Nanoencapsulation of calix[4]arene inclusion complexes

A hexameric resorcinarene nanocapsule in wet CDCl3 forms inclusion complexes of calix[4]arene with tetramethylammonium and trimethylsulfoxonium cations to give highly stable Russian-doll-type multicomponent assemblies. The 2D NOESY experiments revealed the size of the assembly, the close proximity of the encapsulated calix[4]arene molecule to the resorcinarene molecules of the capsule, and the inclusion of the tetramethylammonium cation in the calix[4]arene cavity.     

Study on the intermolecular complexation behavior between p-sulfonatocalix[4]arene with l-tyrosine

The formation of the complexation behavior of host molecules water-soluble p-sulfonatocalix[4]arene (p-SCX4) with l-tyrosine (l-Tyr) guest molecule has been studied by spectrophotometric including fluorescence and nuclear magnetic resonance (NMR) spectroscopy. Experimental conditions including concentration of p-SCX4 and medium acidity were investigated in detail. The results showed that p-SCX4 forms 1:1 complexes with l-Tyr in water. Their stability constant determined by spectrofluorometric titration is 15761 L mol. Moreover, to obtain information about the binding mechanism of the interaction, ¹H NMR studies were carried out showing that the water-soluble p-SCX4 was found to be able to complex the aromatic l-Tyr, and the part of benzene ring of amino acid penetrated into the hydrophobic cavity of calix[4]arene and charged aliphatic chain of l-Tyr stick out of the cavity. In addition, the thermodynamic parameters for the complexation of p-SCX4 with l-Tyr were determined through Van’t Hoff analysis. The obtained data further confirmed the binding mode of p-SCX4 with l-Tyr. The related mechanism is proposed to explain the complexation processes.     

Spectrofluorometric study on the inclusion behavior of p-(p-carboxyl benzeneazo) calix[4]arene with norfloxacin

Spectrofluorometric titrations have been performed to investigate the inclusion behavior of p-(p-carboxyl benzeneazo) calix[4]arene (CBC4A) with norfloxacin (NFLX) in NaAc-HAc buffer solution (pH=5.0). It was found that the fluorescence intensity of NFLX quenched regularly upon the addition of CBC4A. The results indicated 1:1 complex stoichiometry and an association constant of 8.21 x 10(5) L mol(-1) at 20.0 degrees C were calculated by applying a deduced equation. Job's plot also verified the existence of 1:1 inclusion complex. The proposed interaction mechanism indicates that NFLX goes into (or partially goes into) the cavity of CBC4A with the help of hydrogen bonding and other forces. The various factors (pH value, ionic strength, and surfactants) affecting the inclusion process were examined in details.     

去叔丁基杯[8]芳烃乙酸钠对紫杉醇包合作用的研究

采用紫外分光光度法和荧光光谱法研究去叔丁基杯[8]芳烃乙酸钠对紫杉醇的包合和释放过程,考察了二者物质的量之比、温度等因素对包合作用的影响.结果显示去叔丁基杯[8]芳烃乙酸钠在一定条件下与紫杉醇可形成稳定的超分子包合物,包合后水溶性明显提高,且随着去叔丁基杯[8]芳烃乙酸钠/紫杉醇物质的量之比的增加,荧光强度明显增强.去叔丁基杯[8]芳烃乙酸钠今后有望成为紫杉醇类抗肿瘤药物的良好载体.     

Study on Interaction of L-Tryptophan with p-Suffonatocalix[4]arene by Spectrofluorometry

The interactions between L-tryptophan（L-Trp） and water-soluble p-sulfonatocalix[4]- arene （SCX4） were investigated by spectrofluorometry. The effect of pH was discussed. The interaction process was estimated from the thermodynamic viewpoint. The SCX4 was found to be able to adjust its conformation to fit the size of L-Trp, and the benzene of L-Trp penetrated into the hydrophobic cavity of SCX4. Meanwhile, the binding mechanism was further elucidated by IHNMR and molecular mechanics calculations.     

Study on Interaction of L-Tryptophan with p-Sulfonatocalix[4]arene by Spectrofluorometry

A variety of analytical techniques have been employed to investigate the interaction of calixarene with amino acids including 1HNMR1, MALDI-MS2 and calorimetric titration3. Furthermore, spectrofluorometry is another excellent method for its convenience an…     

Spectroscopic studies on inclusion properties of fullerenocalix[4]arene conjugates with metal ions

Metal-chelating properties-in the ground and excited states-of fullerenocalix[4]arenes containing two malonamide substituents at the upper rim and four alkyl ester chains at the lower rim have been studied by means of steady-state absorption, fluorescence spectroscopy, and time-resolved transient absorption spectra. In particular, the influence that Ag+ enforces on the fullerene electronic spectra is due to direct interactions between Ag+ and the surface of C60. The effects stemming from Na+, Mg2+, and Ba2+, on the other hand, are indirect and are introduced through chelating the metal ions to the calix[4]arene moiety. They strongly depend on the molecular structure of the fullerenocalix[4]arenes. No spectroscopic evidence was obtained for any influence caused by Mn2+, although the malonamide groups provide good chelating ability even for this transition metal ion.     

Complexation study and spectrofluorometric determination of the binding constant for diquat and p-sulfonatocalix[4]arene

The interactions between diquat (DQ) and p-sulfonatocalix[4]arene (C4S) were studied in an aqueous solution as a function of the ionic strength. Evidence for the formation of a complex between DQ and C4S was obtained using fluorescence measurements, while the stoichiometry of the complex was confirmed as 1:1 for DQ/C4S using UV–vis spectroscopy. The ionic strength had no influence on the stoichiometry of the complex, but exerted a significant influence on the complexation constant, K_c, decreasing with an increase in the ionic strength. The thermodynamic complexation constant, K_c′, was computed as 5.25±1.11×10⁷ using the extended Debye–Hückel law. The rate constants for the heterogeneous electron transfer for the reduction of DQ at an electrode surface were evaluated as 0.150±0.010 cm s^?1 in the absence of C4S and 0.065±0.010 cm s^?1 when C4S was added to the solution in a 1:1 ratio.     

A novel spectrofluorometric method for the determination of methiocarb using an amphiphilic p-sulfonatocalix[4]arene

The characteristics of host-guest complexation between tetrabutyl ether derivatives of p-sulfonatocalix[4]arene (SC4Bu) and methiocarb [3,5-dimethyl-4-(methylthio) phenyl methylcarbamate] were investigated by fluorescence spectrometry. Upon addition of methiocarb, the fluorescence intensity of SC4Bu was quenched regularly and a slight red shift was observed for the maximum emission peak. These results indicated that the SC4Bu-methiocarb complex was formed a 1:1 mole ratio. An association constant of 1.67×10(4) L mol(-1) was calculated by applying a deduced equation. The interaction mechanism of the inclusion complex was discussed. Based on the results, a novel spectrofluorimetric method was described for the determination of methiocarb with a detection limit at 0.05 μg mL(-1). This method is very simple and shows high sensitivity and selectivity. Moreover, the proposed method was successfully applied to the determination of methiocarb in water samples.     

Voltammetric behavior of C60-p-tert-butylcalix[8]arene inclusion complex film

The C₆₀-p-tert-butylcalix[8]arene inclusion complex film has been directly formed on the surface of a glassy carbon electrode, and its electrochemical behavior in acetonitrile containing tetra-n-butylammonium hexafluorophosphate as the supporting electrolyte studied. The film has a two-electron reduction wave at −1.0 V (vs Ag/AgCl), but limits to the first cathodic potential scan. Received: 16 September 1997 / Accepted: 27 October 1997     

对磺酸基杯[4]芳烃与血红蛋白相互作用的光谱研究

用荧光光谱法和紫外可见分光光度法研究了表面活性剂存在下对磺酸基杯[4]芳烃与牛血红蛋白的相互作用机理。由Stern-Volmer方程及紫外可见吸收光谱图确定对磺酸基杯[4]芳烃对血红蛋白的荧光猝灭过程为动态猝灭,求出了猝灭常数。由热力学参数判断二者之间的作用力主要是疏水作用。依据能量转移理论得出荧光给体-受体间的距离r。在同步荧光光谱中,对磺酸基杯[4]芳烃的加入对血红蛋白构象的改变不大。     

Microwave-assisted synthesis of resorcin[4]arene and pyrogallol[4]arene macrocycles

A series of resorcin[4]arene and pyrogallol[4]arene macrocycles have been synthesized efficiently within 5 min, affording crystalline products suitable for single crystal X-ray diffraction, utilising microwave irradiation in a ‘one-pot’ reaction whilst controlling the selective formation of the rccc cone stereoisomer.     

Head-to-tail self-assembly of a calix[4]arene inclusion polymer controlled by a pendant arm

A calix[4]arene functionalized at one phenolic group with a pendant ethoxy acetate group, forms an inclusion complex that is stable even in the presence of other potential guest molecules.     

Molecular inclusion of organometallic sandwich complexes within hybrid cavitand-resorcin[4]arene receptors

Two different hybrid cavitand-resorcin[4]arenes are shown to be effective and selective receptors for the molecular inclusion of positively charged organometallic sandwich complexes of appropriate size. The binding constants of the 1 : 1 complexes formed with a series of neutral and positively charged metallocenes have been calculated using different titration techniques. The motion of the included metallocene and the kinetics of the complexation process are investigated. The voltammetric behaviour of the inclusion complexes formed with cobaltocenium is also studied.     

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.     

Preparation and property screening of the solid inclusion complex of norfloxacin with p-sulfonated calix[4]arene

The complexation of norfloxacin (NFLX) by p-sulfonated calix[4]arene (SC4A) in aqueous solution has been studied by fluorescence spectroscopy and 1H NMR spectroscopy. A 1:1 stoichiometry and a 8086 L mol(-1) stability constant of the NFLX-SC4A complex was obtained by spectrofluorometric titrations. The equimolar solid state inclusion complex of NFLX-SC4A was prepared by the co-precipitation method and then characterized by various techniques, including differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD), Fourier-transform infrared analysis (FT-IR) and scanning electron microscopy (SEM). The experimental results of these chemical property screenings confirmed that NFLX and SC4A can form a stable host-guest complex in the solid state, and SC4A appears to function as a complexing and solubilizing agent for NFLX.     

Mechanism of hydrogen-bond array isomerization in tetrahydroxycalix[4]arene and tetrahydroxythiacalix[4]arene

Possible rearrangement mechanisms of hydrogen-bond arrays formed at the lower rim of tetrahydroxycalix[4]arene and tetrahydroxythiacalix[4]arene were studied by means of density functional theory and the resolution identity approximation modification of M?ller-Plesset perturbation theory (RI-MP2). Influence of solvent to height of energy barriers was quantified by use of the conductorlike screening model (COSMO) of implicit solvent (chloroform). Generally, two types of mechanisms were investigated. The first is represented by a synchronous single-step jump of all four hydroxyl protons. Pathways of the second mechanism include the rotation of one or more hydroxyl groups around the CAr-O bond. Theoretical results, in agreement with recently published experimental data (Lang et al. J. Chem. Phys. 2005, 122, 044056), prefer a jump mechanism for the methylene-bridged calix[4]arene. Concerning the thiacalix[4]arene, results obtained by COSMO as well as RI-MP2 calculations show that the rotational mechanism is very competitive and it could even be more favorable.     

An inclusion complex between acetonitrile andp-tert-butylcalix[6]arene

p-tert-Butylcalix[6]arene forms a complex with 1.5 acetonitrile molecules, that are included in the macrocycle cavity. This complex crystallizes in the monoclinic system: space groupP2₁/m,a=14.043(4),b=16.916(11),c=14.199(11) Å,=98.27(6)°,V=3338(4) ų,Z=2 (formula units). Refinement led to a final conventionalR value of 0.113 for 1654 reflections. Thepinched cone conformation of the calixarene is the same as that of the neutral and freeR-calix[6]arene already described. The two acetonitrile molecules interact with some phenyl ring -clouds, a methylene bridge and sometert-butyl groups of the calixarene. Supplementary Data relating to this article (atomic coordinates for hydrogen atoms, anisotropic displacement parameters, selected geometrical parameters and observed and calculated structure factors) are deposited with the British Library as Supplementary Publication No. SUP 82188 (16 pages).     

Enantiodiscrimination by inclusion phenomena inside a bis(ethyl lactate) p-tert-butylcalix[4]arene derivative

An ethyl lactate derivative of p-tert-butylcalix[4]arene is able to differentiate the NMR spectra of 3,5-dinitrobenzoyl derivatives of amino acids methyl esters. The origin of enantiodiscrimination in solution was investigated by NMR spectroscopy and comparison with model chiral auxiliaries.