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.     

Water-soluble para-Sulfonated 1,2;3,4-Calix[4]arene-biscrowns in the 1,2-Alternate Conformation

The preparation of a series of p-sulfonated 1,2;3,4-calix[4]arene-biscrowns in the 1,2-alternate conformation is reported. These compounds are of two types:symmetrical p-sulfonated 1,2;3,4-calix[4]arene-biscrowns in which the two crown loops are the same and unsymmetrical p-sulfonated1,2;3,4-calix[4]arene-biscrowns in which the two crown loops are different. The X-ray structures of two synthetic intermediates are given. Preliminary complexation studies showed the ligands to present pronounced Cs⁺/Na⁺ selectivities.     

Synthesis, Structure, and Extraction Properties of paco-Calix[4]arene Crown-6 Ethers

anti-25,27-Bis-n-octyloxycalix[4]arene, the paco-isomer of25,27-bis-n-octyloxycalix[4]arene crown-6 ether, and the paco- and1,3-alt isomers of 25,27-bis-n-octyloxycalix[4]arene t-butylbenzocrown-6 ether were prepared. The crystal structures of anti-25,27-bis-n-octyloxycalix[4]arene, paco-25,27-bis-n-octyloxycalix[4]arene crown-6, and 1,3-alt-25,27-bis-n-octyloxycalix[4]arene crown-6 were determined and thesolution structure of anti-25,27-bis-n-octyloxycalix[4]arene was studied by 2D- and VT-NMR. The extraction of alkali metal nitrates by thepaco-25,27-bis-n-octyloxycalix[4]arene crown-6 and t-butylbenzocrown-6 ethers in 1,2-dichloroethane was compared to that of the corresponding 1,3-alt isomers.     

Calix[4]arenes Bridged with Two Different Crown Ether Loops: Influence of Crown Size on Metal Ion Recognition

A series of calix[4]arene-bis-crownethers were synthesized in a fixed 1,3-alternateconformation with good yields by the reaction of amonocyclic calixcrown ether with multi-ethyleneglycoldi-p-toluenesulfonate in the presence of cesiumcarbonate. In the preparation of the monocycliccalixcrown ethers (1 and 2), the use ofpotassium carbonate as a base provided the best yieldregardless of the template concept. In two phaseextraction and competitive transport experiments forligand-metal complexation, calix[4]arene biscrown(5) provided the best selectivity for potassiumion. When a calixbiscrown ether (4) bearingdifferent sized crown ether loops coordinates to K⁺and Cs⁺, respectively, the changes of peak splittingpatterns and chemical shift on ¹H NMR spectra aredependent on the complexed metal ion species.     

New water-soluble calix[4]arene-bis(benzocrown-6) for caesium-sodium separation by nanofiltration-complexation

Calix-bis(benzocrown-6) 6 and 7 were converted into the water-soluble receptors 9, 10, 12 and 15 by introducing hydroxy, carboxy, sulfato or diethanolamino groups at the para position of the phenolic ring and/or on the benzo-ether moieties. The complexation properties of these ionophores were studied for all alkali cations in methanolic and aqueous media. Stability constants were calculated by UV-Vis spectroscopy. All ligands showed a more or less affinity for the larger cations, depending on the nature and the position of the substituents grafted on the benzo-ether chain only or both on the calixarene ring and the benzo-ether loop. For selective Cs⁺/Na⁺ separation, the efficiency of the ligands was evaluated by means of a nanofiltration system. In comparison with the known tetrahydroxylated bis-crown-6 calix[4]arene 1, compounds 9, 12 and 15 represent the most selective ligands for the Cs⁺ cation in a moderate salted medium ([NaNO₃]=85 g/L).     

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

The dibenzo[3n]crown-n were synthesised starting from bis[2-(o-hydroxyphenoxy)ethyl]ether obtained from bis[2-(o-formylphenoxy)ethyl]ether via Baeyer-Villiger oxidation in H₂O₂/CH₃COOH in a good yield. The cyclic condensation ofbis[2-(o-hydroxyphenoxy)ethyl]etherwith tri- and tetraethylene glycol bisdichlorides andthe bisditosylate of pentaethylene glycol in DMF/Me₂CO₃ afforded the large cyclic ethers of dibenzo[21]crown-7, dibenzo[24]crown-8 and dibenzo[27]crown-9. The structures were analysed with IR, ¹H NMR, ¹³C NMR and low-resolution mass spectroscopy methods. The Na⁺, K⁺, Rb⁺ and Cs⁺ cations' recognition of the molecules were conducted withsteady-state fluorescence spectroscopy. The 1:1 association constants, K_a, in acetonitrile were estimated. Dibenzo[21]crown-7 was the best both for K⁺ and Rb⁺ binding but showed too small an effect on Cs⁺. Dibenzo[24]crown-8 exhibited the binding power in the order of Rb⁺ > K⁺ > Na⁺ > Cs⁺. However, dibenzo[27]crown-9 displayed marked binding with only K⁺ but not with Rb⁺ or with Cs⁺ cations probably due to the heavy atom effect of fluorescence quenching.     

Synthesis and Complexation Studies of a Tetra(N,N-dimethyl) Aminoethylamide p-tert-butyl Calix[4]arene and Its Tetramethylammonium Derivative

We describe the synthesis of two functionalised p-tert-butyl calix[4]arenes: tetra(N,N-dimethyl) aminoethylamide derivative 1 and related tetramethylammonium 2. Their complexation properties towards alkali and zinc metal cations are reported along with complexation of perchlorate anion by 2.     

Solvent Extraction of Sodium and Potassium Ions by Dicarboxylated Calix[4]arenes

The extraction of sodium and potassium ions by 25,27-dicarboxymethyl-26,28-dimethoxy-5,11,17,23-tetra-tert-butyl calix[4]arene (L1H2) in chloroform shows the formation of MLIH and M2LI complexes (M = Na, K). In 1,2-dichloroethane, the MLIH species are formed in the acidic pH range, while only the Na2LI species is found at high pH values. The corresponding extraction equilibrium constants K11 (M) and K21 (M) have been evaluated and show a selectivity in favour of Na+ as compared to K+, whatever the nature of the complexes. In chloroform, this selectivity is much more pronounced considering the 2 : 1 complexes: K11(Na)/K11(K) K21(Na)/K21(K).The coexistence of 1 : 1 and 2 : 1 metal : ligand complexes is also shown in the extraction of sodium in 1,2-dichloroethane by the 25,27-dicarboxymethyl-26,28-dimethoxyethoxy-5,11,17,23-tetra-tertbutyl calix[4]arene (LIIH2), locked in the cone conformation.Structural data of the complexes are discussed on the basis of 1H-NMR spectra. In particular, for LIH2, a conformational change from cone to partial cone upon metal complexation has been evidenced for the complexes KLIH, K2LI and Na2LI.     

Lower Rim Substituted tert-Butyl calix[4]arene (part VII): Ionophoric Properties of Calix[4]arene-crown-6 Derivatives in Plasticized PVC-Membrane Electrodes and in Solution

The synthesis and characterization of p-tert-butylcalix[4]arene-crown-6 derivatives (compounds 2–9) are presented. Their ability to complex alkali, alkaline earth and some “softer” cations was investigated by using these compounds as ionophores in ion-selective membrane electrodes and determining the potentiometric selectivity coefficients and the complex stability constants in the membrane. The selectivities of these compounds depend on the size and nature of the substituents on the distal phenolic oxygens. The complexing properties of the two cone and partial cone conformers of compound 2 in the PVC membrane were compared with those in acetonitrile solution studied by UV absorption spectrophotometry and with alkali metal picrate liquid–liquid extraction.This revised version was published online in July 2005 with a corrected issue number.     

多重氮杂杯[4]芳烃和双杯[4]芳烃的合成与阳离子萃取性能

多重氮杂杯[4]芳烃和双杯[4]芳烃的合成与阳离子萃取性能;杯[4]芳烃;双杯[4]芳烃;多重氮杂;萃取     

Silver(I)-selective electrode based on [Bz2Oxo4(18)dieneS4] tetrathia macrocyclic carrier

A polystyrene-based membrane of 7,8:16,17-dibenzo-6,9,15,18-tetraoxo-1,5,10,14-tetrathiacyclooctadeca-7,16-diene [Bz₂Oxo₄(18)dieneS₄] was fabricated using sodium tetraphenylborate (NaTPB) and dioctyl phthalate (DOP) as anion excluder and plasticizing agent. The best performance was obtained from the membrane with the composition ionophore [Bz₂Oxo₄(18)dieneS₄]:polystyrene:DOP:NaTPB, 5:100:150:10 (w/w). The response of the electrode was linear over a wide range of concentration, 1.26×10^–6–1.00×10^–1 mol L⁻¹ for silver ion with a Nernstian slope of 58.4±0.1 mV per decade and a detection limit of 1.0×10⁻⁶ mol L⁻¹. The electrode was found to be chemically inert and of adequate stability with a response time of 10 s and could be used for a period of 3 months without change of potential. It worked satisfactorily in mixtures containing up to 35% (v/v) non-aqueous content. The proposed membrane sensor had good selectivity for Ag⁺ over a wide variety of metal ions in the pH range 2.2–8.5. It was successfully used as an indicator electrode in potentiometric titration of silver ion. The electrode was also useful for determination of Ag⁺ in waste from photographic films.     

Role of Acid-Base Equilibria in the Reduction of Selenious(IV) Acid

ABSTRACT

Electroanalytical methods have been widely used for determination of Se(IV), but the nature of the reduction processes involved is not well understood. Polarographic reduction occurs in three waves (i₁, i₂, and i₃) the height of which changes with pH. We proved that in wave i₁, H₃SeO₃ ⁺ is reduced, in i₂ H₂SeO₃, and in i₃ HSeO₃ ^-. SeO₃ ^2? is not reducible. All reductions involve a transfer of six electrons and yield selenides. Limiting currents are controlled by the rate of protonation. As proton donors, in addition to H₃O⁺, the acid forms of the buffer present also act. Limiting currents increase markedly with increasing concentration of the buffer. Tenfold increase in buffer concentration can result in up to 200% increase in limiting current.     

Conductance Study of the Thermodynamics of Tl+ ion Complexes with Different 18-Membered Crown Ethers in Binary Dimethylformamide-Acetonitrile Mixtures

A conductance study of the interactionbetween Tl⁺ ion and 18-crown-6 (18C6),dicyclohexano-18-crown-6 (DC18C6), benzo-18-crown-6(B18C6), diaza-18-crown-6 (DA18C6),dibenzyldiaza-18-crown-6 (DBzDA18C6) andhexaaza-18-crown-6 (HA18C6) indimethylformamide-acetonitrile mixtures was carriedout at various temperatures. The formation constantsof the resulting 1 : 1 complexes were determined fromthe molar conductance-mole ratio data and found tovary in the order HA18C6 > DA18C6 > DBzDA18C6 >18C6 > DC18C6 > B18C6. The enthalpy and entropy ofthe complexation reactions were determined from thetemperature dependence of the formation constants.     

Preparation of Benz[b]Indeno[1,2-e]Pyran-11(6H)-Ones and Benz[b]Indeno[1,2-e]Thiopyran-11(6H)-One from Dilithiated 2-Indanone and Lithiated Methyl Salicylates or Lithiated Methyl Thiosalicylate

Dilithiated 2-indanone was prepared with excess lithium diisopropylamide, and the resulting intermediate was condensed with several lithiated methyl salicylates or lithiated methyl thiosalicylate, which was followed by acid cyclization to benz[b]indeno[1,2-e]pyran-11(6H)-ones 3--9 or benz[b]indeno[1,2-e]thiopyran-11(6H)-one 10, which are rare fused-ring indeno-chromones and a new indeno-thiochromone, respectively.     

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.     

Copper Incorporated [Me2(15)dieneN4] Macrocyclic Complex for Fabrication of PVC based Membrane Electrode for Copper

Copper (II) complex of 2,4-dimethyl-1,5,9,12-tetraazacyclopentadeca-1,4-diene, [Me₂(15)dieneN₄] was synthesized and used in the fabrication of Cu²⁺ – selective ISE membrane in PVC matrix. The membrane having Cu(II) macrocyclic complex as electroactive material along with sodium tetraphenyl borate (NaTPB) as anion discriminator. Dibutyl phthalate (DBP) as plasticizer in poly(vinyl chloride) (PVC) matrix was prepared for the determination of Cu²⁺. The best performance was observed by the membrane having Cu(II) complex–PVC–NaTPB–DBP with composition 1:5:1:3. The sensor worked well over a concentration range 1.12 × 10⁻⁶ M–1.0 × 10⁻¹ M between pH 2.1–6.2 and a fast response time 10±2 s and a lifetime of 6 months. Their performance in partially non-aqueous medium was found satisfactory. Electrodes exhibited excellent selectivity for Cu²⁺ ion over other mono-, di-, trivalent cations. It can also be used as indicator electrode in the potentiometric titration of Cu²⁺ against EDTA as well as in the determination of Cu²⁺ in real samples.     

NMR parameters of the tetrahedrane [Fe2(CO)6(μ-SNH)], studied by experiment and DFT

The intramolecular dynamic behavior of the tetrahedrane-type cluster [Fe₂(CO)₆(μ-SNH)] 1 was studied by ¹³C NMR spectroscopy. The ⁵⁷Fe chemical shift of 1 and the coupling constants ¹ J(⁵⁷Fe,¹³C) were measured. These NMR parameters, and also ¹ J(⁵⁷Fe,¹⁵N), were found to be in good agreement with data calculated by using density functional theory (DFT) methods (B3LYP), based on the geometry calculated at the 6-311+G(d,p) level of theory. The isolobal replacement of the Fe(CO)₃ with BH fragments leads to the tetrahedranes [Fe(CO)₃(BH)(μ-SNH)] 2 and [(HB)₂(μ-SNH)] 3. Both were identified by calculations as minima on the respective potential energy surface (PES). However, the tetrahedrane-type structure of 3 is much higher in energy when compared with the planar cyclic isomers 3a and 3b.     

硫、硒杯[4]芳烃萃取银

以5,11,17,23-四（1,1-二甲基乙基）-25,27-二羟基-26,28-二[（2-乙基硫）乙氧基]杯[4]芳烃（1）和5,11,17,23-四（1,1-二甲基乙基）-25,27-二羟-26,28-二[（2-乙基硒）]乙氧基杯[4]芳烃（2）为萃取剂,研究了在弱酸性条件下杯芳烃衍生物与银的络合行为。杯芳烃衍生物与银形成1：1萃取络合物,在大量碱金属、碱土金属、常见过渡金属离子存在下,对银离子有很高的萃取率和选择性。     

Gas-and liquid chromatographic separation of naphthalenophanes of the [2.2] and [3.3] type

Summary Separations of various isomeric naphthalenophanes have been performed in different LC-systems, including those containing Ag⁺ in the mobile phase, and also by high temperature capillary GC. Ag⁺-complexation in the mobile phase of LC-systems can be observed with several of the strained aromatic systems, but most of the separations of practical interest can also be achieved without Ag⁺-complexation. For solubility reasons purification and isolation of certain isomeric species have been performed in normal phase LC-systems only.Dedicated to Prof. Dr. I. Halász to his 60th birthday.     

Hydrogen Bonding and Solvent Effects on Complexation of Alkali Metal Cations by Lower Rim Calix[4]arene Tetra(O-[N -acetyl-D -phenylglycine methyl ester]) Derivative

Complexation of alkali metal cations with 5,11,17,23-tetra-tert-butyl-26,28,25,27-tetrakis(O-methyl-D-α-phenylglycylcarbonylmethoxy)calix[4]arene (L) was studied by means of spectrophotometric, conductometric and potentiometric titrations at 25 °C. The solvent effect on the binding ability of L was examined by using two solvents with different affinities for hydrogen bonding, viz. methanol and acetonitrile. Despite the presence of intramolecular NH···O=C hydrogen bonds in L, which need to be disrupted to allow metal ion binding, this calix[4]arene amino acid derivative was shown to be an efficient binder for smaller Li⁺ and Na⁺ cations in acetonitrile (lg K_LiL > 5, lg K_NaL = 7.66), moderately efficient for K⁺ (lg K_KL = 4.62), whereas larger Rb⁺ and Cs⁺ did not fit in its hydrophilic cavity. The complex stabilities in methanol were significantly lower (lg K_NaL = 4.45, lg K_KL = 2.48). That could be explained by different solvation of the cations and by competition between the cations and methanol molecules (via hydrogen bonds) for amide carbonyl oxygens. The influence of cation solvation on complex stability was most pronounced in the case of Li⁺ for which, contrary to the quite stable LiL⁺ complex in acetonitrile, no complexation was observed in methanol under the conditions used.