122406-45-5

Calix[4]arenes 1 or 2 react with alkyl halides and aqueous potassium hydroxide in the presence of PEG as phase transfer catalyst at room temperature to give the selectively distally dietherified product 3 or 4 in excellent yields. While at the same reacti

Three new calixarenes 3-5 featuring an alkyl residue of different chain lengths attached to one of the central ring methylene groups of the basic calix[4]arene 1 have been prepared. A systematic study that includes also the lower homologous compound 2 showing the effect of the alkyl substitution on the conformational behaviour of the calixarene framework in comparison with the unsubstituted parent compound 1 is reported. The application of special 2D NMR techniques, 2D-EXSY and ROESY methods at various temperatures establishes that calixarenes 2-5 adopt the partial cone conformation of lower symmetry and far less the symmetric cone and 1,2-alternate conformations. In solution, they undergo a fast interconversion with relatively low activation energies of about 15 kcal/mol at room temperature. The conformer distribution is well reproduced by molecular mechanistic calculations (MMFF94), indicating the present conformers to assume the lowest steric energies. A single-crystal X-ray structure of the lateral ethyl derivative 2 corroborates these results, showing the molecule in a sterically favourable partial cone conformation.

Eleven scaffolds of di-ionizable calix[4]arene conformers bearing two pendant groups of N-phenyl-sulfonyl carboxamides were synthesized and examined using isothermal titration calorimetry. The binding mechanisms of those conformers towards alkali metal ca

Fluorescence sensor L designed around a calix[4]arene scaffold, bearing two fluorogenic aminoquinoline moities, has been synthesized. It is found to be selective and sensitive towards Sr2+ and CN? over a wide range of cations and anions in a spectrofluorometric study in acetonitrile. The ion-binding property of L was monitored by fluorescence spectroscopy, UV–vis spectroscopy, ESI-MS, 1H NMR, FT-IR investigation and PXRD study. The host L shows a minimum detection limit which is 1.36 nM for Sr2+ and 1.23 nM for CN? having concentration range 5–120 nM and 5–115 nM respectively. The calculated binding constants for L:Sr2+ and L: CN? are respectively 8.859 × 108 M?1 and 8.574 × 108 M?1. Our host L has been utilised in formation of a user-friendly, affordable, and disposable paper-based analytical device (PAD) for rapid chemical screening of Sr2+ and CN? ion via single strip. Moreover, the optimization of probe L has also been done by the MOPAC-2016 software package using NM7 popular method resulting ?21.71 kcals/mol heat of formation and also determined the HOMO-LUMO energy band gap for L, L:Sr2+ and L: CN?. Further, molecular docking score has been calculated using HEX software. The applicability of our probe in real samples containing Sr2+ and CN? has also been checked by emission study with 94–99% recovery.

In this study, novel p-benzimidazole-derived calix[4]arene compounds with different structures, and a benzothiazole-derived calix[4]arene compound, were synthesized by a microwave-assisted method and their structures were determined by FTIR, 1H NMR, 13C NMR, MALDI-TOF mass spectroscopy, and elemental analysis. The effects of functional calixarenes against bacterial (pBR322 plasmid DNA) and eukaryotic DNA (calf thymus DNA = CT-DNA) were investigated. The studies with plasmid DNA have shown that compounds 6 and 10 containing methyl and benzyl groups, respectively, have DNA cleavage activity at the highest concentrations (10 000 μM). Interactions withplasmid DNA using some restriction enzymes (BamHI and HindIII) were also investigated. The binding ability of p-substituted calix[4]arene compounds towards CT-DNA was examined using UV-vis and fluorescence spectroscopy and it was determined that some compounds showed efficiency. In particular, itwas observed that the functional compounds (10 and 5) containing benzyl and chloro-groups had higher activity (Kb binding constants were found to be 7.1 × 103 M-1 and 9.3 × 102 M-1 respectively) on DNA than other compounds. Competitive binding experiments using ethidium bromide also gave an idea about the binding properties. Docking studies of the synthesized compounds with DNA were performed to predict the binding modes, affinities and noncovalent interactions stabilizing the DNA-compound complexes at the molecular level. Docking results were in good agreement with the experimental findings on the DNA binding activities of compounds. Based on these results, this preliminary study could shed light on future experimental antibacterial and/or anticancer research.

We report both the preparation and sensor evaluation of a new metal-free calixarene bridged binuclear phthalocyanine.

Lower rim 1,3-disubstituted p-tert-butylcalix[4]arene is studied here in its deprotonated form as complexing ligand for iron and chromium chloride. Crystallization of the two complexes from dry THF gives two different stoichiometries and structures, a trinuclear iron compound and a second, mononuclear structure with chromium. In both cases, the ligand adopts an elliptical shape and the metal ions are bound to the lower rim of the calixarene molecule.

A convenient procedure for direct introduction of one formyl group into p-tert-butylcalix[4]arenes through ipso substitution is described.

The versatile calix[4]arene framework yielded chiral diphosphite ligands applicable for Rh-catalyzed asymmetric hydrogenation of dehydroamino acid derivatives. Optimum efficiency was obtained for: R1 =-C(CH 3)3; R2/s

A calixarene having two pyrene moieties on the lower rim has been synthetized; the ratio of the monomer vs. excimer emission was sensitively affected by solvent polarity and added metal ions.

Herein, the synthesis and evaluation of a novel CHEF-PET fluorescence sensor L, based on calix[4]arene comprising two 1-Naphthoicacid groups as binding sites, is described. The selective nature of this fluorescence probe towards Pr3+ and As3+ has been investigated by emission titration, UV–vis titration, 1H NMR spectroscopy, FT-IR, PXRD and ESI-MS investigation. The linear concentration range at pH 3.5 of L for Pr3+ and As3+ is 0–120 nM and 0–145 nM respectively with the detection limit of 1.45 nM for Pr3+ and 1.91 nM for As3+. Through Benesi-Hildebrand equation, the binding ability was found to be 7.377 × 108 M?1 for Pr3+ and 7.842 × 108 M?1 for As3+. The MOPAC-2016 software package has been used to optimize the L using PM7 and the molecular docking study has been carried out using HEX software.

A novel series of 1,3-bis(2-dihydrothiazolyl)thiaalkoxy-p-tert- butylcalix[4]arenes generated by the reaction between 4,5-dihydrothiazole-2- thiol and the different dibromide calix[4]aryl groups have been synthesized and structurally characterized by IR, 1H NMR, 13C NMR, and MS. From their analytical data, it was found that compounds 8, 9, and 10 had cone conformations, whereas compound 11 existed as a mixture conformation. To verify the structure of the synthetic compounds, a single-crystal X-ray structure of compound 8 was obtained. Copyright Taylor & Francis Group, LLC.

Variously substituted titanacalixarenes were synthesised and tested for their performance as catalysts in ethylene polymerisation: p-tert-butylcalix[4] arene was derivatised to afford distal diether p-tert-butylcalix[4]arenes L1-L4, distal dihydroxy-depleted L5, proximal dihydroxy-depleted L6, proximal diether p-tert-butylcalix[4]arene L7, proximal intra-bridged disiloxane L8 and proximal monoether L9. (Dichlorotitana)-p-tert-butylcalix[4]arenes 1-8 and (monochlorotitana)-p-tertbutylcalix[4]arene 9 have been successfully synthesised by reacting L1-L4 with TiCl4·2THF or L5-L9 with TiCl 4. The structural conformation of complexes 1-9 in solution were determined by 1H NMR, 13C NMR, NOESY and COSY spectroscopic studies. Compounds 2, 3 and 4 have been structurally characterised by single-crystal X-ray diffraction. Upon activation with methylaluminoxane, compounds 1-8 revealed low to moderate activities for the production of high-density polyethylene (HDPE) to ultra-high-molecular-weight polyethylene (UHMWPE). 6/MAO gave the best activity at 770 kgPE(molTi) -1h-1.

A series of mixed tetraethers of calix[4]arene and p-tert- butylcalix[4]arene in which two distal substituents are methyl and the other two 1-alkenyl groups with 3, 4 and 5 carbon atom chains have been prepared by two routes which differ in the order in which the groups (methyl or alkenyl) were introduced. The ethers of p-tert-butylcalix[4]arene were isolated as a mixture of cone (minor) and partial cone (major) conformations in dynamic equilibrium. For die ethers of calix[4]arene the conformational outcome depended on the method of synthesis. Up to three conformations could be detected: a cone, a partial cone with an anisyl unit inverted, and a partial cone with an alkenyl-bearing ring inverted. 1H NMR analysis of the complexes formed between these ethers and alkali metal iodides showed that both cone and partial cone complexes of the p-tert-butylcalix[4]arene tetraethers could be detected with lithium iodide, but only cone complexes with the calix[4]arene derivatives. Sodium iodide complexes were also formed with both sets of compounds but in all cases only the cone complex was detected.

A new fluorescence sensor, namely, TDPC, which is composed of a pyrene group connected to calix[4]arene as the fluorogenic unit, has been synthesized, characterized and analyzed with regard to its selective sensing ability for As3+ (0-150 nM), Nd3+ and Br? (0-120 nM), with detection limits of 11.53 nM, 0.65 nM and 11.25 nM, respectively. The binding constant (Ks) was found to be 7.842 × 108 M?1 for As3+, 6.877 × 108 M?1 for Nd3+ and 6.311 × 108 M?1 for Br?. Furthermore, we report an easy-to-use, low-cost and disposable paper-based sensing device for rapid chemical screening of As3+, Nd3+ and Br?. The device comprises a luminescent sensing probe embedded in a cellulose matrix in which resonance energy transfer seems to be the sensing mechanism. It opens up new opportunities for simple and fast screening in remote settings where sophisticated instrumentation is not always available. The MOPAC2016 software package was used to optimize TDPC using the well-established PM7 method, and the HOMO-LUMO energy band gap was calculated for TDPC and TDPC with structures based on As3+, Nd3+ and Br? ions. To determine the influence of different metal ions on TDPC, a molecular docking study was carried out using HEX software. Furthermore, to assess its analytical applicability, the prepared sensor was successfully used for the analysis of two different real samples (an industrial soil sample for Nd3+ and industrial waste water for As3+ and Br?) to validate the proposed method, with recoveries of ions of 95-99%.

In this study, novel pyrazine-2-carboxylate derivatives of calix[4, 8]arene have been synthesised and fully characterised. Furthermore, this study presents removal of carcinogenic azo dyes [Reactive Black 5 (RB5), Trapaeolin 000 (TP), Chicago Sky Blue (CSB), Methyl Orange (MO) and Evans Blue (EB)] from the aqueous solution by solid-liquid extraction using these novel compounds. The maximum sorption of azo dyes was achieved at pH 3. Calix[8]arene derivative (3) showed higher sorption as it formed a more stable complex with azo dyes than calix[4]arene derivative (6). An excellent regeneration for at least five times in sorption capacity indicates that calix[8]arene derivative (3) was highly applicable for the removal of carcinogenic azo dyes from industrial wastewater. The stoichiometric ratio between the calixarene derivatives (3 and 6) and selected azo dyes was estimated through job’s plots.

New fluorescent calix[4]arene derivatives 1, 2, and 3 were synthesized by introducing phenanthridine moieties at a lower calixarene rim. It was shown that due to the prominent fluorescence of compounds 1 and 3, they could be considered as potential sensitive fluorimetric cation sensors. Complexation of the prepared compounds with alkali-metal cations was studied at 25 °C in acetonitrile-dichloromethane and methanol-dichloromethane solvent mixtures (φ = 0.5) by means of fluorimetric, spectrophotometric, potentiometric, and microcalorimetric titrations as well as NMR spectroscopy. The stability constants of the corresponding complexes were determined, as were the enthalpies and entropies of the complexation reactions. In addition, equilibrium constants of ion-pairing reactions between alkali-metal cations and several anions in the solvents used were measured conductometrically. It was found that the cation-binding affinity of ligand 1 with four phenanthridine subunits was much higher than that of 2 and 3, with the complex stabilities in all cases being significantly lower in methanol-dichloromethane mixture compared to that in acetonitrile-dichloromethane. These findings were thoroughly discussed by taking into account the determined thermodynamic complexation data, structural properties of the ligand and free and complexed cations, as well as the solvation abilities of the solvents examined. The conclusions made in that way were corroborated by the results of the molecular dynamics simulations of the systems studied. An attempt to get an insight into the possible structures of the alkali-metal cation complexes with ligand 1 was made by carrying out the corresponding density functional theory calculations.

A pyrenyl linked calix[4]arene fluroionophore has been synthesized and used as a ditopic chemosensing ensemble for Fe3+ and H2PO 4- using emission spectra. The detection limit of the synthesized receptor was found to be 0.88 pM for Fe3+ and 1.11 pM for H2PO4-. Moreover, this probe has been applied for recognition of Fe3+ in blood serum and H2PO 4- in waste water.

Partial etherification of phenolic-OH groups of calix[4]arenes with various alkyl halides/tosylates and K2CO3 under microwave irradiation afforded 1,3-dialkoxycalix[4]arenes in their cone conformation only as predominant/sole product

A series of novel calix[4]arene-based Mannich (5 and 6) and Schiff base (9-11) receptors have been synthesized and characterized by various analytical techniques. Competitive two-phase extraction experiments of these novel calix[4]arene amine- and imine-c

We synthesized the new calix[4]arene amines bearing two and four imidazole or tert-butylamine moieties (9a,b/10a,b) by the reaction of di- or tetra-tosylated calix[4]arene derivatives (7 and 8, respectively) with 1-(3-aminopropyl)imidazole and/or tert-butylamine, respectively. After the characterization of 9a,b/10a,b their extraction abilities toward Cr(VI) anionic species (CAS) was evaluated and compared by the liquid-liquid extraction method. The extraction results revealed that calix[4]arene amine having four imidazole groups (10a) was an efficient anion receptor for CAS. Moreover, the extraction of CAS by 10a in the presence of other anions such as Cl-, NO 3-, and PO43- showed that 10a could be a selective anion receptor for CAS in the presence of those anions.

The fluorescent peptidocalixarenes, 5,11,17,23-tetra-tert-butyl-25,26,27, 28-tetrakis(O-methyl-L-tryptophanylcarbonylmethoxy) calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-25,27-di(O-methyl)-26,28-bis(O-methyl-L- tryptophanylcarbonylmethoxy) calix[4]arene (2), were prepared by introducing tryptophan subunits at a lower calixarene rim. Coordination abilities of 1 and 2 towards Eu(III) and alkali metal cations were studied by spectrophotometric, spectrofluorimetric, conductometric and potentiometric titrations in acetonitrile at 25°C. Rather strong complexation was observed for smaller alkali metal cations Li+ and Na+ (logKLi1 > 6, log KLi2 > 6, log KNa1 = 8.25, logKNa2 = 6.94), and moderate for K+ (logKK1 = 5.09, log K K2 = 4.09). Larger Rb+ and Cs+ cations did not fit in the ion binding site of 1 so no complexation was detected, whereas the more flexible ligand 2 accommodated Rb+ cation (logKRb2 = 3.44). The fluorescence of 1 (λex = 280 nm, λem = 340 nm) was remarkably quenched by Eu(III). Stability constant of 1:1 (Eu3+:1) complex determined spectrofluorimetrically amounted to log KEu1 = 6.16.

The alkylation of (dichlorotantala)-p-tert-butylcalix[4]arenes 1 and 3 by two equivalents of NpMgCl (Np = neopentyl) affords the corresponding unreported (bisneopentyltantala)-p-tert-butylcalix[4]arenes 4 and 5. These complexes can undergo dealkylation by

The ligand X4Me2Imme2 was synthesized from p-tert-butyl-calix[4]arene. Upon reaction with one equivalent of Cu(NCMe)4PF6, it led to the new two-coordinate copper(I) complex [Cu(X4Me2Imme2)]PF6 that was characterized by X-ray diffraction analysis. This complex revealed itself to be totally inert towards dioxygen in the solid state as well as in coordinating or protic solvents.

Reductive cleavage of 25,26,27,28-tetramethoxy-p-tert-butylcalixarene with K results in the formation of 26,28-dimethoxy-p-t-butylcalixarene.The reaction of 25,27-dihyroxycalixarene with NO2BF4 in acetonitrile results in its oxidation to calixdiquinone 6.

Selective 1,3-dialkylation of the phenolic groups of p-tert-butylcalixarene (3) with methyl or benzyl tosylate yields 7a (75percent) and 8 (95percent), respectively.Subsequent bridging of the two remaining phenolic groups in 7a or 8, by reaction with polyethylene glycol ditosylates, gives p-tert-butylcalixarene crown ethers (4b, 4c, and 4e).Reaction of 7a with 3,3''-bis(bromomethyl)-2,2',2''-trimethoxy-5,5',5''-trimethyl-1,1':3',1''-terphenyl (10) in the presence of NaH or KH produces the corresponding NaBr and KBr complexes of the calixspherand 6.Decomplexation of the6*NaBr and 6*KBr complexes in H2O/CH3OH (4:1) requires long reaction times and high temperatures, indicating a high kinetic stability.The X-ray structure of 6*NaPic confirmed the flattened partial cone conformation of the calixarene moiety in this complex.The free energies of complexation (ΔG0) of the calixcrown ether alkali picrate (MPic) complexes vary from -6 to -12 kcal*mol-1 (CDCl3).The calixspherand 6 forms kinetically "stable" complexes with Na(1+) (kd298 = 6.0*1E-9 s-1), K(1+) (kd298 =1.0*1E-8 s-1), and Rb(1+) (kd298 = 6.9*1E-5 s-1).The rates of complexation vary between 1.3*1E4 and 2.5*1E5 M-1 s-1.The calculated free energies of complexation of 6 with MPic salts in CDCl3 at 298 K are -16.8 , -18.1 , and -13.0 kcal*mol-1, respectively.The high thermodynamic and kinetic stabilities of these complexes are explained in terms of a high degree of preorganization of the calixspherand and the highly hydrophobic collar around the molecular cavity.This prevents solvent molecules to assist in the decomplexation process.

Calixarene (1A), p-t-butylcalixarene (1B), and p-allylcalixarene (1C) have been converted to various derivatives, including the methyl, ethyl, allyl, benzyl and trimethylsilyl ethers and the acetates.Although the parent calixarenes exist preferentially in the cone conformation, they are conformationally flexible and at room temperature interconvert at a rate of ca 100 sec-1.All but the methyl ethers, on the other hand, are conformationally rigid at the room temperature.The preferred conformations in most cases are the cone and the partial cone, depending on the derivative formed (i.e. methyl and ethyl ethers favour the partial cone; benzyl and trimethylsilyl ethers favour the cone).In the cases of the allyl ethers and the acetates the p-substituents appear to influence the conformational outcome (i.e. 1A and 1B form the allyl ethers in the partial cone and cone conformation, respectively; 1A and 1B form the acatates in the 1,3-alternate and partial cone conformation, respectively).The conformationally rigid calixarene derivatives in the cone and partial cone conformations belong to the small group of synthetic compounds that contain a permanent cavity (a "changeless calix") whose dimensions are large enough to encapsulate other molecules.