Reactivity of Amphiphilic Calix[4]resorcinolarenes and Phenols in the Reverse Micellar System Sodium Bis(2-ethylhexyl) Sulfosuccinate-Decane-Water

The mechanism of reaction of calix[4]resorcinolarene, aminomethylated calix[4]resorcinolarene, and 2-(dimethylaminomethyl)-4-isononylphenol with ethyl 4-nitrophenyl (chloromethyl)phosphonate in the reverse micellar system anionic surfactant-sodium bis(2-ethylhexyl) sulfosuccinate-decane-water changes compared with direct micellar systems and aqueous-organic solutions. It was shown that the calix[4]resorcinolarenes and phenol studied increase the percolation threshold of the system.     

Effective Synthesis of β-Ketophosphonate Derivatives of Calix[4]resorcinolarenes

An effective method for introduction of -phosphonate fragments to a calix[4]resorcinolarene matrix is presented octa(ketophosphonate)calix[4]resorcinolarenes are prepared. The effectiveness of 2,8,14,20-tetramethyl-4,6,10,12,16,18,22,24-octa[3-(dimethoxyphosphoryl)-2-oxopropyl]calix[4]-resorcinolarene for extraction of lanthanum ions from water to chloroform in the presence of picrate ions, accompanied by formation of a complex is demonstrated.     

Novel acetal-containing calix[4]resorcinolarene-based Mannich bases

The reaction of calix[4]resorcinolarene with methylaminoacetaldehyde dimethyl acetal and formalin gave novel acetal-containing calix[4]resorcinolarene derivatives aminomethylated at the upper rim.     

A paradigm shift in the construction of heterobimetallic complexes: synthesis of group 2 & 4 metal-calix[6]arene complexes

Deprotonation of calix[6]arenes with barium in methanol followed by the addition of [Ti(OPr(i))(4)] or [Zr(OBu(n))(4)] is effective in the formation of novel dimeric 2:1 barium-titanium(IV)/zirconium(IV) calix[6]arene complexes. In these complexes a central Ti(IV)/Zr(IV) coordinated in the exo-position connects the two calix[6]arenes in the 1,3-alternate conformation, each with an endo-barium sharing common phenolate groups with the titanium/zirconium centre and participating in cation-pi interactions. A homometallic barium calix[6]arene dimer was also prepared wherein the calix[6]arenes are in the 1,3-alternate conformation with each coordinating one endo- and one exo-barium centre. The exo-barium cations connect the two calix[6]arenes through bridging methanol ligands. In this and the heterometallic complexes, cation-pi complexation of the Ba(2+) ion within the 1,3 alternate conformation of calix[6]arene facilitates the formation of the dimeric complexes in methanol. In contrast, the smaller Sr(2+) ion did not form similar complexes in methanol, and the formation of an analogous 2:1 strontium-titanium calixarene complex required the use of the more sterically demanding donor alcohol, isopropanol, the resulting complex being devoid of cation-pi interaction. The results show (i) that a subtle interplay of solvation strength, coordination array type and cavity/cation size influences the accessibility of heterobimetallic complexes based on calix[6]arenes, and (ii) a synergistic endo-exo binding behaviour.     

Phosphorylation of Dialkylaminomethyl-substituted Calix[4]resorcinolarenes with Hexaalkylphosphorous Triamides and Phosphorus(V) Dichlorides

A series of aminophosphino cavitands were synthesized by reactions of dialkylaminomethyl-substituted calix[4]resorcinolarenes with hexaalkylphosphorous triamides, and their properties were studied. New aminoalkylated (thio)phosphato(phosphonato) cavitands were prepared by phosphorylation of dialkylaminomethyl-substituted calix[4]resorcinolarenes with phosphorus(V) dichlorides in the presence of a base. Their reactions with electrophilic alkylating agents (methyl trifluoromethanesulfonate, methyl iodide, and triethyloxonium tetrafluoroborate) were examined.     

Catalytic Effect of Reverse Micelles of a Cationic Surfactant on the Reaction of Calix[4]resorcinolarenes with 4-Nitrophenyl Bis(chloromethyl)phosphinate

The presence of the aminomethyl fragment in the calix[4]resorcinolarene molecule favors its phosphorylation in chloroform. Reverse micelles of (2-hydroxyethyl)dimethylpentadecylammonium bromide catalyze this reaction, the catalytic effect being dependent on the length of the hydrocarbon chain of a calixarene and detergent concentration.     

Effect of Micellar Media on Electrochemical Oxidation of Calix[4]resorcinolarenes

Aminomethylated calix[4]resorcinolarenes in aqueous solutions of nonionic (Triton X-100) and ionic (cetyltrimethylammonum bromides) surfactants undergo selective oxidation controlled by the hydrophobicity of the substrates. In the inverted micellar system sodium bis(2-ethylhexyl) sulfosuccinate-decanewater after the percolation threshold, hydrophobized aminomethylated calix[4]resorcinolarenes undergo reversible one-electron oxidation to give the stable phenoxyl radical.     

The aggregartion and catalytic activity of amphiphilic calix[4]resorcinolarenes and phenols in hydrolysis of phosphonous esters in water—dimethylformamide media

The amphiphilic calix[4]resorcinolarenes, aminomethylated calix[4]resorcinolarenes, o-aminomethylphenols, and their quaternary derivatives in water—dimethylformamide media (10—75 vol.% DMF) form aggregates, which catalyze the hydrolysis of phosphonous esters. The ability to self-association and the catalytic activity of the aggregates depend on the hydrophobicity of the amphiphilic compound, the pH of solution, and the content of DMF.     

Aminomethylated calix[4]resorcinolarenes with NH groups on the upper rim of the molecule

The reaction of calix[4]resorcinolarenes with N,N-dimethylethylenediamine and aqueous CH₂O in a molar ratio of 1 : 5 : 5 affords calixarenes containing secondary amino groups arranged on the upper rim of the molecule. When the double amount (with respect to primary amine) of formalin is used (ratio of reactants 1 : 5 : 10), cavitands with four oxazinyl fragments are synthesized.     

One-Electron Transfer in Electrochemical Oxidation of Calix[4]resorcinolarenes and Their Aminomethylated Derivatives

Calix[4]resorcinolarenes in the presence of amine and aminomethylated calix[5]resorcinolarenes in DMF undergo similar multistage electrochemical oxidation. The first stage proceeds at low potentials and involves reversible one-electron transfer with formation of stable phenoxy radicals.     

Cyclic Phosphorochloridites,Phosphorochloridates, and Phosphorochloridothioates Based on Calix[4]resorcinolarenes

Phosphorylation of calix[4]resorcinolarenes with PCl₃ yields cyclic phosphorochloridites. Cavitands containing cyclic phosphorochloridite fragments in the upper rim are readily oxidized with SO₂Cl₂ to the corresponding phosphorochloridates and take up four equivalents of sulfur on heating to form cyclic phosphorochloridothioates.     

Fluorescence Spectral Studies on the Coordination of Calix[4]‐arenes Bearing Boronic Acid Moieties with Monosaccharides

Coordination of ten calix[4]arenes bearing boronic acid moieties with five monosaccharides was studied by fluorescence spectrometry. The stability constants (K₂) of the complexes and Gibbs free energy change ( ‐ ΔG⁰) of the coordination reactions were calculated according to the modified Hilderbrand‐Benesi equation. The results obtained indicated that the coordination ability of D‐( ‐ )‐fructose with calix[4] arenes bearing boronic acid moieties was stronger than that of the other monosaccharides. And these calix[4]arene derivatives might be used for identification of L‐( ‐ )‐sorbose.     

Calix[4]arenes bearing α‐amino‐ or α‐hydroxyphosphonic acid fragments at the upper rim

By the reaction of para‐formylcalix[4]arenes 1–6 with trialkyl phosphites in the presence of dry hydrogen chloride, calix[4]arenes 7–13 possessing dialkylphosphoryl‐hydroxymethyl groupings at the upper rim were synthesized. Calix[4]arenes 18–23 functionalized with dialkylphosphoryl‐alkyl(aryl)aminomethyl groups were obtained by sodium‐promoted addition of dialkyl phosphites to C=N bonds of para‐iminocalix[4]arenes 14–17 . The consecutive treatment of α‐hydroxy‐ or α‐aminophosphonic acid dialkyl esters of calix[4]arenes 7, 10, 18 , and 21 with bromotrimethylsilane and methanol gave dihydroxyphosphoryl derivatives of calix[4]arenes 24–27 . It was shown that calix[4]arenes bearing at the macrocyclic upper rim hydroxymethylphosphonic fragments, as well as bis‐hydroxymethyl(aminomethyl)phosphonic fragments, are able to undergo self‐assembly with formation of dimeric OH···O=P hydrogen bonded associates. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:58–67, 2001     

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.     

The effect of phenoxy oxygen atoms on extremely high extraction ability and less separation efficiency of trivalent rare earth elements with tetraphosphonic acid derivative of calix[4]arene

A cone confomational p-t-octylcalix[4]arene with four methylenephosphonic acids at the lower rim as well as its monomeric analog have been synthesized as a new extraction reagent to investigate the extraction behavior of the nine trivalent rare earth elements: Y, La, Pr, Nd, Sm, Eu, Gd, Ho and Er. The new calix[4]arene exhibited significantly higher extraction capacity than not only the monomeric derivative and the commercial extraction reagent, 2-ethylhexyl hydrogen 2-ethylhexylphosphonate, but also the cone conformational calix[4]arene extractants employed in our previous work, composed of a tetrapropylenephosphonic acid with a longer spacer, a tetraphosphonic acid at the upper rim, and tetraacetic acid at the lower rim. A dependence on the pH was observed for the new extractant in the highly acidic region, and the extraction took place via a simple ion-exchange mechanism. Using slope analysis, the stoichiometries of tetrameric and monomeric extractants to rare earth metal ions were determined to be 2:1 and 3:1, respectively. Using the proposed extraction equations, extraction equilibrium constants and separation factors were estimated. The extremely high extraction ability and moderate separation efficiency were attributed to the chelating effect of the phosphonic acid and the phenoxy oxygen atom. The effect of the phenoxy oxygen atom on extraction ability and separation efficiency of calix[4]arene derivatives was found to be significant.     

Condensation of resorcinol with phosphorylated acetals, synthesis of calix[4]resorcinolarenes with phosphorus-containing alkyl fragments in the lower rim

The reaction of resorcinol with phosphorylated acetals leads to formation of calix[4]resorcinolarenes having phosphonate, phosphinate, or (phosphinothioyl)sulfanylmethyl fragments in the lower rim of the molecule.     

Supramolecular Complexes of Diglycidyl Methylphosphonate with Calix[4]resorcinolarene

Various-composition supramolecular complexes of calix[4]resorcinolarene with diglycidyl methylphosphonate were synthesized in organic solvents. The products have well-defined melting points, they are cleaved by acetylation, but remain unchanged on treatment with triethylamine.     

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.     

Phosphoric acid cation exchanger based on immobilized <Emphasis Type="Italic">cis</Emphasis>-calix[4]resorcinolarene

New phosphoric acid cation exchanger was synthesized on the basis of immobilized calix[4] resorcinolarene and its service characteristics were determined.     

Density functional study of tetraphenolate and calix[4]arene complexes of early transition metals

Density functional calculations have been performed on some calix[4]arenes complexes of early transition metals. Particular emphasis has been placed on the comparison of the main properties of these metal complexes with the analogous metal complexes based on four monodentate phenolate ligands to study the effect of the geometrical constraints imposed by the calixarenes framework on the electronic structure. The results show that the most stable geometry of titanium and molybdenum tetraphenolates is pseudotetrahedral (slightly flattened for molybdenum) and that the distortion to a square planar coordination requires, respectively, 52.0 and 21.5 kcal x mol(-1). However, a significant energy decrease is found when the four phenolate groups are bent in the same hemisphere, reproducing the calix[4]arene geometry. Such a coordination determines the energy decrease of the unoccupied metal d orbitals of sigma and pi symmetry, which leads to an increase of the electron-accepting properties of these metal fragments.