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 structures formed by calix[8]arene derivatives

Octamethoxy calix[8]arenes substituted in the para position by amide, urea, and imide functions were synthesized from the octamethyl ether of tert-butylcalix[8]arene by ipso nitration, reduction, and acylation. Scanning force microscopy of spin coated samples on graphite suggests that these derivatives self-organize into tubular nanorods via hydrogen bonds between p-amide functions. A single-crystal X-ray structure reveals a centrosymmetric conformation for the octanitro derivative. [structure: see text]     

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).     

Selective extraction of Fe3+ by a polymeric calix[4]arene

A polymeric compound containing more than one calixarene molecule was synthesized by reacting the oligomer ( 2 ) with 25,26,27-tribenzoyloxy-28-hydroxy calix[4]arene. After basic hydrolysis of 3a , the polymeric calixarene ( 3b ) was utilized for selective extraction of some metal cations from aqueous phase to organic phase. It was found that the compound ( 3b ) was selective toward Fe³⁺ from an aqueous solution containing Cu²⁺, Ni²⁺, Co²⁺ and Fe³⁺ cations. The mechanism of the extraction process was discussed. © 1994 John Wiley & Sons, Inc.     

Synthesis and extraction studies of polymeric phthalimido functionalized calix[4]arene

The article comprises synthesis and extraction studies of polymeric calix[4]arene having phthalimide groups at the lower rim. The polymeric phthalimido functionalized calix[4]arene was synthesized via radical initiated reactions involving a vinylic monomer 5,11,17,23-tetra-tert-butyl-25-[4-(acrylamido)benzyloxy]-26,28-bis-(2-phthalimido-ethoxy)-27-hydroxycalix[4]arene (5) with styrene. A five atom spacer group was incorporated between the bulky calixarene core and the acrylate moiety in order to minimize steric interactions which proved to impede the polymerization. From the liquid–liquid and solid–liquid extraction studies it has been concluded that the precursor 3 (5,11,17,23-tetra-tert-butyl-25-(4-nitro benzyloxy)-26,28-bis-(3-phthalimidoethoxy)-27-hydroxy-calix[4]arene) is selective for metal cations. The order of extractability of metal cations by the ligand 3 decreases in the sequence: Hg²⁺ > Cd²⁺ > Cu²⁺ > K⁺ > Co²⁺ whereas its polymeric derivative is selective in the sequence: Hg²⁺ > Cd²⁺ > K⁺ > Co²⁺ > Cu²⁺ for the metal cations used in the experiments.     

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.     

Selective electrodes for silver based on polymeric membranes containing calix[4]arene derivatives

Silver ion-selective electrodes were prepared with polymeric membranes based on two calix[4]arene derivatives functionalized by two hydroxy and two benzothiazolylthioethoxy groups. The electrodes all gave a good Nernstian response of 58?mV decade^–1 for silver in the activity range 5 × 10^–6–10^–1 M, the limits of detection reached 10^–5.8 M and exhibited high selectivity towards alkali, alkaline earth and some transition metal ions. The electrode was used as indicator electrode in titrations of Ag⁺ with Cl^– ion.     

Effect of varying bases on preferential crystallization of C-methylresorcin[4]arene and calix[6]arene

Preferential crystallization from a mixture of C-methylresorcin[4]arene (RsC1) and calix[6]arene (Calix6) in the presence of different bases has been investigated. In the presence of pyridine, a boat conformer of RsC1 crystallizes, whereas in the presence of triethylamine, Calix6 crystallizes in a symmetrically distorted conformation. The packing arrangements of the macrocycles show discrete solvent pockets for calixarenes and channels for resorcinarenes.     

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     

Spectrophotometric study of the supramolecular complexes of [60]- and [70]Fullerenes with biscalix[6]arene and crown[4]calix[6]arene

[60]- and [70]Fullerenes have been shown to form 1:1 supramolecular complexes with bis[2-(5,11,17,23,29,35-hexa-tert-butyl-37,38,39,40,41-pentahydroxycalix[6]arenyl-oxy ethyl ether) (1) and 5,11,17,23,29,35-hexa-tert-butyl-37,38,40,41-tetra hydroxyl-39,42-(crown-4)calix[6]arene (2) in CHCl3 medium by electronic absorption spectroscopy. Formation constants (K) of the complexes of [60]- and [70]fullerenes with 1 and 2 have been determined at room temperature from which free energy of formation values of the complexes have been estimated. The very high formation constant value of [60]fullerene/1 complex (5900 dm3 mol-1) in indicative of formation of inclusion complex. Moreover, PM3 calculations reveal that intermolecular interaction between [60]fullerene and 1 proceeds through quite deep energy molecular orbital.     

一种新型杯[4]芳烃的合成

本文通过对特丁基杯[4]芳烃的酚羟基烷基化和苯环特丁基位上的IPSO-硝化制备了一系列对硝基杯[4]芳烃烷基醚,烷基分别是n-C~4H~9(3a)、n-C~8H~1~7(3b)、n-C~1~2H~2~5(3c)和n-C~1~6H~3~3(3d)。^1HNMR表明所有新的杯[4]芳烃都具有锥形(cone)构象。     

Nanoencapsulation of calix[4]arene inclusion complexes

A hexameric resorcinarene nanocapsule in wet CDCl3 forms inclusion complexes of calix[4]arene with tetramethylammonium and trimethylsulfoxonium cations to give highly stable Russian-doll-type multicomponent assemblies. The 2D NOESY experiments revealed the size of the assembly, the close proximity of the encapsulated calix[4]arene molecule to the resorcinarene molecules of the capsule, and the inclusion of the tetramethylammonium cation in the calix[4]arene cavity.     

Band intensity in the IR spectra and conformations of calix[4]arene and thiacalix[4]arene

The experimental IR and Far IR spectra of the calix[4]arene, p-tert-butylcalix[4]arene, thialcalix[4]arene and p-tert-butylthiacalix[4]arene were examined at different temperatures and interpreted. The band frequencies and intensities in the IR spectra of the calix[4]arene and thialcalix[4]arene were calculated. The absorption curves of the four possible calix[4]arene conformations: cone, partial cone, 1,2- and 1,3-alternate were computed. The bands characteristic for each conformation are defined and assigned. The obtained spectra-structure correlation can be used for the characteristic of calixarenes conformation.     

Spectroscopic studies of water-soluble sulfonated calix[6]arene

Fluorescence and absorption studies of water-soluble sulfonated calix[6]arene (SCX6) are reported. Water-soluble calixarenes are potentially useful as host molecules for luminophores, and studies of their spectroscopic characteristics are therefore crucial. The absorption and fluorescence spectra of these molecules in aqueous solution were collected, analyzed, and compared with 4-hydroxybenzene sulfonate at different pHs. A red shift in the absorption spectrum and a change in the fluorescence spectrum of the calixarenes are observed upon an increase in pH from 2.0 to 13.0. Some of these spectroscopic changes are attributed to intramolecular hydrogen bonding between adjacent hydroxyl groups of SCX6 after proton disassociation. The formation of excimers between phenolic groups in the calixarene molecule is proposed. In addition, inner-filter effects of SCX6 are discussed. These inner-filter effects prove to be a disadvantage for the use of SCX6 as a host molecule for complexation studies by use of fluorescence probes whose absorption spectra overlap with those of calixarenes.     

Efficient synthesis of calix[6]tmpa: a new calix[6]azacryptand with unique conformational and host-guest properties

A new C(3v)-symmetrical calix[6]azacryptand, that is, calix[6]tmpa (11), was synthesized by efficient [1+1] macrocyclization reactions. Remarkably, both linear and convergent synthetic strategies that were applied lead to equally good overall yields. Calix[6]tmpa behaves as a single proton sponge and appeared reluctant to undergo polyprotonation, unlike classical tris(2-pyridylmethyl)amine (tmpa) derivatives. It also acts as a good host for ammonium ions. Interestingly, it strongly binds a sodium ion and a neutral guest molecule, such as a urea, an amide, or an alcohol, in a cooperative way. A (1)H NMR study indicated that the ligand, as well as its complexes, adopt a major flattened cone conformation that is the opposite of that observed with the previously reported calix[6]cryptands. Characterization of the monoprotonated derivative 11H(+) by X-ray diffraction also revealed the presence of a 1,3-alternate conformation, which is the first example of its kind in the calix[6]arene family. This conformer is probably also present in solution as a minor species. The important covalent constraint induced by the polyaromatic tmpa cap on the calixarene skeleton, and conversely from the calix core onto the tmpa moiety, is the likely basis for the unique conformational and chemical properties of this host.     

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.     

t-Butylcalix[4]arene host-guest compounds: Structure and dynamics

Despite the proliferation of structural studies on calixarene host-guest compounds, some important structural details remain obscure. In particular, the ubiquitous disorder of the calixt-butyl group often hinders a detailed determination of the non-bonding interactions between host and guest. We propose and develop a synoptic approach in which several complementary characterization techniques (X-ray diffraction and NMR) provide a powerful means of assessing the interplay of structure and dynamics in calixarene-guest compounds. The simplet-butylcalix[4]arene-guest compounds (guest = toluene, nitrobenzene, cyclohexane,n-pentane, l-chlorobutane) are examined with this approach, and new structural and dynamic features are uncovered.Issued as NRCC 39105.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.