Intramolecular hydrogen bonding effect on metal ion complexation of homooxacalix[4]arene bearing tetraamides

N,N-Dipentylamido homooxacalix[4]arene (3) in the C-1,2-alternate conformation provided Pb²⁺ ion selectivity over other metal cations. N-Monopentylamido homooxacalix[4]arene in C-1,2-alternate conformation has an intramolecular hydrogen bonding, causing decrease of the metal ion complex ability.     

New preorganized calix[4]arenes. Part I. A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27,28-Dodecamethyl-5,11,17,23-tetrahydroxycalix[4] arene

A doubly-crowned calix and a double-calixcrown derived from 4,6,10,12,16,18,22,24,25,26,27, 28-dodecamethyl-5,11,17, 23-tetrahydroxycalix[4]arene (1) have been prepared by reaction of appropriate oligoethylene glycol ditosylates with (1) in acetonitrile in the presence of potassium carbonate. A potassium template effect is observed during one of the double cyclizations.     

Synthesis and evaluation of neutral anion receptors based on acylhydrazide-appended calix[4]arenes

A new class of neutral receptors based upon acylhydrazide-appended calix[4]arenes was synthesised and evaluated for recognition of anions. Detailed NMR and single-crystal X-ray analyses of one of the synthesised compounds reveal that anion recognition in such derivatives is achieved through cooperative hydrogen bond interactions. The presence of three centred NH–O and two OH–O hydrogen bonds at the lower rim of the synthesised calixarene architecture apparently helps the molecular scaffold to retain cone conformation to enable deployment of intermolecular hydrogen bonds for selective recognition of HSO₄ ^? ion in preference to F^?, Cl^?, Br^?, I^?, ClO₄ ^?, AcO^? and PF₆ ^? ions.     

Extraction of technetium(vii) by calix[4]arene tetraketones and tetraesters from acidic and basic media

Tetrasubstituted on the lower rim calix[4]arenes, containing carbonyl and ester groups, and existing in a cone conformation are selective and efficient extracting agents for Tc^VII extraction from both acidic and basic solutions.     

Synthesis and anion recognition of neutral receptors based on multiamide calix[4]arene

Two multiamide calix[4]arenes (5, 6) were synthesized and characterized by NMR, MS and elemental analysis. The binding properties of receptors with some anions (π-O₂NPhOPO₃²⁻, π-O₂NPhO⁻, H₂PO₄⁻, Ac⁻, Cl⁻, Br⁻ and I⁻) were studied by UV-Vis spectra. The results indicate that the tetraamide calix[4]arenes (5, 6) have a good selectivity to the anions containing aromatic ring (π-O₂NPhOPO₃ ²⁻, π-O₂NPhO⁻). The 1 : 1 complexes between host and guest were formed through multiple hydrogen bonding and π-π interactions. The hosts 5 and 6 also show a definite binding ability for the anions (H₂PO₄⁻, Ac⁻, Cl⁻) that have no ultraviolet absorption, which provides a simple method of spectrum detection for these anions.     

基于杯[4]芳烃的手性识别*

手性杯芳烃是一类重要的主体化合物,在手性识别、对映体分离和不对称催化等方面有着广泛的用途。[4]芳烃引其稳定的构象和易于修饰的特点,成为研究最为广泛的杯芳烃分子,其中大量的文献报道了能够用于对映体识别和检测的手性[4]芳烃。在手性识别的研究中,荧光、紫外和核磁是3中最常见的研究方法,本文根据这3种方法进行分类,综述了近年来以杯[4]芳烃为分子骨架的手性受体的合成及其在手性识别中的应用。最后对手性[4]芳烃的发展前景作了展望。     

Conformational properties of the calix[4]naphthalenes

The base-catalyzed condensation of 1-naphthol and formaldehyde in refluxing dimethylformamide affords three isomeric cyclic tetramers which are conformationally flexible over a wide temperature range. Their tetrabenzoate esters however show restricted flexibility. Variable-temperature NMR and low-temperature COSY is used to analyze the conformational preferences of these calix[4]naphthalenes.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Molecular Recognition Properties of Biphen[4]arene

Biphen[n]arenes (n=3, 4) are a new family of macrocyclic hosts. Here, we describe the molecular recognition behavior of hydroxylated biphen[4]arene (OHBP4) for the first time. A series of cationic guests with different sizes and shapes, including quaternary ammonium salts ( 1? PF₆ and 2? PF₆), pyridinium‐based guests ( 3? 2 PF₆– 6? 2 PF₆), and cobaltocenium hexafluorophosphate ( 7? PF₆), were chosen as model guest molecules. OHBP4 exhibits good selectivity towards the 2,7‐dibutyldiazapyrenium bis(hexafluorophosphate) ( 4? 2 PF₆) axle to form a [2]pseudorotaxane‐type complex. In contrast, hydroxylated biphen[3]arene (OHBP3) cannot bind with this big guest. In addition, OHBP4 strongly interacts with adamantane derivative 2? PF₆ and cobaltocenium 7? PF₆, which have tridimensional shape and relatively large size. The association constant of the 7 ⁺?OHBP4 complex in 1:1 (v/v) [D₆]acetone/CD₂Cl₂ solution is up to 3100±300 m ^?1.     

Synthesis of New Rigid Dimeric Calix[4]arene

A new Dimeric calixarene from the head to head linkage of two calix[4]arene units fixed in the cone conformation was synthesized via Sonogashira cross-coupling reaction. The structure of 10 was confirmed by NMR, MS and IR-spectroscopy.     

Controlled solvothermal synthesis of PbS quasi-nanorods by calix[4]arene

A new idea of the nanorods preparation and a novel application of calixarenes are presented. Calix[4]arene was introduced into solvothermal system to produce one-dimensional inorganic nanomaterial. The obtained product was characterized by XRD and TEM. Results of the XRD analysis showed that the product was pure cubic phase of PbS with high crystallinity. TEM images revealed that the diameter and length of the PbS nanorods were about 200 nm and up to 3.5 μm, respectively. Optical properties of the product were also studied. PL emission image showed that the product exhibited an emission peak at 308 nm in ultraviolet region showing a blue shift of 14 nm compared to the bulk material. The formation mechanism of PbS nanorods in the presence of calix[4]arene is discussed.     

Synthesis of an unsymmetrically doubly bridged calix[4]arene in the 1,3-alternate conformation

We report the synthesis of the first calix[4]arene constrained to a 1,3-alternate conformation by one crown ether and one di-aza-benzo crown ether bridgings. Preliminary binding properties are also given.     

Merging Molecular Recognition and Gold(I) Catalysis with Triphoscalix[6]arene Ligands

We report the synthesis and characterization of novel triphosphine calix[6]arene ligands. These supramolecular wheels, with recognition features governed by the hydrogen-bonding domain, were employed to synthesize multitasking trinuclear gold(I) complexes as a new platform for the synthesis of interwoven (pseudo)rotaxane species. In parallel, the multivalent, metal-bonded upper rim displayed catalytic features promoting highly selective gold-catalyzed cycloisomerization reactions of 1,6-enynes.     

Highly selective fluorescent recognition of amino alcohol based on chiral calix[4]arenes bearing L-tryptophan unit

Four two-armed chiral calix[4]arenes (1a–1d) functionalised at the lower ring with amino acid units have been synthesised and the structures of these compounds were characterised by IR, MS, ¹H NMR, ¹³C NMR spectra and elemental analysis. Their molecular recognition abilities towards amino alcohol were examined by fluorescence titration experiment in three kinds of solution. The results indicated that these receptors exhibited excellent fluorescent response to phenylglycinol and could distinguish phenylglycinol from phenylalaninol rapidly through the obvious difference in the fluorescent response. Solvent comparative experiments also indicated that acetonitrile was the best solvent to detect these phenomena.     

Isolation and X-ray crystal structure of a stable calix[4]arene monohemiketal

The formation of a stable calix[4]arene monohemiketal is described. X-ray crystallographic data provide conclusive evidence for the presence of a stabilizing hydrogen bond. Supplementary Data. Lists of H-atom parameters and bond lengths and angles involving hydrogens have been deposited with the British Library Document Supply Centre as Supplementary Publication No. SUP 82159 (5 pp.).     

Spectroscopic Study of Molecular Recognition of Ions by Chromogenic Calix[4]arene Derivatives

The complexation properties of three new chromogenic calix[4]arenes ( 1a–c) with aliphatic amines and alkali/alkali earth metal ions have been studied by UV/Vis spectroscopy. 1c shows the greatest complex forming ability and it is selective for Li⁺, Ca²⁺ and certain amines in polar solvents.     

Selective Electrochemical Recognition of o-Phenylenediol by a Novel Calix[4]arene Derivative

A new type of calixarene-modified electrode has been prepared by directly coating the surface of a glassy carbon electrode with tetrahydrofuran solution containing 25,26,27,28-tetra-（3-amidino thiopropoxy）-5,11,17,23-tetratert-butylcalix[4]arene, and applied to the investigation of electrochemical behavior of phenylenediols. The results showed that the modified electrode could selectively recognize o-phenylenediol, making the over-potential of o-phenylenediol dropped and peak current increased greatly. The anodic peak current is proportional to the concentration of o-phenylenediol in the range of 1.0×10^-5-1.0×10^-4 mol·L^-1 with the detection limit （SIN=3） of 1.0×10^-7 mol·L^-1. The recognizing mechanism, including electrochemical process and binging sites, was also discussed using voltammetry.     

一种新型杯[4]芳烃的合成

本文通过对特丁基杯[4]芳烃的酚羟基烷基化和苯环特丁基位上的IPSO-硝化制备了一系列对硝基杯[4]芳烃烷基醚,烷基分别是n-C~4H~9(3a)、n-C~8H~1~7(3b)、n-C~1~2H~2~5(3c)和n-C~1~6H~3~3(3d)。^1HNMR表明所有新的杯[4]芳烃都具有锥形(cone)构象。     

含氮手性杯[4]芳烃对羧酸的手性识别

Chiral nitrogen-containing calix[4]arene was easily synthesized by the reaction of 25,27-di（2-bromoethoxy）- 26,28-dihydroxy-5,11,17,23-tetrakis（t-butyl）calix[4]arene with S-（-）-1-phenylethylamine in excellent yield, and showed good ability to recognize the enantiomers of mandelic acid and 2,3-dibenzoyltartaric acid. This finding has potential application to assay and separation of enantiomers of the carboxylic acids.     

Ab initio and density functional studies of cooperative hydrogen bonding in calix[4]-and calix[6]arenes

The cone conformation of C ₄ symmetry is shown by the Hartree-Fock method (3-21G basis) to be the predominant conformer of calix[4]arene; the compressed cone of C ₂ symmetry is the major conformer of calix[6]arene. Using quantum chemical methods we calculated hydrogen bond cleavage energies for calix[4]-(ab initio and density functional methods) and calix[6]arene (ab initio), and also for the complex of calix[4]arene with carbon disulfide. These energies along with structural data point to the cooperative effect of hydrogen bonds. The results of these studies provided an explanation to the greater conformational lability of calix[6]arene compared with calix[4]arene molecules. It is also predicted that the nucleophilic substitution reaction involving calix[6]arene in the presence of weak bases and in aprotic solvents, as well as in the gas phase, will occur via diastereomeric transition states.