Lower rim substituted p-tert-butyl-calix[4]arene. Part 16. Synthesis of 25,26,27,28-tetrakis(piperidinylthiocarbonylmethylene)-p-tert-butylcalix[4]arene and its interaction with metal ions

The synthesis, characterisation and X-ray crystal structures of p-tert-butyl-calix[4]arene-thioamide L and its complex with lead L-Pb²⁺ is reported. The cation-binding properties in solution have been assessed by liquid-liquid extraction of the metal picrates from water into dichloromethane and by stability constants determination in acetonitrile using UV-absorption spectrophotometry or potentiometry. The compound was used as active material in Pb-ion-selective membrane electrodes. The characteristics of these electrodes as well as the selectivity coefficients for Pb²⁺ cation versus many metal ions tested were obtained. Complex formation constants within the electrode membranes were determined using the sandwich membrane method and were compared to those obtained in acetonitrile. The lead concentration in the scrap-lead was determined with the use of electrodes incorporating the ligand studied.     

Synthesis and complexing properties of four imidazolyl acetamido p-tert-butylcalix[4]arenes

Four imidazolyl acetamido p-tert-butylcalix[4]arenes 5–8 have been prepared by reacting the corresponding methyl esters derivatives 1–4 with histamine in 1:1 mixture of methanol:toluene. The yields ranged from 56 to 68%. 5–8 have been shown to be in cone conformation. The complexation behaviour of 5–8 towards monovalent metal picrates M⁺Pic⁻ with M⁺ = Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ and divalent metal picrates M²⁺(Pic⁻)₂ with M²⁺ = Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Cd²⁺, Zn²⁺ and Co²⁺ are given. Tentative localisation of the metal cations in the receptors is given. The binding properties towards these cations have been determined along with stoichiometries of the complexes.     

Synthesis and complexing properties of 1,5:3,7-doubly bridged calix[8]arenes with mixed spanning elements

Two different bridges were introduced at the 1,5:3,7-positions of p-tert-butylcalix[8]arene 1 using a two-step alkylation procedure. A probable cation template effect in the introduction of the second bridge was evidenced. The obtained bis-bridged derivatives 3 possess encapsulating properties toward alkali cations modulated by the length and nature of the bridges.     

Synthesis and Conformational Studies of Lower Rim Cyanomethyl Substituted Calix[4]arenes

The conformational inversion characteristics of calix[4]arenes carrying cyanomethyl groups on the lower rim have been investigated. Complete conversion from a 1,3-alternate to a partial cone conformation was observed for the 1,3-dicyanomethyl ether of calix[4]arene at room temperature, while at higher temperatures further inversion to a 1:1 mixture of partial cone and cone conformers occurred.     

Synthesis and self-assembly of novel calix[4]arenocrowns: formation of calix[4]areno[2]catenanes

A series of novel calix[4]arenocrowns 1a-c were efficiently synthesized by a one-pot reaction of calix[4]monohydroquinone diacetate 5 with ditosylate 6 and its analogues in the presence of sodium hydroxide. It was found that the calix[4]arenocrowns could form stable pseudorotaxane-type complexes 2a-c with paraquat, and further self-assemble into calix[4]areno[2]catenanes 3a-c with dicationic salt 8 and p-bis(bromomethyl)benzene.     

Calix[4]quinones. Part 4: The ClO2 oxidation of calix[4]arene dialkyl ethers

Except for the special case of calix[4]arene diethyl ether 1, the chlorine dioxide oxidation of dialkyl ethers 2-5 yielded only the corresponding calix[4]diquinone dialkyl ethers 8-11. Chlorine dioxide oxidation of calix[4]arene diethyl ether 1 produced two isomeric products 6 and 7, which were stable enough to be isolated by column chromatography. However, a slow conformational interconversion between isomeric pair 6 and 7 was observed at room temperature, and the equilibrium was reached after 400 h at 18 °C with an amount of 5:3 in favor of syn-isomer.     

杯[4]芳烃衍生物的合成和构象研究

以对取代酚亚甲基桥三聚体和２，６－二溴甲基对取代酚为原料，在ＴｉＣｌ４催化下环化得到６种新的含不同取代基［Ｃｌ，Ｂｒ，ＣＨ３，Ｃ（ＣＨ３）３］的杯［４］芳烃衍生物，核磁共振谱研究表明：它们在溶液中的优势构象为锥形构象。     

Synthesis and characterization of a novel series of pyrimidinylthiaalkoxycalix[4]arenes

A novel series of pyrimidinylthiaalkoxycalix[4]arenes with the reaction between 4,6-dimethylpyrimidine-2-thiol and thedifferent dibromides calix[4]aryl groups have been synthesized and structurally characterized by IR,1H NMR and MS.From theiranalysis data,it was found that compounds 8,9,11 adopted a cone conformation,while compound 10 existed as a mixture ofconformations.     

Synthesis and Complexing Properties of Four New Tetraamido-type p-tert-Butyl Calix[4]arenes Presenting Two Proximal Binding Subunits

The synthesis of four new tetraamido-type p-tert-butylcalix[4]arenes presenting two proximal binding subunits is reported. Complexation of alkalimetals and zinc picrates with these ligands have been carried out and monitored by ¹H-NMR inCDCl₃. It is shown that hard cations are included in the tetraamido cavity while thezinc cation is chelated to the pyridine rings of one of the ligands. The formation of a 1:1:1heterobinuclear complex is also described     

杯[4]芳烃对单糖及嘧啶衍生物的分子识别和分子开关

用AM1和INDO/SCI方法对八羟基杯[4]芳烃与单糖及嘧啶衍生物形成的超分子体系进行理论研究,结果表明,主体通过CH-π相互作用对单糖类进行分子识别,尤其对赤藓糖识别效果更好;主体与嘧啶没有明显的π-π堆砌作用,但能识别含吸电子基团的嘧啶衍生物,据此可设计酸碱调控的分子开关.讨论了配合物的UV谱带与主体相比发生红移的原因.     

Synthesis and Molecular Structures of Tetrasilyl Ethers of Calix[4]arenes

The tetrasilyl ethers calix[4]areneOSiMe₂R (R = Me, H, vinyl, allyl) were prepared by salt elimination; the calix[4]arene was deprotonated with sodium hydride and subsequently reacted with chlorosilanes ClSiMe₂R. In general, DMF was chosen as solvent in order to steer the reactions in terms of a preference for the cone‐conformation of the products. In the case of calix[4]areneOSiMe₃ both, partial‐cone‐ and cone‐conformers, were synthesised. All products were characterised by NMR (¹H, ¹³C, ²⁹Si) spectroscopy, mass spectrometry and single‐crystal X‐ray diffraction.     

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.     

杯[4]间苯二酚芳烃Schiff碱衍生物的合成及其离子萃取性能

通过控制条件,使两种乙氧基羰基甲氧基杯[4]间苯二酚芳烃2a和2b的酯基与1,6-己二胺的一个氨基反应形成酰胺3a和3b,剩余的一个氨基再与水杨醛反应,得到了相应的杯芳烃Schiff碱衍生物4a和4b,对其进行了金属离子的液-液萃取性能研究.结果表明,Schiff碱基团的引入能大大增强杯芳烃与金属离子的配位能力,而杯芳烃空腔的存在又能提高Schiff碱与金属离子的配位选择性.     

Calix[4]quinones III: The Synthesis of p‐Hydroxycalix[4]arenes by Wolff‐Kishner Reduction

The Wolff‐Kishner reduction of the half‐protected ketal calix[4]monoquinone 3 and its basic hydrolysis product 4 produced a partially reducing product 5 . When the same reduction conditions were applied to the calix[4]quinone benzoates 1 and 2 , the corresponding title compounds, p‐hydroxycalix[4]arenes ( 6 and 7 ), were afforded in one step.     

Synthesis, conformational studies and inclusion properties of N-substituted tetrahomodiazacalix[4]arenes

A series of tetrahomodiazacalix[4]arenes (1–8) with different substituents (or substituted) at the upper rim and/or N-side arm has been synthesized with acceptable yields. The compounds were characterized by elemental analysis, IR, MS and NMR methods. In particular, 5 was shown by X-ray crystallography to adopt the cone conformation in the solid state. Two-phase picrate extraction showed that 2 and 6, bearing N-2-picolyl arms, are the best extractants. Of the cations tested, Ag(I) is the best extracted by almost all ligands and the extraction efficiency follows the order 2-picolyl > 3-picolyl > 4-picolyl.     

Synthesis and Properties of Double Calix[4]arene Derivatives Linked by Schiff-base in the Lower Rim

Calixarenesareregardedasthethirdgenerationofh0stmoleculesbecauseoftheirinclusionabilitytocati0ns,anionsandneutralmoleculesI'2.Duringthepastdecademosteff0rtshavebeentakenonthefunctionalizati0n0fcalixareness0thattheycanbeappliedn0tonlyastheionoph0resintheextractionprocess','andassensitivematerialsforionelectrodes"',butalsoastheenZymemimicscatalyzingthecleavageofphosphatediesters"'.Inordertoenablethemtoincludeandrecognizelargerchemicalspecies,manyappr0acheshavebeenusedtoc0nstructoIigo-calixarene…     

Conformational features of calix[4]arenes with alkali metal cations: A quantum chemical investigation with density functional theory

A variety of conformations for three model calix[4]arenes with 8 or 12 OH groups have been investigated by calculations at density functional (RI-BP86) and RI-MP2 level of approximation. The calixarenes form stable complexes with the alkali metal cations of lithium up to caesium. For the investigations all-valence electron basis sets as well as various effective core potentials were probed. The stabilities of complexes were analysed in comparison with the corresponding benzene complexes, M⁺·C₆H₆. The formation of the calixarene metal complexes is considered in two steps, (a) in a distortion from the equilibrium conformation of the free calixarenes and (b) subsequent complexation. The distortion energies are small for the ‘crown’ and larger for the ‘boat’ conformations. On the other hand the latter are more stabilized by significant interaction energy of the cation with two adjacent π-systems of the aromatic rings. As a result, these two conformations are of similar stabilities for K⁺ to Cs⁺ complexes with resorc[4]arenes, with a slight advantage for the ‘boat’ structure. The most stable conformation for the coordination products of these cations with the calix[4]arene with 12 OH groups is a slightly flattened ‘crown’ that is derived by maximum hydrogen bonding of the OH-groups and the most effective cation-π interactions. Special cases are complexes of Li⁺ and Na⁺ which in most instances prefer the coordination on the oxygen atoms of the upper rim of the calixarene cavities and thus form ‘boat’-like structures.     

Synthesis and cation binding properties of new arylazo- and heteroarylazotetrathiacalix[4]arenes

New macrocyclic tetrathiacalix[4]arenes have been synthesized by incorporating arylazo-, thiazoleazo- and β-naphthylazo- units in the tetrathiacalix[4]arene molecular architecture through diazotization and coupling reactions. The new compounds have been characterized by ¹H NMR, ¹³C NMR and FAB-MS spectroscopic analysis. X-ray crystallography for one of the new dyes (4a) reveals that the compound is present in the cone conformation. The synthesized macrocycles have been examined for their binding with alkali (Li⁺, Na⁺, K⁺, Cs⁺ and Rb⁺), alkaline earth (Ca²⁺, Mg²⁺ and Ba²⁺) and transition metal cations (Cr³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Hg⁺, Hg²⁺, Pd²⁺ and Pt²⁺) by UV-visible spectroscopy to reveal selective bathochromic shifts for heavier alkali metal ions (cesium and rubidium) and palladium in a 1:1 and 2:1 stoichiometry respectively. The study has a significant bearing on the development of useful ionic filters and sensor materials.     

Wide- and narrow-rim functionalised calix[4]arenes: synthesis and characterisation

Functionalisation of calix[4]arene at both the wide and narrow rims leads to the formation of compounds containing bipyridyl, via an amide linkage, at the wide rim and having either a butyl chain, a benzyl group or an alkyl ester functionality at the narrow rim. All compounds were characterised using ¹H and ¹³C NMR spectroscopies. Initial binding studies with Ru(bipy)₂Cl₂ are reported.