Binding properties and self-assembly of C2v-symmetrical resorcin[4]arene tetrabenzoates

In the crystalline state two molecules of resorcin[4]arene tetrabenzoates and four chloride anions form molecular wraps containing two Et₃NH⁺ cations. The structure and composition of the wraps depend on the length of the alkyl chains at the narrow rim of the macrocycle. Resorcin[4]arene tetrabenzoates interact with ammonium salts in CDCl₃.     

Synthesis of a deep-cavity thiacalix[4]arene

A novel thiacalix[4]arene derivative bearing four phenyl groups on the upper rim was prepared by the direct condensation of biphenyl-4-ol with elemental sulphur. As revealed by X-ray diffraction analysis, this compound adopts the cone conformation in the solid state, thus creating a cavity with an extended π-aromatic system potentially applicable for solid-state inclusion of suitable molecules. Subsequent alkylation (RI/K₂CO₃/acetone, R=Me, Et, Pr) yielded tetraalkylated derivatives, which were studied for their conformational preferences using ¹H NMR spectroscopy. While the Me or Et derivatives are conformationally mobile and exhibit thermodynamic equilibria of several conformers in solution (CDCl₃ or CD₂Cl₂), the corresponding propoxy derivative is infinitely stable at room temperature.     

Interactions of a water-soluble calix[4]arene with spermine: solution and solid-state characterisation

Abstract

The octaanionic 5,11,17,23-tetrasulfonato-25,26,27,28-tetrakis(hydroxycarbonylmethoxy)-calix[4]arene (cone conformation) (C₄TsTc) was investigated as a sensor for the biogenic tetracationic polyamine, spermine _.(H₄Spe⁴⁺). Fluorescence titration experiments of the water-soluble calixarene with spermine showed the formation of the 2:1 and 1:1 calixarene:spermine complexes in solution. The single crystal X-ray diffraction analysis of [(NaC₄TsTc)₄·(H₄Spe)₇] confirmed the formation of 2:1 and 1:1 calixarene:spermine species and showed that the water-soluble calixarene binds the spermine either by partially hosting it in the inner cavity or through the carboxylate groups on the lower rim. In order to investigate the effect of multivalent systems, supramolecular assemblies of octaanionic calixarene molecules templated by meso-tetrakis(4-N-methylpyridyl)porphyrin (H₂T₄) in different stoichiometric porphyrin:calixarene ratios (1:4 and 3:4) were also tested for spermine binding in solution. Fluorescence titration experiments with the 1:4 and 3:4 H₂T₄:C₄TsTc supramolecular complexes showed that the multivalent assemblies are more sensitive to the presence of spermine than the calixarene alone.     

Regioselective Bridging Calix[6]arenes: Synthesis and X-ray Structure of Trisbridged Calix[6]arene

The preparation and characterization of gold nanoparticles (～6 nm in diameter) modified with mono-6-thio-β-cyclodextrin (II) is described. The resulting monolayer-protected gold nanoparticles are water-soluble and more stable. The concentration of II plays a crucial role for the distribution of the modified nanoparticles. When the ratio of concentration of II to HAuCl₄,[II]/[HAuCl₄] ≥ 0.93, a stable gold nanoparticle with uniform distribution and diameter of 6.0 ± 0.9 nm will be obtained. The recognition of modified gold nanoparticles to organic guest molecule is researched. The modified gold nanoparticles can make the electrochemical reduction current of nitrobenzene decrease and can be self-assembled in three-dimensional to form spherical clusters with ligand of methylene green.     

Synthesis and spectroscopic studies of isosteviol-calix[4]arene and -calix[6]arene conjugates

Novel calix[4]arene derivatives functionalized with two or four isosteviol units at the upper rim and a new calix[6]arene having six isosteviol moieties at the lower rim have been synthesized. The structures of these compounds have been confirmed by NMR and mass spectrometry data. All ¹H and ¹³C NMR chemical shifts of isosteviol were fully assigned by extensive NMR spectroscopic methods, and used to clarify the structures and conformations of isosteviol-calixarene conjugates.     

New lanthanide-based complexes constructed from cucurbit[6]uril: Synthesis,structures and properties

Three lanthanide-based complexes, {Gd₂(H₂O)₁₀(CB[6])₂}·CB[6]·6Cl·12H₂O (1), {[Gd₂(H₂O)₈CB[6]₂]·(CuCl₄)·4Cl·46H₂O}_n (2), and {Dy₂(NO₃)₂(H₂O)₁₀(CB[6])}·4NO₃·14H₂O (3) (CB[6] = cucurbit[6]uril), were prepared with cucurbit[6]uril (CB[6]). These complexes were characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR spectroscopy, UV–Vis spectroscopy, thermogravimetric analysis and magnetization measurements. Crystallographic results showed that 1 and 3 are dinuclear and crystallize in the triclinic space group Pī, whereas 2 is a 1-D zigzag supramolecular chain that crystallizes in the monoclinic system in C2/c. The results indicated that temperature has a big effect on the supramolecular assemblies and a different structure inducer also leads to the formation of different coordination polymers. Frequency dependence in the ac susceptibility signals was observed in 3.     

Synthesis of [60]fullerene-glycopyranosylaminopyrimidin-4-one conjugates

The synthesis of several C₆₀ derivatives containing a 6-(β-d-glycopyranosylamino)pyrimidin-4-one unit and a C₆₀-uridine conjugate is described. The fullerene derivatives bearing a 4-(β-d-glycopyranosylamino)pyrimidin-4-one moiety were synthesised by 1,3-dipolar cycloaddition reactions of C₆₀ with azomethine ylides generated in situ from the corresponding 5-formylpyrimidin-4-one derivatives and N-methylglycine. The synthesis of the C₆₀-uridine conjugate involved the selective protection of the 2′- and 3′-hydroxyl groups of uridine, esterification, cyclopropanation of C₆₀ and, finally, the deprotection of the hydroxyl groups. One of the fullerene-glycopyranosylaminopyrimidin-4-one conjugates was characterised by single-crystal X-ray crystallography. Differentiation between pairs of diastereoisomers, for several fullerene derivatives, was achieved through the study of their gas-phase fragmentations.     

Anion receptors based on ureido-substituted thiacalix[4]arenes and calix[4]arenes

The regioselective nitration of 25,27-dipropoxythiacalix[4]arene was carried out as a key step in the synthesis of thiacalix[4]arene derivative bearing two arylureido functions on the upper rim. The preorganisation of ureido units using the thiacalix[4]arene/calix[4]arene moieties as a molecular scaffold gave novel anion receptors. These compounds, albeit based on hydrogen bonding interactions, show good complexation ability even in highly HB-competitive solvent, such as DMSO. Direct comparison of otherwise identical structures 6a and 7a revealed remarkable dominance of the thiacalix[4]arene derivative over its classical analogue in anion binding.     

Amphiphilic dipyrrinones: methoxylated [6]-semirubins

Replacing the typical β-alkyl substituents of [6]-semirubin and [6]-oxosemirubin, two intramolecularly hydrogen-bonded bilirubin analogs, with methoxy groups produces amphiphilic dipyrrinones. Synthesized from the respective 9H-dipyrrinones prepared by base-catalyzed condensation of 3,4-dimethoxypyrrolin-2-one with the appropriate pyrrole α-aldehyde, the 2,3-dimethoxy and 2,3,7,8-tetramethoxy analogs of [6]-semirubin are yellow-colored dipyrrinones that form intramolecularly hydrogen-bonded monomers in CDCl₃, as deduced from ¹H NMR NH chemical shifts. They are monomeric in CHCl₃, as determined by vapor pressure osmometry. In contrast, in the solid, X-ray crystallography reveals supramolecular ribbons of intermolecularly hydrogen-bonded (dipyrrinone to dipyrrinone and acid to acid) 2,3,7,8-tetramethoxy-[6]-semirubin. The latter is approximately 20 times more soluble in water than the parent [6]-semirubin with four β-methyl groups.     

One methylene too far: The solid state structure of the para-sulfonatomethylcalix[4]arene

We report here, the first crystallographic structure of the new water soluble calixarene, para-sulfonatomethylcalix[4]arene. Anchoring a methylene group between the aromatic core of the calixarene and sulfonate groups extended the hydrophobic cavity but led to a more flexible macromolecule allowing formation of hydrogen bonds between vicinal sulfonate groups, causing the groups to point towards the cavity and effectively close it, with S  S distances of 9.7 Å × 7.9 Å. The packing motif consists of bilayers of para-sulfonatomethylcalix[4]arene along both the a and b axis.     

Desymmetrized Leaning Pillar[6]arene

In this work, a novel version of macrocyclic arenes, namely leaning pillar[6]arenes, was discovered and it can be considered as a tilted version of a pillar[6]arene with two hydroxy/alkoxy functionalities removed. Through a facile two‐step synthetic approaches, in conjunction with a diversity of post‐modification possibilities, a series of leaning pillar[6]arenes, with good cavity adaptability and enhanced guest‐binding capability, was synthesized, and their self‐assembly in single‐crystal states is presented. DFT calculations demonstrated that the lower rotational barrier of unsubstituted phenylene rings, the uneven electron density centered at the leaning phenyl rings, and the polarization effect along the edge generated by the hydrogen‐bond‐induced orientation of hydroxy groups greatly affected the host‐guest properties, and meanwhile provided an intuitive explanation for the pillar‐like and rigid structure of traditional pillar[6]arenes. Significantly, the crystal structure of cyclo‐oligomeric quinone was obtained by direct oxidation of leaning pillar[6]arenes.     

Synthesis and structure of bis(methylaluminium · HCCH3) p-tert-butylcalix[4]arene

Treatment of p-tert-butylcalix[4]areneH₄ iwth AlMe₃ in toluene at elevated temperature affords after work-up the complex {[MeAl(NCMe)]₂(p-tert-butylcalix[4]arene)}, which adopts a flattened partial cone conformation as characterized by X-ray crystallographu.     

Synthesis, Structure, and Extraction Properties of paco-Calix[4]arene Crown-6 Ethers

anti-25,27-Bis-n-octyloxycalix[4]arene, the paco-isomer of25,27-bis-n-octyloxycalix[4]arene crown-6 ether, and the paco- and1,3-alt isomers of 25,27-bis-n-octyloxycalix[4]arene t-butylbenzocrown-6 ether were prepared. The crystal structures of anti-25,27-bis-n-octyloxycalix[4]arene, paco-25,27-bis-n-octyloxycalix[4]arene crown-6, and 1,3-alt-25,27-bis-n-octyloxycalix[4]arene crown-6 were determined and thesolution structure of anti-25,27-bis-n-octyloxycalix[4]arene was studied by 2D- and VT-NMR. The extraction of alkali metal nitrates by thepaco-25,27-bis-n-octyloxycalix[4]arene crown-6 and t-butylbenzocrown-6 ethers in 1,2-dichloroethane was compared to that of the corresponding 1,3-alt isomers.     

Conformational behaviour of tetramethoxythiacalix[4]arenes: solution versus solid-state study

The conformational behaviour of simple thiacalix[4]arene derivatives was studied using a combination of NMR spectroscopy and X-ray diffraction analysis. The 25,26,27,28-tetramethoxythiacalix[4]arene was found to adopt an unprecedented solid-state structure, where the cone and 1,3-alternate conformers co-exist in the crystal lattice in the 3:1 ratio. This phenomenon reflects the basically distinct conformational behaviour of thiacalix[4]arene skeleton as compared with classical calixarenes.     

Asymmetric calix[4]-thiacalix[4]arene tubes: Synthesis and ionophore properties

Asymmetric p-tert-butylcalix[4]-p-R-thiacalix[4]arene tubes (R = tert-Bu, H, 1-adamantyl) were prepared for the first time by reaction of tosyloxyethoxy derivative of p-tert-butylcalix-[4]arene and the corresponding p-R-thiacalix[4]arenas in acetonitrile in the presence of K₂CO₃. Complex formation of compounds obtained with sodium, potassium, and rubidium iodides in CDCl₃-CD₃OD, 4:1, was studied by means of ¹H NMR. The ionophore properties of the molecule were governed by the character of substituents on the upper rim of the thiacalixarene fragment, and only the molecular tube containing a fragment of the p-(1-adamantyl)-thiacalix[4]arene quantitatively bound potassium ions (quickly) and rubidium ions (slowly).     

Synthesis,X-ray crystal structure and cation binding properties of a tetrahomodioxacalix[4]arene tetraester

Treatment ofp-t-butyltetrahomodioxacalix[4]arene with ethyl bromoacetate yields a tetraester derivative (4) whose crystal and molecular structure have been determined and whose ion binding properties have been assessed by phase transfer and stability constant measurements. Colorless transparent triclinic crystals (obtained from methoxyethanol) C₆₂H₈₄O₁₄,a = 10.347(2),b = 11.583(2),c = 13.448(3) Å, = 72.04(2), = 86.50(2)°, = 81.23(2)°, space group ,Z = 1, MoK radiation = 0.70930 Å. Refinement was carried out using 2221 reflections withI > 1.5(I). The complexation properties resemble those of calix[6]arene hexaester (6), although weaker, with a preference for the larger alkali cations. Ca²⁺ and Ba²⁺; though not extracted, are more strongly complexed than alkali cations. Eu³⁺ is better complexed than Na⁺.Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82106 (22 pages) and at the Cambridge Crystallographic Data Centre, University Chemical Laboratory, Lensfield Road, Cambridge CB2 9EW, U.K.     

Unexplored metallic cation effect in the acidity constants of p-t-butylthiacalix[4]arene,p-t-butylcalix[4]arene and p-t-butylcalix[6]arene in aqueous-organic media

The influence of the metallic cation of the base (Li⁺, Na⁺ or K⁺) was determined on the acid–base constants of p-t-butylthiacalix[4]arene (TC4), p-t-butylcalix[4]arene (CA4) and p-t-butylcalix[6]arene (CA6) in ethanol/water in an large interval of pH values by potentiometry and spectrophotometry. The pK_a values determined by both methods correlate very well and these are characteristic for each macrocycle with influence of the cation of the base without a straight evidence of an effect by the size of the metallic cation. In the case of TC4, pK_a1 and pK_a2 were lower to Li⁺ and Na⁺ than with K⁺. For CA4, an effect of K⁺ on the pK_a2 with respect to Li⁺ was observed. A very different behaviour was observed for CA6 with Li⁺ and K⁺ showing a lower pK_a2 and a higher pK_a3 than with Na⁺. These effects were interpreted on the basis of the interaction/complexation of each cation with each macrocycle.     

25,26,27,28-羟乙氧基-杯[4]芳烃的合成

以对叔丁基苯酚为原料,经4步反应合成了新的杯[4]芳烃衍生物--25,26,27,28-羟乙氧基-杯[4]芳烃,其结构经~1H NMR和MS表征.     

Properties of a Tetrahomodioxacalix[6]arene Derivative

The synthesis and X-ray crystalstructure of a novel tetrahomodioxacalix[6]arenehexamethylester 2 arepresented. Preliminary investigations of alkali metal ioncomplexation showed that 2 is apoor extractant with selectivity for lithium.     

苄连氮基桥联的双杯[4]芳烃的合成

对叔丁基杯[4]芳烃-1, 3-二醛基衍生物1分别与水杨醛腙、水合肼进行“1＋2”和“2＋2”缩合反应, 方便地合成了苄连氮基取代或桥联的新型杯[4]芳烃衍生物2和双杯[4]芳烃衍生物3, 产率分别为84%和81%. 新化合物的结构与构象经元素分析、质谱、核磁共振谱和1H-1H COSY谱图等表征证实, 双杯[4]芳烃衍生物3为空间结构完全对称的具有管状三维空腔的杯式构象.