Intermolecular complexation thermodynamics between water-soluble calix[4]arenes and diazacycloalkanes

Calorimetric titration experiments have been performed in pH 2.0 and 7.2 phosphate buffer solutions at 298.15 K to calculate the complex stability constants (K_S) and thermodynamic parameters (ΔG°, ΔH°, and TΔS°) for the stoichiometric 1:1 inclusion complexation of water-soluble calix[4]arene tetrasulfonate (CAS) and thiacalix[4]arene tetrasulfonate (TCAS) with some diazacycloalkane guests, i.e. piperazine (1), homopiperazine (2) and 1,5-diazacyclooctane (3). The results indicated that complexes of CAS and TCAS with diazacycloalkane guests were enthalpy-stabilized, and an acidic environment was more favorable to host-guest complexation than a neutral one. CAS forms more stable complexes with guest molecules than TCAS due to the more favorable enthalpic gain.     

Interactions of a water-soluble calix[4]arene with spermine: solution and solid-state characterisation

Abstract

The octaanionic 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis(hydroxycarbonylmethoxy)-calix[4]arene (cone conformation) (C₄TsTc) was investigated as a sensor for the biogenic tetracationic polyamine, spermine _.(H₄Spe⁴⁺). Fluorescence titration experiments of the water-soluble calixarene with spermine showed the formation of the 2:1 and 1:1 calixarene:spermine complexes in solution. The single crystal X-ray diffraction analysis of [(NaC₄TsTc)₄·(H₄Spe)₇] confirmed the formation of 2:1 and 1:1 calixarene:spermine species and showed that the water-soluble calixarene binds the spermine either by partially hosting it in the inner cavity or through the carboxylate groups on the lower rim. In order to investigate the effect of multivalent systems, supramolecular assemblies of octaanionic calixarene molecules templated by meso-tetrakis(4-N-methylpyridyl)porphyrin (H₂T₄) in different stoichiometric porphyrin:calixarene ratios (1:4 and 3:4) were also tested for spermine binding in solution. Fluorescence titration experiments with the 1:4 and 3:4 H₂T₄:C₄TsTc supramolecular complexes showed that the multivalent assemblies are more sensitive to the presence of spermine than the calixarene alone.     

Structural characterisation and photophysical properties of lanthanoid complexes of a tetra-amide functionalised calix[4]arene

Abstract

Lanthanoid complexes of a tetra-amide substituted calix[4]arene in the cone conformation are characterised by single crystal X-ray structure determination. The structural analysis shows that the metal ions are coordinated to the calixarene through the eight O donor atoms, along with one aqua ligand which is located within the cavity of the calixarene. The calixarene ligand was covalently incorporated into a polymethylmethacrylate monolith through p-allyl functional groups, followed by loading with a range of lanthanoid cations giving rise to light-emitting materials. The emission from the hydrid materials was found to be comparable to the solution phase emission.     

Spectroscopic behavior on the formation complex of three double-armed calix[4]arene derivatives with lanthanoid nitrates in acetonitrile

The complexation spectroscopic behavior of three p-tert-butylcalix[4]arene Schiff bases i.e. 5,11,17,23-tetra-tert-butyl-25,27-bis[2-[N-(3-nitrobenzylidene)amino]ethoxy]-26,28-dihydroxycalix[4]arene (1), 5,11,17,23-tetra-tert-butyl-25,27-bis[2-[N-(2-hydroxybenzylidene)amino]ethoxy]-26,28-dihydroxycalix[4]arene (2), and 5,11,17,23-tetra-tert-butyl-25,27-bis[2-[N-(2-hydroxy-3-methoxybenzylidene)amino]ethoxy]-26,28-dihydroxycalix[4]arene (3) with lanthanoid nitrates (Tb3+ and Eu3+) has been investigated in anhydrous acetonitrile at 25 degrees C by using UV-vis and FT-IR as well as fluorescence spectra. The results obtained indicated that the spectroscopic behavior of compounds 1-2 upon complexation with lanthanoid ions did not show any significant larger difference in comparison with free compounds 1 and 2, which may be contributed to the poor binding ability. Contrary to compounds 1 and 2, the lower rim functional groups in compound 3 can form two large pi electron conjugate system with lanthanide ion and encapsulate lanthanide ions tightly, displaying the novel spectroscopic behavior upon complexation with lanthanide ions. As compared with compound 3, the formation complexes of compound 3 with Tb3+ and Eu3+ showed new broad intense absorption at 398 nm, respectively, and IR spectra showed that O-H stretching vibration at 3413.40 cm(-1) displayed a large drop. It is interestingly noted that the narrow emission line spectra were observed only for 3 complex with Tb3+, but did not for 3-Eu3+ complex. In the 3-Eu3+ complex, the broad-band emission at lambda(max) = 534 nm was obtained at the excitation of 398 nm. The spectroscopic behavior of three calix[4]arene derivatives upon complexation with lanthanoids was discussed from the relationship between the host structure and the properties of guest lanthanide ions.     

Novel anion receptors based on thiacalix[4]arene derivatives

Starting from the thiacalix[4]arene tetraacetate, novel derivatives bearing four ureido or thioureido functions on the lower rim have been prepared. As proven by NMR titrations, these compounds can bind anions via hydrogen bonding interactions and represent the first example of anion receptors in the thiacalixarene series.     

(1+1) or (2+2) Coupling for bis(tosyloxyethoxy)benzenes with calix[4]arene and thiacalix[4]arene

As bifunctional reagents, bis(tosyloxyethoxy)benzenes can react with p-tert-butylcalix[4]arene or p-tert-butylthiacalix[4]arene to afford intramolecularly bridged (1+1) or intermolecularly bridged (2+2) products. It was found that the bridging pattern strongly depended on the structure of bis(tosyloxyethoxy)benzene and the kind of calixarene. For the ortho-isomer of bis(tosyloxyethoxy)benzene, intramolecularly bridged calix[4]arene and thiacalix[4]arene were the main products. For the para-isomer, the bridging reaction was in a (2+2) fashion. As for the meta-isomer, double thiacalix[4]arene and intramolecularly bridged calix[4]crown were synthesized.     

Inclusion Complexation of Diphenylamine-4-diazonium Chloride and p-Sulfonatocalix[4]arene

Inclusion complexation of p-sulfonatocalix[4]arene (SC4A) and diphenylamine-4-diazonium chloride (DDC) in aqueous solution was investigated in this study. The inclusion of DDC in the cavity of SC4A leads to ¹H NMR chemical shifts of DDC moving towards higher magnetic field. The complexation of SC4A also results in a bathochromic shift and a decrease in optic intensity of the absorption spectrum of DDC. In the presence of SC4A, the thermal stability of DDC in aqueous solution increases significantly while its photosensitivity still remains high.     

Complexation of amino acids derivatives in water by calix[4]arene phosphonic acids

Series of the calix[4]arene phosphonic acids with various substituents at the lower rim was synthesized. Complexing properties of these receptors towards methyl esters of six amino acids strongly depended on the calix[4]arene conformation flexibility. The complex formation processes were monitored using ¹H NMR spectroscopy (deuterated phosphate buffer at pD 7.3, 22 °C) and association constant values were evaluated. Inherently mobile calix[4]arene molecule 3 occurred in cone conformation in aqueous solution turned out to be more effective in complexation of the basic amino acids methyl esters compared to the rigid 2 and flexible 4. Mixed 1:2 and 2:1 (host–guest) complexes were observed for compound 1 with all amino acids methyl esters.     

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.     

Complexation of di-benzyloxy ether derivatives of calix[4]arene with alkali earth metal cations

The synthesis and complexing abilities of 26,28-bis-benzyloxy-25,27-dihydroxy-5,11,17,23-tetra-tertbutyl-calix[4]arene towards alkali earth metal ions Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺ in a methanol-chloroform mixture have been evaluated at 25°C, using UV-Vis spectrophotometric techniques. The results showed that the ligand is capable to complex all alkali earth cations by 1:1 metal to ligand ratios. The selectivity presented considering the calculated stability constants are in the order Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺ towards the ligand.     

Microcalorimetric titration of a tetra-p-sulphonated calix[4]arene with α,ω-alkyl diammonium ions in an aqueous solution

25,26,27,28-Tetrahydroxycalix[4]arene-5,11,17,23-tetrasulphonate was in a heat-conduction calorimeter titrated with α,ω-alkyl diammonium ions, n=(3–7), in an aqueous solution at pH 7.1. Apparent concentration binding constants (K_c) and enthalpy changes are reported for a 1 : 1 binding model at minimized concentration ranges. The standard Gibbs energy change, ΔG⁰=−RTln K_c, has a non-linear dependence of the alkyl chain length, n. The interaction is strongest at n≥5. A similar trend is observed for the enthalpy change. However, the fit of the experimental data to the 1 : 1 model was quite poor and neither 1 : 2 nor 2 : 1 models gave any further improvement. Concentration-dependent results were also obtained. It is therefore concluded that the interaction observed is more complex.     

Metallic macrocycle with a 1,3-alternate calix[4]arene salicylideneamine ligand

The calix[4]arene-based podand which incorporates two salicylideneamine units in 1,3-alternate positions of the lower rim has been prepared and subjected to complexation studies with transition metal ions. The nickel and copper complexes form a 2 : 2 stoichiometric metallic macrocyclic framework.     

Synthesis and characterization of chiral catenanes based on rigid calix[4]arene

A new class of chiral calix[4]arene-based [2]catenanes was synthesized in excellent yields of 51-80%. They exhibit unique dynamic properties according to variable temperature NMR experiments. The enantiomeric pure (+)-catenane was prepared in 66% yield starting from (−)-calix[4]arene.     

1,3-Bis(pyren-1-yliminomethyl)calix[4]arene as a selective fluorescent turn-on sensor for mercury(II) ion

A novel calixarene-based diimine, 1,3-bis(pyren-1-yliminomethyl)calix[4]arene (5), serves as a turn-on-type fluorescent sensor, which selectively detects Hg²⁺ in THF/H₂O (99:1, v/v) in the presence of various other metal ions. Such selectivity is not seen with half salen 1 derived from salicylaldehyde and 1-aminopyrene. ¹H NMR analysis reveals that it is a chemodosimetric sensor based on its hydrolysis mediated by Hg²⁺ to release 1-aminopyrene molecules as fluorescent chromophores.     

Synthesis of novel redox calix[4]arene derivative with 1,3-substituted large conjugated ferrocene bridge

A novel redox calix[4]arene derivative with 1,3-substituted large conjugated ferrocene bridge was designed and synthesized in high yield.Its structure was characterized by element analysis,IR,ESI-MS,NMR spectrum,etc.The primary study of cyclic voltammetry showed it possessed excellent reversible electrochemistry response property.     

Functionalisation of the upper rim of calix[4]arene via alcoholysis and hydrosilylation reactions

Metalation of 5,17-dibromo-25,26,27,28-tetra propoxy calix[4]arene (1) with n-BuLi in THF at −78 °C gave organolithium reagent, which reacted with Me₂HSiCl to give 5,17-bis(dimethylsilyl)-25,26,27,28-tetra propoxy calix[4]arene (2). The Si-H groups of calixarene 2 were treated with methanol, ethanol, propanol, butanol, pentanol, hexanol, 2-propanol and 2-methyl propanol in the presence of Karstedt catalyst (platinum(0)-1,3-divinyl-1,1,3,3-tetramethyl disiloxane complex, solution in xylene) to give the corresponding 5,17-bis(alkoxydimethylsilyl)-25,26,27,28-tetra propoxy calix[4]arene (3). Moreover, calixarene 2 was easily functionalized with a variety of alkenes using Karstedt catalyst to give the corresponding organosilylated calix[4]arene (4).     

Potentiometric evaluation of calix[4]arene anion receptors in membrane electrodes: phosphate detection

Ion-selective membrane electrodes doped with the urea- or thiourea-functionalised calix[4]arenes, 5,11,17,23-tetra-tert-butyl-25,27-bis[[4-N′-(phenylureido)butyl]oxy]-26,28-dipropoxy calix[4]arene (I) and 5,11,17,23-tetra-tert-butyl-25,27-bis[[4-(N′-phenylthioureido)-butyl]oxy]-26,28-dipropoxy calix[4]arene (II), were evaluated for anion sensing. Potentiometric results show that these calixarene ionophore-based membrane electrodes exhibit a good sensitivity to aqueous solutions of the monohydrogen orthophosphate species HPO₄²⁻ in the concentration range 5.0 × 10⁻⁵ to 1.0 × 10⁻¹ M, with near-Nernstian response slopes of −33.0 and −28.0 mV dec⁻¹ for ionophores I and II, respectively. Selectivity coefficient values for monohydrogen orthophosphate over a range of common anions were determined by the fixed interference and matched potential methods and indicated that these membrane electrodes exhibit a good selectivity for HPO₄²⁻ with respect to the other anions, including sulfate and nitrate.     

The complexation of ferrocene derivatives by a water-soluble calix[6]arene

The complexation of several ferrocene derivatives by the water-soluble hostp-sulfonato-calix[6]arene was investigated using electrochemical and¹H-NMR spectroscopic techniques. The electrochemical results indicate that both oxidation states of the guests are bound to the calixarene host, although the oxidized (ferrocenium) forms are complexed more strongly than the reduced (ferrocene) species.¹H-NMR spectroscopic data indicate that the complexation phenomena involves the inclusion of the guest's ferrocene moiety into the flexible calixarene cavity.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

5,11,17,23-四叔丁基-25,26,27,28-四[3-(甲氧基羰基)苄氧基]杯[4]芳烃包合性能的研究

杯芳烃是继冠醚和环糊精后的第三代主体化合物 .这类主体分子不仅可以识别和络合阳离子 ,而且还具有包合中性有机分子的性能 [1～ 5] .杯 [4]芳烃类包合物的晶体结构测定表明 ,它们可分为分子内和分子间包合两种类型 [3 ,5] ,前者是客体分子被包合在主体分子的空穴内 ,后者是客体分子被包合在主体分子之间 .对叔丁基杯 [4]芳烃的下沿酚氧基与上沿均可进行化学修饰得到不同的杯 [4]芳烃衍生物 .最早报道的对叔丁基杯 [4]芳烃及其衍生物的分子内包合物是与甲苯或乙腈的 1∶ 1包合物 [4 ,5] ,客体分子依靠 CH3 -π的作用被包结在主体分子内[6]…     

Synthesis of a novel fluorescent anthryl calix[4]arene as picric acid sensor

A novel and sensitive fluorescence sensor has been designed by click chemistry. Based on the obvious and selective fluorescence quenching of anthryl calix[4]arene, a sensitive and robust platform were developed for visual detection of picric acid (TNP) in the mixture of nitro aromatics. The computational calculations revealed the formation of host–guest complex driven by π–π stacking interactions.