showed that the adsorption is promising and follows Langmuir adsorption isotherm. Whereas, PAN/p-MC4 nanofibers followed pseudo- second order kinetics during adsorption experiments. The PAN/p-MC4 nanofibers showed excellent adsorption capacity (qo) of 65.35 mg/g for Cu2+ at pH 5 in 60 min under shaking speed of 120 rpm. Moreover, PAN/p-MC4 nanofibers had been used to remove Cu2+ from real surface water samples. According to the results, PAN/p-MC4 nanofibers are more effective adsorbent for removing Cu2+ from contaminated water. [ABSTRACT FROM AUTHOR]

The current work explores the antioxidant and antimicrobial activity of a newly synthesized calix[4] arene acetanilide derivative (3), which was synthesized through Mannich reaction by the treatment of calix[4] arene with acetanilide, formaldehyde and acetic acid in tetrahydrofuran, The antioxidant activity was determined by using DPPH method. Results show that the new synthesized compound 3 has good antioxidant activity. The antimicrobial activity of 3 was staunched against different types of microorganisms, i.e. gram-negative and gram-positive bacterial strains (Escherichia Coli ATCC 8739 and Staphylococcus Aureus ATCC 10231) along with a fungus (Aspergillus Niger ATCC 16405). A suitable agar medium (Mueller Hinton agar) was applied for the growth of microorganisms. Kirby-Bauer well agar diffusion method was used to check the antimicrobial activity. The bacterial strains zone has been observed in between 250–4000 µg/ml. It is noticed that compound 3 has very good effect against fungus A niger as compared to bacterial strains. Its minimum inhibitory concentration (MIC) against A. niger, S. aureus and E. coli is found to be 250, 500 and 1000 µg/mL, respectively. Consequently, the study has been compared with the reported calix[4] arene derivatives and it has been revealed that the compound 3 is a good antimicrobial agent. Hence, it could be inferred that compound 3 is considerably effective against selected microorganisms and may be used as a medicine in near future and beneficial for the human. [ABSTRACT FROM AUTHOR]

This study describes the removal of methyl orange (MO) and methyl red (MR) dyes from water samples using morpholinomethylcalix[4]arene immobilised silica (MIS) resin. The silica surface has been modified by p-morpholinomethylcalix[4]arene moiety and was characterised by FT-IR spectroscopy and SEM techniques. The adsorption capacity of MIS-resin was checked through batch adsorption experiments under the optimised conditions of pH, MIS-resin dose, time, and temperature. Results show that adsorption of MO and MR dyes are highly affected by the change in pH; thus, the higher adsorption percentages were achieved at pH 5.3 and 6.6 respectively. The adsorbent dosage has been optimised and it was noticed that the maximum adsorption was achieved by using 40 mg.L−1 of MIS-resin dose. The adsorption rate of dyes was investigated by applying the pseudo-first and second-order kinetic models and it has been observed that the experimental data shows a better correlation coefficient with the pseudo-second-order kinetic model. The feasibility of adsorption was analysed by thermodynamic parameters such as ∆H°, ∆G°, and ∆S° values indicate that the adsorption of dyes is exothermic and spontaneous. The equilibrium data have been validated using Langmuir and Freundlich models and the Langmuir model has a good correlation coefficient (R2 0.99). The MIS-resin was applied onto industrial effluents and it has been observed that the prepared resin is a very efficient adsorbent for the treatment of dyes contaminated wastewater. The adsorption of MO and MR dyes onto MIS-resin was well defined by computational chemical modelling at the B3LYP/LANL2DZ/6-311++G (d,p) level using G09W software. [ABSTRACT FROM AUTHOR]

Calixarenes are known as fascinated macromolecules due to their flexible structure that can be cast into different fields of application. These macromolecules have been used as quick and highly selective functional material for the extraction and separation of metal ions. This study explores metal ion removal efficiency of new calixarene coated silica resin from aqueous environment through solid phase extraction. The calixarene-coated silica resin (CCS resin) was synthesized and characterized by FTIR, SEM, XRD, EDS and BET. Static and dynamic adsorption experiments were followed to check the removal efficiency of CCS resin. Adsorption experiment shows that, CCS resin has strong potential for the removal of divalent and trivalent metal ions as compare to monovalent metal ions. Adsorption data have been evaluated by applying Langmuir, Freundlich, D-R models and Thomas dynamic adsorption models. The adsorption isotherm of the CCS resin agreed well with the Langmuir adsorption equation with regression coefficient of 0.99 and good monolayer adsorption capacities such as 3.22, 2.95, 3.04, 3.11, 2.81 and 2.82 (mol.g−1) for Hg2+ Pb2+ La3+ Cr3+ Al3+ and Fe3+ respectively. The D-R isotherm model suggests that the adsorption process follow ion exchange mechanism with mean sorption energy falls in the range of 9.0–16 KJ.mol−1. Moreover, the exhaustion capacity of column was calculated by using the Thomas model, which shows very small qo value with good fit to data (R2 =0.99). The thermodynamic and kinetic studies have also been performed, which reveals that the reaction is spontaneous and exothermic in nature and follows pseudo second-order kinetics. [ABSTRACT FROM AUTHOR]

p-Aminophenol is an important organic molecule which is widely used in pharmaceutical as well as in dye industries for the synthesis of various drugs and corrosion resistant paints respectively. In order to synthesize this important organic molecule, CuO nanoparticles were functionalized with diamide derivative of calix[4] arene (3). The functionalized nanoparticles (4) were characterized with different analytical techniques such as FT-IR, XRD, SEM and EDX. The synthesized catalyst (4) was used to convert p-nitrophenol,in presence of sodium borohydride, into p-aminophenol which is an industrially important organic molecule. This reaction was monitored by Ultraviolet visible (UV-Vis) spectroscopy. The catalytic conversion took 35-40 seconds. The reaction followed pseudo first order kinetics and rate constant was determined as 1.386 min−1. N [ABSTRACT FROM AUTHOR]

In this study, a novel derivative of functionalised Calix[4]arene chem-sensor (4-amino thiazole 2-thiol-Calix[4]arene (R-Sensor)) was investigated, using the FT-IR spectroscopic method. Fluorescent properties and the ability to detect the sensor toward different cation ions in acetonitrile aqueous solution were investigated using the UV–Vis method, fluorescence titration, and Job's plot method. The results showed that among the studied cations, the presence of Pt(II) has a greater effect on the intensity and wavelength of the emission. In addition, the optimised structure and electronic properties of this R-sensor was studied, using the density functional theory (DFT), B3LYP and M062X methods, at the LANL2DZ (6-311 + G/CPCM and 6-311++G/CPCM) basis set, and quantum theory of atoms in molecules (QTAIM). The results of these theoretical-computational studies showed that the selectivity of this sensor is related to its molecular structure, electronic properties, and surface electrostatic properties. Theoretical studies have shown that electronic properties such as energy gap, sensitivity, and charge/energy transfer change dramatically in the presence of Pt(II) cations. In addition, the molecular competitive tests showed that this R-sensor could be a good candidate for monitoring/measuring Pt(II) in physiological samples/ environments. [ABSTRACT FROM AUTHOR]

A new 1,3-distal diphenyl(4-piperidin)methanol-appended calix[4]arene derivative 3 has been successfully synthesized and characterized using FTIR, NMR and elemental analysis techniques. Synthesized 1,3-distal diphenyl(4-piperidin)methanol-appended calix[4]arene derivative 3 has been then grafted onto [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane-modified Fe3O4 magnetic nanoparticles to produce 1,3-distal diphenyl(4-piperidin)methanol-substituted calix[4]arene derivative-grafted EPPTMS-MN (4). The structure and surface morphology of 1,3-distal diphenyl(4-piperidin)methanol-substituted calix[4]arene derivative-grafted EPPTMS-MN have been determined by a combination of FTIR, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) techniques. Moreover, anion binding capabilities of 1,3-distal diphenyl(4-piperidin)methanol-substituted calix[4]arene derivative-grafted EPPTMS-MN toward HCr2O7-, and H2AsO4- ions have been evaluated. The results indicate that 1,3-distal diphenyl(4-piperidin)methanol-substituted calix[4]arene derivative-grafted EPPTMS-MN exhibited 80% sorption efficacy toward Cr(VI), whereas ∼8% sorption efficacy for As(V) was obtained. [ABSTRACT FROM AUTHOR]

Calix[n]arenes, as the 'third-generation' host molecules, are cyclic oligomer, featuring a unique three-dimensional structure with a hydrophobic cavity, allowing the interaction with many size-matched guest molecules, and a surface which can be functionalised at both the upper and lower rims with several functional groups to tailor the recognition properties towards a specific class of analytes for various applications. In the last two decades, due to their configuration, unique molecule recognition function and aggregation properties, calixarenes and their derivatives have attracted considerable attention as a new versatile scaffold for highly sensitive detection and site-oriented immobilisation in biosensor development. In this review, the development of sensors featuring calixarene-based transducers tuned for binding many analytes, ranging from simple (i.e., amino acids and neurotransmitters) to complex (i.e., enzymes and antibodies) organic molecules, was described. The rational design, the synthetic strategies fine-tuned to prepare these complex structures and their grafting in surface modification were included. [ABSTRACT FROM AUTHOR]

This study deals with investigation of selectivity of p-morpholino-methylcalix[4]arene appended silica from a group of metal ions having similar charge and radii. The values of distribution ratio revealed that modified silica possess higher selectivity for Cu2+. In addition, relative selectivity coefficients of modified silica were found to be 24.1, 13.8, 8.6 and 4.01 for Cu2+/Ni2+, Cu2+/Co2+, Cu2+/Cd2+, Cu2+/Pb2+, respectively. The maximum adsorption capacity was 1.5 mmolg−1. The reusability data suggested no any loss of adsorption capacity of this material up to 10 cycles. The developed material was also applied for determination of copper in lake water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Dyes are a potential menace and are considered major contributors to environmental pollution. However, the cleanliness of the environment from colored toxicants is a challenging task of the contemporary era. In this regard, this approach is based on the confiscation of hazardous dyes. The main features of this work are the synthesis and the application of newly synthesized calix[4]arene grafted Amberlite XAD-4 (resin 5) for the selected methyl orange (MO) and methyl red (MR) azo dyes removal from aqueous environment. The adsorption ability of resin 5 for the selected azo dyes was evaluated through optimizing various parameters. Moreover, treatment with real water samples reveal that newly synthesized resin is an extremely effective adsorbent for the removal of the selected azo dyes from aqueous media. [ABSTRACT FROM AUTHOR]

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

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

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

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

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

The chiral calix[4]arene derivative (6)bearing anL-prolinamido group has been designed and proved to be a water compatible efficient organocatalysts for a direct enantioselective aldol reaction. Compound6catalyzes the aldol reaction of cyclohexanone and a variety of aromatic aldehydes yielding anti-aldol products in high yield with enantioselectivities of up to 93% and diastereoselectivity of up to 95:5. [ABSTRACT FROM AUTHOR]

Carboxylate functionalized calix[4]arene derivatives with ter-butyl groups at the upper rim exhibits gel formation in presence of Cu(ClO4)2, DMF, methanol and water with specific ratio (5:3:2). In presence of other metal ions or with different combination of solvents gel formation didn't occur. The morphology of the gel has been investigated by SEM and TEM study. Detail study revealed that gel formation takes place when network structure is formed immobilizing the solvent(s) molecule in the cavity through nonbonding interaction. This gel material functions as a colorimetric sensing agent for iodide. The binding constant for iodide and LOD was also determined. [ABSTRACT FROM AUTHOR]

A number of calix[4]arene-based molecules were designed incorporating amide moiety with variation in conformation, rigidity at the binding sites and steric crowding at the upper rim to investigate the anion sensing property of this series of ionophores. These compounds were synthesised and characterised, molecular structures of two of the compounds were established by single-crystal X-ray study. Anion binding property of these ionophores, investigated with the aid of1H NMR and UV–vis spectroscopy, revealed that three (1–3) out of four ionophores strongly interact with F−, in addition, ionophore2interacts with CN−and, ionophore3interacts with CH3COO−andand ionophore4does not interact with any anions. NMR titration was carried out to determine binding constant with strongly interacting anions. Crystal structure analysis revealed that strong intramolecularinteraction in4prevented the anions to interact with the N–H protons of the amide moiety. Interestingly,2with F−and CN−exhibits sharp colour change in acetonitrile–chloroform. Apparently, conformation of the calix moiety, flexibility of the binding sites and intramolecular H-bonding played critical role towards determination of selectivity. Computational study was performed to investigate the interaction site(s) and also to corroborate some of the experimental results. Anion binding study of functionalised calix[4]arenes revealed that conformation, flexibility and intramolecular interaction in calix moiety play critical role to determine ion selectivity. One of the receptors performs as sensitive colorimetric sensor for F−and CN−, computational study also corroborates most of the experimental results. [ABSTRACT FROM PUBLISHER]

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

In this work, two novel chemosensors based on calix[4]arene bearing (thio)barbituric acid groups (BC1andBC2) were synthesised, and their structures were characterised by HRMS, NMR and FTIR. Furthermore, their binding properties towards various biologically relevant metal ions were studied by fluorescence titrations,1H NMR spectroscopies and Job’s plot evaluations. The chemosensorBC1displayed excellent binding affinity and selectivity towards Cu2+, which was characterised using fluorescence spectroscopy. On the other hand,BC2exhibited a very remarkable fluorescence enhancement as well as visible colour change from pale green to sunset yellow, in presence of Hg2+ions. Finally, Job’s plot method revealed 1:1 binding stoichiometry for bothBC1:Cu2+complex andBC2:Hg2+complex. [ABSTRACT FROM AUTHOR]

Calix[4]arene amide derivatives were employed as new additives within the sol-gel encapsulation of lipase fromCandida rugosa(CRL) to improve its catalytic properties. Evaluation of catalytic activity of the encapsulated lipases was acheived by enantioselective hydrolysis of both racemates, Naproxen methyl ester and 2-phenoxypropionic acid methyl ester, in aqueous buffer solution/isooctane reaction system. Results show that enantioselectivity was improved by using calix[4]arene amide derivatives-based encapsulated lipases. The reaction of naproxen methyl ester resulted in 47.6% conversion (x) in 24 h with 88.9% enantiomeric excess of substrate (ees), analogous to an enantioselectivity (E) value of 297 (E= 137 for the encapsulated free enzyme). The conversion of 2-phenoxypropionic acid methyl ester, obtained was 48.4% withEvalue of 327, enantiomeric excess of substrate (ees) of 92% for the reaction time of 1 h (E= 211 for the encapsulated free enzyme). [ABSTRACT FROM AUTHOR]

This study involves the copper selective chromogenic response of 5, 11, 17, 23-Tetrakis (N-pyrrolidinomethyl)-25, 26, 27, 28-tetrahydroxycalix[4]arene based mannich base (3). Complexation ability of (3) was explored by examining the effect of a series of various metal ions, such as Li+, Na+, K+, Ag+, Ba2+, Ca2+, Mn2+, Mg2+, Sr2+, Ni2+, Cd2+, Co2+, Cu2+, Hg2+, Pb2+, Zn2+, Fe2+, Fe3+, and Al3+, by using UV-visible spectroscopy. Ligand (3) exhibited pronounced selectivity toward Cu2+even in the presence of various co-existing ions. The stoichiometric analysis, i.e., Job's plot revealed that (3) form 1:1 complex with Cu2+ion in DMF-H2O system. The complexation phenomenon was confirmed by FT-IR spectroscopy that favors the selective nature of (3) with Cu2+. [ABSTRACT FROM PUBLISHER]

Two new benzothiazolyl calix[4]arene-based multitopic molecular receptorsL-1andL-2 have been synthesised and evaluated for recognition of ionic toxicants. The receptors selectively interact with copper, silver and fluoride ion toxicants as assessed through UV-visible, NMR and colorimetric techniques. The stability ofL-1:Cu+2andL-2:Cu+2complexes was found to be higher than that of complexes formed with Ag+and F&#x2013.complexes in the presence of trifluoroacetic acid. Superiority ofL-1overL-2for analysis of identified toxicants has been determined by measurement of binding constants. [ABSTRACT FROM AUTHOR]

Experimental and theoretical binding studies of representative alkali, alkaline earth, transition, heavy metal and lanthanide cations by tetra- and di-substituted calix[4]arene amide derivatives (diethyl amide1a–cand morpholide amide2a–c) in the cone conformation were carried out. Binding was assessed by extraction experiments of the metal picrates from water to dichloromethane and proton NMR titrations. Density functional theory calculations were also performed to determine the binding energy of the complexes formed and to analyse the host–guest interaction modes. In the cases of ligands1band2cwith Na+and Ag+picrates, the extraction energy was also determined using the polarisable continuum model. The results are discussed in terms of the nature of the amide residue and the substitution pattern (1,3 vs. 1,2). Both tetra-amide derivatives are good extractants, showing preference for Na+, Ca2+, Ag+and Pb2+cations, mainly di-ethylamide1a. Concerning di-amide derivatives, the relative position of the substituents seems to be more important than the nature of the amide group in the extraction process. Proton NMR studies indicate the formation of 1:1 complexes between the amides and the cations studied, and DFT data show that all ligands form the most stable complexes with La3+. The binding properties of1a-cand2a-ctowards several metal cations were determined by UV spectrophotometry, proton NMR spectrometry and DFT methods. [ABSTRACT FROM AUTHOR]

Five diglycolamide-appended calix[4]arene (C4DGA) ligands, viz. C4DGA with no substituent (L-I),n-propyl (L-II), 3-pentyl (L-III),n-octyl (L-IV) and both side (L-V) substituents were evaluated for the separation of carrier free90Y from a90Y–90Sr mixture using the flat sheet supported liquid membrane technique. Based on the results of earlier batch studies, the transport properties of the C4DGA ligands towards Y(III) and Sr(II) were monitored at two different feed acidities. The transport rates were significantly lower for 6 M HNO3as compared to 3 M HNO3as the feed. After 6 h, the observed trend of Y(III) transport with the C4DGA ligands using a feed of 3 M HNO3was:L-I~L-III>L-V>L-IV>L-IIwhich changed toL-III>L-I > L-IV>L-V>L-IIfor 6 M HNO3as the feed. With 3 M HNO3as feed, >97% Y(III) transport was obtained withL-IandL-IIIin 6 h. Comparative Sr(II) transport was negligible resulting in high decontamination factors. In a one-step separation process, usingL-Ias the carrier ligand, pure90Y was obtained as the respective complex with either EDTA or DOTA. The highlights of this liquid membrane-based separation method comprise: its easiness, one-step separation, low ligand inventory, relatively pure product and continuous method. [ABSTRACT FROM AUTHOR]

A new series of water-compatible proline catalysts (4–6) derived from calixarene bearing a hydrophobic nature have been synthesised. It was found that the compound4was a highly efficient organocatalyst for aldol reactions occurred in the water. Under optimised reaction conditions, high yields (up to 82%), good enantioselectivities (eeup to 81%) and high diastereoselectivities (dr up to 91:9) were obtained. [ABSTRACT FROM AUTHOR]

The first example of calixarene-modified multi-walled carbon nanotubes was prepared in good yield. The absorption experiments for organic dyes indicated that it possessed excellent adsorption capacities for four tested organic dyes. By simple esterification of hydroxyl carbon nanotubes (CNTs) with calix[4]arene carboxyl derivative3, the first example of calixarene-modified multi-walled CNTs5was prepared in good yield. Its structure was characterized by Fourier translation infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TG). The absorption experiments for organic dyes indicated that calixarene-modified multi-walled CNTs5possessed excellent adsorption capacities for four tested organic dyes. The adsorption capacities for Orange G sodium salt, Brilliant ponceau 5R, neutral red and methylene blue were 0.572 mmol/g (258 mg/g), 0.434 mmol/g (262 mg/g), 0.865 mmol/g (249 mg/g) and 0.830 mmol/g (310 mg/g), respectively. The adsorption processes were exothermic and spontaneous, and obeyed pseudo second-order model and the Langmuir isotherm equation. The adsorption capacities kept stable in the range of pH = 3–10. [ABSTRACT FROM PUBLISHER]

In this study, two new Cu(II) complexes ofp-tert-butylcalix[4]arene amide derivatives (8,9) have been synthesised and investigated their DNA cleavage and antimicrobial activities. On the basis of spectral studies, a smaller distortion of square planar geometry has been proposed for both of the copper(II) complexes. The DNA cleavage studies show that the ligands are not efficacious, whereas the complexes have high activity. Futhermore, in order to determine the site of DNA cleavage, the DNA interactions of these compounds were investigated with some restriction enzymes. In addition, all synthesised compounds were screened for antimicrobial activities against some bacteria and for antifungal activities against yeast strains. The results showed that ethyl ester and furfuryl amide derivatives of the calixarenes are more efficient than other compounds against tested bacteria. However, complexes have not been effective. In case of DNA interaction studies, compounds were very effective against plasmid DNA. [ABSTRACT FROM AUTHOR]

The size limit of substituents allowingO-through-the-annulus rotation of substituted calix[4]arenes was further extended to the propargyloxy group in 24-propargyloxy-25,26,27-tris(N,N-dimethylcarbamoylmethoxy)-p-tert-butylcalix[4]arene by demonstrating its free but slow motion affording equilibrium between the partial cone and 1,2-alternate conformers. The effect of solvent and upper rim substituents R1on the conformational inversion was investigated by means of1H NMR. The rotational isomerisation of the parent (R1= H) analogue could not unambiguously be detected. The experimental results were supported by comprehensive density functional theory studies. [ABSTRACT FROM AUTHOR]

The extraction of actinide ions such as Am(III), Pu(IV), Np(IV), U(VI) and Pu(VI) was studied from simulated high-level waste (SHLW) solutions using several diglycolamide-functionalised calix[4]arene (Calix-DGA) ligands dissolved in the room temperature ionic liquid (RTIL) [C8mim][NTf2]. The Calix-DGA ligands were three lower-rim functionalised ligands with varying alkyl substituents (L-I, L-II and L-III), an upper-rim functionalised ligand (L-IV) and an upper- and lower-rim functionalised ligand (L-V). The SHLW solutions used contained 0.5 M HNO3and the extraction trend of the actinides was found out to be Am(III) > Pu(IV)∼Np(IV)≫and the extraction efficiency of the Calix-DGA ligands for Am(III) being L-V>L-I>L-II>L-IV>L-III. Reasonably, good extraction of Am(III) was obtained with 5.0 × 10− 4 M ligand solutions suggesting that higher concentrations of the ligand can be used for a higher loading of the metal ions. The extraction of other metal ions representing fission products, structural materials and process chemicals was studied by Inductively Coupled Plasma –Atomic Emission Spectroscopy analysis. The extraction mechanism follows the cation-exchange mechanism often observed with RTIL-based extraction systems. Enthalpy changes were measured from van't Hoff plots and were found to be significantly different than those observed with tracer studies reported previously. [ABSTRACT FROM AUTHOR]

This article highlights a newly synthesized 5,11,17,23-tetra-tert.butyl-25,26,27,28-tetrakis(hydrazidecarbonylmethoxy)-calix[4]arene (3) impregnated resin4and it's sorption ability for the removal of selected oxoanions, i.e., (arsenate and dichromate) from aqueous environment. Resin4was characterized by using FT-IR spectroscopy, scanning electron microscope (SEM), elemental, and thermogravimetic (TGA) analyses techniques. Sorption study was carried out through static and dynamic methods with continuous flow operation to evaluate the potency of resin4under various conditions. Several parameters, such as effect of sorbent dosage, contact time, pH, and initial concentration were optimized through batch experiments. Results justify that % sorption of these oxoanions is highly dependent on pH of the solution. Equilibrium was achieved in 45 min, while sorption efficiency of resin4can be better explained by Langmuir and Temkin isotherm models. Furthermore, kinetically both oxoanions follow pseudo second order model. Additionally, sorption of arsenate more appropriately could be explained by Moris-Weber diffusion kinetic model. For the dynamic method, Thomas model was used to calculate the kinetic coefficient (kTH) and maximum sorption capacity (qo) of resin4which are 3.84 and 5.94 ml mg−1min−1and 0.185, 0.160 mg g−1for As (V) and Cr (VI) respectively. Furthermore, resin4has been found as potential sorbent for removal of these oxoanions from contaminated surface water samples. [ABSTRACT FROM AUTHOR]

In the present article a comparative extraction efficiency of dichromate by a calix[4]arene derivative (d) and a newly synthesized calix[4]arene appended Amberlite XAD-4 resin (5) are reported. The liquid and solid phase extraction methods have been applied to ascertain the extraction efficiency of both the calix[4]arene derivative and the resin. Different parameters have been optimized such as pH, dosage, concentration, and temperature. Analysis of experimental data has been carried out by log-log plot analyses and the determination of characteristic parameters of each isotherm model such as Freundlich, Langmuir, and Dubinin-Radushkevich (D-R). The kinetic adsorption experiments show that the adsorption process follows pseudo second order kinetics. The adsorption mechanism has been investigated by Reichenberg (R-B) and Morris-Webster equations. From the thermodynamic parameters it is concluded that the adsorption process is endothermic and spontaneous in nature at higher temperature. The results show that the resin-5 has good capability to efficiently remove dichromate from aqueous media. [ABSTRACT FROM AUTHOR]

Three novel calix[4]arene, thiacalix[4]arene and calix[6]arene crown ether derivatives6,7and8with integral crown ether rings were designed and synthesized in ideal yields by multiple procedures. The liquid-liquid extraction experiment showed that they possessed excellent extraction abilities towards three cationic and one anionic dyes [Orange I (OI), Methylene blue (MB), Neutral red (NR), Brilliant green (BG)]. The highest extraction percentage of compound8for Neutral red was 88.2%. Their complexation UV-Vis spectra with four dyes indicated 1:1 complexes between host and guest in DMSO solution. The complexation results and IR spectra suggested the crown ether ring, the bridging functional groups, and the cavity of calixarene unit participated in the complexation for dyes. The larger calixarene cavity was favorable for binding dyes. The association constant of compound8with BG was as high as 6.4×105M−1. [ABSTRACT FROM PUBLISHER]

The present article demonstrates synthesis of 25,27-bis-N-(N,N-diethyl-2-aminoethyl-amidomethoxy)-26,28-dihydroxycalix[4]arene (4), its characterization and extraction ability toward the oxoanions such asHCr2O−7/Cr2O2 −7. The extraction efficiency was evaluated by using Pederson extraction method and data was analyzed through log-log plot analysis. The extraction was performed at varying pHs, i.e., pH 2–7. The analysis of results reveals that ligand4is a good extractant for dichromate at pH 3. The stoichiometric calculations obtained from Job's plot and log-log plot analyses reveals that it forms ligand:anion complex in 1:2 ratio. [ABSTRACT FROM PUBLISHER]

This study reports the synthesis and complexation properties of five new Schiff base derivatives of calix[4]arene (4-8), which have been synthesized from the condensation of bis(3-aminopropoxy)calix[4]arene with respective aldehyde (2-pyrrolecarbaldehyde, 2-thiophenecarboxaldehyde, furfural, l-methylpyrrol-2-carboxaldehyde, or biphenyl-4-carboxaldehyde). In this synthesis, the role of a different binding site of calix[4]arene in the extraction of dichromate anions has been observed. The complexation properties of the new Schiff base derivatives of calix[4]arene toward HCr2O7-/Cr2(>7- ions were studied by liquid-liquid extraction experiment. The results showed that the receptor 8 is more effective than other compound (4-7) for the removal of dichromate anion. The protonated Schiff base forms of the receptors were effective for transferring the HCnOy- anion from aqueous phase to a dichloromethane phase. [ABSTRACT FROM AUTHOR]

This study comprises the synthesis of newp-tert-butylcalix[4]arene with different amide functional groups and summarises an investigation of their DNA cleavage activities. The structural investigations of the synthesised compounds were examined by FTIR,1H NMR,13C NMR, elemental analysis and FAB-MS techniques. The interaction between these compounds and pBR322 plasmid DNA has been investigated via agarose gel electrophoresis and, according to the results, compounds5,7,8and13exhibit efficient DNA cleavage activity. In the electrophoresis images of5,7and8, Form IV which is small DNA fragment was observed in addition to supercoiled Form I, open circular Form II and linear Form III. [ABSTRACT FROM AUTHOR]

Extraction of Am3+was done using a both-side diglycolamide-functionalised calix[4]arene with eight DGA pendent arms (Calix8DGA) in several organic diluents. The observed extraction trend was nitrobenzene>n-dodecane (with 5%isodecanolas phase modifier) > phenyltrifluoromethylsulphone (PTMS) > hexone∼2-nitrophenyloctylether∼1-octanol>chloroform at 0.1 M HNO3, which changed at higher acidities (3 M) showing crossovers between the nitrobenzene–n-dodecane and the PTMS–hexone pairs. The Am3+extraction as a function of the nitric acid concentration showed increasingDvalues with increasing acidities. The extraction behaviour was correlated with various parameters such as Schmidt's diluent parameter, dielectric constant and so on. The nature of the extracted species was ascertained in various diluents by the slope analysis method, while temperature variation studies were carried out to determine the thermodynamic parameters, which in turn explain the extraction mechanism. The separation behaviour of Am3+with respect to UO22+and Sr2+was also investigated in these diluents. [ABSTRACT FROM AUTHOR]

Four new dendritic structures carrying perfluorobenzyl bromide on the surface and calix[4]arene and cyclam as a core were synthesized by using the convergent approach. These structures were determined by1H-NMR,13C-NMR and elemental analysis. Thermal stabilities of fluorinated dendritic structures were investigated using thermogravimetric analysis. Activation energies and thermal degradation of the structures were calculated with the Ozawa method. Thermogravimetric analysis of the dendritic structures reveals that the thermal stability of the structures increases with an increase in the number of the fluorine atoms. Dendritic structures synthesized were tested for their antimicrobial activity against,Salmonella typhimuriumNRRLB,Micrococcus luteus,Pseudomonas aeruginosa, Enterococcus fecalisATCC-29212,Bacillus cereusATCC-117787,Klepsiella pneumoniae, Bacillus subtilisNRS-744and Proteus vulgoris, Yersinia enterolitica, Saccharomyces cereviciae. The structures showed comparative activity against different strains of bacteria. Biological activities of the dendritic structures were seen to increase with an increase in fluorination and the number of nitrogen atoms. [ABSTRACT FROM AUTHOR]

In the present study, two novel calix[4]arene receptors containing triphenylamine units in 1,3-alternateconformation have been synthesized and characterized in detail. First, the 25,27-dipropoxy-26,28-bis[(3-aminopropyl)oxy]-calix[4]arene4and 25,26,27,28-tetra[(3-aminopropyl)oxy]-calix[4]arene7were prepared by using convenient reagents. Then, these amino derivatives of calix[4]arene were converted to Schiff base derivatives appended to triphenylamine of calix[4]arene (5and8) using 4-formyltriphenylamine via condensation. The 1,3-alternateconformation of the synthesized calix[4]arenes was determined by1H and13C NMR analyses. Also, their structures have been characterized by using1H and13C NMR, infrared, and elemental analyses. Supplemental materials are available for this article. Go to the publisher's online edition ofSynthetic Communications® to view the free supplemental file. [ABSTRACT FROM PUBLISHER]

A series of novel polycalix[4]arenes bearing triazole units, polytriazolecalixamides (PTCAs) and polytriazolecalixarenes (PTCs) were prepared by direct polycondensation of a new bistriazole-substituted dicarboxylic acid of calix[4]arene with commercial diamines and by click reaction of bisethenylcalixarene with diazides, respectively. These polycalixarenes were obtained in high yields and possessed inherent viscosities in range 0.42–0.59 dl/g. These polymers were readily soluble in polar aprotic solvents such asN,N-dimethylformamide, dimethyl sulfoxide andN-methyl-2-pyrrolidone at room temperature. Nanocrystalline structures of PTCAs and amorphous PTCs were determined by XRD patterns and confirmed by differential scanning calorimetry as well as transmission electron microscopy and atomic force microscopy imaging techniques. Glass transition temperatures were between 134 and 165°C. Thermogravimetric analysis showed that the polycalixarenes displayed high thermal stability ranged from 273 to 360°C at a point of 10% weight loss, and char yields were about 43.2–61.6% at 600°C in nitrogen. All of these polymers showed promising sorption properties towards risky transition metal ions such as Cu2+, Cr2+, Co2+, Cd2+and especially Pb2+in solid–liquid extraction, which fulfill our needs in synthesizing novel high-performance polymers. [ABSTRACT FROM AUTHOR]

Two novel 1,2-3,4-bridged and 1,3-bridged calix[4]arenes6and9based on larges-triazine conjugate systems were designed and synthesized in high yields. The liquid-liquid extraction experiment showed that they possessed excellent extraction abilities towards one cationic and three anionic dyes [Orange I (OI), Methylene blue (MB), Neutral red (NR), Brilliant green (BG)]. The highest extraction percentage of compound9was 91.2% for BG. The complexation UV-Vis spectra of compounds6and9with four dyes indicated the existence of complexation action between hosts and guests with 1:1 ratio of complexation in DMSO solution. The association constants suggested that the 1,2-3,4-bridging structure was more favorable for producing excellent complexation abilities than 1,3-bridging structure. The association constant of compound9with BG was as high as 4.5 × 106M−1. [ABSTRACT FROM PUBLISHER]

Novel polyamides bearing calix[4]arene and triazole units, polytriazolecalixamides (PTCAs), were prepared by direct polycondensation of a new bistriazole substituted dicarboxylic acid derivative of calix[4]arene with commercial diamines. The polytriazolecalixamides were obtained in high yields and possessed inherent viscosities in the range of 0.42–0.59 dl/g. These polytriazolecalixamides were readily soluble in polar aprotic solvents such as NMP, DMSO, DMAc at room temperature and in THF by heating. Nanocrystalline structures were determined by XRD patterns and confirmed by DSC as well as TEM and AFM imaging techniques. The photophysical study was performed by UV-absorption spectroscopy and maximum wavelength for each polymer specified in details. Glass transition temperatures were between 134 and 154°C. Thermogravimetric analysis showed that these polyamides displayed high thermal stability ranged from 273 to 312°C at the point of 10% weight loss, and char yields were about 51.4–67.4% at 600°C in nitrogen. All of these nanocrystalline polycalixamides showed promising sorption properties towards transition metal ions such as Cu2+, Cr2+, Co2+, Cd2+and especially Pb2+in solid-liquid extraction which fulfill our needs in synthesizing novel high performance polyamides. [ABSTRACT FROM PUBLISHER]

Novel basket-shaped molecules having calix[4]arene as central rigid core possessing azomaterial in outer space unit in the lengthening arm were synthesised and characterised by elemental analysis and different spectroscopic methods such as Fourier Transform Infrared (FT-IR), electron spin ionization (ESI)-MASS,1H nuclear magnetic resonance (NMR) and13C NMR. Mesomorphism behaviour of novel materials was studied using optical polarising microscopy, differential scanning calorimetry and higher-temperature powder X-ray diffraction method to confirm smectic C phase. In most of the compounds, we found rod-like mosaic texture and focal conic textures of smectic C phases. Nematic phases were also quite often found in materials during cooling and heating stage from isotropic phases. The dielectric measurements have been carried out for the determination of real and imaginary parts of the permittivity of the newly designed scaffolds. These studies will give adequate prospects in the field of supramolecular system, especially in calixarene organisation to explore new epoch of calixarene-based liquid crystals with different linking groups. [ABSTRACT FROM AUTHOR]

In this study, both boron-doped and -undoped poly(vinyl alcohol)/Calix[4]arene fibers were prepared by using an electrospinning technique. Obtained fibers were characterized by FT-IR, DSC, and SEM techniques. The DSC results show that the degradation of the boron-doped fibers started at much higher temperatures. This result indicates the addition of boron increased the thermal stability of the fibers. SEM pictures show that both of the fiber samples are nonbeaded with diameters ranging from 0.5 to 1 µm. The fiber diameters are not homogeneous and uniformly distributed for boron-undoped samples. [ABSTRACT FROM PUBLISHER]

A new fluorescent molecular receptor3based on theconeconfirmation of calix[4]arene appended with 2-[4-(N,N-dimethylaminophenyl)iminoethoxy] moieties was synthesised, which exhibits selective fluorescence ‘Turn-On’ response in the presence of only Hg2+ions among the various metal ions tested with a detection limit up to the nanomolar range. The fluorescence behaviour of receptor3in the presence of Hg2+ions is attributed to the alteration in electronic properties of3, i.e. working of intramolecular charge transfer (ICT) phenomenon on Hg2+ions complexation. The nitrogen atoms of the imino moieties got involved in the coordination with mercury ions, which enhances the electron-withdrawing ability of imino nitrogen atoms and, hence, leads to an ICT process consequently resulting in the appearance of an emission band at 444 nm. [ABSTRACT FROM PUBLISHER]

In this study, 5,11,17,23-tetrakis[(N-ethylpiperazine)methyl]-25,26,27,28-tetrahydroxycalix[4]arene (3) and 5,11,17,23-tetrakis[(4-carboethoxy-N-piperidino) methyl]-25,26,27,28-tetrahydroxycalix[4]arene (4) were synthesized in one step according to the Mannich reaction by the treatment of calix[4]arene with a secondary amine (N-ethylpiperazine, ethyl-4-piperidincarboxylate) and formaldehyde. The calix[4]arene derivatives (3, 4) were characterized by a combination of FTIR, 1H NMR and elemental analyses. The synthesized compounds were used in an esterification reaction as the phase transfer catalyst. The catalytic efficiency of the calix[4]arenes 3 and 4 was evaluated by carrying out the ester-forming reaction of alkali metal carboxylates (sodium butyrate or sodium caprylate) with p-nitrobenzyl bromide. It was observed that the ester-forming reaction of alkali metal carboxylates with p-nitrobenzyl bromide, using calix[4]arene-based catalyst 3 as a phase-transfer catalyst in dichloromethan, provided the best yields. [ABSTRACT FROM AUTHOR]

A series of polyamides having calix[4]arene units in the backbone which are called polycalixamides were prepared by direct polycondensation of dicarboxylic acid derivative of calix[4]arene with commercial diamines. The polycalixamides were obtained in high yields and possessed inherent viscosities of 0.42–0.55 dl/g and glass transition temperatures between 145 and 172°C. These polycalixamides were amorphous and therefore readily soluble in polar aprotic solvents such as NMP, DMSO, DMAc and THF. According to thermogravimetric analysis, these polymer series displayed high thermal stability ranged from 330 to 353°C at the point of 10% weight loss and char yields between 40.7–58% at 700°C in nitrogen. The temperature of maximum decomposition applied in DTG curves of polymers were among 326 to 369°C. The photophysical study was performed by UV-absorption spectroscopy and maximum wavelength for each polymer specified in details. It is found that these polyamides were highly efficient for sorption of Cu2+, Cr2+, Co2+ and Cd2+ in solid-liquid extraction. [ABSTRACT FROM PUBLISHER]

By formylation of 1,3-bisubstituted calix[4]arene anthraquinone derivative 1 in hexamethylenetetramine/trifluoroacetic acid system, the corresponding formylated gecalix[4]arene anthraquinone derivative 2 was synthesized in yield of 63%. By further reacting compound 2 with salicylic hydrazide, 2,4-dinitrophenyl hydrazine, nicotinyl hydrazine or phenyl thiosemicarhazide, novel calix[4]arene derivatives with anthraquinone and hydrazone groups 3a–3d were obtained in yields of 74–83%. The extracting experiments for series of metallic cations showed that compounds 3a–3d possessed high extracting abilities and extracting selectivity for tested cations. The complexation UV-Vis spectra for a series of anions indicated compounds 3a–3d exhibited the strong complexation abilities for tested anions. The 1H-NMR titration study showed that compound 3d possessed excellent complexation abilities for ion-pair of NaH2PO4 in 1:1 host-guest complex with the association constant of 4.6 × 104 M−1. [ABSTRACT FROM PUBLISHER]

Novel anthraquinone-modified calix[4]arene was synthesized by click chemistry and exhibited selective fluorescent enhancement in the presence of Ca2+, which is attributed to photo-induced electron-transfer effect from the 1,2,3-triazole ring. The enhanced fluorescence was further quenched by F−  ion. Thus, the potential Ca2+ and F−  ion switched INHIBIT logic gate has been constructed. [ABSTRACT FROM PUBLISHER]

The competitive solvent extraction of alkaline earth metals using different nano-baskets was investigated. The novelty of this work is to study the correlations between the isomer structure of calixarenes and their extraction properties. The objective was to quantify the effects of aryl groups in the ionisable pendant moieties, calixarene conformation, steric orientations (cis- and trans-) and relative positions (ortho- and para-) of pendant moieties upon the extraction efficiency, pH1/2 and the selectivity of calix[4]arene complexes. Alkaline earth metals were extracted from aqueous solutions into chloroform by di-ionisable calix[4]arenes and were measured using ion chromatography. The results revealed that alternation of aryl group in the pendant moieties, changing their orientation from cis- to trans-analogues as well as from ortho- to para- analogues, showed no changes in the selectivity, the extraction efficiency and the pH1/2 of calix[4]arene complexes. Changing the scaffold of calixarene's ring to the cone, 1,2-alternate and partial-cone conformers altered their complexation ability towards alkaline earth metals and their extraction efficiency. [ABSTRACT FROM PUBLISHER]