Mesoporous MCM-41 as Drug Host System

Among the large number of applications of mesoporous MCM-41 materials, we have recently developed their new use as drug delivery system. Since this kind of materials consist on a disordered network of siloxane bridges and free silanol groups, these latter could be the reacting sites against appropriate guest chemical species.In this work, this application of mesoporous MCM-41 as drug delivery system has been studied from the host-guest interaction point of view. Two factors could affect that interaction: the structure of pore wall surface, and the functional groups present in the organic molecule. Hence, two approaches have been performed: functionalising pore wall groups and changing the drug.     

Crystal structures of heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin complexes with (R)- and (S)-Flurbiprofen

Hepatakis(2,3,6-tri-O-methyl)--cyclodextrin (TM--CDx) forms crystalline complexes with (R)-Flubiprofen (R-FP), C₆₃H₁₁₂O₃₅C₁₅H₁₃O₂F·H₂O, and (S)-Flurbiprofen (S-FP), C₆₃H₁₁₂O₃₅C₁₅H₁₃O₂F. The crystal structures were determined by X-ray analysis. Crystals of both compounds are orthorhombic and the space group isP2₁2₁2₁ with cell dimensions:a=15.092(2),b=21.714(3), andc=28.269(4) Å for theR-FP complex, anda=15.271(2),b=21.451(3) andc=27.895(3) Å for theS-FP complex. The macrocyclic ring of TM--CDx is markedly distorted because of the inability to form intramolecular hydrogen bonds and the steric hindrance involving methyl groups. In both complexes, the phenyl group is inserted into the host cavity from the O(2), O(3) side, which is wider than the O(6) side. The biphenyl moiety ofR-FP is fixed in theR-configuration within the host cavity. The phenyl group ofS-FP is disordered, andR-andS-configurations are statistically distributed with equal probability. TM--CDx molecules are stacked along theb axis to form a column structure. The TM--CDx molecule is laterally shifted with respect to the column axis, and a half of the guest molecule protrudes outside from the crevis of the column. The carboxyl group ofR-FP forms a hydrogen bond with water located outside the host cavity, while the carboxyl group ofS-FP is hydrogen-bonded to an oxygen atom of an adjacent TM--CDx. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82064 (24 pages).     

Design of supramolecular metal complex catalytic systems for petrochemical and organic synthesis

Specific features of the behavior of the supramolecular metal complex catalysts based on calixarenes, cyclodextrins, and dendrimers in the reactions of hydroformylation, Wacker oxidation, hydroxylation of aromatics, 2-naphthol coupling, and oxidative coupling of styrenes and benzene were studied. The factors affecting the catalytic activity and selectivity are discussed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 766–778, April, 2008.     

超分子自由基:构筑、调控与功能

自由基既是新型功能材料的构筑基元,也是常见的反应中间体.调控自由基的活性,具有重要的理论意义和应用价值.为此,我们提出了"超分子自由基"的概念,系指通过非共价作用稳定或活化的自由基.基于葫芦脲的主客体化学,构筑了不同结构的超分子自由基,借助葫芦脲分子的结构特征,从三个方面对自由基的活性进行调控：（1）利用葫芦脲的空间位阻效应和静电效应,稳定自由基阴离子,从而构筑了新型有机近红外光热转换材料,并应用于选择性抗菌;（2）利用葫芦脲的静电效应,活化自由基阳离子,实现了对芬顿氧化反应的显著加速;（3）利用葫芦脲主客体化学的动态可逆性,实现了对反应中间体活性的自适应调控,从而显著地提升了醇氧化反应的催化效率.上述研究表明,构筑简便、活性可调的超分子自由基在功能材料和超分子催化领域具有广阔的应用潜力,未来有望得到进一步的发展.     

Host-guest complexation behaviour of emissive calix[3]naphthobipyrrole toward aromatic guests

A new hexapyrrolic macrocycle composed of three naphthobipyrrole units has been synthesized which exhibited different emission changes with hydrogen pyrophosphate and benzoate ions. Phosphate ions caused red shifting of the fluorescence band of calixnaphthobipyrrole while benzoate ions resulted in quenching of the same. The fluorescence quenching was further utilized for investigating binding preferences of the probe with neutral aromatic guest molecules substituted with groups having varied electron withdrawing abilities. The extent of quenching with the neutral guests increased with the increasing electron deficiency on the aromatic ring of the guest. The fluorescence quenching has been ascribed to electron transfer from the host to the guest species.     

Utilization of Donor–Acceptor Interactions for the Catalytic Acceleration of Nucleophilic Additions to Aromatic Carbonyl Compounds

A conceptually new method for the catalytic electrophilic activation of aromatic carbonyl substrates, by utilizing donor–acceptor interactions between an electron‐deficient macrocyclic boronic ester host ( [2+2] _BTH‐F ) and an aromatic carbonyl guest substrate, was realized. In the presence of a catalytic amount of [2+2] _BTH‐F , dramatic acceleration of the nucleophilic addition of a ketene silyl acetal towards either electron‐rich aromatic aldehydes or ketones was achieved. Several control experiments confirmed that inclusion of the aromatic substrates within [2+2] _BTH‐F , through efficient donor–acceptor interactions, is essential for the acceleration of the reaction.     

主-客体化学研究进展

以分子识别为基础的主－客体化学作为新兴交叉学科，已成为当今研究的热点。本文概述了主体分子的类型、结构特征、分子识别特性及其在某些领域的应用。参考文献56篇。     

Electrochemical determination of electroinactive guests of b-cyclodextrin at a self-assembled monolayer interface

A novel determination method of electroinactive molecules by means of electrochemical technique is presented. A new self-assembled monolayer containing cyclodextrin(CD) is prepared with mono(6-o-p-tolylsulfonyl)-b-cyclodextrin. Although this derivatization process leads to a b-CD coverage of 10% of a full monolayer, this layer shows an effective host-guest response to ferrocene. The interfacial ferrocene complexation gives a response similar to that expected for a Langmuir adsorption isotherm yielding a stability constant of 4.2×104 mol-1@L and a maximum ferrocene coverage of 8.6′10-12 mol/cm2. The redox peak currents of the surface-confined ferrocene de-crease upon addition of competing b-CD guest species to the solution, such as m-toluic acid(mTA) and sodium dodecyl sulfonate(SDS). This principle has been used for the determination of the electroinactive molecules, mTA and SDS in the concentration ranges of 0.8-2.7 mmol/L and 5-100 nmol/L, respectively.     

Interaction of host-guest complexes of cucurbit[n]urils with double probe guests

Since the structure of cucurbituril(Q[6]) has been determined in 1981[1] and its homologues cucurbit [n = 5,7,8 and 10]uril(Q[5], Q[7], Q[8] and Q[10]) have been reported in 2000[2,3], 2002[4], a series of host-guest complexes[5—7], novel supramolecular as-semblies[8—10], molecular encapsulates[11,12] and mo-lecular containers[13,14] based on Q[n] have been stud-ied extensively. All cucurbituril homologues have common char-acteristic features, i.e. hydrophobic cavity, and polar carbonyl gr…