Synthesis and complexation study of calix[4]arene diamine derivative incorporated in a polymeric backbone with chiral monomers

The novel chiral polymeric compounds containing more than one calix[4]arene have been synthesized by reacting a new calix[4]arene diamine derivative with two chiral monomers. These newly prepared compounds were studied by extraction of toxic heavy metal (Cu²⁺, Co²⁺, Cd²⁺, Hg²⁺), silver and alkali metal (Na⁺, K⁺) cations from aqueous phase. It was observed that the resulting calixarene-based polymers have a good complexing ability towards silver, alkali metal and toxic heavy metal cations.     

Synthesis of novel chiral Schiff base and amino alcohol derivatives of calix[4]arene and chiral recognition properties

In the present study, the synthesis and liquid phase extraction properties towards some amino acid methylesters and amino alcohols of Schiff base and amino alcohol substituted calix[4]arene are reported. The Schiff base substituted calix[4]arene 5 has been synthesized via condensation reaction involving 5,17-diformyl-11,23-di-tert-butyl-25,27-di[3-(4-formylphenoxy)propoxy]-26,28 dihydroxycalix[4]arene 4 and (R)-(?)-2-phenylglycine methyl ester in CHCl₃:MeOH. To give the amino alcohol substituted calix[4]arene 6, the synthesized chiral compound 5 was reduced by LiAlH₄. The new chiral Schiff base and amino alcohol derivatives of calix[4]arene have been characterized by a combination of FT-IR, ¹H NMR, ¹³C NMR, FAB-MS and elemental analysis. Also, the extraction behaviors of 5 and 6 towards some selected amino acid methylesters and amino alcohols have been studied by liquid–liquid extraction.     

The Preorganization Effect of the Calix[4]arene Platform on the Extraction Properties of Acetylhydrazide Groups with Transition Metal Ions

The binding properties of the cone conformer of O,O,O,O-tetrakis[hydrazinocarbonylmethyl]-4-tert-butylcalix[4]arene, the cone and the 1,3-alternate conformers of the corresponding thia analogue have been evaluated by means of liquid–liquid extraction for a large variety of metal ions. The extraction constants and the stoichiometries of the complexes formed have been determined. Comparison of the extraction properties of calix[4]arenes with their acyclic monomeric analogue clearly demonstrated, that the preorganization of acetylhydrazide groups on the calix[4]arene platform is the cause for a significant improvement of its binding properties. The presence of additional “soft” nitrogen binding sites in acetylhydrazide derivatives of calix[4]arenes compared to their amide derivatives leads to a shift from their classical selectivity for alkali and alkaline earth cations to transition metals. The cone conformer of tetrathiacalix[4]arene shows higher selectivity in a series of d-metal ions compared with its “classical” analogue. The 1,3-alternate conformer exhibits an excellent extraction selectivity for Cu²⁺ and Hg²⁺.     

Synthesis and amino acid extraction abilities of chiral calix[4]arene triamides containing amino alcohol units

Herein the synthesis and extraction abilities of new d-/l-phenylalaninol substituted p-tert-butylcalix[4]arene triamide derivatives (3 and 4) towards amino acids are reported. These compounds (3 and 4) have been easily synthesized via aminolysis of p-tert-butylcalix[4]arene trimethylester (2) with d-/l-phenylalaninol in methanol-toluen solvent system at one step. The extraction properties of the prepared chiral calix[4]arene triamide derivatives (3 and 4) towards some selected amino acid methylesters are studied by liquid–liquid extraction. Results show that these chiral calix[4]arene triamide derivatives (3 and 4) exhibited a good affinity towards all amino acid species without any remarkably discrimination.     

Synthesis and Comparison of Extraction Properties of p‐tert‐Butylcalix[n]arene Nitrile Derivatives for Selected Metals and Dichromate Anions

The article describes the syntheses and extraction properties of two p‐tert‐butylcalix[6]arene nitrile derivatives (3 and 4). The trinitrile derivative 3 has been synthesized from 5,11,17,23,29,35‐hexa‐tert‐butyl‐37,38,39,40,41,42‐hexahydroxy‐calix[6]arene 1. The compound 1 was directly converted to its hexanitrile derivative (4). In these syntheses, it was considered to explore the role of nitrile sites in the extraction of various metal cations and HCr₂O₇ ^?/Cr₂O₇ ^2? anions. The liquid‐liquid extraction properties of 3 and 4 towards selected alkali/transition metal cations and HCr₂O₇ ^?/Cr₂O₇ ^2? anions are reported. It has been observed that receptor 3 does not extract alkali/transition metal cations effectively, but shows affinity towards HCr₂O₇ ^?/Cr₂O₇ ^2? anions at low pH. The compound 4 is an effective form for transferring Ni²⁺ selectively, while it shows poor transferring ability for HCr₂O₇ ^?/Cr₂O₇ ^2? anions from an aqueous into a dichloromethane layer. It was observed that the cavity size of the calix[n]arenes and the cooperativity of the functionalities play important roles in two phase extraction systems.     

Synthesis and application of an efficient calix[4]arene-based anion receptor bearing imidazole groups for Cr(VI) anionic species

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^?, NO₃^?, and PO₄^3? showed that 10a could be a selective anion receptor for CAS in the presence of those anions.     

通过杯芳烃片段桥联合成杯[4]冠4齐聚物及其络合性能研究

通过杯芳烃片段桥联合成杯[4]冠4齐聚物,并通过两相萃取实验评估其络合性能。络合研究表明,酰胺型杯[4]冠4齐聚物（TCA[4]-III）对软金属银、铅离子和氨基酸具有选择性络合。其对色氨酸和组氨酸的萃取率分别高达87.9% 和 91.5%。     

Selective extraction of toxic heavy metals and biological activity studies using pyrimidylthioamide functionalised calix[4]arene

The current study comprises synthesis of pyrimidylthioamide derivatized calix[4]arene (5), and its comparative liquid–liquid extraction properties with the compound 4 towards the selected transition metal ions (Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, Hg²⁺ and Cd²⁺) were investigated. Experimental results revealed that the compound 5 shows better efficiency and affinity for Pb²⁺ and Hg²⁺ ions as compared to compound 4. The antibacterial and antifungal effects of compound 5 were also investigated on various bacteria and fungi. It has been observed that compound 5 has some effects against Salmonella typhimurium NRRLB 4420, Bacillus cereus ATCC 11778, Staphylococcus aureus NRRL B767 and Bacillus subtilis NRS 744.     

Enantioselective Recognition of Calix[4]arene Derivative Bearing Bicyclic Guanidinium for D/L Amino Acid Zwitterions

The p‐tetra‐tert‐butyl calix[4] arene derivatives (3 and 4) with (5,5) chiral bicyclic guanidinium, as the receptors of amino acid zwitterions, have been synthesized via a O‐alkylation reaction of p‐tetra‐tert‐butyl calix [4] arene with cbJoromethyl chiral bicyclic guanidinium 2 in the presence of anhydrous K₂CO₃ in acetonitrile. The results obtained from liquid‐liquid competitive extraction experiments indicate that the two receptors may selectively recognize L‐aromatic amino acids, and that the enantioselective recognizability of the receptor 4 with two chiral bicyclic guanidinium units reachs up to about 90% for L‐Phe.     

Stereochemical control of calixarenes useful as rigid and conformationally diversiform platforms for molecular design

Stereochemical problems and related functions of calix[4]arenes, calix[6]arenes and their chiral derivatives have been reviewed. In p-tert-butylcalix[4]arene (1H₄) and its mono-, di-, tri-, and tetra-O-alkyl derivatives (1H₃R, 1H₂R₂,1HR₃, and 1R₄, respectively), 23 different homologues can exist (including 1H₄). We found that the OH group in the unmodified phenol unit is permeable through the calix[4]arene ring. Thus, several conformational isomers become equivalent after the ‘oxygen-through-the-annulus’ rotation of the OH group and the number of possible homologues is reduced to 13 (including 1H₃). We report in this paper the syntheses of all of these possible conformational isomers using a protection-deprotection method with a benzyl group and metal template effects. On the other hand, all possible chiral isomers that can be derived from calix[4]arene by modification of the OH groups have been systematically classified. Molecular asymmetry can be generated not only by different substituents but also by conformational isomerism. The numbers of chiral isomers are 17 for tetra-O-substituted calix[4]arenes, 9 for tri-O-substituted calix[4]arenes, 3 for di-O-substituted calix[4]arenes, and 0 for mono-O-substituted calix[4]arenes. Chiral calix[4]arenes can also be designed by the introduction of a substituent into the m-position of a phenol unit or by the use of a dissymmetric ‘stapling reaction’ in proximal phenol units. In p-tert-butylcalix[6]arene, the conformational behaviour is totally different from that in p-tert-butylcalix[4]arene. A large degree of conformational freedom remains in the framework, and both ‘oxygen-through-the-annulus rotation’ and ‘para-substituent-through-the-annulus rotation’ can take place. However, when metal cations are bound to calix[6]aryl esters, the conformation is changed to a cone type. Bridging and capping are powerful methods to immobilize the conformation of calix[6]arenes. In addition, definitive evidence for ring immobilization was obtained from the absence of racemization in the chiral calix[6]arene. A successful example of chiral recognition for α-amino acid derivatives was achieved by using chiral homooxacalix[3]arene which has ‘pseudo C₂ symmetry’. These examples indicate that calixarenes serve as rigid and conformationally diversiform platforms for the design of novel functional supramolecules.     

Synthesis and chiral recognition properties of two novel chiral calix[4]arene tartaric ester derivatives

Two new chiral calix[4]arene derivatives containing tartaric acid ester moieties were synthesized. The chiral calix[4]arenes are in a ‘cone’ conformation according to NMR spectroscopy. The chiral recognition capabilities of 1–4 toward the guests, 1,2-propanediol and serine methyl ester hydrochloride (SerOMe), were investigated (¹H NMR spectroscopy). The extraction properties of compounds 1 and 2 toward selected α-amino acid methyl esters were also studied.     

Synthesis of nucleobase-calix[4]arenes via click chemistry and evaluation of their complexation with alkali metal ions and molecular assembly

In this study, calix[4]arene derivatives (11–14) bearing a single nucleobase (adenine, thymine, cytosine or guanine) were synthesised via click chemistry. The complexation ability of the synthesised derivatives with alkali metal ions was measured using MALDI-TOF mass spectrometry, and their molecular assembly in CDCl₃ was determined using ¹H NMR. Calix[4]arene derivatives (11–14) formed 1:1 complexes with all alkali metal ions and the rank order for the complexation selectivity was Rb⁺ > Cs⁺ > K⁺ ? Na⁺ > Li⁺. The attachment of nucleobase at the upper rim of calix[4]arene had little effect on its complexation selectivity for alkali metal ions. Thymine-, adenine- and guanine-calix[4]arenes formed self-assembled structures in CDCl₃ via base–base interactions. In addition, adenine-calix[4]arene (11) bound to thymine-calix[4]arene (12) to form a discrete species via Hoogsteen hydrogen bonding.     

Synthesis and Comparison of Extraction Properties of p‐tert‐Butylcalix[n]arene Nitrile Derivatives for Selected Metals and Dichromate Anions

The article describes the syntheses and extraction properties of two p‐tert‐butylcalix[6]arene nitrile derivatives (3 and 4). The trinitrile derivative 3 has been synthesized from 5,11,17,23,29,35‐hexa‐tert‐butyl‐37,38,39,40,41,42‐hexahydroxycalix[6]arene 1. The compound 1 was directly converted to its hexanitrile derivative 4. In these syntheses, it was thought to explore the role of nitrile sites in the extraction of various metal cations and HCr₂O₇ ^?/Cr₂O₇ ^2? anions. The liquid‐liquid extraction properties of 3 and 4 towards selected alkali/transition metal cations and HCr₂O₇ ^?/Cr₂O₇ ^2? anions are reported. It has been observed that receptor 3 does not extract alkali/transition metal cations effectively, but shows affinity towards HCr₂O₇ ^?/Cr₂O₇ ^2? anions at low pH. The compound 4 is an effective form for transferring Ni²⁺ selectively, while it shows poor transferring ability for HCr₂O₇ ^?/Cr₂O₇ ^2? anions from an aqueous into a dichloromethane layer. It was observed that the cavity size of the calix[n]arenes and the cooperativity of the functionalities play important roles in two phase extraction systems.     

Preparation of Calix[4]arene Alkylamine Derivatives by Mannich Reaction and use as Phase-Transfer Catalysts for Esterification Reaction

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.     

Synthesis and extraction studies of polymeric phthalimido functionalized calix[4]arene

The article comprises synthesis and extraction studies of polymeric calix[4]arene having phthalimide groups at the lower rim. The polymeric phthalimido functionalized calix[4]arene was synthesized via radical initiated reactions involving a vinylic monomer 5,11,17,23-tetra-tert-butyl-25-[4-(acrylamido)benzyloxy]-26,28-bis-(2-phthalimido-ethoxy)-27-hydroxycalix[4]arene (5) with styrene. A five atom spacer group was incorporated between the bulky calixarene core and the acrylate moiety in order to minimize steric interactions which proved to impede the polymerization. From the liquid–liquid and solid–liquid extraction studies it has been concluded that the precursor 3 (5,11,17,23-tetra-tert-butyl-25-(4-nitro benzyloxy)-26,28-bis-(3-phthalimidoethoxy)-27-hydroxy-calix[4]arene) is selective for metal cations. The order of extractability of metal cations by the ligand 3 decreases in the sequence: Hg²⁺ > Cd²⁺ > Cu²⁺ > K⁺ > Co²⁺ whereas its polymeric derivative is selective in the sequence: Hg²⁺ > Cd²⁺ > K⁺ > Co²⁺ > Cu²⁺ for the metal cations used in the experiments.     

Polymer Supported Calix[4]arene Schiff Bases: A Novel Chelating Resin for Hg2+ and Dichromate Anions

This article describes the synthesis and characterization of two new calix[4]arene Schiff bases and their polymeric resins. The extraction properties of these “proton switchable extractants” with alkali, transition, post transition metal cations and for dichromate anions are reported. The two new calix[4]arene based Schiff bases (5 and 6) have been synthesized from 5,17‐diformyl‐25,27‐dipropoxy‐26,28‐dihydroxycalix[4]arene (4) by treatment with 3‐amino‐methylpyridine and 1,8‐diaminooctane in two separate reaction flasks following the same procedure. Compounds 5 and 6 have been appended to a polymeric resin by treatment with Merrifield resin through a nucleophilic substitution reaction. The receptor compounds (3 and 5–8) do not extract alkali metal cations, but show some selectivity toward transition metal cations, and a particularly high selectivity to Hg²⁺ and Pb²⁺. The protonated forms of all of the calixarene‐based receptors are good extractants for transferring Cr₂O₇ ^2?/HCr₂O₇ ^? anions from an aqueous into a dichloromethane layer.     

An inherently chiral calix[4]crown carboxylic acid in the partial cone conformation

We have designed and synthesized an inherently chiral calix[4]arene partial cone conformer, in which a crown-4 ether moiety, a carboxyl group, and a propyl group are convergent. Chemical resolution was achieved by use of (S)-BINOL as a chiral auxiliary. ¹H NMR titration data revealed that the title compound does not have the ability to differentiate both enantiomers of chiral amine and aminoalcohol guests. The approximately symmetric calix[4]arene skeleton of the partial cone conformer is presumed to be responsible for its undesirable chiral recognition ability.     

Chiral calix[4]arenes bearing α-hydroxy amide units as membrane carriers for amino acid methyl esters

Novel chiral calix[4]arene derivatives functionalized at the lower rim have been prepared from the reaction of p-tert-butylcalix[4]arene diamine or acylhydrazine derivative with mandelic acid or hydroxyisovaleric acid. The structures of these receptors were characterized by FTIR, ¹H, ¹³C and 2D COSY NMR spectroscopy and elemental analysis. The transport of amino acid derivatives (phenylalanine, phenylglycine and tryptophan methyl ester hydrochlorides) was studied through bulk liquid membrane in the presence of chiral calix[4]arene derivatives. The receptors have been found to act as carriers for transport of aromatic amino acid methylesters from the aqueous source phase to the aqueous receiving phase. The transport rate and L/D selectivity of amino acid esters studied depend strongly upon the structure of the chiral receptors and guests. The best enantioselectivity was obtained in the case of phenylglycine methyl ester for all chiral carriers.     

Salt-Bridge Supported Bilayer Lipid Membrane Modified with Calix[n]arenes as Alkali Cation Sensors

ABSTRACT

Potentiometric behaviors of a salt-bridge supported bilayer lipid membrane (Sb-BLM) modified with Calix[n]arene (n=4, 6, 8) derivatives are described for some alkali metal ions. The modified Sb-BLM was used as an alkali cation sensor. The membrane potentials were observed to generate Nernstian responses to the concentration of alkali metal ions in electrolyte. The Sb-BLM modified with the calix[n]arenes show high selectivity for individual alkali metal ions: Calix[8]arenes for K⁺, calix[6]arenes for Cs⁺ Calix[4]arenes show no selectivity for any alkali ions. The interacting mechanism is also discussed.     

Synthesis of Chiral Calix[4]arene Derivative and Evaluation of its Recognition Properties

The article describes the synthesis and extraction properties of a new chiral calix[4]arene Schiff base ligand 5, which has been synthesized from 5,17-diformyl-25,27-bis-(4-nitrobenzyloxy)-26,28-dihidroxycalix[4]arene (4) by treatment with (S)-(-)-1-phenylethylamine. In this synthesis, it was thought to explore the role of chiral, as well as Schiff base sites in the recognition of targeted species ions (such as dichromate anions) as well as neutral/chiral molecules. At low pH, the ligand 5 is more effective for transferring the dichromate anions from an aqueous into a dichloromethane layer; may be due to the protonation of nitrogen atoms.

The extraction properties of ligand 5 towards the some selected α -amino acid methylesters are also reported. However, the ligand 5 did not display any selectivity towards the selected α-amino acid methylesters.