Outer Surface Interactions Research Articles

TMeQ[6]-based supramolecular frameworks assembled through outer surface interactions and their potential applications

Cucurbit[n]uril(Q[n])-based supramolecular frameworks assembled through outer surface interactions are characterized by their simple composition, convenient preparation, high yields and controllable structures. The most prominent characteristic of these frameworks is their diversity, with various synthesis methods, structural characteristics, structure directing agents and basic building blocks of Q[n]s. In this work, a symmetric tetramethyl-substituted Q[6] (TMeQ[6]) is selected as the basic building block, with three different TMeQ[6]-based supramolecular frameworks obtained from 1-, 3- and 5 mol/L aqueous H2SO4 solutions, respectively. The outer surface interactions between TMeQ[6] and the adjacent SO42− anions or TMeQ[6] units are the main driving forces for the formation of these frameworks, which exhibit adsorption properties for fluorophore dyes and organic isomers. These adsorption characteristics may lead to the application of these frameworks in the synthesis of solid fluorescent sensors for volatile organic compounds and the adsorptive separation of alkane isomers.

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

ABSTRACT 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 reported cucurbituril Q[6] was selected as the basic building block and three Q[6]-based supramolecular frameworks were obtained from aqueous HCl solutions in the presence of [CdCl4]2− respectively. The OSIQs are the main driving forces for the formation of these frameworks. This study shows the diversity of the QSFs.

Synthesis, Adsorption, and Recognition Properties of a Solid Symmetric Tetramethylcucurbit[6]uril-Based Porous Supramolecular Framework

In this work, we reported a porous supramolecular framework (A) constructed of a symmetric tetramethylcucurbit[6]uril (TMeQ[6]) in aqueous HCl solutions; the driving force was the outer surface interaction of cucurbit[n]urils, as well as hydrogen bonding between latticed water molecules and portal carbonyl oxygens of TMeQ[6]. Adsorption experimental results revealed that the porous supramolecular framework can absorb certain fluorophore guests (FGs) to form luminescent assemblies (FG@As) by fluorescence enhancement or colour change, and some of them can respond to certain volatile organic compounds. Thus, the TMeQ[6]-based supramolecular framework could be used as a sensor for certain gas or volatile compounds.

Selective Recovery and Detection of Gold with Cucurbit[n]urils (n = 5-7).

Environmentally benign methods for gold recovery and detection are highly desirable for a sustainable future. Herein, we demonstrate a selective recovery and detection strategy of gold with cucurbit[n]urils (Q[n = 5-7]) by means of outer-surface interactions. Tetrachloroaurate anion ([AuCl4]-) is able to be rapidly precipitated with Q[n] in forms of supramolecular adducts. X-ray crystallography of four Q[n = 5-7]·[AuCl4]- complexes reveal that strong outer-surface interactions between Q[n = 5-7] and [AuCl4]- are the major driving force for the formation of Q[n = 5-7]·[AuCl4]- complexes. Impressively, each Q[6] macrocycle is surrounded by 12 [AuCl4]- anions. Each of these 12 [AuCl4]- anions is connected to four adjacent [AuCl4]- anions, leading to the formation of a three-dimensional supramolecular framework with tubular channels. In addition, we found an interesting inclusion complex [Au(OH2)4]3+⊂Q[7] in the Q[7]·[AuCl4]- complex, which is the first example of hydrated metal cation encapsulated inside the cavity of Q[n]. Spectroscopic data suggest that Q[n = 5-7] possess a high affinity and selectivity for [AuCl4]- even in the presence of other transition-metal ions. Q[n] modified electrodes are found to be an effective material for the detection of trace gold in dilute solutions.

Specific Recognition of Methanol Using a Symmetric Tetramethylcucurbit[6]uril-Based Porous Supramolecular Assembly Incorporating Adsorbed Dyes

A symmetric tetramethylcucurbit[6]uril-based porous supramolecular assembly was prepared in an aqueous H2SO4 solution (5M). The driving force for the formation of this assembly is mainly the outer surface interaction of Q[n], which includes the ion-dipole interaction of SO42− anions and the positive electrostatic potential of the outer surface of the symmetric tetramethylcucurbit[6]uril (TMeQ[6]), the dipole-dipole interactions between the positive electrostatic potential of the outer surface of TMeQ[6] and portal carbonyl oxygens of TMeQ[6], and the hydrogen bonding between lattice water molecules and portal carbonyl oxygen atoms in TMeQ[6]. The TMeQ[6]-based porous supramolecular assembly exhibits the characteristics of absorbed fluorophore guests (FGs), such as dyes and polycyclic compounds with different fluorescence characteristics. Moreover, the resulting luminescent assemblies (FG@As) can respond to certain volatile organic compounds; in particular, the luminescent assemblies of rhodamine B or pyrene display a unique fluorescence enhancement in response to methanol.

Noncomplexed Cucurbituril-Mediated Structural Evolution of Layered Uranyl Terephthalate Compounds.

Template synthesis is one of the most feasible ways to explore new uranyl compounds with intriguing structures and properties. Here we demonstrate the preparation of six novel "sandwichlike" uranyl coordination polymers (UCPs) based on two-dimensional uranyl-terephthalate acid (H2TP) networks using CBn (n = 5, 6, 8) as template ligands in the presence of different cations (Na+, K+, Cs+, or H2N(CH3)2+). Compound 1 ([UO2(TP)2][Na2(CB5)(H2O)](H2O)5) is composed of layered uranyl-TP networks with the complex of CB5 and sodium cations as template ligands. In compound 2 ([(UO2)2(TP)3]2(CB6)(H2O)10), CB6 located between uranyl-TP networks contacts them by π-π interactions and hydrogen bonds. Compound 3 ([(UO2)2(TP)3]2[Na2(H2O)10(CB6)]) is the same as compound 2 except for sodium cations bonding with CB6. Similarly in compound 4 ([(UO2)2(TP)3][Cs(H2O)3(CB6)]), CB6 is a capsulelike structure capped with two cesium cations and interacts with uranyl-TP networks through π-π and C-H···π interactions. Compound 5 ([(UO2)2(TP)3(HCOO)2][K(H2O)2(CB5)]2[H2N(CH3)2]2(CB6)(H2O)6) consists of both templates of CB6 and CB5 in which each CB5 is capped with one potassium cation while the H2N(CH3)2+ cation is held at CB6 portals. In compound 6 ([(UO2)2(TP)3]2[UO2(TP)2(H2O)2][Cs(CB8)3(H2O)4](H2O)16), CB8 ligands are connected by cesium cations to form a triangle motif and are further located between the uranyl-TP networks as template agents. All of the 2D layered structures with free CBn or cation-anchored CBn intercalate into the laminates of uranyl-terephthalate and shows a cucurbituril-mediated structural evolution. The regulating role of CBn as structure-directing template agents for the construction of layered UCPs through outer-surface interactions with layers of uranyl terephthalate is demonstrated, especially for the case of CB6 with contractive interlayer spacing.

Preparation and adsorption properties of a facile solid cucurbit[8]uril-based porous supramolecular assembly

Cucurbit[8]uril (Q[8]) was used as the building block for the facile preparation of Q[8]-based supramolecular assemblies in aqueous HCl solutions (A). The Q[8]-based supramolecular assembly was constructed of Q[8] molecules held together through outer surface interactions of cucurbit[ n]urils, and hydrogen bonding between latticed water molecules and portal carbonyl oxygens of Q[8]. The porous structure resulted in different adsorption properties for different fluorophore guests (FGs), including dyes and fused-ring compounds, and fluorescence enhancement or colour changes resulted in luminescent materials (FG@As). Moreover, some of the FG@A systems could selectively respond to certain volatile organic compounds, for which they can be used as solid sensors.

Outer surface interactions to drive cucurbit[8]uril-based supramolecular frameworks: possible application in gold recovery.

Q[8]-based honeycomb-like frameworks can be obtained in [AuCl4]--free aqueous HNO3 solution and aqueous HCl and HNO3 solutions that contain [AuCl4]-. The outer surface interaction of Q[8] with planar inorganic anions [AuCl4]- and NO3- is the main driving force. These frameworks exhibit a high selectivity for imprisoning [AuCl4]- that could establish a process for gold recovery.

A novel CB[6]-based supramolecular assembly exhibiting highly selective multi-responsive fluorescence sensing for trace amounts of Fe3+ ions and acetone molecules

A novel CB[6]-based supramolecular assembly (1) has been synthesized under solvothermal condition. Single-crystal X-ray diffraction analysis revealed that the 3D framework is constructed via the outer-surface interaction between free CB[6]s and 2,6-Naphthalenedisulfonic acid anion (NDS2-). The fluoresce investigation demonstrated that 1 can highly selective and sensitive sense of Fe3+ ions in aqueous solution at about 1 ppm level, and it also can sensitive detection of acetone molecules at very low volume fraction, when the concentration reached 5.0 vol%, the fluorescence was almost quenched 100%. It has rarely been reported for CB[n]-based multi-responsive supramolecular assemblies. In connection to these, the probable sensing mechanisms were also discussed in this paper. This work sheds light on the design and preparation of new multifunctional CB[n]-based supramolecular assemblies with potential applications in the fluorescent sensor.

Hexamethylcucurbit[3,3]uril-Based Porous Supramolecular Assemblies and Their Adsorption Properties.

In the present work, we selected hexamethylcucurbit[3,3]uril (Me6Q[3,3]) as a building block and obtained two Me6Q[3,3]-based porous supramolecular assemblies from neutral water (A) and aqueous HCl solutions (B), respectively. Both Me6Q[3,3]-based assemblies are constructed of Me6Q[3,3] molecules through the typical outer surface interaction of cucurbit[n]urils, as well as hydrogen bonding between latticed water molecules and portal carbonyl oxygens of Me6Q[3,3]. The assemblies present different porous structure features and exhibit different adsorption properties for eight common volatile organic compounds. However, the two porous assemblies exhibit similar adsorption properties for certain fluorophore dyes, including rhodamine B (G1), fluorescein (G2), and pyrene (G3), and form solid colored fluorescent compounds, some of which exhibit responses to the selected volatile organic compounds.

4-Sulfocalix[4]arene/Cucurbit[7]uril-Based Supramolecular Assemblies through the Outer Surface Interactions of Cucurbit[n]uril.

Upon mixing of aqueous solutions of the freely soluble building blocks cucurbit[7]uril (Q[7]) and 4-sulfocalix[4]arene (SC[4]A), white microcrystals instantly separate in near-quantitative yield. The driving force for this assembly is suggested to be the outer-surface interaction of the Q[n]. Dynamic light scattering, scanning electron microscopy, and NMR (diffusion-ordered NMR spectroscopy) analyses have confirmed the supramolecular aggregation of Q[7] and SC[4]A. Titration 1H NMR spectroscopy and isothermal titration calorimetry have shown that the interaction ratio of Q[7] and SC[4]A is close to 3:1. Moreover, the Q[7]/SC[4]A-based supramolecular assembly can accommodate molecules of some volatile compounds or luminescent dyes. Thus, this work offers a simple and highly efficient means of preparing adsorbent or solid fluorescent materials.

A new cucurbit[6]uril based supramolecular assembly for sensing small organic solvents and rapid adsorption of Reactive Blue 19 Dye

A new cucurbit[6]uril based supramolecular assembly [Cd2(SIP)2 (H2O)8·CB[6]·4H2O]2− (1) was successfully synthesized by the solvothermal reaction. X-ray diffraction analysis revealed that the outer surface interactions of CB[6] can be the driving forces in the formation of such novel CB[6]-based supramolecular assembly. Interestingly, it was shown potential application for the luminescence sensing of small organic solvent molecules. Furthermore, it can also absorb Reactive Blue 19 Dye (RB19) fast.

Cucurbit[6]uril-based multifunctional supramolecular assemblies: synthesis, removal of Ba(ii) and fluorescence sensing of Fe(iii).

A novel cucurbit[6]uril-based (Q[6]) supramolecular assembly {(NH4)2·Q[6]·(HDTNB)2·2H2O} (1) with a three-dimensional (3D) framework structure was successfully constructed via outer-surface interactions between Q[6] and a flexible aromatic compound, 5,5'-dithiobis-(2-nitrobenzoic acid) (H2DTNB), as a structure-directing agent. It is interesting to find that assembly 1 can selectively capture Ba(ii) cations among the common alkaline-earth metal ions of Mg(ii), Ca(ii), Sr(ii) and Ba(ii), resulting in the formation of an isomorphic 3D assembly {Ba(H2O)2Q[6]}·(HDTNB)2 (2). Furthermore, both assemblies 1 and 2 exhibit the selective sensing of Fe(iii) ions through fluorescence quenching, which has rarely been reported for Q[n]-based supramolecular assemblies.

Multiple Efficient Fluorescence Emission from Cucurbit[10]uril-[Cd4Cl16]8--Based Pillared Diamond Porous Supramolecular Frameworks.

Cucurbit[10]uril (Q[10] or CB[10]), with the largest rigid cavity (ca. 1.0 nm) yet characterized in the cucurbiturils family, and indeed among all artificial macrocyclic receptors to date, has been successfully exploited to construct a novel Q[10]-[Cd4Cl16]8--based pillared diamond porous supramolecular framework. Single-crystal X-ray diffraction analysis revealed that the three-dimensional open-nanotube-type porous framework is constructed from free Q[10] molecules and [Cd4Cl16]8- cluster anions through the outer surface interactions of Q[10]. Notably, the Q[10]-based porous framework host can accommodate guest dyes, such as rhodamine B (G1), pyrenemethanamine hydrochloride (G2), and bathocuproine hydrochloride (G3), to form solid materials with efficient red-green-blue (RGB) fluorescence. This work not only exemplifies a facile approach for the construction of macrocycle-based porous frameworks but also offers a simple, lower cost, yet still highly efficient means of preparing multi-emitting, including white-light-emitting, solid luminescent materials.

Inverted cucurbit[6]uril supramolecular assemblies formed in the presence of tetrachlorozincate anions

We investigated the interactions in an inverted cucurbit[6]uril (iQ[6]) with a series of 1,ω-alkyldimins and their supramolecular assemblies in the presence of the tetrachlorozincate anion ([ZnCl4]2−) structure directing agent. iQ[6] forms an outer surface interaction with [ZnCl4]2− to form different iQ[6]/[ZnCl4]2−-based supramolecular assemblies with different length 1,ω-alkyldimins. Interestingly, most 1,ω-alkyldimins were not visible in crystals structures in the presence of concentrated HCl. The porous iQ[6]/[ZnCl4]2−-based supramolecular assemblies could be used as materials for adsorbing volatile compounds.

Interaction of Cyclopentano Cucurbit[6]uril with Alkaline Earth Cations and Supramolecular Assemblies with Aid of [ZnCl4]2–

AbstractIn this study, we investigated the interaction of a fully substituted cyclopentano cucurbit[6]uril (CyP6Q[6]) with alkaline earth cations (AE2+) and corresponding supramolecular assemblies in the presence of tetrachloridozincate anions ([Zn(H2O)Cl3]− or [ZnCl4]2−). Single‐crystal X‐ray diffraction analysis revealed that the CyP6Q[6]−Mg2+−ZnCl2−HCl interaction system yielded an adduct of [Mg(H2O)6]2+ with CyP6Q[6]. The CyP6Q[6]−Ca2+, Sr2+ and Ba2+−ZnCl2−HCl interaction systems yielded linear AE2+/CyP6Q[6]/AE2+‐type coordination polymers that filled the cells in the [ZnCl4]2−‐based honeycomb‐like framework. Unlike unsubstituted Q[n] systems in which [ZnCl4]2− anions surround Q[n] molecules via outer surface interaction of Q[n], electrostatic interactions between [ZnCl4]2− anions and the coordinated AE2+ cations results in the formation of [ZnCl4]2−‐based honeycomb‐like frameworks.

Outer Surface Interactions of Cucurbit[6]uril That Trigger the Assembly of Supramolecular Three-Dimensional Polycatenanes.

A supramolecular polycatenane stabilized by outer surface interactions between cucurbit[6]uril (Q[6] or CB[6]) cations and [CdCl4 ]2- is reported. The arrangement of the poly-interlocked supramolecular framework is evidently constructed by a favorable combination of weak non-covalent interactions such as hydrophobic effects, hydrogen bonding, ion-dipole interactions, and C-H⋅⋅⋅Cl interactions in the solid state. Further study suggests that such 3D poly-interlocked species could be rapidly precipitated from the mixture solution in high yield owing to electrostatic interaction of the [CdCl4 ]2- anion with the electropositive outer surface of Q[6] host. This work thus demonstrates a simple, low-cost, and efficient non-covalent approach for the construction of a infinite 3D interlocked structure in water besides through coordination or covalent bonds.

Supramolecular coordination assemblies of a symmetrical octamethyl-substituted cucurbituril with alkali metal ions based on the outer-surface interactions of cucurbit[n]urils

Interactions of alkali cations (A+ = Na+, K+, Rb+, Cs+) with a symmetrical octamethyl-substituted cucurbituril (OMeQ[6]) have been investigated in the presence of different structure-directing agents. Single-crystal X-ray diffraction analysis has revealed that the interaction results in the formation of coordination complexes of OMeQ[6] with K+ and Cs+ cations in OMeQ[6]–ACl–HCl systems, whereas no complexes were obtained from systems containing Na+ and Rb+ in the presence of polychloride cadmium anions such as [Cd2Cl8]4−, [CdCl4]2−, or [Cd2Cl7]3− as structure-directing agents; in the presence of p-hydroxybenzoic acid (Hyb) as a structure-directing agent, the interaction results in the formation of coordination complexes of OMeQ[6] with Na+ and Cs+ cations in OMeQ[6]–ACl–H2O systems. More importantly, in the presence of these different structure-directing agents, OMeQ[6] or OMeQ[6]/A+ complexes can form different supramolecular assemblies based on the outer surface interaction of Q[n].

Supramolecular Assemblies of Cucurbit[10]uril Based on Outer Surface Interactions

Using an established method, we isolated a large quantity of cucurbit[10]uril (Q[10]) and prepared Q[10]-based supramolecular assemblies via different approaches. For example, the structure-directing agent [CdCl4]2– was used or the Q[10] molecule itself acted as a self-structure-directing agent to form different Q[10]-based supramolecular assemblies through the outer surface interaction of Q[10]. Generally, the Q[10]-based supramolecular assemblies possess porous features that suggest that Q[n]-based compounds could be used to manufacture molecular sieves and sensors and applied in absorption and separation technologies.

Coordination of fully substituted cyclopentano cucurbit[5]uril with alkaline earth cations in the presence of tetrachlorozincate anions

In this study, fully substituted cyclopentano cucurbit[5]uril (CyP5Q[5]) were coordinated with an alkaline earth cations (AE2+) in the presence of tetrachlorozincate anions ([ZnCl4]2−). Single-crystal X-ray diffraction analysis revealed that the CyP5Q[5]–Mg2+–[ZnCl4]2−–HCl interaction system yielded an Mg2+/Cl−@CyP5Q[5]-type molecular bowl, with a chloride anion in the cavity of the CyP5Q[5] moiety. The CyP5Q[5]–Ca2+ and Sr2+–[ZnCl4]2−–HCl interaction systems yielded isolated AE2+/CyP5Q[5]/AE2+-type molecular capsules, again with a chloride anion in the CyP5Q[5] cavity. A honeycomb effect was evident in all three systems, in which the of the [ZnCl4]2− anions surround the CyP5Q[5] molecules through outer surface interactions between Q[n] and electrostatic interactions with AE2+ cations, resulting in the formation of porous supramolecular assemblies. Direct coordination between Ba2+ and CyP5Q[5] yielded zigzag coordination polymers. The CyP5Q[5]/AE2+-based supramolecular assemblies (AE=Mg, Ca, Sr, Ba) presented different porous conformations and displayed differential absorption of volatile compounds.