Anthocyanin Color Stabilization by Host-Guest Complexation with p-Sulfonatocalix[n]arenes

Flavylium-based compounds in their acidic and cationic form bring color to aqueous solutions, while under slightly acidic or neutral conditions they commonly bring discoloration. Selective host-guest complexation between water-soluble p-sulfonatocalix[n]arenes (SCn) macrocycles and the flavylium cationic species can increase the stability of the colored form, expanding its domain over the pH scale. The association constants between SCn and the cationic (acid) and neutral basic forms of flavylium-based compounds were determined through UV-Vis host-guest titrations at different pH values. The affinity of the hosts for synthetic chromophore was found to be higher than for a natural anthocyanin (Oenin). The higher affinity of SC4 for the synthetic flavylium was confirmed by ¹H NMR showing a preferential interaction of the flavylium phenyl ring with the host cavity. In contrast with its synthetic counterpart, the flavylium substitution pattern in the anthocyanin seems to limit the inclusion of the guest in the host’s binding pocket. In this case, the higher affinity was observed for the octamer (SC8) likely due to its larger cavity and higher number of negatively charged sulfonate groups.     

Recent progress in the research on the host-guest chemistry of pillar[n]arenes

Pillar[n]arene, as a new kind of macrocyclic host molecule, is a cyclic oligomer, which has a unique rigid structure with a hydrophobic cavity and can interact with many size-matched guest molecules. In this review, the molecular recognition, self-assembly and applications of the pillar[n]arenes in the past two years were described. On the basis of previous scientific research, a variety of pillar[n]arene-based supramolecular systems responsive to specific external stimuli such as pH, redox, gas, light, etc. has been constructed. Pillar[n]arenes have exhibited great potential in constructing these fantastic supramolecular systems based on host-guest recognition, including nanomaterials, controllable drug delivery, transmembrane channels, chemosensors and catalytic entities. These supramolecular systems have a wide range of applications in the material, biology, detection and catalysis field, but their applications are not limited to these fields.     

杯芳烃和柱芳烃桥梁部位的衍生及其功能化

随着大环化学的快速发展,对杯芳烃、柱芳烃及其他类似化合物的桥梁亚甲基部位进行高效修饰的方法日益引起人们的关注.桥梁部位修饰后的大环衍生物,在不改变其原有属性的基础上增加了新的功能,不仅可以引入更多的功能基团,而且可以通过主客体的自组装行为,进一步拓展杯芳烃和柱芳烃等超分子大环在药物递送、化学传感、荧光体系构建等诸多领域...     

Calix[n]arenes as Synthetic Membrane Transporters: A Minireview

Several potential applications of functionalized calix[n]arenes as carriers in transport through membranes of various biological compounds aiming their separation are reviewed. Specific aspects of membrane transport and the use of calix[n]arenes for building synthetic ion channels are discussed.     

A Preliminary Investigation of the Solution Complexation of 4-Sulphonic calix[n]arenes with Testosterone

The complexation between water soluble calixarenes and testosterone has been studied. Stability constants of the host guest complexes of 4-sulphonic calix[n]arenes (n = 4, 6 and 8) with testosterone in water and buffers (pH 5.8, 7.3 and 10.0) were determined from phase solubility curves. These solubility curves indicated that the complexes were all of the A_L type. The constants were in the range 26–341 M^-1, dependent on the size of the calixarene and the pH of the solutions.     

Anti-thrombotic Activity of Water-soluble Calix[n]arenes

The parent p-sulfonato-calix[n]arenes and six O-monosubstituted derivatives were investigated in vitro for anticoagulant activity. Different concentrations of calixarenes were tested, showing that the compound 49-mono-(2-carboxymethoxy)-5,11,17,23,29,35,41,47-octa-sulfonato-calix[8]arene (C8SMA) has a significantly strong prolongation on the activated partial thromboplastin time (APTT) and on the thrombin time (TT) than the other calixarenes. Secondly, investigation of whether the anticoagulant behaviour was via interaction with antithrombin or Heparin Cofactor II was determined. Thrombin inhibition mediated by antithrombin (AT) and Heparin Cofactor II (HCII) activation was investigated in comparison to the biological activators, Heparin (Hep) and Dermatan sulfate (DS). The results show that the 49-mono-(2-carboxymethoxy)-5,11,17,23,29,35,41,47-octa-sulfonato-calix[8]arene (C8SMA) and 5,11,17,23,29,35-hexa-sulfonato-calix[6]arene (C6S) produce activation of HCII at 500 μM comparable to that induced by DS at 100 μM. However, activation of AT by all of the investigated calixarenes is between 10 and 50 times lower than that observed in the presence of heparin. The mechanism of the anticoagulant effect of these calixarenes is as activators of HCII and not as activators of AT.in final form: 24 November 2004This revised version was published online in July 2005 with a corrected issue number.     

Piling Up Pillar[5]arenes To Self‐Assemble Nanotubes

New liquid‐crystalline pillar[5]arene derivatives have been prepared by grafting first‐generation Percec‐type poly(benzylether) dendrons onto the macrocyclic scaffold. The molecules adopt a disc‐shaped structure perfectly suited for self‐organization into a columnar liquid‐crystalline phase. In this way, the pillar[5]arene cores are piled up, thus forming a nanotubular wire encased within a shell of peripheral dendrons. The capability of pillar[5]arenes to form inclusion complexes has been also exploited. Specifically, detailed binding studies have been carried out in solution with 1,6‐dicyanohexane as the guest. Inclusion complexes have also been prepared in the solid state. Supramolecular organization into the Col_h mesophase has been deduced from X‐ray diffraction data and found to be similar to that observed within the crystal lattice of a model inclusion complex prepared from 1,4‐dimethoxypillar[5]arene and 1,6‐dicyanohexane.     

Azobenzene-bridged calix[8]arenes

An azobenzene bridge was introduced into the lower (or smaller) rim of p-tert-butylcalix[8]arene (1) and 1,5-calix[8]crown-3 (2) to form 1,4-singly bridged (3) and 1,5:3,7-doubly bridged (4) calix[8]arene derivatives, respectively. Trans and cis isomers of conformationally rigid 4 were isolated. The quantum yields of the trans-cis photoisomerisation reactions have been measured.     

Synthesis, conformational studies and inclusion properties of N-substituted tetrahomodiazacalix[4]arenes

A series of tetrahomodiazacalix[4]arenes (1–8) with different substituents (or substituted) at the upper rim and/or N-side arm has been synthesized with acceptable yields. The compounds were characterized by elemental analysis, IR, MS and NMR methods. In particular, 5 was shown by X-ray crystallography to adopt the cone conformation in the solid state. Two-phase picrate extraction showed that 2 and 6, bearing N-2-picolyl arms, are the best extractants. Of the cations tested, Ag(I) is the best extracted by almost all ligands and the extraction efficiency follows the order 2-picolyl > 3-picolyl > 4-picolyl.     

Salt-Bridge Supported Bilayer Lipid Membrane Modified with Calix[n]arenes as Alkali Cation Sensors

ABSTRACT

Potentiometric behaviors of a salt-bridge supported bilayer lipid membrane (Sb-BLM) modified with Calix[n]arene (n=4, 6, 8) derivatives are described for some alkali metal ions. The modified Sb-BLM was used as an alkali cation sensor. The membrane potentials were observed to generate Nernstian responses to the concentration of alkali metal ions in electrolyte. The Sb-BLM modified with the calix[n]arenes show high selectivity for individual alkali metal ions: Calix[8]arenes for K⁺, calix[6]arenes for Cs⁺ Calix[4]arenes show no selectivity for any alkali ions. The interacting mechanism is also discussed.     

美洛昔康与4-磺化杯[4]芳烃包合作用的荧光光谱研究

采用荧光光谱研究了不同酸度下美洛昔康(ME)与4-磺化杯[4]芳烃(SCX4)的包合作用.结果表明,在酸性和中性条件下,美洛昔康与4-磺化杯[4]芳烃均形成1∶1的包合物;以包合形成常数为包合物稳定性的量度,不同酸度下形成的包合物的稳定性排序为碱性>中性>酸性.     

Dynamic materials fabricated from water soluble pillar[n]arenes bearing triethylene oxide groups

Recent advance on dynamic materials fabricated from water soluble pillar[n]arenes with triethylene oxide groups was summarized.     

Crystallographic and Inclusion Properties of some Diacetylated Calix[4]arenes

Three 5,17-diacetylcalix[4]arene derivatives 3–5 have been prepared, evaluated for inclusion properties, and their single crystal X-ray structures determined. The diacetyl calixarenes 3 and 4 were obtained by acetylation of their parent dimethoxy 1 or dipropoxy 2 compounds, respectively, whereas 5,17-diacetyl-25,26,27,28-tetrapropoxycalix[4]arene 5 was prepared by alkylation of 4. Crystallisation of 3 resulted in no inclusion from chloroform, but yielded lattice inclusion compounds from acetonitrile or acetone. The calixarene 3 maintains its cone conformation in these crystals, but displays degrees of distortion depending upon the included solvent. Crystal structures of solvent-free 4 and 5 are also described. A new preparation of the monomethoxy derivative 6 is described, and its X-ray structure with chloroform guest is analysed.     

Sequential Chiral Induction and Regulator-Assisted Chiral Memory of Pillar[5]arenes

Chirality transfer is widely observed in life processes, and many artificial chiral transfer systems have been developed. In these systems, chiral information is transferred from chiral inducers to chiral acceptors by a direct chiral induction process and a direct chiral memorization process. We have developed ternary nondirect chiral transfer systems based on pillar[5]arenes, in which a third factor was introduced as a regulator. The planar chirality of an acceptor was induced and memorized by a chiral inducer with precise control by a regulator. In the chiral induction period, the feed sequence of the chiral inducer and regulator affected the chiral induction behavior of the chiral acceptor. The chiral memory ability of the acceptor was substantially improved by the combined action of the chiral inducer and regulator.     

杯芳烃与NO2硝化反应的研究

系统地研究了羟基杯[n]芳烃、甲氧基杯[n]芳烃和对特丁基杯[n]芳烃(n＝4, 6, 8)与NO₂气体的硝化反应, 发现可以成功地得到25,26,27,28-四羟基杯[4]芳烃、37,38,39,40,41,42-六羟基杯[6]芳烃以及25,26,27,28-四甲氧基杯[4]芳烃的对位全硝化产物, 产率分别为90%, 70%和40%; 尤其是25,26,27,28-四羟基杯[4]芳烃与NO₂的反应20 min即可完成. 认为共振式酚氧负离子结构是影响该类硝化反应的关键, 并对反应机理进行了探讨.     

基于甲氧基柱[5]芳烃的聚丙烯酸酯有机膜对对硝基苯衍生物的吸附行为

柱芳烃是一类有别于冠醚、杯芳烃、葫芦脲等的柱状大环分子,具有独特的富电子空腔和口腔的可修饰性。 它们可以包结多种有机污染物,对有机污染物的吸附和脱除具有广泛的应用前景。 本文通过核磁共振和紫外滴定的方法首先研究了对硝基苯衍生物与甲氧基柱[5]芳烃(MeP5A)的包结行为,测定了包结常数。 在此基础上,将MeP5A物理混合到聚丙烯酸酯(PA)乳液中,首先制备了甲氧基柱[5]芳烃/聚丙烯酸酯(MeP5A/PA)共混乳液,然后通过静电纺丝技术,得到了MeP5A/PA纳米纤维膜。 采用红外光谱、扫描电子显微镜对MeP5A/PA纳米纤维膜的结构和形貌进行了表征。 将MeP5A/PA纳米纤维膜用于4种对硝基苯衍生物的吸附实验。 结果表明,对硝基苯乙腈显示出与MeP5A最强的包结作用,其K_a=(6.0±0.3)×10² L/mol,PA膜中引入MeP5A,增大了吸附量,但并未改变纤维状形貌。 MeP5A/PA纳米纤维膜的最佳吸附平衡时间为2 h,且MeP5A/PA纳米纤维膜中MeP5A的含量越高,吸附量越大。 但当吸附溶液中MeP5A浓度达到4 mmol/L时(对应的膜中含有的MeP5A物质的量为1.4×10^-2 mmol),其吸附基本达到平衡,继续增加MeP5A物质的量,其吸附量变化不大。     

A Facile Method to Synthesize Spiro-calix[4]arenes

Calixarenes have absorbed considerable interests for their outstanding abilities of recognition for cations, anions and organic molecules1. In order to include larger and more complex molecules, polytopic receptors were designed from two or more host macrocycles linked by one or several links. Therefore, double-calixarenes and oligocalixarenes have been synthesized and reviewed2. Among these polytopic receptors, double-calixarenes can be used as the mimic of ion channel or to self-organize koi…     

Head-to-tail connected double calix[4]arenes

Summary New macrotricyclic compounds consisting of two calix[4]arene substructures connected by aliphatic chains of various length (three to five carbon atoms) between two oppositep-positions and two distal phenolic oxygens have been synthesized. Starting withp-tert-butyl-calix[4]arene, two O-protected phenolic units are attachedvia ether links in 1,3-position by reaction with the corresponding tosylates. After deprotection, the new calix[4]arene is formed by fragment condensation with 2,6-bisbromomethylated 4-alkylphenols. The structure of one example (8c) has been confirmed by single crystal X-ray analysis. Both calixarene parts assume the cone conformation, a molecule of acetonitrile being included in both cavities.

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Doppelte Calix[4]arene in Kopf-Schwanz-Verknüpfung

Zusammenfassung Neue makrotricyclische Verbindungen, in denen zwei Calix[4]aren-Einheiten durch aliphatische Ketten unterschiedlicher Länge (drei bis fünf C-Atome) zwischen zwei gegenüberliegendenp-Positionen und zwei gegenüberliegenden Phenolsauerstoffen verknüpft sind, wurden hergestellt. Ausgehend vonp-tert-Butyl-calix[4]aren werden zunächst zwei O-geschützte Phenolbausteine in 1,3-Stellung durch Umsetzung mit den entsprechenden Tosylaten etherartig gebunden. Nach Abspaltung der Benzylether-Schutzgruppe wird durch Fragmentkondensation mit 2,6-bisbrommethylierten 4-Alkylphenolen das neue Calix[4]aren gebildet. Für8c wurde die Struktur durch Einkristallröntgenstrukturanalyse bestätigt. Beide Calixarenteile nehmen diecone-Konformation ein, wobei in die beiden Hohlräume je ein Molekül Acetonitril eingeschlossen wird.