Supramolecular nano networks formed by molecular-recognition-directed self-assembly of ditopic calix[5]arene and dumbbell [60]fullerene

Dumbbell fullerene 1 and ditopic bisdouble-calix[5]arene 2 were synthesized. Their iterative host-guest complexations create the supramolecular nano network. Scanning electron microscopy revealed the formation of the branched fiber, possessing a length of more than 100 mum and widths of 250-500 nm on a glass plate. More detailed information was given by atomic force microscopy. The formed fibers on a mica plate have widths of 60-90 nm and heights of 1.2-1.9 nm. The nanosize assemblies are probably composed of a bundle of 40-60 polymer chains created by entangling the alkyl side chains with van der Waals interaction.     

Study on thermal decomposition of calix[6]arene and calix[8]arene

Thermal decomposition kinetics of calix[6]arene (C6) and calix[8]arene (C8) were studied by Thermogravimetry analysis (TG) and Differential thermal analysis (DTA). TG was done under static air atmosphere with dynamic heating rates of 1.0, 2.5, 5.0, and 10.0 K min⁻¹. Model-free methods such as Friedman and Ozawa–Flynn–Wall were used to evaluate the kinetic parameters such as activation energy (E _a) and pre-exponential factors (ln A). Model-fitting method such as linear regression was used for the evaluation of optimum kinetic triplets. The kinetic parameters obtained are comparable with both the model-free and model-fitting methods. Within the tested models, the thermal decomposition of C6 and C8 are best described by a three dimensional Jander’s type diffusion. The antioxidant efficiency of C6 and C8 was tested for the decomposition of polypropylene (PP).     

Novel tungsten calix[8]arene complexes

p-tert-Butylcalix[8]areneH8 reacts with WCl6 forming a number of new metallocalix[8]arenes, one of which is reduced to give the first example of a metal-metal triple bond supported by a large calixarene ligand; the degree of metallation and conformations adopted by the newly generated metallocalix[8]arene systems are determined by single crystal X-ray diffraction.     

Supramolecular interaction between water-soluble calix[4]arene and ATP--the catalysis of calix[4]arene for hydrolysis of ATP

The catalysis effect of water-soluble calix[4]arene C[4] (calix[4]arene-5,11,17,23-tetrasulfonate) on hydrolysis of ATP in aqueous solution was studied by HPLC. Using laser photolysis and pulse radiolysis, the supramolecular interaction between water-soluble calix[4]arene and ATP was investigated.     

Supramolecular polymeric complexes of calix[8]arenes

Formation of ionic complexes of calix[8]arenes with polymers of various basicities was studied, and previously unknown ternary polymeric complexes of calix[8]arenes of the ion-ion (polymer-calixarene-uranyl ion) and ion-hydrophilic molecule-hydrophobic molecule (polymer-calixarene-fullerene) types were prepared.     

Supramolecular systems formed by calix[4]resorcinarenes and surfactants in chlorophorm

Capacity titration and ¹H NOESY 2D NMR were applied to investigation of intermolecular interactions and aggregation of amphiphilic calix[4]resorcinarenes (CRA 1, 2) modified with 1,2,4-triazine (1) and oxazine (2) functions in chloroform in the presence of cationic (3) and non-ionic (4) surfactants (SAA). Critical concentrations of micelle formation (CMC) indicate that the ability of CRA 1, 2 to form supramolecular aggregates like micelles or hybrid micelles with SAA 3, 4 only weakly depends on the constitution of CRA functional groups. In the case of the hybrid micelles, when CMC are defined by the nature of surfactants 3 or 4, the methyl and methylene groups of the hydrophobic fragments (CRA 1, 2) were found to interact with the hydroxy groups of SAA 3 and ethylene oxide moieties of SAA 4.     

Comparative study of the response of membrane electrodes based on calix[6]arene and calix[8]arene derivatives to organic ammonium ions.

p-tert-Butylcalix[8]arene-octaacetic acid octaethyl ester and calix[8]arene-octaacetic acid octaethyl ester well recognized 2-phenylethylamine and phenylalanine methyl ester compared with the corresponding calix[6]arene derivatives. Moreover, the calix[8]arene derivatives, especially one having tert-butyl groups, gave better selectivity against biologically active amines having a complicated structure, such as norephedrine. We considered the interaction between calixarenes and organic ammonium ions from the viewpoint of molecular symmetries.     

Aminolysis reaction of calix [ 4 ] arene esters and crystal structures and conformational behaviors of calix[4]arene amides

We first make use of aminolysis of calix[4]arene esters to synthesize calix[4]arene amides. When the two ethyl esters of the calix[4]arene esters are aminolysized, the 1, 3-amide derivative is formed selectively. The crystal structures of the calix-[4]arene with two butyl amide (3b) and four butyl amide moieties (4b) were determined. The intermolecular hydrogen bonds make 4b form two-dimensional net work insolid state. The 1H NMR spectra prove that 3b is of a pinched cone conformation, while 4b and tetraheptylamide-calix[4]arene (6b) take fast interconversion between two C2v isomers in solution and appear an apparent cone conformation at room temperature. As decreasing temperature, the interconversion rate decreases gradually and, finally, the interconversion process is frozen at Tc = -10℃, which makes both conformations of 4b and 6b the pinched cone structures. The hydrogen bond improves the interconversion barrier, and the large different values of the potential barrier between 6b and 4b (or 6b) may     

Sterically and guest-controlled self-assembly of calix[4]arene derivatives

In solvents such as chloroform or benzene, tetraurea calix[4]arenes 1 form dimeric capsules in which one solvent molecule is usually included as guest. To explore the structural requirements for the formation of such hydrogen-bonded dimers we replaced one p-tolylurea residue by a simple acetamide function. The resulting calix[4]arene 2 a, substituted at its wide rim with one acetamide and three p-tolylurea functions, assumes a C(1)-symmetrical conformation in apolar solvents as shown by (1)H NMR, which is not compatible with the usual capsule. In the crystalline state, four molecules of 2 a, adopting a pinched cone conformation, assemble into a quasi S(4)-symmetrical tetramer stabilized by a cyclic array of 24 NH.O==C hydrogen bonds and four NH.pi interactions. Four acetamide groups are hydrogen-bonded to each other and pack tightly in the center of the assembly. All polar residues are buried inside the tetramer, the surface of which is lipophilic. Extensive NMR studies revealed similar structures in apolar solvents such as [D]chloroform or [D(6)]benzene for calixacetamides 2 a-c. The formation of these tetramers in solution is critically dependent on the size of the amide fragment, so that propionamide 2 d, butyramide 2 e, and p-tolylamide 2 f form only ill-defined aggregates. This is caused by steric crowding inside the tetrameric assembly. The tetramers persist during molecular dynamics simulations, and the optimized average structure of the MD run is similar to that found in the crystalline state. Theoretical studies revealed that cooperation of hydrogen bonds with multiple NH.pi, C--H.pi, and pi.pi attractions make the tetramer more stable than the capsular dimer with the solvent as guest. In the presence of tetraethylammonium salts, however, compounds 2 a-e form dimeric capsular assemblies, each incorporating a single ammonium cation. Only one of two possible regioisomeric dimers is formed, in which both acetamide groups are surrounded by two urea residues. These examples give striking evidence of how self-assembly in solution can be strongly dependent on subtle structural factors and of how the formation of dimeric capsules can be induced by the presence of an appropriate guest.     

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.     

对硝基杯[8]芳烃的合成及其与奥克托今的配合

以对叔丁基苯酚与多聚甲醛为原料合成了对硝基杯[8]芳烃.利用紫外光谱研究了对硝基杯[8]芳烃与奥克托今(HMX)在氯仿中的配合性能.用量子化学半经验AM1和ab initio HF/3-21G方法,分别得到主、客体及其超分子体系几何全优化结构.结果表明,主客体分子形成了1: 1的配合物,标准状况下对硝基杯[8]芳烃与HMX形成超分子体系后较单体能量之和减少60.76 kJ/mol,主客体间可形成氢键.对硝基杯[8]芳烃与HMX超分子体系的稳定常数Kw从288 K的1.138×1012降至408 K时的1.121×105.     

Heterodimerization studies of calix[4]arene derivatives in polar solvents

[reaction: see text] Several calix[4]arene derivatives propylated on the lower rim and substituted on the upper rim with amino or carboxyl groups have been synthesized. Examples include calixarenes substituted with alanino (C- and N-linked), amino, carboxy, carboxyphenyl, and amidino groups. The self-assembly of these derivatized calixarenes into heterodimers has been studied by NMR in DMSO-d(6) or CD(3)OD with 5% aqueous phosphate buffer.     

Thermal analysis of charge-transfer complex formed by nitrogen dioxide and substituted calix[4]arene

Simultaneous thermal analysis with evolved gas analysis (STA-EGA) was used to study the ability of 1,3-alternate conformer of tert-butylcalix[4]arene with four n-propoxy substituents (1) to be applied for detection of nitrogen dioxide in reversible sensors. Solid calixarene 1 forms an intensively colored charge-transfer complex (CTC) with gaseous NO₂/N₂O₄. Using the STA-EGA method, the nature and conditions of CTC bleaching were characterized, including the conditions of its reversible change of color from white to dark blue and back at CTC formation and decomposition. For this, the thermal stability of CTC and its regeneration products were studied. This, together with the ion thermograms for evolved gases, gives the information on the oxidation of 1 by nitrogen dioxide if present.     

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.     

Lower rim substituted p-tert-butyl calix[4]arene; Part 14. Synthesis, structures and binding studies of calix[4]arene thioamides

A number of p-tert-butylcalix[4]arene thioamides were synthesized and characterized by ¹H-NMR and elemental analysis. Compounds 1–5 are O-substituted derivatives with –CH₂–C(=S)–N–X groups, where NX = morpholidyl, NEt₂, NHC₂H₄Ph, NHCH₂Ph and NHEt, respectively. The X-ray structures of the ligands 1, 3, 5 and of the complex 3·Pb(ClO₄)₂, (compound 6), are presented and their slightly distorted cone conformation is established. The influence of the nature of the thioamide functions (secondary or tertiary) on the extractability of some selected metal cations was investigated. Whereas all these calixarenes show the highest extraction level for Ag⁺, tertiary thioamides are more efficient extractants for Pb²⁺ than secondary thioamides.     

Crystal structures of a calix[4]arene controlled by two affixed pyrene units

The synthesis and crystal structures of a calix[4]arene (1) with two affixed pyrene units and its corresponding inclusion compound with chloroform (1a) are reported. In both cases, stacking structures resulting from the influencing control of the pyrene units are observed. The occurrence of infinite or dimeric stack motifs of the pyrene units is dependent on the absence or presence of the included guest solvent.

     

The selective functionalisation and difunctionalisation of p-substituted calix[6]arene and calix[8]arenes using hydrophilic moieties

Methodologies to access water soluble large ringed calixarenes in good yield using efficient synthetic procedures have been investigated. Symmetrical partial functionalisations at the lower rim are described using activated [n]ethylene glycol chains and the addition behaviour contrasted with that of bromoalkanenitriles which proceeds with no observed regioselectivity. Full functionalisations of the calixarenes bearing hydrophilic groups are then investigated and a two-step procedure established which appears to be generally applicable for the addition of different [n]ethylene glycol chains. Furthermore, difunctionalisation under different reaction conditions are described. Throughout, strategies for the characterisation of these high mass compounds are outlined.     

Computational study of calix[4]arene derivatives and complexation with Zn

High level DFT was applied to study structure and conformational equilibrium of amino and mercaptocalix[4]arenes possessing methylene groups or sulfur atoms at their four junctions. All the calculations point to cone and 1,3-alternate as the most stable conformers for sulfur and methylene bridged compounds, respectively. The presence of four sulfur atoms in place of the methylene bridges can lead to novel features in the complexation with transition metals. The host–guest 1:1 complexes between Zn²⁺ and each conformer of tetraaminothiacalix[4]arene were also investigated at the same DFT level. The four nitrogens of amino groups play a dominant role in the interaction with Zn²⁺ via distorted tetrahedral coordination for 1,3-alternate, or distorted square planar for partial cone and 1,2-alternate. On the other hand, the 2:1 complexes with cone show that the sulfur bridges can also bind Zn²⁺ and contribute to form two sets of five-membered chelated rings with two N donor atoms.     

Thermal behaviour of some ester derivatives of p-tert-butyl calix[n]arene

The thermal behaviour of three ester derivatives of p-tert-butyl calix[n]arene (n?=?4, 6 and 8) in comparison with the parent calixarene was investigated by means of the thermogravimetric (TG) and differential thermogravimetic (DTG) analysis and differential scanning calorimetry (DSC). The thermal stability domains, the composition of the pyrolysis products and the thermal effects, were determined on the basis of TG, DTG and DSC plots registered in nitrogen flow. Attempts to analyse the evolved gases by TG-FTIR coupling were also performed. It was demonstrated that the stability of the calix[n]arene derivatives depends on both the size of the hydrophobic cavity and number of the substituting groups grafted on the calix[n]arene skeleton.