Double-cavity nor-seco-cucurbit[10]uril-based supramolecular assembly for selective detection and removal of trinitrophenol

The effective removal and selective detection of explosive and toxic pollutant trinitrophenol (TNP) is an attractive but challenging field.Herein,a double-cavity nor-seco-cucurbit[10]uril (ns-Q[10])-based supramolecular assembly 8-HQ@ns-Q[10]was fabricated and its structure was characterized by X-ray single crystal diffraction.In this assembly,the stoichiometric ratio of ns-Q[10]and 8-hydroxyquinoline (8-HQ) is 1:2,which is also attributed to the special double-cavity structure of ns-Q[10].The luminescence sensing experiments showed that 8-HQ@ns-Q[10]can be used as a good fluorescence-enhanced sensing material (enhanced 27-fold) for the rapid detection of explosives and the aqueous contaminant TNP,with a limit of detection (LOD) of 2.07×10^(-5)mol/L,without interference from other phenolic compounds.Furthermore,TNP can be efficiently removed in the presence of assembly 8-HQ@ns-Q[10],and the removal efficiency is more than 89%.Therefore,the supramolecular assembly 8-HQ@ns-Q[10],as a fluorescenceenhanced luminescence sensor and adsorption material,has rich research value and potential application prospect when applied to the detection and removal of TNP in aqueous environment.

Supramolecular assemblies of cucurbit[n]urils and 4-aminopyridine controlled by cucurbit[n]uril size(n=5,6,7 and 8)

The binding interactions between 4-aminopyridine(4-AP) and a series of cucurbit[n]urils(Q[5], Q[6],TMe Q[6], Q[7], Q[8]) have been studied using1H NMR spectroscopy, UV–vis absorption spectroscopy,isothermal titration calorimetry(ITC) and X-ray crystallography. The data indicates that the Q[5]@4-AP complex exhibits exo binding, which is not observed in the other four host-guest complexes. Furthermore,X-ray crystallography clearly reveals how the Q[n]s bind with 4-AP to form complexes, for example Q[5]forms an outer-surface complex, whilst Q[6], TMe Q[6] and Q[7] formed 1:1 host and guest type complexes, and Q[8] formed a stable 1:2 ternary complex due to its large cavity, which can accommodate two 4-AP molecules.

A novel pillar[5]arene-cucurbit[10]uril based host-guest complex: Synthesis, characterization and detection of paraquat

The macrocyclic family comprising pillar[n]arenes and cucurbit[n]urils have received much attention recently. However, studies on the construction of supramolecular complexes formed directly with derivatized pillar[n]arenes and cucurbit[n]urils are scant. Given the interest in such systems, herein we have synthesized a new type of naphthalene-derivatized pillar[n]arene NTP5 and selected Q[10] as the host molecule. The 4-[2-(1-naphthalenyl)ethenyl]pyridine of NTP5 is encapsulated by Q[10] and formed a hostguest complex in water-acetic acid(1:1) solution accompanied by enhanced fluorescence, which changed the morphology of NTP5 from a sphere to a porous form. In addition, the fluorescence of Q[10]-NTP5 can be quenched by the addition of the highly toxic pesticide paraquat(PQ), and the mechanism was shown to be the formation of a new charge transfer ternary system of Q[10]-NTP5-PQ. This work provides new ideas for the contribution of supramolecular assemblies based on derivatized pillar[n]arenes and their combination with cucurbit[n]urils and reveals their potential applications.

Controllable fabrication of a supramolecular polymer incorporating twisted cucurbit[14]uril and cucurbit[8]uril via self-sorting

A linear supramolecular polymer with controllable features based on twisted cucurbit[14]uril(tQ[14])and cucurbit[8]uril(Q[8])was firstly fabricated via an effective self-sorting strategy.Herein we designed a monomer,1–butyl–1?-(naphthalen-2-ylmethyl)-4,4?-bipyridinium bromide(BNB),that contains bipyridyl,aliphatic butyl and aromatic naphthyl groups,simultaneously.Two host molecules,tQ[14]and Q[8]were employed to develop an effective strategy for constructing a linear supramolecular polymer with con-trollable features.The alkyl groups on both sides of BNB could insert into the two cavities of tQ[14],the naphthyl part of BNB viaπ-πstacking in Q[8]cavity,serving as the driving force for supramolecular polymerization.Through self-sorting of the monomer,tQ[14]and Q[8],led to the formation of the linear supramolecular polymer.Depolymerization could be achieved by addition of adamantane hydrochloride(AH)which driven two BNB guest molecules out of the Q[8]cavity.This self-sorting strategy has great potential,not only for designing supramolecular polymer materials with different controllable structures through introduction of multiple functional groups,but also for broadening the application of twisted cucurbit[14]uril in supramolecular chemistry.

Preparation and characterization of inclusion complexes of antitumor camptothecin with cucurbit[n=7,8]urils

The slightly water-soluble anticancer drug camptothecin(CPT) and its inclusion complexes with cucurbit[n = 7,8]uril(Q[n](n = 7,8)) were investigated.The formation of 1:2 complexes with Q[n](n = 7,8) in aqueous solution was confirmed by fluorescence spectroscopy and the apparent stability constants were determined to be higher than 3.01 × 1012 L2/mol2.The solid inclusion complexes of CPT and Q[n](n = 7,8) were also prepared by the co-evaporation method and characterized by Fourier transformation-infrared spectroscopy,differential scanning calorimetry and powder X-ray diffraction.Aqueous solubility and dissolution studies indicate that the complexes exhibited significantly increased dissolution rates compared with the pure drug and physical mixtures.The potential of Q[7] or Q[8] for stabilizing lactone modality of CPT was investigated by the High Performance Liquid Chromatography(HPLC) method.The results reveal more than 63% CPT lactone form(active form) in CPT-Q[7] or Q[8] complexes compared to only 36% CPT lactone form in the absence of Q[7] or Q[8] after being incubated in the phosphate buffer solution(pH 7.4 at 37 °C) for 5h.

Supramolecular Self-assembly Formed from Cucurbit[8]uril and p-Hydroxybenzoic Acid

The binding behavior of cucurbit[8]uril(Q[8])and p-hydroxybenzoic acid(p-HBA)has been investigated using ^(1)H NMR titration experiments,UV-Vis absorption,isothermal titration calorimetry(ITC),and X-ray crystallography.Results revealed that the Q[8]can accommodate two p-HBA molecules to form a 1:2 host-guest inclusion complex in solution,namely(p-HBA)2@Q[8].From a poorly scattering crystal,we were able to identify two symmetry unique Q[8]rings,but with different p-HBA fillings.The structure can be represented as Q[8]+1.5 p-HBA,which gives Q[8]@(p-HBA)2∙Q[8]@p-HBA as the structural formula.This supramolecular structure was screened for its ability to capture iodine.The experimental results showed that the adsorption efficiency of the supramolecular organic framework material for iodine capture was 43.8%,with an equilibrium adsorption capacity of 223.3 mg/g.

Effects of Inclusion of Chrysin in Cucurbit[8]uril on Its Stability, Solubility and Antioxidant Potential

The host-guest interaction between cucurbit[8]uril（Q[8]） and chrysin（CHR） has been studied by means of 1H NMR, mass spectrometry（MS）, differential thermal analysis（DTA）, and UV-Vis spectrophotometry. The results show that CHR forms a 1：1 inclusion complex with Q[8], with a binding constant of CHR with Q[8] by UV absorp- tion being 5.4 × 106. Phase solubility experiments show a 5.13-fold increase in the solubility of CHR through interac- tion with Q[8] {c（Q[8]）=10-4 real/L}. A study of the evolution of UV absorption spectra with time shows that Q[8] significantly increases the stability of CHR. The antioxidant activity of CHR-Q[8] has been tested by the ABTS me- thod. The CHR-Q[8] inclusion complex shows a better scavenging effect towards the ABTS radical than CHR, with respective IC50 values of 1.05 ×10-6 and 3.07× 10-6 mol/L. In vitro release studies have shown that CHR-Q[8] has a sustained release effcct.

Synthesis and characterization of a sensitive and selective Fe^(3+) fluorescent sensor based on novel sulfonated calix[4]arene-based host-guest complex

A novel fluorescent sensor was prepared from sulfonated calix[4]arene(SC4A)by the host-guest com-plexation method using the fluorescent dye rhodamine B(RB)as a structure-directing agent.The crystal structure of the host-guest complex(RB@(SC4A)_(3))was confirmed by X-ray diffraction studies while its performance and sensing mechanism for metal ion pollutants were characterized using fluorescence and nuclear magnetic resonance spectroscopies.The results showed that RB@(SC4A)_(3) had a triangular branch structure resulting from host-guest mediation of the interactions between the three SC4A host molecules and the three terminal groups of the guest molecule RB.The host-guest complex exhibited sensitive and selective sensing towards Fe^(3+)ions via a fluorescence quenching mechanism.The results indicated that RB@(SC4A)_(3) could be a promising sensitive and selective fluorescent sensor for metal ion pollutants mon-itoring.It also provided new insights into the synthesis of calixarene-based host-guest complex.

Zwitterionic cellular polymer enabled reductive fixation of CO_(2) for N-methylation of amines

Using heterogeneous catalysts to promote the construction of the C–N bond between amines and CO_(2) under mild conditions is a challenge yet.Herein,we synthesized a novel zwitterionic polymer(PDDC)with a cellular structure via self-complexation of copolymer bearing both quaternary ammonium cation and carboxylate anion.PDDC was employed as a recyclable catalyst for N-methylation of atmospheric CO_(2) and various amines with hydrosilane as a reductant,affording more than 17 N-methylamines in good to excellent yields(up to 99%)under mild conditions.The behavior of PDDC in the reaction medium was disclosed by using a dynamic light scattering study,revealing that the decreased hydraulic radius of particle size contributes to exposing more active sites and increasing reaction activity.Utilizing a series of designed experiments and density functional theory calculations uncovered the crucial role of the prepared zwitterionic polymer during the reaction procedure of CO_(2) conversion.

Synthesis and fluorescence properties of a 1,3-disubstituted thiacalix[4]arene crown-5 armed with phenothiazine moieties

A new thiacalix[4]arene phenothiazine derivative(2) based on a thiacalix[4]crown with a 1,3-alternate conformation has been synthesized and characterized. In THF-water mixture, Compound 2 exhibits a strong fluorescence emission, with a large Stokes shift(λex/em = 357 nm/505 nm, Δλ = 148 nm), which helps to avoid interference in excitation and emission. For the metal ions tested, the fluorescence of Compound 2 was quenched only by Fe3+ and Cr3+ ions. Evidence for the hydrolysis reaction promoted by the metal ions is given by X-ray crystallography, mass spectra(MS), infrared(IR) spectra, and fluorescence spectroscopy data.

Host-guest complexes of a water soluble cucurbit[6]uril derivative with some dications of 1,ω-alkyldipyridines:~1H NMR and X-ray structures

Interactions between a symmetrical tetramethyl-substituted cucurbit[6]uril (host:TMeQ[6]) and 1,ω-alkylenedipyridine (ω = 2,4,6,8,10) dicationic guests were investigated using 1H NMR spectroscopy and single crystal X-ray crystallography. In these inclusion complexes,combined cavity and portal binding in TMeQ[6] were observed,and the length of the bridged alkylene was found to play an important role not only in balancing the overall hydrophilic/hydrophobic interaction between the host and the guest,but also in defining the structure of the resulting inclusion complexes. For the guest 1,2-ethylenedipyridine (Edpy),TMeQ[6] includes a positively charged pyridine ring of Edpy to form an unsymmetrical inclusion complex; for the guest 1,4-butylenedipyridine (Bdpy),TMeQ[6] includes a positively charged pyridine ring of Bdpy,but the different competitive interactions in and between the related inclusion complexes could lead to a fast exchange between the hosts and guests. For the guests with longer bridge chains,such as 1,6-hexamethylenedipyridine (Hdpy) or 1,8-octylenedipyridine (Odpy),a stable pseudorotaxane inclusion complex is formed by combining the hydrophobic cavity and the outer portal dipoleion interactions. However,for 1,10-decatylenedipyridine (Ddpy),the two TMeQ[6] host molecules include the two end pyridine rings of Ddpy and form a dumbbell inclusion complex.

Selective detection of Zn^(2+) and Cd^(2+) ions in water using a host-guest complex between chromone and Q[7]

In this paper,the host-guest interaction of cucurbit[7]uril(Q[7]) and chromone(CMO) has been developed as a fluorescent probe for the highly selective detection of Zn2+ and Cd^(2+) in water based on a chelation-enhanced fluorescence(CHEF) mechanism.There was a good linear relationship between the fluorescence intensity of the CMO@Q[7] probe and the concentration of Zn^(2+ )or Cd^(2+) in the range of 0-3.0×10^(-5) mol/L and the detection limit for Zn^(2+) and Cd2+ was found to be 2.03×10^(-6) mol/L and 1.89×10^(-6)mol/L,respectively.The X-ray crystal structure indicated that different coordination fashions were triggered by Zn^(2+) and Cd^(2+ )in the CMO@Q[7] complexes,respectively.However,both metal ions coordinated with the carbonyl oxygen of CMO,which was encapsulated in the cavity of Q[7],thus leading to the enhancement of recognition fluorescence emission of CMO.

Cucurbit[6]uril-based supramolecular frameworks assembled via the outer surface interaction of cucurbit[n]urils

Curcurbit[n]uril(Q[n])-based supramolecular frameworks(QSFs) constructed from the outer surface interaction of Q[n]s(OSIQ) have the characteristic of simplicity,diversity and modulability.Their simplicity is reflected in their simple composition and preparation methods used for QSFs.The diversity of supramolecular organic frameworks(SOFs) is reflected in the synthesis methods and structural characteristics of the as-obtained QSFs,as well as the variety of structural directing agents and basic building blocks used to prepare QSFs.The modulability is reflected by the controllable channel size in the QSFs,which can be adjusted using different sizes of Q[n]s.In this work,the first re ported cucurbituril Q[6]was selected as the basic building block and three Q[6]-based su p ramolecular frameworks were obtained from aqueous HCl solutions in the presence of [CdCl_(4)]^(2-)respectively.The OSIQs are the main driving forces for the formation of these frameworks.This study shows the diversity of the QSFs.

Unprecede nted tunable hydrophobic effect and anion recognition triggered by AIE with Hofmeister series in water

An un precedented tun able hydrophobic effect in self-assembly of a small cationic organic fluorophore(NI-TPy^(+))-based with aggregation-induced emission(AIE)property was realized in aqueous solution.The amplification of hydrophobicity was found to be significantly dependent upon the increasing aggregates of NI-TPy^(+),which enabled the study of the hydrophobic binding of chaotropic anions with the Hofmeister series.

Recognition of glycine by cucurbit[5]uril and cucurbit[6]uril:A comparative study of exo-and endo-binding

Recognition features of glycine(Gly)with cucurbit[5]uril(Q[5])and cucurbit[6]uril(Q[6])both in aqueous solution and solid state were investigated by 1 H NMR spectroscopy and X-ray crystallography.1 H NMR data indicate that the Gly is located outside of the portals of the Q[5],exhibiting exo binding with the Q[5].In the case of the Q[6],the Gly shows endo binding or a dual binding mode(endo and exo binding)with the host,which depends on the amount of the host in the aqueous solution.X-ray crystallography clearly display that the Gly forms 2:1 exclusion complex with the Q[5],and 2:1 inclusion complex with the Q[6].Interestingly,hydrogen bondings between the encapsulated Gly molecules in the Q[6]were observed.

Study on the Interaction and Properties of Cucurbit[8]uril with Oroxin B

The interaction between cucurbit[8]uril(Q[8])and oroxin B(ORB)was investigated by UV-visible(UV-Vis)spectroscopy,isothennal titration calorimetry(ITC),mass spectnim(MS)and nuclear magnetic resonance(NMR)spectroscopy.The results showed that ORB formed a 2:1 inclusion complex with Q[8]with a binding constant of 8.266×10^5L^2·mol^-2.ORB had good scavenging ability for 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate)(ABTS)tree radicals(IC50=5.74μmol/L)and the addition of Q[8]did not significantly affect the antioxidant activity of ORB(IC50=5.76μmol/L).A phase solubility experiment revealed a 1.86-fold increase in the solubility of ORB when c(Q[8])=100μmol/L.bi vitro dmg release experiments showed that the release rate for ORB@Q[8]complex was lower than that of ORB in artificial intestinal juice,and higher than that of ORB in artificial gastric juice.

Host-guest interaction tailored cucurbit[6]uril-based supramolecular organic frameworks(SOFs) for drug delivery

An approach for the construction of crystalline porous supramolecular organic frameworks (SOFs) via outer-surface interactions of cucurbit[6]uril (Q[6]) with high yield is presented. This approach enables the noncovalent integration of guest molecules into ordered topologies and creates new host-guest-complex-based SOFs;i.e., the topology can be predesigned and constructed by using [ZnCl_(4)]^(2-) anions to induce the formation of solid Q[6]-SOFs, and the pore wall surface can be easily modified by the Q[6]-encapsulated guest molecules. In addition, one of prepared solid Q[6]-SOFs showed a high drug-loading capacity and smart potential release control for drug-delivery applications.

Cucurbit[n]uril-calix[n]arene-based supramolecular frameworks assembled using the outer surface interactions of cucurbit[n]urils

Based on the crystal structures of two cucurbit[6]uril/calix[n]arene-based supramolecular frameworks reported by Long and co-workers,we further investigated the interactions of cucurbit[6]uril with 4-sulfocalix[4]arene and 4-sulfocalix[6]arene using ^(1)H NMR spectroscopy and isothermal titration calorimetry(ITC),respectively.Moreover,solid fluorescent materials were prepared via the adsorption of fluorescent dyes by these porous supramolecular frameworks,which exhibit a selective response to certain volatile organic compounds.

Direct coordination of metal ions to cucurbit[n]urils

Cucurbit[n]urils (Q[n]) are promising ligands for the coordination of metal ions, metal complexes or clusters, and form various Q[n]-based complexes. Among the Q[n] complexes, those formed by direct coordination between Q[n]s and metal ions are particularly important. The direct coordination of metal ions to cucurbit[n]urils leads to the formation of Q[n]-based molecular capsules, tubular polymers and molecular bracelets, which could have nanoscale applications in drug delivery, molecular devices and new materials.

Complexation of sym-bis(benzimidazole)-2,2'-ethylene salts with cucurbit[6]uril derivatives:A potential axle molecule for pseudorotaxanes

Sym-bis（benzimidazole）-2,2＇-ethylene cations act as a new axle template for threading cucurbit[6]uril derivatives on,forming[2]pseudorotaxane and[3]pseudorotaxane.These new complexes have been studied using 1 H NMR,UV-vis absorption spectroscopy and X-ray analysis.Changes in the 1 H NMR spectra indicate that the two types of pseudorotaxane can be formed by varying the host concentration. UV-vis absorption titration experiments at different pH values demonstrate that interesting pK_a shifts of the bis-benzimidazole derivatives can be induced by the host-guest complexation.The associated constants were calculated to be 2.81×10^4 L/mol and 9.06×10^6 L/mol for the[2]pseudorotaxanes and ｜3]pseudorotaxanes,respectively.Furthermore,X-ray diffraction studies of the solid state structures provide unequivocal proof of the host concentration dependent pseudorotaxane,which is strongly in line with the evidences in solution.