Synthesis and crystal structures of Ag and Hg complexes of bis(N-heterocyclic carbenes) on p-tert-butylcalix[4]arene platform

A series of p-tert-butylcalix[4]arene 1,3-diimidazolium salts were successfully prepared by the alkylation of p-tert-butylcalix[4]arene with dibromoalkanes, and sequential substitution reaction with 1-alkylimidazole. Furthermore, coordination reactions of p-tert-butylcalix[4]arene 1,3-diimidazolium salts with silver oxide and mercury acetate gave novel Ag and Hg complexes of bis(N-heterocyclic carbenes) on p-tert-butylcalix[4]arene platform. The single-crystal structures of four p-tert-butylcalix[4]arene 1,3-diimidazolium salts and three metal complexes were successfully determined by X-ray diffraction. An Ag–Ag argentophilic interaction (Ag–Ag bond length is 3.1599(6) Å) is formed between the two Ag–NHC complexes and a dimetallic coordination mode exists in Hg–NHC complexes.     

Synthesis and structural characterization of a binuclear zirconium complex of tetraanionic p-tert-butylthiacalix[4]arene bridged by methanol

A zirconium complex with the p-tert-butylthiacalix[4]arene anion was synthesized and its crystal structure was determined by single-crystal X-ray analysis. The complex [Zr(μ₂-CH₃OH)(p-tert-butylthiacalix[4]arene)]₂·9H₂O (1) belongs to the orthorhombic system, space group Pnnm, with a?=?20.436(16), b?=?12.160(8), c?=?20.305(12)?Å, V?=?6774(7)?ų and Z?=?2. In Complex 1 zirconium coordinates to four phenolic anions of the deprotonated p-tert-butylthiacalix[4]arene and is bridged by two methanol molecules; the p-tert-butylthiacalix[4]arene adopts a cone conformation.     

Calix[8]arene anions: solid state structure of an inclusion compound with a tetrabutylammonium cation

Octakis(dimethylsiloxy)-octa-p-tert-butylcalix[8]arene was prepared from the parent p-tert-butylcalix[8]arene and 1,1,3,3-tetramethyldisilazane. Desilylation of the siloxy-calix[8]arene with tetrabutylammonium fluoride hydrate under different conditions afforded di- and tetraanionic derivatives. Determination of the solid state structure of the dianion revealed the formation of an inclusion compound with one tetrabutylammonium cation inside the macrocyclic cavity.     

Synthesis and Conformational Characteristics of Benzyl-Substituted p-tert-Butylcalixarenes

(m-Methylbenzyloxy)-, bis(p-methylbenzyloxy)-, and bis(m-methylbenzyloxy)-p-tert-butylcalix[4]arenes were prepared by reactions of p-tert-butylcalix[4]arene with p- and m-methylbenzyl bromides in the presence of alkali metal carbonates. Silylation of these derivatives gave (m-methylbenzyloxy)bis(trimethylsilyloxy)-, bis(m-methylbenzyloxy)bis(trimethylsilyloxy)-, and bis(p-methylbenzyloxy)bis(trimethylsilyloxy)-p-tert-butylcalix[4]arenes. With phase-transfer catalysis, bis(p-methylbenzyloxy)bis(2-propenyloxy)- and bis(m-methylbenzyloxy)bis(2-propenyloxy)-p-tert-butylcalix[4]arenes were obtained. Alkylation of the monosubstituted calixarene yields the corresponding trisubstituted derivative.     

p-tert-Butylcalix[5]arene: a New Synthetic Pathway and Crystal Structure of the N,N-Dimethylformamide Complex

The formation of p-tert-butylcalix[5]arene by the opening ofp-tert-butyldihomooxacalix [4]arene and the addition of a monomer has beenstudied. Various facets, including the effects of bases and the nature ofthe monomer added to the p-tert-butyldihomooxacalix[4]arene, have beeninvestigated. p-tert-Butylcalix[5]arene can be prepared in yields up to30%. The structure of its 1 : 2 complex with DMF has been determinedby X-ray crystallography. Crystals are triclinic, space group P¯1, a =1428.2(3) pm, b = 1837.3(3) pm, c = 1276.1(2) pm, = 108.98(1)°, = 105.02(2)°, = 95.21(1)°, Z = 2, D _c = 1.059 kg m^-3,final R value = 0.087. The macrocycle adopts a cone conformation, one guestenclosed inside the cavity, the other one outside.     

Synthesis and photochemical reaction of cyclic oligomers: Synthesis and photopolymerization of novel C‐methylcalix[4]resorcinarene and p‐alkylcalix[n]arene derivatives containing spiro ortho ether groups

New photoreactive calixarene derivatives containing spiro ortho ester groups (calixarenes 3a–3c ) were synthesized by the reaction of 2‐bromomethyl‐1,4,6‐trioxaspiro[4.4]nonane with 2,8,14,20‐tetramethyl‐4,6,10,12,16,18,22,24‐octakis(carboxymethoxy)calix[4]resorcinarene, 5,11,17,23,29,35‐hexamethyl‐37,38,39,40,41,42‐hexakis(carboxymethoxy)calix[6]arene, and 5,11,17,23,29,35,41,47‐octa‐tert‐butyl‐49,50,51,52, 53,54,55,56‐octakis‐(carboxymethoxy)calix[8]arene, which were prepared by the reaction of C‐methylcalix[4]resorcinarene, p‐methylcalix[6]arene, and p‐tert‐butylcalix[8]arene, respectively. The thermal stability of the obtained calixarene derivatives containing spiro ortho ester groups was examined with thermogravimetric analysis, and it was found that these calixarene derivatives had good thermal stability. The photoinitiated cationic polymerization of spiro ortho ester groups in calixarene derivatives 3a–3c was examined with certain photoacid generators in the film state. Interestingly enough, the reaction of calixarene derivatives did not proceed with only photoirradiation; however, the reaction proceeded smoothly when the photoirradiation was followed by heating. Furthermore, calixarene 3a , composed of a C‐methylcalix[4]resorcinarene structure, showed the highest photochemical reactivity in this reaction system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1293–1302, 2002     

Conformational Effects of Regioisomeric Substitution on the Catalytic Activity of Copper/Calix[8]arene C−S Coupling

Functionalization of the phenolic rim of p-tert-butylcalix[8]arene with phenanthroline to create a cavity leads to formation of two regioisomers. Substitution of positions 1 and 5 produces the known C_2v-symmetric regioisomer 1,5-(2,9-dimethyl-1,10-phenanthroyl)-p-tert-butylcalix[8]arene ( L^1,5 ), while substitution of positions 1 and 4 produces the C_s-symmetric regioisomer 1,4-(2,9-dimethyl-1,10-phenanthroyl)-p-tert-butylcalix[8]arene ( L^1,4 ) described herein. [ Cu(L^1,4)I ] was synthesized from L^1,4 and CuI in good yield and characterized spectroscopically. To evaluate the effect of its cavity on catalysis, Ullmann-type C−S coupling was chosen as proof-of-concept. Selected aryl halides were used, and the results compared with the previously reported Cu(I)/ L^1,5 system. Only highly activated aryl halides generate the C−S coupling product in moderate yields with the Cu(I)/ L^1,4 system. To shed light on these observations, detailed computational investigations were carried out, revealing the influence of the calix[8]arene macrocyclic morphology on the accessible conformations. The L^1,4 regioisomer undergoes a deformation that does not occur with L^1,5 , resulting in an exposed catalytic center, presumably the cause of the low activity of the former system. The 1,4-connectivity was confirmed in the solid-state structure of the byproduct [ Cu(L^1,4 − H) (CH₃CN)₂] that features Cu(I) coordinated inside a cleft defined by the macrocyclic framework.     

(1+1) or (2+2) Coupling for bis(tosyloxyethoxy)benzenes with calix[4]arene and thiacalix[4]arene

As bifunctional reagents, bis(tosyloxyethoxy)benzenes can react with p-tert-butylcalix[4]arene or p-tert-butylthiacalix[4]arene to afford intramolecularly bridged (1+1) or intermolecularly bridged (2+2) products. It was found that the bridging pattern strongly depended on the structure of bis(tosyloxyethoxy)benzene and the kind of calixarene. For the ortho-isomer of bis(tosyloxyethoxy)benzene, intramolecularly bridged calix[4]arene and thiacalix[4]arene were the main products. For the para-isomer, the bridging reaction was in a (2+2) fashion. As for the meta-isomer, double thiacalix[4]arene and intramolecularly bridged calix[4]crown were synthesized.     

Extraction and DFT study on the complexation of H3O+ ion with tetrakis(2-ethoxyethoxy)-tetra-p-tert-butylcalix[4]arene

Abstract  

Extraction experiments in the two-phase water/nitrobenzene system and γ-activity measurements were used to determine the stability constant of protonated tetrakis(2-ethoxyethoxy)-tetra-p-tert-butylcalix[4]arene in nitrobenzene saturated with water. Density functional theory (DFT) calculations were applied to derive the most probable structure of the tetrakis(2-ethoxyethoxy)-tetra-p-tert-butylcalix[4]arene·H₃O⁺ complex species.     

FT-IR and FT-Raman study of hydrogen bonding in p-alkylcalix[8]arenes

The FTIR and FT Raman spectra of p-alkylcalix[8]arenes (alkyl = tert-butyl, isononyl) were recorded. Analysis of IR spectra showed that the cyclic cooperative intramolecular hydrogen bond is realized in calix[8]arene. It was found that the strength of the cyclic cooperative intramolecular hydrogen bond in the series of alkyl derivatives of calix[8]arenes depends very little on the replacement of the p-tert-butyl groups by the more bulky isononyl group. From our data follows that the orientation of aromatic fragments in calixarene molecules depends on the type of alkyl substituent.An analysis of the changes in the IR spectra with heating and dissolution shows that the conformation of the “pleated-loop” is retained in p-tert-butylcalix[8]arene. It turned out that the intramolecular hydrogen bond is a “probe” of the conformation of calixarene molecules and IR spectroscopy is a unique method that allows one to follow the slightest nuances of changes in the H-bound system of these supermolecules.     

Novel PEGylated calix[5]arenes as carriers for Rose Bengal

Amphiphilic PEGylated calix[5]arenes 1 and 2 were obtained in one step from the parent p-tert-butylcalix[5]arene and p-methylcalix[5]arene. Very low critical micellar concentrations (0.5 and 4.5 μM for 1 and 2 respectively) were determined by the Rose Bengal micellization method. Aggregation features were studied by means of ¹H and DOSY NMR as well as by AFM. Release of Rose Bengal from the micellar environment was accomplished by increasing the temperature.     

One‐Step Synthesis of Singly Bridged Biscalix[4]arenes with Oligooxyethyleneethyl Spacers

Here we describe the one‐step synthesis of a series of singly bridged biscalix[4]arene derivatives connected by ethylene or oligooxyethyleneethyl chain through the reaction of calix[4]arene with corresponding ethylene or oligoethylene glycol ditosylates in the presence of sodium hydride in toluene. A 1,2‐bis(ethylene) doubly bridged bis‐p‐tert‐butylcalix[4]arene was also obtained as a by‐product.     

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.     

新型大环分子受体: 四同二氧杂杯[6]芳烃衍生物的合成及其络合性质

Several tetrahomodioxacalix[6]arene hexaesters, hexaacid and hexaamide derivatives were synthesized from tetrahomodioxacalix[6]arene by etherification with ethyl bromoacetate. It was found that p-tert-butyltetrahomodioxacalix[6]arene hexaethylester exhibited high selectivity towards lithium ion. p-tert-Butyltetrahomodioxacalix[6]arene hexaamides showed high ion-binding ability towards transition metal ions.     

Hard–Soft Receptors, Tetrakis[(N,N-diethylaminocarbonyl)methoxy] thiacalix[4]arene Derivatives with cone and 1,3-alternate Conformation

Direct O-alkylation of p-tert-butyltetrathiacalix[4]arene with N,N-diethylchloroacetamide afforded two conformational isomers (1,3-alternate and cone) of tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene and 1,3-disubstituted bis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene, depending on the base used. The complaxation behaviors of the tetrakis isomers were assessed by ¹H NMR titration experiments. Evidence of 1:2 (homo- and hetero-dinuclear) complexes formation of 1,3-alternate-tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene with alkali (K⁺ and Na⁺) or transition (Ag⁺) metal ions was obtained. Interestingly, it was found that the cone-tetrakis[(N,N-diethylaminocarbonyl)methoxy]thiacalix[4]arene required a prior Ag⁺ complexation to form 1:2 heterodinuclear complex. Received in final form: 26 January 2005     

Solvent extraction of europium trifluoromethanesulfonate into nitrobenzene in the presence of p-tert-butylcalix[6]arene and p-tert-butylcalix[8]arene

From extraction experiments and ??-activity measurements, the extraction constants corresponding to the general equilibrium Eu³⁺(aq) + 3A^?(aq) + L(nb) ? EuL³⁺(nb) + 3A^?(nb) taking part in the two-phase water?Cnitrobenzene system (A^? = CF₃SO₃ ^?; L = p-tert-butylcalix[6]arene, p-tert-butylcalix[8]arene; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Further, the stability constants of the EuL³⁺ complexes in nitrobenzene saturated with water were calculated for a temperature of 25 °C as log ?? _nb(EuL³⁺) = 6.4 ± 0.1 (L = p-tert-butylcalix[6]arene) and log ?? _nb(EuL³⁺) = 11.3 ± 0.1 (L = p-tert-butylcalix[8]arene).     

Extraction of Cesium-137 and Americium-241 by Calix[n]arenes from Carbonate-Alkaline Media

Trends of cesium-137 and americium-241 extraction from carbonate–alkaline media with p-tert-butylcalix[n]arenes with macrocycles of different size (n = 4, 6, 8), including monofunctional derivatives with lipophilic substituents for increasing their solubility in organic media, were studied. It was demonstrated that O-n-octyl ethers of p-tert-butylcalix[6]arene appeared to be the most efficient extractants for Cs(I) cations, while it was p-tert-butylthiacalix[4]arene for and americium(III) cations.     

Structures and properties of solvated and unsolvated isopropyl functionalised calix[4]arenes

The tetra-isopropyl ethers of calix[4]arene and p-t-butylcalix[4]arene have been isolated in the cone conformation, and structurally characterised as chloroform solvates. Thermogravimetric analysis demonstrated that the parent isopropylcalix[4]arene solvate is significantly more stable than the p-t-butylcalix[4]arene analogue, retaining the solvent up to a temperature of 125°C. It was found that the calix[4]arene ether sublimes at atmospheric pressure, and solvent-free crystals appropriate for structure determination were produced at reduced pressure. The p-t-butylcalix[4]arene ether was also isolated without solvent in the lattice, but in this case the calixarene was crystallised from acetone, as sublimation did not produce crystals of sufficient quality.     

Membrane extraction of organic compounds. 3. A new receptor fragment for carboxylate groups based of the calix[4]arene platform

A new type of macrocyclic receptor able to bind organic substrates containing carboxy and carboxylate groups was designed on the basis of 1,3-disubstituted calix[4]arenes. A series of disubstitited calix[4]arenes were prepared in 60—80% yields by selective 1,3-alkylation of p-tert-butylcalix[4]arene. The compounds obtained were tested as carriers for dl-tartaric, glycolic, dl-amygdalic, and dl-glutamic acids through liquid membranes immobilized on a polymer matrix. The structural factors favorable for the transport of these hydrophilic substrates through lipophilic membranes were established.     

Synthesis and Complexation Properties of a New Class of Receptors based on a cone-configurated tetra-p-(tert-butyl)calix[4]arene and bipyridyl subunits

0The bipyridyl-armed tetra-p-(tert-butyl)calix[4]arenes 1 – 5 were synthesized from tetra-p-(tert-butyl)-calix[4]arene A and 6-(bromomethyl)-6′-methyl-2,2′-bipyridine ( B ) by direct base-strength-driven regioselective O-alkylation or by stepwise procedures. Preliminary complexation studies of the ligands 1 – 3 with Cu^I affording the complexes 6 – 8 are described.