DFT-calculated structure of protonated tetraphenyl <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[4]arene tetraketone

Using DFT calculations, two of the most probable structures (A, B) of the tetraphenyl p-tert-butylcalix[4]arene tetraketone·H₃O⁺ cationic complex species were derived. The hydroxonium ion H₃O⁺, placed in the coordination cavity formed by the calix[4]arene lower-rim groups, is bound by strong hydrogen bonds to the phenoxy oxygen atoms of the calix[4]arene ligand (structures A, B) and also to one carbonyl oxygen (structure B). Correspondence: Emanuel Makrlík, Faculty of Applied Sciences, University of West Bohemia, Pilsen, Czech Republic.     

Synthesis of new <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[4]arene derivatives containing photopolymerizable 1,3-butadiyne fragments

Successive functionalization of p-tert-butylcalix[4]arene afforded a bifunctional derivative containing photopolymerizable pentacosa-10,12-diynoic acid fragments on the upper rim and propargyl groups on the lower rim of the macrocycle having a cone structure. The functionalization can be readily accomplished via copper-catalyzed azide–alkyne cycloaddition under mild conditions.     

Stability constants of some metal cation complexes of tetraphenyl <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[4]arene tetraketone in nitrobenzene saturated with water

Abstract  From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium taking place in the two-phase water–nitrobenzene system (M²⁺ = Ca²⁺, Ba²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, UO₂ ²⁺, Mn²⁺, Co²⁺, Ni²⁺; 1 = tetraphenyl p-tert-butylcalix[4]arene tetraketone; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the 1 · M²⁺ complexes in water-saturated nitrobenzene were calculated; they were found to increase in the cation order Ba²⁺, Mn²⁺ < Co²⁺ < Cu²⁺, Ni²⁺ < Zn²⁺, Cd²⁺, UO₂ ²⁺ < Ca²⁺ < Pb²⁺. Graphical abstract        

Synergistic extraction of some univalent cations into nitrobenzene by using sodium dicarbollylcobaltate and hexaethyl <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[6]arene hexaacetate

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M⁺ (aq) + NaL⁺ (nb) ⇔ ML⁺ (nb) + Na⁺ (aq) taking place in the two-phase water–nitrobenzene system (M⁺ = H₃O⁺, \textNH₄⁺ {\text{NH}}_{4}{}^{+} , Ag⁺, Tl⁺; L = hexaethyl p-tert-butylcalix[6]arene hexaacetate; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the stability constants of the ML⁺ complexes in nitrobenzene saturated with water were calculated; they were found to increase in the following order: \textAg ⁺   <  NH₄ ⁺   <  \textH ₃ \textO ⁺   <  \textNa ⁺   <  \textTl ⁺ . {\text{Ag}}^{ + } \, < \,\hbox{NH}_{4}{}^{ + } \, < \,{\text{H}}_{ 3} {\text{O}}^{ + } \, < \,{\text{Na}}^{ + } \, < \,{\text{Tl}}^{ + }.     

Synthesis of acridinyl- and fluorenylidenehydrazido derivatives of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-Butylcalix[4]arene

p-tert-Butylcalix[4]arenes substituted at the lower rim by acetic acid hydrazide residues reacted with methoxy(ethoxy)acridine and fluoren-9-one derivatives to give a series of calixarenes containing N′-fluorenylidene- and N′-acridinylacetohydrazide residues. It was found that modification of the hydrazide moiety does not affect the conformation of the initial macroring and that it can lead in some cases to unsymmetrically substituted calixarenes.     

Synthesis of Bisthiacalix[4]arene: Reaction of Piperazine with Monoacrylamide Derivative of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-Butylthiacalix[4]arene

The reaction of acryloyl chloride with the monoamine derivative of p-tert-butylthiacalix[4]arene was used to synthesize p-tert-butylthiacalix[4]arene monoacrylamide in the 1,3-alternate conformation. The effect of the nature of the amine on the result of its Michael reaction with the synthesized p-tert-butylthiacalix[4]arene monoacrylamide was studied. The latter was reacted with piperazine to obtain bisthiacalix[4]arene with the macrocyclic fragments in the 1,3-alternate conformation.     

Synthesis of Mono- and Tetraalkylamide Derivatives of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-Butylthiacalix[4]arene

Mono- and tetrasubstituted derivatives of p-tert-butylthiacalix[4]arene containing acrylate and acrylamide fragments are synthesized for the first time. The Michael aza-addition of benzylamine to the synthesized acrylamide and acrylate thiacalixarene derivatives is studied.     

Mono-<Emphasis Type="Italic">meso</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylporphyrin

Summary. Treatment of meso-tetra(tert-butyl)porphyrin with sulfuric acid/n-butanol affords a mixture of porphyrin and mono-tert-butylporphyrin in relatively high yield.     

<Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-Butylcalix[8]arene loaded silica gel for preconcentration of uranium(VI) via solid phase extraction

This paper reports silica gel loaded with p-tert-butylcalix[8]arene as a new solid phase extractor for determination of trace level of uranium. Effective extraction conditions were optimized in column methods prior to determination by spectrophotometry using arsenazo(III). The results showed that U(VI) ions can be sorbed at pH 6 in a mini-column and quantitative recovery of U(VI) (>95–98%) was achieved by stripping 0.4 mol L⁻¹ HCl. The sorption capacity of the functionalized sorbent is 0.072 mmol uranium(VI) g⁻¹ modified silica gel. The relative standard deviation and detection limit were 1.2% (n = 10) for 1 μg uranium(VI) mL⁻¹ solution and 0.038 μg L⁻¹, respectively. The method was employed to the preconcentration of U(VI) ions from spiked ground water samples.     

Polymorphism of 4-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[4]arene upon the formation and thermal destruction of its complex with acetonitrile

It is demonstrated that combined analysis of powder X-ray diagrams and differential scanning calorimetry allows us to reveal complex polymorphic transformations of 4-tert-butylcalix[4]arene upon the formation and thermal destruction of its complex with acetonitrile. The stability of 4-tert-butylcalix[4]arene polymorph containing no solvent molecules in the crystal lattice after the removal of acetonitrile is assumed.     

Chemoselective acylation of monosubstituted thiacalix[4]arene with di-<Emphasis Type="Italic">tert</Emphasis>-butyl dicarbonate

Mono-, di-, and tetrasubstituted derivatives of p-tert-butylthiacalix[4]arene containing tert-butylcarbamate, tert-butylcarbonate, and tert-butyl fragments have been prepared for the first time. Depending on the reaction conditions (reagents ratio, temperature, and the presence of a base), the interaction of the monoamine derivative of p-tert-butylthiacalix[4]arene with di-tert-butyl dicarbonate can lead to the formation of mono-, di-, and tetrasubstituted products.     

New synthetic approach to aminoethoxy derivatives of <Emphasis Type="Italic">p</Emphasis>-(<Emphasis Type="Italic">tert</Emphasis>-butyl)calix[4]arene

A new procedure has been proposed for the synthesis of mono- and bis(2-aminoethoxy)-p-(tertbutyl) calix[4]arenes from the corresponding mono- and bis[2-(1,3-dioxoisoindol-2-yl)ethoxy]-p-(tert-butyl)-calix[4]arenes.     

Tetra-<Emphasis Type="Italic">O</Emphasis>-acetyl-tetra-<Emphasis Type="Italic">O</Emphasis>-phosphoryl-tetra-<Emphasis Type="Italic">C</Emphasis>-naphthyl-resorcin[4]arene. Synthesis and receptor properties toward organic amines

Directed modification of rctt-tetra-C-naphthyl resorcin[4]arene afforded a heterofunctionalized derivative containing specifically oriented phosphoryl and acetyl groups, and its ability to form complexes with organic amines was studied. The structure and stereochemistry of the resulting complexes depended on the amine nature.     

Structure-property relationship for clathrates formed in systems with guest vapor and 1,3-disubstituted <Emphasis Type="Italic">tert</Emphasis>-butylcalix[4]arene

Structure-property relationship was studied for a series of clathrates formed in the systems that model guest-host interactions on the surface of chemical odor sensors of quartz microbalance type. The clathrates of 5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26,28-bis(2-naphthylmethoxy)calix[4]arene (1) obtained by the saturation of its powder with gaseous organic compounds (guests) with the unity thermodynamic activity at 298 K were studied. The stoichiometry and temperature at the starting and ending points of thermal dissociation were determined for all the clathrates and stable intermediates by thermal gravimetric analysis. A sorption isotherm was determined for one guest-host combination; it indicates the formation of a stable clathrate in the system and phase transition of host upon reacting with guest. Decrease in thermal stability of the clathrates of 1 with guests of greater size was observed for studied pairs of homologous guests.     

Interaction of 9-substituted anthracenes with oxidation systems <Emphasis Type="Italic">tert</Emphasis>-butylhydroperoxide-metal <Emphasis Type="Italic">tert</Emphasis>-butoxide

9-R-Anthracenes (R = Me, Ph) are effective acceptors of peroxyl and metalalkoxyl radicals in the systems tert-butylhydroperoxide-metal tert-butoxide (M = Al, V, Cr; C₆H₆, 20°C). Isolation of 9-R-9,10-dihydro-9,10-di-tert-butylperoxyanthracenes, 10-R-10-tert-butylperoxy-9-anthrones as major products reliably confirms the formation of tert-butylperoxy radicals and can be used for quantitative assessment of their content.     

Titanium tetra-<Emphasis Type="Italic">tert</Emphasis>-butoxide-<Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide oxidizing system: Physicochemical and chemical aspects

The reaction of titanium tetra-tert-butoxide with tert-butyl hydroperoxide (1: 2) (C₆H₆, 20 C) involves the steps of formation of the titanium-containing peroxide (t-BuO)₃TiOOBu-t and peroxytrioxide (t-BuO)₃TiOOOBu-t. The latter decomposes with the release of oxygen, often in the singlet form, and also homolytically with cleavage of both peroxy bonds. The corresponding alkoxy and peroxy radicals were identified by ESR using spin traps. The title system oxidizes organic substrates under mild conditions. Depending on the substrate structure, the active oxidant species can be titanium-containing peroxide, peroxytrioxide, and oxygen generated by the system.     

Determination of tyrosine using <Emphasis Type="Italic">p</Emphasis>-sulfonated calix[<Emphasis Type="Italic">n</Emphasis>]arene modified electrode

Cyclic voltammetry was used to detect p-sulfonated calix[n]arenas (SCnA) how to immobilize on gold surface. P-sulfonated calix[n]arenes not only increased the specific surface area of the modified electrode, but also improved the enrichment ability of tyrosine. This led to a significant increase in peak current, and improved the sensitivity of tyrosine determination on the p-sulfonated calix[n]arenes-modified electrode. The modified electrode showed good catalytic ability of l-tyrosine oxidation reaction. The peak current of l-tyrosine increased and the oxidation peak potential shifted negatively with cavity size of the SCnA-modified electrode, which indicated that the catalytic ability of the modified electrode to l-tyrosine oxidation reaction was also enhanced. For the tyrosine guest molecule, the order of electrochemical activity and magnitude of catalytic ability of the oxidation reaction of the three modified gold electrodes was as follows: SC4A?>?SC6A?>?SC8A. The electrode had high selectivity and stability for the determination of tyrosine, with a wide linear range, low detection limit and high sensitivity at different concentrations under different pH values. This resulted in an accurate, fast, sensitive electrochemical method for the determination of tyrosine. The sensor was used for the determination of tyrosine in human urine with satisfactory results.     

Heterospin biradicals based on new piperidineoxyl-substituted 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzoquinone

A nucleophilic addition reaction of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (OH-TEMPO) to 3,6-di-tert-butyl-o-benzoquinone was used to obtain a new sterically hindered o-benzoquinone (1) containing 2,2,6,6-tetramethylpiperidineoxyl functional group, which was characterized by IR spectroscopy, mass spectrometry, elemental analysis, and X-ray diffraction. A one-electron reduction of 1 with potassium and thallium is an efficient method for the generation of earlier unknown heterospin biradicals 5a and 5b, respectively, containing nitroxide and o-semiquinone radical centers. Analysis of the hyperfine structure of the ESR spectra of biradicals 5a and 5b in solution showed that they belong to the group of heterospin biradicals with strong (J >> a) and fast exchange interaction between the radical centers.     

Extraction of uranium and transuranium elements with <Emphasis Type="Italic">tert</Emphasis>-butylthiacalix[4]arene from carbonate-alkaline solutions

Extraction efficiency of uranium and transuranium elements (Np, Pu, Am and Cm) with tert-butylthiacalix[4]arene TCA from carbonate-alkaline solutions is studied and compared with that of europium (III). Plutonium (III, IV) extraction efficiency with TCA is found to be lower comparing with that of trivalent americium and europium. Extraction efficiency of studied radionuclides decreases as following: Am ? Eu ? Pu (III), U(VI), Np (V) > Pu (IV) at pH 12. Carbonate concentration increase in aqueous phase suppresses significantly extraction of all studied radionuclides, except americium. This condition can be used for americium individual recovery from complex radioactive carbonate-alkaline solutions.