Study on the Film Properties and Recognition for Metal Ions of Calix[4]arenes Derivative by Langmuir Monolayer

Calixarene molecules are very powerful ligand for ions and small molecules, and have been studied with several techniques as models for host‐guest systems. In this approach, the formation of Langmuir monolayer properties of three kinds calix[4]arene derivative were characterized and one of them, p‐tert‐butylthiacalix[4]arene (TCA), was chosen as object to study its Langmuir monolayer affected by different subphase conditions. The purpose of this study is to investigate the molecular recognition ability of TCA for metal ions at the water‐air interface. Changing the composition of aqueous subphase (containing various metal ion solutions respectively) produced strong variations on the monolayer parameters, indicating a different selectivity of the TCA ligand for the different metal cations. In particular, high selectivity for transition metal ions was found. Limiting area values are discussed in relation to the orientation of the cone‐shaped molecules at the water‐air interface.     

Synthesis,structures, and conformational characteristics of calixarene monoanions and dianions

The synthesis, complete characterization, and solid state structural and solution conformation determination of calix[n]arenes (n = 4, 6, 8) is reported. A complete series of X-ray structures of the alkali metal salts of calix[4]arene (HC4) illustrate the great influence of the alkali metal ion on the solid state structure of calixanions (e.g., the Li salt of monoanionic HC4 is a monomer; the Na salt of monoanionic HC4 forms a dimer; and the K, Rb, and Cs salts exist in polymeric forms). Solution NMR spectra of alkali metal salts of monoanionic calix[4]arenes indicate that they have the cone conformation in solution. Variable-temperature NMR spectra of salts HC4.M (M = Li, Na, K, Rb, Cs) show that they possess similar coalescence temperatures, all higher than that of HC4. Due to steric hindrance from tert-butyl groups in the para position of p-tert-butylcalix[4]arene (Bu(t)C4), the alkali metal salts of monoanionic Bu(t)C4 exist in monomeric or dimeric form in the solid state. Calix[6]arene (HC6) and p-tert-butylcalix[6]arene (Bu(t)C6) were treated with a 2:1 molar ratio of M(2)CO(3) (M = K, Rb, Cs) or a 1:1 molar ratio of MOC(CH(3))(3) (M = Li, Na) to give calix[6]arene monoanions, but calix[6]arenes react in a 1:1 molar ratio with M(2)CO(3) (M = K, Rb, Cs) to afford calix[6]arene dianions. Calix[8]arene (HC8) and p-tert-butylcalix[8]arene (Bu(t)()C8) have similar reactivity. The alkali metal salts of monoanionic calix[6]arenes are more conformationally flexible than the alkali metal salts of dianionic calix[6]arenes, which has been shown by their solution NMR spectra. X-ray crystal structures of HC6.Li and HC6.Cs indicate that the size of the alkali metal has some influence on the conformation of calixanions; for example, HC6.Li has a cone-like conformation, and HC6.Cs has a 1,2,3-alternate conformation. The calix[6]arene dianions show roughly the same structural architecture, and the salts tend to form polymeric chains. For most calixarene salts cation-pi arene interactions were observed.     

Study of the Molecular Recognition of Nucleotides and Bases by a Novel Calixarene Derivative Containing Uracil

A calix[4]arene derivative containing uracil, 5‐(uracil‐N¹‐acetamido)‐25,26,27,28‐tetrahy droxycalix[4]‐arene (UC), was designed and synthesized. The interaction with nucleotides and bases has also been studied by ESI‐MS and π‐A isotherms. The results of ESI‐MS showed that UC could recognize adenine and adenosine from other nucleotides and bases. In addition, π‐A isotherms at the air‐water interface indicated that there was interaction between UC and the species in the subphase, and the respective complexes were formed in the monolayer. The mean molecular area at zero surface pressure increased with the sizes of the nucleotides and bases in the subphase in the order: water<adenine<adenosine<ATP·Na₂.     

Tube-type coordination polymers: two- and four-silver(I)-mediated linear networking of calix[4]arene tetracarboxylates

Two calix[4]arene tetracarboxylates, [calix[4]arene tetraacetate (K(4)CTA) and calix[4]arene tetrabenzoate (K(4)CTB)] as their potassium salts, have been prepared. Employing these as precursors, two Ag(I) coordination polymers incorporating calix[4]arene units have been successfully prepared and their X-ray crystal structures have been determined. In these, the CTA and CTB derivatives are linearly bound to two and four silver atoms, respectively, to generate unusual tubular nanostructures. A comparative NMR study was undertaken to investigate the nature of the metal ion blocking of the tube as observed in the CTA-derived structure. The thermal properties for both coordination polymers were also examined.     

邻甲氧基羰基苄氧基取代杯[4]芳烃衍生物的合成及其性？…

杯芳烃是继冠醚、环糊精之后的第三代主体分子 [1] .据文献 [2 ,3]报道 ,在杯 [4]芳烃下沿酚氧原子上连接乙酸酯得到的四取代衍生物对 Na+ 有很高的选择性 ,核磁与晶体结构研究均证实这是由于羧酸酯的羰基和酚氧基参与了对 Na+ 的配位 ,而且配位基团所形成的包络空间大小与钠离子相匹配 .一般认为 ,随着包络空间改变 ,对金属离子的识别作用会有所变化[4] .但目前对这方面的工作并没有给予更多的重视 .我们发现 ,用 2 -溴甲基苯甲酸甲酯与杯 [4 ]芳烃反应 ,得到了一种新的四取代杯 [4]芳烃衍生物 2 ,萃取研究结果表明 ,该化合物对钾离子有较…     

Alkali-metalated forms of thiacalix[4]arenes

The alkali metal salts [TCALi4] (1), [TCANa4] (2), and [TCALK4] (3) of fully deprotonated p-tert-butyltetrathiacalix[4]arene (H(4)TCA) are readily available from the reactions of thiacalix[4]arene and n-BuLi, NaH, or KH as deprotonating reagents. Crystals of the sodium salts 2 and the potassium salt 3 suitable for X-ray diffraction were obtained in the form of the pyridine solvates [(TCA)2Na8.8py] (2.8py) and [(TCA)2K(8).8py] (3.8py). These molecules are dimers in the solid state but are structurally not related. In addition, the reaction of H(4)TCA and lithium hydroxide afforded the structurally characterized complex [(TCA)Li5(OH).4THF] (4). The molecular structure of 4 as well as the structures of 2.8py and 3.8py reveal a close relationship to the corresponding alkali metal salts of the calix[4]arenes.     

Studies on Mixed Monolayers and Langmuir-Blodgett Films of Schiff-Base Complex Cu(SBC(18))(2) and Calix

Mixed monolayers of Schiff-base complex Cu(SBC(18))(2) with an octadecyl hydrocarbon chain and Calix[4]arene without a long alkyl chain at an air/water interface were studied in ultrapure water at different temperatures. Interface behavior and thermodynamic estimation of the mixed monolayer indicate that a strong intermolecular interaction exists between the mixed components (Cu(SBC(18))(2) and calix[4]arene) and the two-dimensional miscibility decreases with the molar fraction of Cu(SBC(18))(2). It is noticeable that the calix[4]arene monolayer can be transferred successfully onto solid substrates due to the introduction of Cu(SBC(18))(2). FTIR transmission and UV-Vis absorption spectra of mixed LB films provide further evidence of molecular interaction between the headgroups. Copyright 2001 Academic Press.     

Interaction of monolayers of calix[4]resorcinarene derivatives with copper ions in the aqueous subphase

Stable monolayers of novel amphiphilic calix[4]resorcinarene derivates at the air–water interface were prepared. Their interactions with copper ions from the aqueous subphase were investigated by measuring surface pressure–area and surface potential–area isotherms, as well as by Brewster angle microscopy. Theoretical aspects of interpreting the dependence of the surface pressure on the bulk copper ions concentration were discussed. The interaction of copper ions with calix[4]resorcinarene derivates was interpreted in terms of Gibbs–Shishkovsky adsorption equation.     

Synthesis and crystal structure of uranium(IV) complexes with calix[n]arenes (n = 4, 6 and 8): mononuclear, polynuclear and 1D polymeric species

Reactions of UCl4 with calix[n]arenes (n = 4, 6) in THF gave the mononuclear [UCl2(calix[4]arene - 2H)(THF)2].2THF (.2THF) and the bis-dinuclear [U2Cl2(calix[6]arene - 6H)(THF)3]2.6THF (.6THF) complexes, respectively, while the mono-, di- and trinuclear compounds [Hpy]2[UCl3(calix[4]arene - 3H)].py (.py), [Hpy](4)[U2Cl6(calix[6]arene - 6H)].3py (.3py), [Hpy]3[U2Cl5(calix[6]arene - 6H)(py)].py (.py) and [Hpy]6[U3Cl11(calix[8]arene - 7H)].3py (.3py) were obtained by treatment of UCl4 with calix[n]arenes (n = 4, 6, 8) in pyridine. The sodium salt of calix[8]arene reacted with UCl4 to give the pentanuclear complex [U{U2Cl3(calix[8]arene - 7H)(py)5}2].8py (.8py). Reaction of U(acac)4 (acac = MeCOCHCOMe) with calix[4]arene in pyridine afforded the mononuclear complex [U(acac)2(calix[4]arene - 2H)].4py (.4py) and its treatment with the sodium salt of calix[8]arene led to the formation of the 1D polymer [U2(acac)6(calix[8]arene - 6H)(py)4Na4]n. The sandwich complex [Hpy]2[U(calix[4]arene - 3H)2][OTf].4py (.4py) was obtained by treatment of U(OTf)4 (OTf = OSO2CF3) with calix[4]arene in pyridine. All the complexes have been characterized by X-ray diffraction analysis.     

Synthesis and metal ion complexation studies of proton-ionizable calix

A series of novel N-chromogenic calix[4]arene azacrown ethers were synthesized as selective extractants of potassium ion. 1,3-Alternate calix[4]arene azacrown ethers were prepared by reacting 25,27-dipropyloxy-26,28-bis(5-chloro-3-oxapentyloxy) calix[4]arenes with p-toluenesulfonamide in the presence of potassium carbonate. The coupling reaction of calix[4]arene azacrown ether with 2-hydroxy-5-nitrobenzyl bromide in the presence of triethylamine in THF gave the chromogenic calix[4]arene azacrown ether in moderate yield. These compounds show high potassium selectivity over other metal ions as shown by two-phase extraction, bulk liquid membrane, and 1H NMR studies on a ligand-metal complex. It is assumed that the OH of the chromogenic group attached on nitrogen can assist the complexation by encapsulation of the metal.     

Studies on Mixed Monolayers and Langmuir–Blodgett Films of Schiff-Base Complex Cu(SBC18)2 and Calix[4]arene

Mixed monolayers of Schiff-base complex Cu(SBC₁₈)₂ with an octadecyl hydrocarbon chain and Calix[4]arene without a long alkyl chain at an air/water interface were studied in ultrapure water at different temperatures. Interface behavior and thermodynamic estimation of the mixed monolayer indicate that a strong intermolecular interaction exists between the mixed components (Cu(SBC₁₈)₂ and calix[4]arene) and the two-dimensional miscibility decreases with the molar fraction of Cu(SBC₁₈)₂. It is noticeable that the calix[4]arene monolayer can be transferred successfully onto solid substrates due to the introduction of Cu(SBC₁₈)₂. FTIR transmission and UV-Vis absorption spectra of mixed LB films provide further evidence of molecular interaction between the headgroups.     

Self-assembled monolayers of organosulphur molecules bearing calix[4]arene moieties

We investigate the self-assembly of modified calix[4]arene on gold surfaces. Calix[4]arene was modified through a reaction sequence which led to assembling of the crown-5 moiety and to the insertion of two thioether groups into the starting molecule. The so-obtained calix[4]arene-crown-5 bis(7-thiatridecyloxy) (hereafter called calix[4]arene) was in the stable 1,3-alternate conformation. The calix[4]arene/gold interface was investigated by means of spectroscopic ellipsometry (SE), scanning tunneling microscopy (STM) and cyclic voltammetry (CV). SE data indicate a layer thickness compatible with the formation of a monomolecular layer. This result is confirmed by STM imaging which shows the formation of a high density of small pits, one gold layer deep, a typical feature of self-assembled organosulphur monolayers on gold. CV measurements performed in presence of the [Ru(NH(3))(6)(2+/3+)] redox couple indicate a passivation of the metal electrode, resulting in a reduction of the redox current, after the layer deposition. CV has also been used to investigate the selectivity properties of calix[4]arene-covered gold electrodes by measuring the redox current decrease in the presence of different salt solutions. It is found that calix[4]arene-covered electrodes are able to complex K(+) and Ba(2+), while no complexation is observed in the case of Li(+), Na(+), Cs(+), Mg(2+) and Ca(2+).     

Comparative study of calix[4]arene derivatives: implications for ligand design

The first comparative theoretical study of three parent calix[4]arene analogues (calix[4]arene, thiacalix[4]arene, and homooxacalix[4]arene) has been performed using molecular dynamic simulations and density functional theory (MPWB1K/6-311G^∗∗//B3LYP/6-311G^∗∗) methods. The theoretical observations herein including optimized geometry, polarity, and atomic charge data provide that homooxacalix[4]arene would offer more efficient platform for metal ion recognition compared to thiacalix[4]arene or calix[4]arene.     

Origins of cooperative noncovalent host-guest chemistry in mixed valence complexes

The electronic effects resulting from noncovalent host-guest interactions between calix[6]arene and a ruthenium dimer, [Ru3O(OAc)6(CO)(ppy)]2-mu-pz (ppy=4-phenyl pyridine, pz=pyrazine), are presented. The noncovalent interaction is between the calix[6]arene and the ppy ligands of the dimer. The dimer can bind 2 equiv of calix[6]arene. The complex [Ru3O(OAc)6(CO)(ppy)]2-mu-pz forms a highly stable mixed valence ion with strong electronic coupling between the two Ru3 clusters. The strength of the electronic interaction is found to be moderated by calix[6]arene binding. Addition of calix[6]arene to the mixed valence ion causes the electronic coupling to decrease. The binding of calix[6]arene is found to be cooperative. The origins of cooperative binding are developed in terms of the potential energy surfaces associated with the symmetric and asymmetric mixed valence ion. In particular, it is found that symmetry breaking (through the binding of a single calix[6]arene) destabilizes the mixed valence state. Restoration of symmetry (through the binding of a second calix[6]arene) increases the stability of the mixed valence ion and provides an additional driving force for the binding of the second calix[6]arene.     

Assembly of a supramolecular capsule on a molecular printboard

A molecular capsule based on ionic interactions between two oppositely charged calix[4]arenes, 1 and 2, was assembled both in solution and on a surface. In solution, the formation of the equimolar assembly 1.2 was studied by (1)H NMR, ESI-MS, and isothermal titration calorimetry, giving an association constant (K(a)) of 7.5 x 10(5) M(-1). A beta-cyclodextrin self-assembled monolayer (beta-CD SAM) on gold was used as a molecular printboard to anchor the tetraguanidinium calix[4]arene (2). The binding of tetrasulfonate calix[4]arene 1 was monitored by surface plasmon resonance spectroscopy. Rinsing of the surface with a high ionic strength aqueous solution allows the removal of the tetrasulfonate calix[4]arene (1), while by rinsing with 2-propanol it is possible to achieve the complete desorption of the tetraguanidinium calix[4]arene (2) from the beta-CD SAM. The K(a) for the capsule formation on a surface is 3.5 x 10(6) M(-1), thus comparing well with the K(a) determined in solution.     

N-硫脲基套索杯[4]冠醚与四硫脲基杯[4]芳烃的合成

控制反应物的物质的量比, 杯式对叔丁基杯[4]-1,3-二乙酸乙酯衍生物1与5或50倍二乙烯三胺反应, 分别得到杯[4]氮杂冠醚2和开链的氮杂杯[4]芳烃衍生物3. 化合物2和3进一步与异硫氰酸苯酯反应得到首例侧链含硫脲基的套索杯[4]氮杂冠醚4和含4个硫脲基的杯[4]芳烃衍生物5, 产率为92%和87%. 新化合物的结构与构象经元素分析、红外、质谱、核磁共振谱等表征证实.     

下缘芳香取代结构对杯[4]芳烃Langmuir膜的影响

The Langmuir monolayer properties of lower rim aromatically substituted calix[4]arenes, 5,11,17,23-tetra-tert-butyl-25,27-bis（2-naphth-1＇-ylacetylaminoethoxy）-26,28-dihydroxylcalix[4]arene （BNAEC）, 5,11,17,23-tetra-tert- butyl-25,27-bis（2-benzoylamino ethoxy）-26,28-dihydroxylcalix[4]arene （BBAEC） and 5,11,17,23-tetra-tert-butyl- 25,27-bis（2-cinnamoylaminoethoxy）-26,28-dihydroxylcalix[4]arene （BCAEC）, have been studied. Film balance measurements and Brewster angle microscopy （BAM） observation demonstrate that all the compounds can form Langmuir monolayers with different molecular limiting areas. BNAEC or BBAEC monolayer is able to form condensed domains during compression, while BCAEC monolayer can never form condensed domain. BNAEC monolayer is more readily to form condensed domain than BBAEC monolayer. Moreover, BNAEC monolayer can form the total condensed phase during compression even when T=28℃, while BBAEC monolayer can not when T 〉 10 ℃. The results imply that different lower rim aromatic substitutions affect essentially the intermolecular interaction and molecular packing in the monolayer at air/water interface.     

Physicochemical Characterization of Hydrated 4-Sulphonato-Calix[n]arenes: Thermal,Structural, and Sorption Properties

In this study, the thermal behavior of three hydrated water-soluble 4-sulphonato calix[n]arenes was investigated. The melting points, heats of fusion, and heats of solution of the calix[4]arene, calix[6]arene and calix[8]arene were 277, 262, and 270°C; 192, 242 and 351 kJ/mol; and 30, 58 and 63 kJ/mol, respectively. Lower heat of fusion, smaller increase in entropy and smaller heat of solution of the calix[4]arene compared to the calix[6]arene and calix[8]arene showed that less heat was required to break up the crystal lattice of the smaller macromolecule. This apparent anomaly is rationalized in terms of smaller cooperativity of interaction between the molecules of calix[4]arene in the crystal lattice, although the strength of the individual interactions is stronger as evidenced by the higher melting point. TGA analysis indicated that about 17–20% of water was associated with the calix[n]arenes. Both TGA and hot stage microscopy results indicated that upon heating these molecules underwent stepwise water loss. TGA kinetics showed that the 4-sulphonato-calix[8]arene lost water easier than the other two calixarenes. The moisture adsorption behavior of all calixarenes followed type II isotherms. For the same amount of material, the calix[6]arene adsorbed more moisture than the calix[4]arene and the calix[8]arene. Moreover, dehydrated less crystalline 4-sulphonic-calix[n]arenes powders are hydroscopic.

     

Calix[4]Resorcinarene Macrocycles Interactions with Cd2+, Hg2+, Pb2+, and Cu2+ Cations: A QCM‐I and Langmuir Ultra‐thin Monolayers Study

Stable ultra‐thin Langmuir monolayers of calix[4]resorcinarene derivatives, namely: C‐dec‐9‐enylcalix[4]resorcinarene‐O‐(R+)‐α‐methylbenzylamine (Ionophore I ), and C‐dec‐9‐enylcalix[4]resorcinarene‐O‐(S‐)‐α‐methylbenzylamine (Ionophore II ), were prepared at the air‐water interface. Their interactions with a series of heavy metals (HM) ions (Cu²⁺, Pb²⁺, Hg²⁺ and Cd²⁺) present in the aqueous subphase were investigated by measuring surface pressure‐area isotherms, at different concentrations. The surface pressure‐area (Π‐A) isotherms were stable and demonstrated the HM amounts influence on the limiting area (A_lim) values, therefore confirming the examined macrocycles capability to host the metallic toxicants. Additionally, a HM concentration dependence was realized and interpreted by a selective tendency of both ionophores towards Cu²⁺ and Cd²⁺ ions over Pb²⁺ and Hg²⁺, especially at high concentrations. The HM ions interactions with the applied calix[4]resorcinarene Langmuir ultra‐thin monolayers were interpreted based on the Gibbs‐Shishkovsky adsorption equation. Moreover, quartz crystal microbalance with impedance measurement (QCM‐I), was applied for the detection of HM ions in solutions. The QCM‐I results showed the effectiveness of the coated QCM‐I crystals in detecting the ions at different concentrations. The detection limit values were in the order of 0.16, 0.3, 0.65, 1.1 ppm (Ionophore I), as well 0.11, 0.45, 0.2, 0.89 (Ionophore II) for the Cu²⁺, Pb²⁺, Hg²⁺ and Cd²⁺ cations, respectively. Additionally, a selective tendency of both ionophores towards copper ions was shown.     

Lower rim substituted tert-butylcalix[4]arenes. Part 8: Calix[4]arenes with dialkoxyphosphoryl functions. Synthesis and complexing properties

New compounds: 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-diisopropoxyphosphorylpropoxy)calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-methoxyethoxyphosphorylpropoxy)calix[4]arene (2) were synthesized and their ionophoric properties in ion-selective membrane electrodes were studied in comparison with already described by us 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(3-diethoxyphophorylpropoxy)calix[4]arene (3). Complexes of 1 with calcium(II), lanthanum(III), europium(III) and gadolinium(III) nitrates were prepared in direct reaction of the ligand and appropriate metal salts. They were characterized by spectral data (IR, UV/Vis, luminescence, NMR, ESI-MS) and elemental analysis. The similarity in complexing behavior of the (dialkoxyphosphoryl)propoxy-calix[4]arenes toward calcium and some lanthanides was observed.