Calix[4]arene-functionalized naphthalene and perylene imide dyes

[reaction: see text] Calix[4]arenes bearing one, two, or four 1,8-naphthyl imide groups at the wide rim and bis-calix[4]arenes connected via perylene-bisimide dye spacers have been synthesized. The low-temperature NMR spectrum of the tetranaphthylimide suggests, in agreement with a crystal structure, a C2-symmetrical pinched cone conformation stabilized via face-to-face pi-pi interactions between opposite naphthylimide groups. UV-vis and fluorescence studies have been carried out for the perylene bis-calix[4]arene dyes.     

Calixarenes. 23. the complexation and catalytic properties of water soluble calixarenes

A series of-water-soluble calixarenes containing dialkylamino groups and carboxyl groups have been prepared by the p-quinonemethide route of functionalization. The formation of host-guest complexes between these calixarenes and nine aromatic hydrocarbons ranging in size from durene to decacyclene has been investigated, and a correlation between the dimensions of the hydrocarbons and the “lower rim” of the calixarene, containing the array of OH groups, has been made. A study of the effect on the acid-catalyzed hydration of N-benzyl-1,4-dihydronicotinamide by p-(carboxy-ethyl) calix[n]arenes (n = 4,5,6,7,8) has shown that the calix[6]arene is more effective than either its larger or smaller analogs.     

Synthesis and conformational study of the first triply bridged calix[6]azatubes

[reaction: see text] The first C(3)(v)- and D(3)(h)-symmetrical triply bridged calix[6]azatubes were prepared in good yields from the known 1,3,5-tris-methylated calix[6]arene through an efficient [1 + 1] macrocyclization reaction. A remarkably regioselective hexa ipso-nitration reaction led to a calix[6]azatube substituted at the wide rim in alternate position by tBu and nitro groups. A (1)H NMR study showed that, whereas the parent bis-calix[6]arenes self-include their methoxy groups, thereby closing their inner tube, the nitro-substituted calix[6]azatube undergoes a conformational change with the expulsion of the methoxy groups, hence presenting a three-dimensional structure open for host-guest applications.     

New artificial receptors from selectively functionalized calix[4]arenes

Abstract

The development of new synthetic methods for the monoalkylation of calix[4]arenes at the lower rim allows the synthesis of a new class of trihydroxamate siderophores. Three chelating hydroxamic acid units are introduced through a sequence of reactions which blocks the macrocycle in the cone conformation. The new ligands obtained form neutral 1:1 complexes (FeL) with iron (III), which are stable in EtOH/H₂O 9:1 at pH 2–7. Calix[4]arene bis-crown ethers are prepared by exploiting the selective 1,2-(proximal) functionalization of calix[4]arenes at the lower rim. These ligands are, however, less effective in complexing alkali metal cations compared with the 1,3-calix[4]arene crown-ethers which, in their partial cone structure, offer a better shielding for the complexed cations. Rigid upper rim-bridged calix[4]arenes potentially useful for the inclusion of neutral molecules are prepared by exploiting the selective 1,3-diformylation of calix[4]arene at the upper rim. Finally a new chloromethylation method for calix[4]arenes blocked in the cone conformation is described together with the synthesis of new cavitands.     

DNA condensation and cell transfection properties of guanidinium calixarenes: dependence on macrocycle lipophilicity, size, and conformation

Calix[n]arenes functionalized with guanidinium groups at the upper rim and alkyl chains at the lower rim bind to DNA, condense it, and in some cases, promote cell transfection depending on their structure and lipophilicity. Atomic force microscopy (AFM) studies indicate that upon DNA binding the hydrophobic association of the lipophilic chains of cone guanidinium calix[4]arenes drives the formation of intramolecular DNA condensates, characterized by DNA loops emerging from a dense core. Furthermore, hexyl and octyl chains confer to these calixarenes cell transfection capabilities. Conversely, larger and conformationally mobile calix[6]- and calix[8]arene methoxy derivatives form intermolecular aggregates characterized by "gorgonlike" structures composed of multiple plectomenes. These adducts, in which interstrand connections are dominated by electrostatic interactions, fail to promote cell transfection. Finally, calix[4]arenes in a 1,3-alternate conformation show an intermediate behavior because they condense DNA, but the process is driven by charge-charge interactions.     

上端含长链烷基的手性杯[4]芳烃合成

脱叔丁基的杯[4]芳烃与长链的叔醇或者叔氯代烷烃进行傅-克反应, 在其上端引入长链烷基. 然后在下端引入光学活性的1-苯基乙胺基团, 得到了一系列上端含长链烷基的手性杯[4]芳烃.     

Direct access to upper rim substituted mono- and diaryloxy calix[4]arenes via bis(spirodienone) route

A seemingly ipso-like nucleophilic substitution of the upper rim of p-tert-butylcalix[4]arene is accomplished by an indirect method involving calix[4]arene derived bis(spirodienone). This method not only provides both mono and 1,3-diaryloxy calixarenes but also enables the synthesis of upper rim monothio substituted calix[4]arenes. A modification of the methodology can be successfully extended for the selective synthesis of mono- and 1,3-diquinone calix[4]arenes having free hydroxyl groups at the lower rim, in fewer steps.     

para‐Sulfonated Calixarenes Used as Synthetic Receptors for Complexing Photolabile Cholinergic Ligand

The water‐soluble tetra‐, hexa‐ and octasulfonated calix[4]arenes, calix[6]arenes, and calix[8]arenes 1 – 3 , respectively, were investigated as potential synthetic receptors for photolabile cholinergic ligand A , a photolytic precursor of choline. Ligand A is a bifunctional molecule carrying a photolabile 2‐nitrobenzyl group at one end and a choline moiety at the other end. Results from NMR studies have shown that calixarenes 1 – 3 form stable 1 : 1 complexes with A , having similar binding potential to that observed with the cholinergic enzymes acetylcholinesterase and butyrylcholinesterase. Further studies have suggested that calix[8]arene forms a ditopic complex by binding concomitantly to both the cationic choline moiety and the aromatic photolabile group of A , whereas calix[4]arene and calix[6]arene form monotopic complexes with A . The ditopic complex between calix[8]arene and A results from mutually induced fitting process, while the monotopic complexes between calix[4]arene and A can be regulated by pH: at neutral pH, calix[4]arene specifically binds the cationic choline moiety, while, at acidic pH, it complexes unselectively both the cationic choline moiety and the aromatic group of A . Our results show that para‐sulfonated calixarenes are versatile artificial receptors which bind in various ways to the bifunctional photolabile cholinergic ligand A , depending on their size, geometry, and state of protonation.     

Calix[4]arene stabilized Transition Metal Imido Complexes

The usage of calix[n]arenes as ancillary poly(phenolate) ligands is a rapidly developing area in coordination chemistry. This article focuses on the synthesis, structure and reactivity of calix[4]arene‐ and calix[4]arene ether‐stabilized imido complexes of group 4 — 6 transition metals as well as on the comparison of calix[4]arene dialkyl ethers in particular with other widely employed related ligand systems such as salenes, porphyrins and tetraazaannulenes. Contrary to these nitrogen containing systems, it is much easier to control the charge of the ligand system through the degree of alkylation of the calixarene's lower rim without a major change in the geometry of the resulting metal complex. This could lead to isoelectronic and structurally closely related transition metal complex fragments for metals in neighboring groups of the periodic table or for metals in different oxidation states. The “intrinsic” reactivity of metal imido linkages might therefore be explored using calix[4]arenes and calix[4]arene ethers and first results are summarized in this research report.     

Energies of charge transfer and supramolecular interactions of some mono O-substituted calix[6]arenes with [60]fullerene by absorption spectrometric method

Equilibria for the formation of supramolecular complexes of [60]fullerene with a series of mono O-substituted calix[6]arenes, namely: (i) 37-methoxy-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (1), (ii) 37-allyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (2), (iii) 37-phenacyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (3), (iv) 37-ethylester-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (4) and (v) 37-benzyl-38,39,40,41,42-pentahydroxy-5,11,17,23,29,35-hexa(4-tert-butyl)calix[6]arene (5) have been studied in CCl4 medium by absorption spectroscopic technique. The stoichiometry has been found to be 1:1 ([60]fullerene:calix[6]arene) in each case. An absorption band due to charge transfer (CT) transition is observed in each case in the visible region. The vertical ionisation potentials (I(D)(v)) of all the calix[6]arenes under study have been estimated utilising CT transition energy. The experimental I(D)(v) values also yield a good estimate of the electron affinity of [60]fullerene. The degrees of CT in the ground state of the complexes have been found to be very low (about 0.15%). Resonance energy of the complexes have been estimated. Thermodynamic parameters for the supramolecular complex formation of [60]fullerene with mono O-substituted calix[6]arene receptors are reported. It is observed that among the calix[6]arenes under the present study, only 1 and 4 form inclusion complexes with [60]fullerene. This has also been substantiated by theoretical calculation using PM3 method. Thus presence of one substituent group (of different types) on the lower rim of the calix[6]arene molecule has been shown to govern the host-guest complexation process.     

Transition metal-directed self-assembly of calix[4]arene based dithiocarbamate ligands

The transition metal-directed self-assembly of dithiocarbamate ligand functionalized upper and lower rim calix[4]arenes affords novel dimeric bimetallic bis(calix[4]arene) species as determined by a combination of analytical methods including X-ray crystallography. An exception is a zinc(II) dithiocarbamate upper rim calix[4]arene assembly which is monomeric in nature. Electrochemical investigations reveal the bimetallic copper(II) bis(calix[4]arene) systems can electrochemically sense dihydrogen phosphate and carboxylate anions via significant cathodic perturbations of the respective copper(II)/(III) dithiocarbamate oxidation wave.     

Calixarene-based surfactants: evidence of structural reorganization upon micellization

The self-aggregation of five amphiphilic p-sulfonatocalix[n]arenes bearing alkyl chains at the lower rim was investigated by NMR spectroscopy and electrical conductivity. The critical micelle concentration was determined, and the tendency of this special class of surfactants to self-aggregate in aqueous solution was analyzed as a function of the alkyl chain length and the number of aromatic units in the macrocyclic ring. The structure of the surfactants in the monomeric and micellized states was elucidated by means of (1)H NMR and, in the case of the calix[6]arene derivative, with 2D NMR experiments. While all amphiphilic calix[4]arenes studied here are blocked in the cone conformation, in the monomeric state the calix[6]arene adopts a pseudo-1,2,3-alternate conformation and the calix[8]arene is conformationally mobile. These calixarenes undergo an aggregation-induced conformational change, adopting the cone conformation in the micelles. The structure and size of the aggregates were studied by diffusion ordered spectroscopy (DOSY) experiments, and the results indicate that these surfactants self-assemble into ellipsoidal micelles.     

The enhancement of luminescent properties of Tb3+ complexes with tetra-1,3-diketone ligands promoted by the tetrathiacalix[4]arene scaffold

This is the first report on the synthesis and characterization of tetra-1,3-diketone derivatives of tetrthia- and calix[4]arenes substituted by acetylacetonyl or dipivaloylmethanyl moieties at the upper rim and bearing hydroxyl groups at the lower rim as ligands for Tb³⁺ complexes. The spatial structure and tautomeric content for the synthesized ligands have been determined by means of X-ray, IR and NMR spectroscopy. Comparison of the sensitizing properties of tetrathiacalix[4]arenes and their calix[4]arene analogues on the Tb³⁺-centered luminescence in DMF solutions has been performed. A substantial enhancement of the luminescent properties of Tb³⁺- complexes with tetra-1,3-diketone ligands promoted by the tetrathiacalix[4]arene scaffold was established.     

An Interesting Approach to Bis-calix[5]arene Analogue from Calix[6]arene

Calix [n] arenas {n = 4, 6 or 8} are easily prepared from formaldehyde and para-substituted phenols via cyclic condensation under alkaline conditions in one step. It is not surprising that the calyx [n] arene (n = 4, 6, 8) chemistry has been developing very rapidly during the latest 20 years1. However, it is not the case for calixarenes with odd benzene rings (for example, n = 5). The yield of p-tert-butylcalix [5] arene synthesized in one-step from p-tert-butylphenol and formaldehyde was a…     

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.     

Azocalixarenes.8: synthesis and investigation of the absorption spectra of di-substituted azocalix[4]arenes containing chromogenic groups

The synthesis of series of chromogenic di-substituted azocalix[4]arene derivatives is described. A ketone moiety as a different chelating agent is grafted on the lower rim of p-tert-butylcalix[4]arenes. Eight novel azocalix[4]arenes (1–8) are prepared by linking 2-, 3- and 4-nitroaniline, 4-phenylazoaniline, 3- and 4-chloroaniline or 2- and 4-methylaniline to 25,27-diacetonyloxy-26,28-dihydroxy-11,23-di-(tert-butyl)calix[4]arene through a diazo-coupling reaction, and characterized by UV–Vis, FT-IR and ¹H-NMR spectroscopic techniques and elemental analysis, consecutively. The absorption spectra of the di-substituted azocalix[4]arenes are discussed, according to effect of varying pH and solvent upon the absorption ability of azocalix[4]arenes. The colors of these azocalix[4]arenes are compared with respect to nature of their aromatic rings and substituents there in. Concentration effects on the visible absorption maxima of these compounds are also reported.     

Calixarenes with nitrogen or phosphorus substituents on the lower rim

Calix[n]arenes (n=4,6) with diphenylphosphinite groups appended to their lower rim have been synthesized by reaction first with base, followed by chlorodiphenylphosphine. The reaction has also been carried out with the partially methoxylated calix[n]arenes. Calix[6]arenes with phosphate groups selectively bridging adjacent pairs of oxygens have been synthesized by reaction first with base, followed by ethyl dichlorophosphate. Calix[n]arenes (n=4,6) with 2-aminoethyloxy groups appended to the lower rim have been synthesized both by the reduction of an amide or nitrile group. Calixarenes with 2-hydroxyethyloxy and 2-bromoxyethyloxy groups appended to the lower rim have also been prepared. A route to preparing calixarene-functionalized polymers by the alkylation of polyethyleneimine is also described.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Chemical Chromogenic Sensors Based on Calixarenes: Syntheses and Recognition Properties for Alkylamines

Nitration of 1,3-distal dialkylated calix[4]arenes wasinvestigated in order to prepare chromogenic sensor compounds. There were three kinds of separableproducts, which came from the nitration and oxidation of the phenol moieties. The coneconformation of calix[4]arenes containing a quinone structure was first determined. And the effectof the structure of reactants for the nitration and oxidation is also discussed. Dinitratedcalix[4]arenes possess recognition ability for the alkylamines, which can be as the chromogenicsensors for determining the alkylamines. The recognition behavior was due to the protontransfer between alkylamine and calix[4]arenes, and the resulting ammonium phenoxide wasstabilized by the phenoxide oxygen atom and the carbonyl at the lower rim with hydrogen bonding.     

A New Family of Indoaniline-Derived Calix[4]arenes: Synthesis and Optical Recognition Properties as a Chromogenic Receptor(1)

A new family of indoaniline-derived calix[4]arenes has been synthesized for the purpose of developing a new chromogenic receptor. A condensing reaction of calix[4]arene (1) with 4-(diethylamino)-2-methylaniline hydrochloride (2) in the presence of an oxidizing agent under alkaline conditions affords mono- (3), 1,2-bis- (4), 1,3-bis- (5), and tetrakisindoaniline-derived (6) calix[4]arenes after careful column chromatography. Compound 3 is crystallized from a CHCl(3)-MeOH solution, and the crystal structure was determined by X-ray analysis. The crystal is monoclinic, space group P2(1)/n, Z = 4, a = 19.507(6) ?, b = 18.591(6) ?, c = 8.524(2) ?, beta = 94.69(2) degrees. The final R value for 2406 reflections of F(o) > 3sigma(F(o)) is 0.085. A unique intramolecular hydrogen-bonding network involving the carbonyl oxygen of indoaniline for 3 implied that the quinone carbonyl group as an acceptor of the chromophore can easily be subjected to an electrostatic interaction in the lower rim. Indeed, 1,3-bis(indoaniline)-derived 2,4-bis((ethoxycarbonyl)methoxy)calix[4]arene 7, prepared by the reaction of 5 with ethyl bromoacetate in the presence of NaH, is capable of undergoing an efficient ion-dipole interaction between the binding cation and the two quinone carbonyl groups of the chromophores, so that a selective Ca(2+)-induced pronounced color change (wavelength change > 100 nm) occurs with an association constant on the order of 10(6) in 99% EtOH, making 7 of potential use as an optical sensor for Ca(2+) detection. The IR and NMR studies have indicated that Ca(2+) is encapsulated in the cavity made by the distally located OCH(2)CO(2) groups on the lower rim of the cone-shaped calix[4]arene segment. Interestingly, however, the shape of the cavity in which Ca(2+) has been encapsulated does not have a C(2) axis of symmetry, as inferred from the (1)H-(1)H COSY experiment. On the other hand, 1,2-bis(indoaniline)-derived analogue 8 shows no response with metal ions, which can be interpreted to mean the absence of a cavity for encapsulation on the lower rim.     

Fourfold tetraurea calix[4]arenes--potential cores for the formation of self-assembled dendrimers

Wide rim tetraurea calix[4]arenes monofunctionalized at the narrow rim by COOH or NH2 have been synthesized in five steps from t-butylcalix[4]arene tripropylether. Their covalent linkage via the narrow rim to a central calix[4]arene fixed in the 1,3-alternate conformation led to pentacalix[4]arenes 9 bearing four tetraurea derivatives in the cone conformation in a flexible tetrahedral arrangement. Their self-assembly via the formation of hydrogen bonded dimeric capsules has been studied under different conditions. A fourfold heterodimerisation of tetrakis-tetraurea derivatives of type 9 with tetratosylurea 10 has been confirmed by 1H NMR-spectroscopy and dynamic light scattering.