Synthesis and Host Properties of (1,3)- p-tert-Butylcalix[5]crown-6 Derivatives Incorporating the 1,1'-Binaphthalene-2,2'-dioxy Subunit

Alkylation of p-tert-butylcalix[5]arene (1) with 2,2'-bis(5-tosyloxy-3-oxa-1-pentyloxy)-1,1'-binaphthalene ((±)-2) in the presence of CsF affords selectively racemic 1,3-bridged calix[5] [5]crown-6-triol 3, along with very small amounts of the (1,2)-bridged regioisomer 4. Compound 3 has been converted into tri-methoxy and tri--picolyloxy derivatives 5 and 6, respectively, by exhaustive alkylation with the appropriate electrophile and base. The direct separation of the enantiomers of racemates 3 and 6 was achieved by HPLC, using a chiral stationary phase (Chiralpak AD). Hosts 5 and 6 are able to selectively form 1 : 1 endo-cavity complexes with the linear RNH₃ ⁺ ions.     

Regioselective intramolecular bridging of p-tert-butylcalix[10]arene

The synthesis and characterization of a series of regioselective intramolecular bridging of calix[10]arene are described for the first time. Reacting p-tert-butylcalix[10]arene with tri-ethylene glycol ditosylate using K₂CO₃ as a base in toluene, 1,2-calix[10]crown-4 2a, 1,4-calix[10]crown-4 2b and 1,6-calix[10]crown-4 2c were obtained in yields of 9%, 14% and 7%, respectively. While using Cs₂CO₃/acetone instead of K₂CO₃/toluene, the 1,4-calix[10]crown-4 2b was obtained selectively in good yield up to 50%.     

Crystal Structure and Complexing Properties of p-tert-butylcalix[6]-1,4-2,5-bis(crown-4)

The X-ray structure of the alreadypublished p-tert-butylcalix[6]-1,4-2,5-bis(crown-4)1 is reported. Extraction of solid ammoniumpicrate in chloroform-d indicates thecation to be located outside of the calixcrown andforming a 1:2 (metal-ligand) complex.     

Unexplored metallic cation effect in the acidity constants of p-t-butylthiacalix[4]arene,p-t-butylcalix[4]arene and p-t-butylcalix[6]arene in aqueous-organic media

The influence of the metallic cation of the base (Li⁺, Na⁺ or K⁺) was determined on the acid–base constants of p-t-butylthiacalix[4]arene (TC4), p-t-butylcalix[4]arene (CA4) and p-t-butylcalix[6]arene (CA6) in ethanol/water in an large interval of pH values by potentiometry and spectrophotometry. The pK_a values determined by both methods correlate very well and these are characteristic for each macrocycle with influence of the cation of the base without a straight evidence of an effect by the size of the metallic cation. In the case of TC4, pK_a1 and pK_a2 were lower to Li⁺ and Na⁺ than with K⁺. For CA4, an effect of K⁺ on the pK_a2 with respect to Li⁺ was observed. A very different behaviour was observed for CA6 with Li⁺ and K⁺ showing a lower pK_a2 and a higher pK_a3 than with Na⁺. These effects were interpreted on the basis of the interaction/complexation of each cation with each macrocycle.     

Excellent Ag+ selective receptors: Syntheses and complexation properties of novel biscalix[4]arene with benzalazine groups

By reacting mono-substituted or 1,3-bi-substituted [2-(p-formylphenyloxy)ethyloxy]-p-tert-butylcalix[4]arene (3 or 4) with hydrazine hydrate in ‘1+2’ or ‘2+2’ condensation mode, novel benzalazine-bridging biscalix[4]arenes 5 and 7 were conveniently obtained in the yields of 76 and 81%, respectively. Condensation of compound 4 and salicylide hydrazone gave a novel calix[4]arene benzalazine derivative 6 in the yield of 85%. The structures and conformations of all new compounds were characterised by elemental analyses, ESI-MS, ¹H NMR and ¹H–¹H COSY techniques. Biscalix[4]arene 7 adopts a symmetrical cone conformation with tube cavity. The liquid–liquid extraction experiment showed that all new hosts possessed excellent complexation abilities towards soft metal cations. Compound 7 exhibited high complexation selectivity towards Ag⁺. The Ag⁺/Na⁺ and Ag⁺/Hg²⁺ extraction percentages of host 7 were as high as 73.1 and 54.9, respectively. The UV–vis spectra complexation experiments revealed that the complexation constant of receptor 7 with Ag⁺ was 1.9 × 10⁵ M^? 1 and the 1:1 stoichiometry of receptor 7–Ag⁺ complex was formed. The ¹H NMR spectra complexation experiments suggested that Ag⁺ was bound in a cavity composed of two benzalazine groups on bridging chains.     

Preparation and Evaluation of P-tert-Butyl-calix[8]arene-bonded Silica Stationary Phase for High Performance Liquid Chromatography

ABSTRACT

A new p-fert-butyl-calix[8]arene-bonded silica gel stationary phase was synthesized through heterogeneous functionalisation of suspended porous silica. A characterization of its structure was carried out by using elemental analysis, FTIR and ¹³C solid state NMR spectroscopy. Chromatographic performance of the new packing material was investigated by employing polycyclic aromatic hydrocarbons (PAHs) as probes and using methanol-water as mobile phase. The investigations show that the new stationary phase behaves as a reversed phase stationary phase. The liquid chromatographic separation of PAHs solutes on the new bonded phase was compared with that on a p-tert-butyl-calix[4]arene-bonded silica stationary phase. The new p-tert-butyl-calix[8]arene-bonded phase exhibited higher retention and better separation selectivity, although the carbon content and coverage of the new packing material was lower than that of the p-tert-butyl-calix[4]arene bonded silica stationary phase. A possible retention mechanism for the new packing material was also proposed.     

p-tert-Butyldihomooxacalix[4]arene/p-tert-Butylcalix[4]arene: Transition and Heavy Metal Cation Extraction and Transport Studies by Ketone and Ester Derivatives

The binding properties of two phenylketones (2a and 3a) and two ethylesters (2b and {3b) derived from p-tert-butyldihomooxacalix[4]arene or from p-tert-butylcalix[4]arene, in the cone conformation, towards transition (Ag⁺, Ni²⁺, Cu²⁺, Co²⁺, Zn²⁺, Fe²⁺ and Mn²⁺) and heavy (Cd²⁺, Hg²⁺ and Pb²⁺) metal cations have been determined by extraction studies with metal picrates and liquid membrane transport experiments with the same salts. The affinity of these ligands for Ag⁺ has also been investigated by ¹H NMR spectroscopy. Both ketones are better extractants than the esters, and show a strong preference for Ag⁺, while Cu²⁺ is the most extracted cation with the esters. ¹H NMR titrations with AgSO₃CF₃ indicate 1 : 1 complexes for all ligands, those with ketones are more stable, on the NMR time scale, than those with esters. Both esters are good carriers for Ag⁺, and 2b exhibits the highest transport rate (4.7 mol h^-1) found until now with dihomooxacalix[4]arene derivatives.     

p-tert-Butylcalix[4]arene Derivatives Containing Azathiol Receptors and Their Recognition towards Hg(II)

25,27(2,2'-bis(ethoxybenzyl))-1,9-diimine-3,7-dithianonane-p-tert-butylcalix[4]arene (3),25,27(4,4'-bis(ethoxybenzyl))-1,9-diimine-3,7-dithianonane-p-tert-butylcalix[4]arene (4),25,27(2,2'-bis(ethoxybenzyl))-1,8-diimine-3,6-dithianonane-p-tert-butylcalix[4]arene (5) and25,27(4,4'-bis(ethoxybenzyl))-1,8-diimine-3,6-dithianonane-p-tert-butylcalix[4]arene (6) havebeen synthesized by condensation reactions between25,27(2,2'-bis(ethoxybenzaldehyde))-p-tert-butylcalix[4]arene (1) and25,27(4,4'-bis(ethoxybenzaldehyde))-p-tert-butylcalix[4]arene (2) and appropriateamines. Reduction of 3 and 4 withNaBH₄ and subsequent protonation byHCl/CH₃OH resulted in25,27(2,2'-bis(ethoxybenzyl))-1,9-diaza-3,7-dithianonane-p-tert-butylcalix[4]arenedihydrogenchloride (7) and25,27(4,4'-bis(ethoxybenzyl))-1,9-diaza-3,7-dithianonane-p-tert-butylcalix[4]arenedihydrogenchloride (8), respectively. Complexation studies of 7 and 8 withZn(II), Cd(II) and Hg(II) ions were carried out bypotentiometric titration. Compounds 7 and8 selectively form 1 : 1 complexes with Hg(II), andtheir stability constants (log Ks) were estimated tobe 4.47 ± 0.08 and 3.20 ± 0.13, respectively. From spiecies distribution plots, 7 and 8were found to form the highest amount of 1 : 1 complexes with Hg(II) at pH 8.7 and 9.1, respectively.     

New Calix[4]arene-monobenzo- and -dibenzo-crown-6 as Cesium Selective Ionophores in the Radioactive Waste Treatment: Synthesis, Complexation and Extraction Properties

Cesium possesses two long lived isotopes ¹³⁵Cs and ¹³⁷Cs and the first one has a very long (2.3 × 10⁶ y) half life and is one of the most mobile nuclides in a repository.Calix[4]arene-crowns-6 in the 1,3-alternate conformation areemerging as a new class of ionophores exhibiting a very high efficiency and selectivity in the complexation of cesium ion and itsremoval from highly acidic ([HNO₃] = 3–4 M) radioactive waste having also high sodium nitrate concentration ([NaNO₃] = 2–4 M). In order to improve both efficiency and cesium selectivity we have synthesised the novel calix[4]arene dibenzo-crowns-6 1 and 2 and thecalix[4]arene-monobenzocrown-6 3 in 1,3-alternate conformationand evaluated their complexation properties towards alkali metal cations in homogeneous solution and in two phase systems, togetherwith their performance in radioactive waste treatment. All data confirm the higher Cs/Na selectivity of the 1,3-alternate calix[4]crown-6 1–3 containing aromatic rings in the polyether loop, in comparison to previously synthesised compounds of the same series.     

Cesium Complex of an Unsymmetrical Calix[4]crown-dibenzocrown-6

An unsymmetrical calix[4]-bis-crown ether having both conventional crown-6 and dibenzocrown-6 rings in a fixed 1,3-alternate conformation was synthesized with good yield by the reaction of a monocyclic calix[4]crown-6 with dibenzodimesylate in the presence of cesium carbonate. The cesium ion selectivity among alkali metal ions increased compared to symmetrical calix[4]-bis-crown-6. The solid state structureof the ligand-cesium complex illustrates a 1:2 complex ratio. On the contrary, insolution, e.g., extraction equilibrium and ¹H NMR experiment gave a 1:1 complex ratio. From the result of the chemical shift change upon metal ion complex, the cesium ion seems to prefer the dibenzocrown loop to the conventional crown-6 ring.     

含卤素端基的单取代对-叔丁基杯[6]芳烃的合成与表征

用THF作为反应溶剂, K₂CO₃作碱, 对-叔丁基杯[6]芳烃与二溴丁烷、二溴己烷和1,4-二氯丁炔-2反应以中等产率选择性地合成了含有卤素端基的单取代对-叔丁基杯[6]芳烃2a～2c. 2a和2b可与对甲苯磺酸甲酯(MeOTs)反应高产率地得到全甲基化产物3a和3b. 通过核磁共振谱(¹H NMR)和质谱(FAB-MS)表征, 发现所有化合物都具有预期结构, 2a～2c和3b在室温下是锥式构象, 而3a没有固定构象.     

Synthesis of a Fullerene Derivative of Benzo[18]crown-6 by Diels-Alder Reaction: Complexation Ability,Amphiphilic Properties,and X-Ray Crystal Structure of a Dimethoxy-1,9-(methano[1,2]benzenomethano)fullerene[60] Benzene Clathrate

A fullerene derivative 1 of benzo[18]crown-6 was obtained by Diels-Alder addition of fullerene[60](C₆₀) to the ortho-quinodimethane prepared in situ from 4,5-bis(bromomethyl)benzo[18]crown-6 ( 3 ) with Bu₄NI in toluene. Extraction experiments show that the complexation of K⁺ ions strongly increases the solubility of 1 in protic solvents like MeOH. Using Langmuir-Blodgett techniques, monolayers of the highly amphiphilic fullerene-derived crown ether 1 and its K⁺ ion complex were prepared. An X-ray crystal structure was obtained from a benzene clathrate of comparison compound 2 , synthesized by Diels-Alder reaction of C₆₀ with the ortho-quinodimethane derived from 1,2-bis(bromomethyl)-4,5-dimethoxybenzene ( 4 ). Both the fullerene molecule 2 and the benzene molecule are fully ordered in a crystal packing which is stabilized by intermolecular van-der-Waals contacts between the benzene ring and the C-spheres, intermolecular C…?C contacts between the C₆₀ moieties, and intermolecular O…?C contacts between the O-atoms of the veratrole moieties and fullerene C-atoms.     

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.     

Selective complexation of alkali metal ions using crown ethers derived from calix[4]arenes: a computational investigation of the structural and energetic factors

A systematic analysis of the structural, energetic, and thermodynamic factors involved in alkali metal (i.e., Na⁺, K⁺, Rb⁺, and Cs⁺) complexation by four calix[4]arene crown-6 ethers in the 1,3-alternate conformation is presented here. The ligands (or hosts) in this work are identical to, or closely related to, the four molecules whose selectivity towards complexing Na⁺, K⁺, Rb⁺, and Cs⁺ from aqueous solutions was studied experimentally by Casnati et al. (Tetrahedron 60(36):7869–7876, 2004). By dividing the complexation process into three different contributions, namely, the binding energy of the ion to the crown, the elastic energy of the crown, and the solvation effect, it becomes clear that the primary factor that determines ion selectivity in crown-6-ethers is not the size of the crown, as currently believed. All four crown ethers preferentially complex with the smallest ion (Na⁺) in the gas phase. In the condensed phase, these crown-6 ethers preferentially complex with the larger ions only because the aqueous solvation energies of the alkali metal ions make it thermodynamically less favorable to extract the smaller ions from aqueous solutions. This suggests that the current understanding of the factors influencing the selectivity of metal ion complexation by crown ethers may be in need of revision.     

A Synthetic Cation-Transporting Calix[4]arene Derivative Active in Phospholipid Bilayers

One order of magnitude: The transport of Na⁺ and K⁺ ions through a phospholipid bilayer occurs with much higher conductance levels with 1 and 2 than with typical Na⁺-transporting proteins or gramicidin. However, the cations do not appear to pass through the calix[4]arene ring, which has a rigid 1,3-alternate conformation. diazacrown=10-benyzl-1,10-diaza[18]crown-6 group.     

The Synthesis of Novel Crown Ethers. Part IV. Coumarin Derivatives of [18]crown-6 and Cation Binding from Fluorescence Spectra

4-H, 4-methyl and 4-phenyl-1-benzopyran-2-one derivatives of [18]crown-6 derivatives were synthesised from 6,7- and 7,8-dihydroxy-1-benzopyran-2-one reacting with pentaethylene glycol ditosylate in K₂CO₃/DMF/water. The products were identified by elemental analysis, EI-GC-mass spectra and ₁H-NMR spectroscopy. The Na⁺ association constants of some coumarin derivatives were determined with an ion selective electrode in water. The Na⁺ , K⁺, Ba²⁺ and Sr²⁺ binding role of such compounds were particularly observed as remarkable alterations in acetonitrile. The 1 : 1 associations constants of K⁺ and Na⁺ with some coumarin-[18]crown-6 derivatives estimated by this way in acetonitrile exhibited the utility of complexing enhanced quenching fluorescence spectra for the ion binding power of the such macrocycles.     

The Synthesis of Dibenzo[3n]crown-n by Novel Methods and their Cation Binding Studied by Fluorescence Spectroscopy. Part IV

The dibenzo[3n]crown-n were synthesised from1,2-bis(o-hydroxyphenoxy)ethane obtained from 1,2-bis(o-formylphenoxy)ethane via Bayer-Willigeroxidations with H₂O₂/CH₃COOH in good yields. The cyclic condensation of 1,2-bis(o-hydroxyphenoxy)ethanewith dichlorides, and ditosylates of polyethylene glycols in DMF/Me₂CO₃ gave the macrocyclesdibenzo[15]crown-5, dibenzo[18]crown-6, dibenzo[21]crown-7 anddibenzo[24]crown-8. The structures were identified using IR, mass, ¹H and ¹³C NMR spectroscopy. Therecognition of the molecules for the cations, Li⁺, Na⁺, K⁺, Rb⁺ and Zn²⁺were conducted quantitatively with steady state fluorescencespectroscopy. The 1:1 association constants in acetonitrileshowed a good relation of the appropriate size of the macrocyclic ether towards the fitting cationradii. Namely, dibenzo[15]crown-5 was the best for Li⁺ binding and more than 100 times better thanNa⁺ and K⁺. Dibenzo[21]crown-7 was excellent for Rb⁺ binding while K⁺ is 100 timesless preferred. The largest crown ether studied, dibenzo[24]crown-8, exhibited the order of binding power,Rb⁺ > K⁺ > Na⁺. Zn²⁺ displayed, however, a marked binding with only dibenzo[18]crown-6.p>     

Hard–Soft Receptors, Tetrakis[(N,N-diethylaminocarbonyl)methoxy] thiacalix[4]arene Derivatives with cone and 1,3-alternate Conformation

Direct O-alkylation of p-tert-butyltetrathiacalix[4]arene with N,N-diethylchloroacetamide afforded two conformational isomers (1,3-alternate and cone) of tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene and 1,3-disubstituted bis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene, depending on the base used. The complaxation behaviors of the tetrakis isomers were assessed by ¹H NMR titration experiments. Evidence of 1:2 (homo- and hetero-dinuclear) complexes formation of 1,3-alternate-tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene with alkali (K⁺ and Na⁺) or transition (Ag⁺) metal ions was obtained. Interestingly, it was found that the cone-tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene required a prior Ag⁺ complexation to form 1:2 heterodinuclear complex. Received in final form: 26 January 2005     

CARBODIPHOSPHAN (2.4.6-tBu3C6H2[sbnd]P[dbnd]2)C: REAKTION MIT ELEKTROPHILEN

Abstract

The reaction of Ar[sbnd]P[dbnd]C[dbnd]P[sbnd]Ar (Ar=2.4.6-^tBu₃C₆H₂) with electrophiles (H⁺, S₈) proceeds at the phosphorus atom with subsequent cyclisation of an o-^tbutyl group.     

Experimental Evidence for a Calix[4]arene-Proton Complex

From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium H⁺(aq) + 1 ·Na⁺(nb) ⇆ 1 ·H⁺(nb) + Na⁺(aq) taking place in the two-phase water-nitrobenzene system (1 = p-tert-butylcalix[4]arene-tetrakis(N, N-diethylacetamide); aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K _ex(H⁺, 1 ·Na⁺) = −1.4 ± 0.1. Further, the stability constant of the p-tert-butylcalix[4]arene-tetrakis(N,N-diethylacetamide)-H⁺ complex in water saturated nitrobenzene was calculated for a temperature of 25°C as log β_nb(1 · H⁺) = 8.1 ± 0.1.