Host-guest chemistry and light driven molecular lock of Ru(bpy)(3)-viologen with cucurbit[7-8]urils

Host-guest chemistry and photoinduced electron-transfer processes have been studied in the systems containing Ru(bpy)3 complex covalently linked to viologen as a guest molecule and cucurbit[n]urils (n = 7, 8) as host molecules in aqueous solution. The Ru(bpy)3-viologen complex, [Ru(2,2'-bipyridine)2(4-(4-(1'-methyl-4,4'-bipyridinediium-1-yl)butyl)-4'-methyl-2,2'-bipyridine)]Cl4 (denoted as Ru2+-MV2+, 1) was shown to form stable 1:1 inclusion complexes with cucurbit[7]uril (CB[7]) and cucurbit[8]uril (CB[8]). The binding modes are slightly different with CB[7] and CB[8]. CB[7] preferentially binds to part of the viologen residue in 1 together with the butyl chain, whereas CB[8] preferentially encloses the whole viologen residue. Photoinduced intramolecular electron transfer from the excited-state of the Ru moiety to MV2(+) which is inserted into the cavity of the CBs occurred. Long-lived charge-separated states Ru3(+)-MV(+*) were generated with the lifetimes of 280 ns with CB[7] and 2060 ns with CB[8]. This shows that CBs can slow down the charge recombination within supramolecular systems, and the difference in lifetimes seems to be due to the difference in binding modes. In the presence of a sacrificial electron donor triethanolamine, light-driven formation of a dimer of MV(+*) inside the CB[8] cavity was observed. This "locked" molecular dimer can be "unlocked" by molecular oxygen to give back the original form of the molecular dyad 1 with the MV2(+) moiety inserted in the cavity of CB[8]. The processes could be repeated several times and showed nice reversibility.     

Facile synthesis of cucurbit[n]uril derivatives via direct functionalization: expanding utilization of cucurbit[n]uril

A long-standing problem in cucurbituril chemistry is answered through the first direct functionalization of cucurbit[n]uril (CB[n]; n = 5-8)) leading to perhydroxyCB[n] which can be further modified to provide tailored CB[n] derivatives with desired functional groups and good solubility. Anchoring a CB[6] derivative on the surface and its potential application as a sensor are demonstrated. A CB[6] derivative forms nanospheres with possible use in protein and peptide drug delivery.     

The formation of cucurbit[n]uril (n = 6, 7) complexes with amino compounds in aqueous formic acid studied by capillary electrophoresis

For analytes involved in dynamic equilibrium processes, capillary electrophoresis is a powerful method of determining binding constants. In this work, the complex formation between cucurbit[n]uril (CB[n] n = 6, 7) and some amino compounds was studied by capillary electrophoresis in aqueous formic acid (65% v/v). Four groups of positional and structural isomers (o, m, p-methylanilines; m, p-nitroanilines; benzidine and o-tolidine; alpha, beta-naphthylamines and 1,5-diaminonaphthalene) were selected as model compounds for study of their host-guest inclusion complexation. The interactions between CB[n] (n = 6, 7) and the model compounds were also investigated using a molecular modeling method. The results indicate that the interactions of the compounds with CB[n] (n = 6, 7) are strongly affected by the position of the substituent(s) on the aromatic ring and the ion-dipole interaction between guest molecule and CB. Furthermore, the type and the concentration of CBs on the separation and migration behavior of the amino compounds were also studied.     

Cucurbit[10]uril-based chemistry

With the biggest cavity in the cucurbit[n]urils (CB[n]s) family, CB[10] has shown its unique molecular recognition properties. This review gives a brief summary of the research progresses in the CB[10]-based chemistry, involving its purification and applications in fields such as molecular recognition and molecular assembly.     

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...     

Supramolecular nano drug delivery systems mediated via host-guest chemistry of cucurbit[n]uril (n = 6 and 7)

As a novel family of macrocyclic molecules,cucurbit[n]urils(CB[n]s) have emerged as promising building blocks of supramolecular nano drug delivery systems(SNDDS) in recent years.Direct encapsulation of amphiphilic guests by CB[6] and CB[7] can modulate their amphiphilicity,resulting in formation of supramolecular amphiphiles that self-assemble into supramolecular nanoparticles for drug delivery.Additionally,CB[n]'s host-guest chemistry on the surface of mesoporous nanoparticles makes CB[n] an ideal blocking agent to control drug release from delivery vehicles.These SNDDS possess intrinsic stimuli responsiveness towards external guest or host,which can further incorporate re s ponsiveness to a variety of other stimuli including pH,thermal,redox,photo and enzyme,to realize multiple stimuli-responsive drug release.Moreover,the recent breakthrough in direct functionalization of CB[n]s has provided a feasible method for preparing superior CB[6] and CB[7] derivatives that can be employed to build multifunctional SNDDS with unoccupied macrocycles located on surface,which could be decorated with various functional "tags" through host-guest chemistry.In this review,we summarized the recent progress of CB[6] and CB[7] based SNDDS through formation of supramolecular amphiphiles,supramolecular nanovalves as well as supramolecularly tailorable surface,which we hope to further promote the development of CB[n]s family as building blocks for advanced SNDDS.     

Gold nanoparticles in organic capsules: a supramolecular assembly of gold nanoparticles and cucurbituril

Gold nanoparticles (相似文献   

Daisy chain assembly formed from a cucurbit[6]uril derivative

The building block synthesis of a derivative of CB[6] that bears a reactive propargyloxy group and its functionalization by click chemistry to yield 1 which contains a covalently attached isobutylammonium group is presented. Compound 1 undergoes self-assembly to yield a cyclic [c2] daisy chain assembly (1(2)) in water. The behavior of 1(2) in response to various stimuli (e.g., guests and CB[n] receptors) is described.     

The cucurbit[n]uril family

In 1981, the macrocyclic methylene-bridged glycoluril hexamer (CB[6]) was dubbed "cucurbituril" by Mock and co-workers because of its resemblance to the most prominent member of the cucurbitaceae family of plants--the pumpkin. In the intervening years, the fundamental binding properties of CB[6]-high affinity, highly selective, and constrictive binding interactions--have been delineated by the pioneering work of the research groups of Mock, Kim, and Buschmann, and has led to their applications in waste-water remediation, as artificial enzymes, and as molecular switches. More recently, the cucurbit[n]uril family has grown to include homologues (CB[5]-CB[10]), derivatives, congeners, and analogues whose sizes span and exceed the range available with the alpha-, beta-, and gamma-cyclodextrins. Their shapes, solubility, and chemical functionality may now be tailored by synthetic chemistry to play a central role in molecular recognition, self-assembly, and nanotechnology. This Review focuses on the synthesis, recognition properties, and applications of these unique macrocycles.     

Supramolecularly Catalyzed Polymerization: From Consecutive Dimerization to Polymerization

Herein, we propose a new method for promoting covalent polymerization by supramolecular catalysts. To this end, we employed cucurbit[8]uril (CB[8]) as a supramolecular catalyst, and successfully prepared polyelectrolytes in an aqueous solution by taking advantage of the CB[8]‐enhanced photodimerization of Brooker merocyanine moieties. Interestingly, 10 mol % CB[8] is enough to effectively catalyze this polymerization, because CB[8] can be spontaneously replaced by terminal groups from photodimerized products. In addition, the molecular weights of the obtained polyelectrolytes can be varied by the irradiation time or the monomer. By combining supramolecular catalysis and polymer chemistry, this line of research may enrich the methodology of polymerization and open up new horizons for supramolecular polymer chemistry.     

核磁共振方法研究瓜环[n](n=7,8)与枸橼酸西地那非的相互作用

利用1H NMR技术、电喷雾质谱、红外光谱以及紫外吸收光谱法等手段研究了瓜环[n](n=7,8)与枸橼酸西地那非的相互作用。结果表明:枸橼酸西地那非与两种瓜环都形成了1∶1的包结配合物,但是其配合物的作用模式随瓜环的大小而不同。通过计算得出瓜环[n](n=7,8)与枸橼酸西地那非的包结常数分别为958和1530 L/mol,说明瓜环对枸橼酸西地那非具有潜在的缓释作用。     

葫芦脲在色谱固定相中的研究进展

葫芦脲是超分子化学中继冠醚、环糊精、杯芳烃之后发展起来的又一类新型高度对称的桶状大环主体分子,是一种由多个甘脲单元组成的大环穴状配体,被誉为"第四代超分子化合物"。由于其具有特殊的分离选择性和稳定性,在超分子化学和色谱的交叉领域备受关注。本文从葫芦脲的结构特征出发,侧重概述了葫芦脲同系物及其衍生物在色谱固定相中的研究现状和进展。     

Recent advances in upper rim functionalization of resorcin[4]arene derivatives: Synthesis and applications

Abstract

During the last decades, resorcin[4]arenes have drawn much attention in the field of supramolecular chemistry because of their practical applicability in different areas. Therefore, many scientists have investigated this class of derivatives in recent years. In this article, we comprehensively reviewed a brief literature survey on the chemistry of upper rim functionalization of calix[4]resorcinarene derivatives and their applications concerning optical chemosensors, liquid crystal materials, host-guest systems, catalysis, drug delivery, biological activities, and analytical applications. This short review describes the survey of literature synthesis and upper rim functionalization of resorcin[4]arenes and their different application published in the last six years (2015–2020).     

Polysaccharide-based supramolecular drug delivery systems mediated via host-guest interactions of cucurbiturils

With excellent biocompatibility and biodegradability,natural polysaccharides and their derivative s have exhibited great potential in constructing drug delivery ve hicles for tissue engineering and therapeutics.Cucurbit[n]uril(CB [n])-mediated reversible crosslinking of polysaccharides possess intrinsic stimuliresponsiveness towards competitive guests and have been extensively investigated to fabricate various particles and hydrogels for multiple stimuli-re sponsive drug release by incorpo ration with other stimuli including photo,redox,and enzyme.Through host-guest interactions between CB[6] and aliphatic diamines,functional tags covalently connected with CB[6] can be readily anchored into polysaccharidebased hydrogels,realizing multiple functionalization.The rheological prope rty and drug release profile of polysaccharide-based supramolecular hydrogels can be facilely tuned through CB [8]-mediated dyna mic homo or hetero crosslinking of polysaccharides and/or other polymers.In this review,we introduce and summarize recent progress regarding polysaccharide-based supramolecular drug delivery systems mediated via host-guest interactions of CB[6] and CB[8],covering both bulk hydrogels and particular systems.At the end,possible utilization of CB[7]-based host-guest interactions in constructing polysaccharide-based drug delivery systems and future perspectives of this research direction are also discussed.     

紫精与八元瓜环的超分子组装及光切割质粒DNA

利用紫精可以活化水中溶解氧的特性, 设计合成了苯-紫精化合物(BEV). 利用紫外吸收、电化学及核磁等方法研究了BEV与八元瓜环CB[8] 之间的相互作用. 实验结果表明, 2种化合物可以进行主客体超分子自组装形成1∶ 1的二元包合物BEV-CB[8]. 同时, 分别考察了化合物BEV和BEV-CB[8]与小牛胸腺DNA的相互作用, 并采用琼脂糖凝胶电泳研究了氙灯光照下化合物对pBR322 DNA的切割能力. 结果表明, CB[8]的引入改变了化合物BEV与DNA的作用方式, 使嵌入作用和静电作用增强. 光照结果说明只有超分子BEV-CB[8]在光照下可以完全切割质粒DNA, 即CB[8]的存在明显提高了BEV对质粒DNA的切割效率.     

Diastereoselective formation of glycoluril dimers: isomerization mechanism and implications for cucurbit[n]uril synthesis

Cucurbit[6]uril (CB[6]) is a macrocyclic compound, prepared in one pot from glycoluril and formaldehyde, whose molecular recognition properties have made it the object of intense study. Studies of the mechanism of CB[n] formation, which might provide insights that allow the tailor-made synthesis of CB[n] homologues and derivatives, have been hampered by the complex structure of CB[n]. By reducing the complexity of the reaction to the formation of S-shaped (12S-18S) and C-shaped (12C-18C) methylene bridged glycoluril dimers, we have been able to probe the fundamental steps of the mechanism of CB[n] synthesis to a level that has not been possible previously. For example, we present strong evidence that the mechanism of CB[n] synthesis proceeds via the intermediacy of both S-shaped and C-shaped dimers. The first experimental determination of the relative free energies of the S-shaped and C-shaped dimers indicates a thermodynamic preference (1.55-3.25 kcal mol(-)(1)) for the C-shaped diastereomer. This thermodynamic preference is not because of self-association, solvation, or template effects. Furthermore, labeling experiments have allowed us to elucidate the mechanism of this acid-catalyzed equilibrium between the S-shaped and C-shaped diastereomers. The equilibration is an intramolecular process that proceeds with high diastereoselectivity and retention of configuration. On the basis of the broad implications of these results for CB[n] synthesis, we suggest new synthetic strategies that may allow for the improved preparation of CB[n] (n > 8) and CB[n] derivatives from functionalized glycolurils.     

Aggregates of cucurbituril complexes in the gas phase

The self-organization of cucurbit[n]uril (n = 7 and 8, CBs) complexes was probed by electrospray mass spectrometry. The self-association of CB complexes is a general phenomenon but shows some dependence on the absence, presence, and type of included guest molecules.     

Guest Inclusion in Cucurbiturils Studied by ESR and DFT: The Case of Nitroxide Radicals and Spin Adducts of DMPO and MNP

We present an ESR and DFT study of the interaction of cucurbiturils CB[6], CB[7], and CB[8] with di-tert-butyl nitroxide ((CH(3))(3)C)(2)NO (DTBN) and with spin adducts of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) and 2-methyl-2-nitrosopropane (MNP). The primary goal was to understand the structural parameters that determine the inclusion mechanism in the CBs using DTBN, a nitroxide with great sensitivity to the local environment. In addition, we focused on the interactions with CBs of the spin adducts DMPO/OH and MNP/CH(2)COOH generated in aqueous CH(3)COOH. A range of interactions between DTBN and CBs was identified for pH 3.2, 7, and 10. No complexation of DTBN with CB[6] was deduced in this pH range. The interaction between DTBN and CB[7] is evident at all pH values: "in" and "out" nitroxides, with (14)N hyperfine splitting, a(N), values of 15.5 and 17.1 G, respectively, were detected by ESR. Interaction of DTBN with CB[8] was also detected for all pH values, and the only species had a(N) = 16.4 G, a result that can be rationalized by an "in" nitroxide in a less hydrophobic environment compared to CB[7]. Computational studies indicated that the DTBN complex with CB[7] is thermodynamically favored compared to that in CB[8]; the orientations of the NO group are parallel to the CB[7] plane and perpendicular to the CB[8] plane (pointing toward the annulus). Addition of sodium ions led to the ESR detection of a three-component complex between CB[7], DTBN, and the cations; the ternary complex was not detected for CB[8]. The DMPO/OH spin adduct was stabilized in the presence of CB[7], but the effect on a(N) was negligible, indicating that the N-O group is located outside the CB cavity. Computational studies indicated more favorable energetics of complexation for DMPO/OH in CB[7] compared to DTBN. An increase of a(N) was detected in the presence of CB[7] for the MNP/CH(2)COOH adduct generated in CH(3)COOH, a result that was assigned to the generation of the three-component radical between the spin adduct, sodium cations, and CB[7].     

Acyclic congener of cucurbituril: synthesis and recognition properties

The cucurbit[n]uril (CB[n]) family of macrocycles occupies a prominent role in molecular recognition and self-assembly studies despite the current inability to access specific cucurbit[n]uril homologues, derivatives, and analogues by straightforward tailor-made synthetic procedures. In this paper, we explore an approach that circumvents the challenges posed by the tailor-made synthesis of macrocyclic CB[n] by preparing 1, which functions as an acyclic CB[6] congener. The o-xylylene connections to the glycoluril rings preorganize 1 into the (a,a,a,a)-1 conformation required for binding and reduce its tendency to undergo self-association. We surveyed the binding properties of 1 toward 16 amines (K(a) 相似文献