Synthesis and complexation properties of carbonyl-containing thiacalix[4]arenes

Stereoisomers of thiacalix[4]arenes unsubstituted at the upper rim and containing four carbonyl fragments have been synthesized for the first time. Their structures were studied by 1D and 2D NMR spectroscopy, IR spectroscopy, and mass spectrometry. The complexation properties of the macro-cycles toward alkaline metal cations were estimated by the picrate extraction method. The absence of the preorganization effect in the case of the thiacalixarenes unsubstituted at the upper rim is the main reason for the sharp decrease in their extraction ability. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1448–1456, July, 2008.     

Synthesis and complexation properties towards metal ions of new tri-substituted thiacalix[4]arenes

New thiacalix[4]arenes appended with three amide functions have been prepared. Their conformations have been solved thanks to ¹H NMR 2D correlation spectroscopy (COSY) and nuclear overhauser and exchange spectroscopy (NOESY). The complexation ability of these ligands towards various metal ions (Cd^2 + , Pb^2 + , Pd^2 + , Ni^2 + , Hg^2 + , Hg⁺, Ag⁺, Zn^2 +  and Cu^2 + ) has been investigated by the UV–vis absorption and the stoichiometry of the metal–ligand complexes was determined.     

The use of a lyotropic liquid-crystalline medium and residual dipolar coupling constants for determination of the spatial structure of thiacalix[4]arenes in solutions

The possibility of using an approach for the elucidation of the spatial structure of functionalized thiacalix[4]arenes based on the determination the residual dipolar coupling constants between the ¹H and ¹³C nuclei separated by one chemical bond (¹ D _CH) in lyotropic liquid-crystalline media (poly--benzyl-L-glutamate and CDCl₃) is demonstrated for the first time. This approach was used to distinguish between the cone and 1,3-alternate conformations of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(2-oxopropyloxy)-2,8,14,20-tetrathiacalix[4]arene. The results were confirmed by the data from 2D NMR (¹H—¹H) NOESY experiments for these compounds in an isotropic solvent (CDCl₃).     

Synthesis of （p-Formylphenyl）azo Calix[4]arenes

Five novel azo calix[4]arenes were reported. The p-aminobenzaldehyde was diazotized with sodium nitrite in aqueous hydrochloride solution. Mono-, bis-, tris- and tetrakis(p-formylphenyl)azo calix[4]arenes (including proximal and distal isomers) were obtained respectively by diazo-coupling in different molar ratio to calix[4]arene(1) under pH=7.5--8.5 at 0-5℃. All (p-formylphenyl)azo calix[4]arenes were characterized by ^1H NMR, ^13C NMR, IR, MS (ESIMS) spectroscopies and elemental analysis.     

Cu and CN-selective fluorogenic sensors based on pyrene-appended thiacalix[4]arenes

Two new fluorescent sensors 1 and 2 based on thiacalix[4]arenes bearing pyrene moieties have been synthesized in cone conformation. The binding abilities of these sensors towards different cations such as lithium, sodium, potassium, nickel, cadmium, copper, zinc, lead, silver, mercury and anions like fluoride, chloride, bromide, iodide, cyanide, acetate, hydrogen sulfate and nitrate have been examined by UV-vis and fluorescence spectroscopies. These receptors show pronounced selectivity for copper and cyanide ions. In CH₂Cl₂/CH₃CN (1:1), the presence of Cu(II) ion induces the formation of 1:1 (H/G) complex with receptor 1 and 1:2 (H/G) complex with receptor 2. The cyanide ions form a 1:1 (H/G) complex with both receptors.     

Synthesis and binding studies of novel bisthiacalix[4]arenes with diimime linkages

A series of novel bisthiacalix[4]arenes with diimine linkages of different aromatic or heteroaromatic dialdehydes have been synthesized. The structure of one of the bisthiacalixarene has been analyzed by X-ray crystallography. These molecules quantitatively extract silver ion from aqueous into organic phase under neutral conditions.     

Phase behaviour,structural properties and intermolecular interactions of systems based on substituted thiacalix[4]arene and nonionic surfactants

Supramolecular organised materials were prepared from nonionic surfactants and the following macrocyclic ionic liquids: n-tert-butylthiacalix[4]arenes containing quaternary ammonium fragments with amino acid substituents. Tetraethylene glycol monododecyl ether and decadiethylene glycol monododecyl ether were used as nonionic surfactants. They form lamellar and hexagonal mesophases in aqueous media, respectively. Liquid crystal and structural properties of these systems were studied. Intermolecular interactions of system components leading to formation of lyomesophases were estimated. Molecular structure of thiacalixarene contributes to the formation of a hydrogen bonding with surfactants. This process, in turn, initiates formation of a denser packed hexagonal structure.     

X-ray guided H NMR analysis of pinched cone calix[4]arenes

The analysis of structural parameters of azobenzene- and stilbene-bridged calix[4]arene obtained from AM1 calculation are in good agreement with those obtained from X-ray crystallography. The bridge longer than 9.0 Å such as p,p-trans-azobenzene and p,p-trans-stilbene cannot be constructed over the narrow rim of calix[4]arene through two ethylene oxide linkers. The m,m-stilbene bridge is the most promising photo switch because its shorter cis stereoisomer (5.85 Å) allows calix[4]arene to assume the perfect cone conformation, whilst its longer trans stereoisomer (8.00 Å) forces calix[4]arene to adapt a pinched cone conformation. The pinched cone conformation has longer distances between the neighbouring phenoxyl groups causing the weaker intramolecular hydrogen bonding and the upfield shifts of the phenolic proton signals to below 7.00 ppm. This upfield shift is useful for quick identification of pinched cone conformation of new calix[4]arene compounds.     

The conformation and dynamic behaviour of tetrathiacalix[4]arenes functionalized by hydrazide and hydrazone groups

The ¹H, ¹³C and ¹⁵N NMR data, conformation and dynamic behaviour of the new tetrathiacalix[4]arenes functionalized by hydrazide and hydrazone groups are reported and compared with the result of earlier investigations of 4-tert-butylphenoxyacetylhydrazones. The unusual fact of formation of N,N′-diacetylhydrazine bridge and factors leading to its formation in the cone conformer of calixarene has been discussed. The barriers of rotation of hydrazone fragments of tetrathiacalix[4]arenes were determined by NMR-measurements at various temperatures. The structure of 1,3-alternate conformer of 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis[hydrazinocarbonylmethyl]-2,8,14,20-tetrathiacalix[4]arene in solution is compared with crystal structure obtained by the X-ray analysis.     

Synthesis of New Calix[4]arenes Functionalizated by Acetylhydrazide Groups

A series of new calix[4]phenols, calix[4]resorcinols and calix[4]pyrogallols with acetylhydrazide substitutes has been␣synthesized with high yields by hydrazinolysis of ester group containing calix[4]arenes. The synthesized calix[4]phenols adopt the cone conformation while the calix[4]resorcinol and calix[4]pyrogallol derivatives prefer the boat conformation. The amide fragment of the hydrazide groups predominantly exists in the trans-conformation. The binding ability of synthesized calix[4]arenes toward transition and alkali metals by solvent extraction has been investigated.     

Cyanocalix[4]arenes: synthesis,crystal structures and reactivity studies

Abstract

Herein, we describe an improved method to synthesise mono-, di- and tetra-cyanocalix[4]arene and report their crystal structure determinations. We also report our attempts to further functionalise the cyanocalix[4]arenes into dithiadiazolyl-calix[4]arenes, and propose a hypothesis as to why the cyano group on a calix[4]arene is an extremely challenging group to modify.     

Electrochemical Properties of Multilayered Coatings Implementing Thiacalix[4]arenes with Oligolactic Fragments and DNA

Layer‐by‐layer assembling of polyelectrolyte complexes on glassy carbon electrode utilizing derivatives of p‐tert‐butylthiacalix[4]arene modified with oligolactic acid in cone, partial cone and 1,3‐alternate configurations has been performed and characterized by atomic force microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. Structure, surface morphology and permeability of the coatings depended on the number and nature of individual layers. Configuration of macrocyclic core influenced the charge distribution and flexibility of polyelectrolytes and the electrochemical properties of the coatings. Partial substitution of oligolactic derivatives with the DNA molecules allowed distinguishing native, thermally and oxidatively damaged DNA by ferricyanide ion signals. The relationships between the coating structure and the content can be further used for development of electrochemical sensors devoted to the detection of specific DNA interactions.     

新型偶氮杯[4]芳烃的合成与构象研究

使用相应的w-硫醚羧酸酰氯与杯[4]芳烃或者偶氮杯[4]芳烃酰化合成了一类新型的杯[4]芳烃衍生物。分离得到六个新化合物4a-4c和5a-5c，并使用MALDI, EA, ¹H和¹³C NMR进行了表征。NMR图谱表明偶氮杯[4]芳烃衍生物 5a-5c均为1,3-转换构型，而4a-4c则均为锥式构型。对偶氮杯[4]芳烃衍生物5a-5c的红外和紫外性质也进行了研究。     

Design, synthesis, characterization, and preliminary complexation studies of chromogenic vanadophiles: 1,3-alternate thiacalix[4]arene tetrahydroxamic acids

New chromogenic supramolecular vanadophiles were designed and synthesized by incorporating hydroxamic acid chains on a 1,3-alternate thiacalix[4]arene scaffold and were found to show high affinity toward vanadate ions. The article describes a comprehensive design process to devise a tailor-made co-ordination cavity for vanadate ions by pre-organization of hydroxamic acid chelating moieties on a 1,3-alternate thiacalix[4]arene scaffold. These receptors simultaneously co-ordinate two vanadate ions giving a highly ‘staggered’ geometry with almost D_2d symmetry. Proposed structures and complexation behavior of the receptors were explained by critical examination of FTIR, UV-visible, mass, and ¹H NMR data.     

Synthesis, NMR, X-ray structural analyses and complexation studies of new Ag selective calix[4]arene based dipodal hosts—a co-complexation of neutral and charged species

New podands based on the p-tert-butylcalix[4]arene unit with substitution at the lower rim incorporating imine units, have been synthesized in high yield by simple condensation method. These podands have been shown to extract and transport Ag⁺ selectively over alkali, alkaline earth metal cations, Zn²⁺, Pb²⁺ and Hg²⁺ ions, from neutral aqueous phase to organic phase. In all the ligands the calix unit has been found to be present in a cone conformation except for the one having pyridine as end group, at the ortho position. It has been isolated in two conformations; cone and 1,2-alternate. To the best of our knowledge, this may be the first 1,3-lower rim substituted calix[4]arene to exist in a 1,2-alternate conformation and is among a few known compounds with this conformation in the general class of calix[4]arenes. A complex of this ligand, which happens to be the highest extractant of Ag⁺ has been isolated and characterized using mass, ¹H and ¹³C NMR spectroscopy's and elemental analysis. The spectroscopic evidence and molecular modelling studies performed on the complex suggest a participation of the imine and pyridine nitrogens and two of the ether oxygens in coordination to the metal ion. The X-ray crystal structures of three of the ligands establish the formation of inclusion complexes with polar acetonitrile solvent molecules. The ¹H and ¹³C NMR spectra of all the compounds, taken in CDCl₃, show the presence of acetonitrile molecules in the cavity of the calix[4]arene, indicating inclusion of the neutral guest molecules in the solution phase as well. For one of the podands X-ray crystal structure has shown a formation of clatharate complex of chloroform with the ligand which has rarely been found in the case of calix[4]arenes.     

1H and 7Li NMR Study on the Complex Formation of Lithium Cations with Pyridinium Derivatives of Calix[4]arenes

Complexation of lithium ions by three chromoionophoric calix[4]arenes has been studied by ¹H and ⁷Li NMR spectroscopy. The signalling unit of the chromoionophores is the N-methylpyridinium(methyleneimino) group in conjugation with a phenolic group of the calixarene ring while the coordination spheres contain esteric (ethoxycarbonylmethoxy) or etheric (ethoxy, propoxy) units. ¹H NMR and NOESY measurements suggest the dominance of cone conformations of the calixarene rings with slight, solvent-dependent distortions. Complexation occurs only in the presence of a weak base. The interaction with lithium ions causes a broadening of both the ¹H and ⁷Li NMR signals. Analysis of the chemical shifts in the three complexes indicates a different coordination environment for the lithium with the calixarene containing esteric groups from those having etheric groups. This explains the differences in the stabilities of the lithium complexes of the two types of calixarenes.     

Synthesis and properties of mono-O-[(N-(aminoalkyl)aminocarbonyl)-methoxy]thiacalix[4]arenes and novel mono-O-bridged bisthiacalix[4]arene

A simple method for thiacalix[4]arene O-monoamide preparation with high yields using 5,11,17,23-tetra-tert-butyl-28-(ethoxycarbonyl)methoxy-2,8,14,20-tetrathiacalix[4]arene reaction with diaminoalkanes is reported. The solid state cyclization reaction of the acylethylenediamines function of 5,11,17,23-tetra-tert-butyl-28-O-[(N-(2-aminoethyl)aminocarbonyl)-methoxy]thiacalix[4]arene leading to the formation of the 5,11,17,23-tetra-tert-butyl-28-[2-methoxy-imdazoline]thiacalix[4]arene compound is described for the first time for the calixarene macrocycle family. Finally, preliminary results show that O-mono-amide-thiacalixarene derivatives are promising candidates for the production of self-assembled materials and efficient precursors for the synthesis of bisthiacalix[4] arenes.     

Regioselective Synthesis and Inclusion Properties of distal-Bis[(2-pyridylmethyl) oxy]tetrathiacalix[4]arenes

Regioselective synthesis of bis[(2-pyridylmethyl)oxy]tetrathiacalix[4]arenes was accomplished by a protection–deprotection method using benzyl groups as a protecting group. The conformational studies of distal-bis[(2-pyridylmethyl)oxy]thiacalix[4]arenes in solution and solid state are described. The two-phase solvent extraction data indicated that bis[(2-pyridylmethyl)oxy]tetrathiacalix[4]arenes show strong Ag⁺ (E%, 97%) affinity. In contrast, no significant E% is observed for K⁺. A good Job plots proves 1:1 coordination of 1,3-alternate -3 with Ag⁺ cation. ¹H-NMR Titration of 1,3-alternate- 3 with AgSO₃CF₃ also clearly demonstrates that a 1:1 complex is formed with retention of the original symmetry. The conformational changes of pyridine moiety from the original outward orientation of the ring nitrogen to the inside orientation toward the thiacalixarene cavity were observed in the process of Ag⁺ complexation. The down-field shifts of the benzene protons of the benzyl group were also observed and attributed to the conformational deviation from the original face to face overlapping.     

Phosphite ligands derived from distally and proximally substituted dipropyloxy calix[4]arenes and their palladium complexes: Solution dynamics, solid-state structures and catalysis

Two bisphosphite ligands, 25,27-bis-(2,2′-biphenyldioxyphosphinoxy)-26,28-dipropyloxy-p-tert-butyl calix[4]arene (3) and 25,26-bis-(2,2′-biphenyldioxyphosphinoxy)-27,28-dipropyloxy-p-tert-butyl calix[4]arene (4) and two monophosphite ligands, 25-hydroxy-27-(2,2′-biphenyldioxyphosphinoxy)-26,28-dipropyloxy-p-tert-butyl calix[4]arene (5) and 25-hydroxy-26-(2,2′-biphenyldioxyphosphinoxy)-27,28-dipropyloxy- p-tert-butyl calix[4]arene (6) have been synthesized. Treatment of (allyl) palladium precursors [(η³-1,3-R,R′-C₃H₄)Pd(Cl)]₂ with ligand 3 in the presence of NH₄PF₆ gives a series of cationic allyl palladium complexes (3a-3d). Neutral allyl complexes (3e-3g) are obtained by the treatment of the allyl palladium precursors with ligand 3 in the absence of NH₄PF₆. The cationic allyl complexes [(η³-C₃H₅)Pd(4)]PF₆ (4a) and [(η³-Ph₂C₃H₃)Pd(4)]PF₆ (4b) have been synthesized from the proximally (1,2-) substituted bisphosphite ligand 4. Treatment of ligand 4 with [Pd(COD)Cl₂] gives the palladium dichloride complex, [PdCl₂(4)] (4c). The solid-state structures of [{(η³-1-CH₃-C₃H₄)Pd(Cl)}₂(3)] (3f) and [PdCl₂(4)] (4c) have been determined by X-ray crystallography; the calixarene framework in 3f adopts the pinched cone conformation whereas in 4c, the conformation is in between that of cone and pinched cone. Solution dynamics of 3f has been studied in detail with the help of two-dimensional NMR spectroscopy.The solid-state structures of the monophosphite ligands 5 and 6 have also been determined; the calix[4]arene framework in both molecules adopts the cone conformation. Reaction of the monophosphite ligands (5, 6) with (allyl) palladium precursors, in the absence of NH₄PF₆, yield a series of neutral allyl palladium complexes (5a-5c; 6a-6d). Allyl palladium complexes of proximally substituted ligand 6 showed two diastereomers in solution owing to the inherently chiral calix[4]arene framework. Ligands 3, 6 and the allyl palladium complex 3f have been tested for catalytic activity in allylic alkylation reactions.     

Synthesis,extraction and chromogenic properties of Amidoazocalix[4]arenes and their telomer derivatives

The synthesis, extraction and chromogenic properties of calix[4]arenes, carrying phenylazo and amido groups on their upper and lower rims, respectively, are described. Novel azocalix[4]arene amides (1a–d, 2a–d, 3a–d) and some of their telomers (T1a–T1d) have been synthesised and characterised by spectroscopic methods as well as elemental analysis techniques. Compounds 1c and 2b were additionally characterised by two-dimensional nuclear magnetic resonance spectroscopic methods. Some of the compounds were examined by absorption spectra using different solvents. The colour changes of the resulting solutions can be observed by the ‘naked eye’. Metal extraction abilities of compounds have been investigated comparatively. Telomer structures of azocalix[n]arenes exhibited higher extraction rates compared to those of their monomers. Products obtained under this study, especially telomers, can be used in the field of ion-selective electrodes.