Outer Surface Interactions Research Articles

Cucurbit[8]uril-modulated discrete pyrene dimers fluorescent sensor for nitroaromatic compounds and latent fingerprints visualization

As a promising class of luminescent materials, π-conjugated organic aromatic molecules are usually subject to aggregation-caused quenching (ACQ) effect, which limits their wide application. Currently, obtaining structurally visualized solid luminescent materials of polycyclic aromatic hydrocarbons (PAHs) without complex synthetic purification steps remains a challenging topic. Herein, we focus on the supramolecular assembly strategy to constructed a solid fluorescent material (HPTS@Q[8]@Rb+) by co-assembling cucurbit[8]uril (Q[8]) with 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) and rubidium ions based on the coordination and outer surface interactions of Q[8]. HPTS@Q[8]@Rb+ exhibited good fluorescence properties with quantum yields of 2.28 % and 73.15 % in solid state and aqueous suspensions, respectively, providing a good sensing platform for nitroaromatic compounds (NACs), especially for 2,4,6-trinitrophenol (PA) and 4-nitroaniline (4-NA) with remarkable quenching constants (KSV=4.06×104 M−1 for PA and KSV=2.95×104 M−1 for 4-NA) in working range of 0–3.33×104 M and 0–5.0×104 M, respectively. Moreover, a fluorescent fingerprint powder was prepared by combining montmorillonite (MMT) for high-resolution visualization of latent fingerprints (LFPs) without substrate limitation. This study demonstrates the synthesis of Q[n]-based fluorescent material, the anion-rich aromatic compounds can be used as potential moieties for assembly with Q[n], providing a facile and promising approach to develop PAHs-based luminescent materials. This supramolecular self-assembly strategy provides a fundamental design principle for the creation of diverse functional crystalline solid materials.

Unprecedented stepwise electron transfer and photocatalysis in supramolecular assembly derived hybrid single-layer two-dimensional nanosheets in water

Herein, a simple and effective outer-surface interactions assisted supramolecular hierarchical assembly has been first exploited to uniformly distribute tungstosilicic acid (TSA) inside the porous structure of cucurbit[10]uril-based single-layer 2D supramolecular-organic-frameworks (Q[10]-SOFs) in water. Importantly, the 2D Q[10]-SOFs can further serve as light harvesting antenna, achieving fast energy transfer to the embedded redox-active TSA upon photoexcitation, resulting in efficient visible light-driven selective oxidation of benzyl alcohols into the corresponding aldehydes in high yield at room temperature. Further studies revealed that the integrated of 2D Q[10]-SOFs and TSA played a key role in the catalytic process, due to the presence of a novel stepwise electron transfer route in the single-layer hybrid 2D structures.

Preparation of a class of cucurbit[6]uril-light rare-earth-based supramolecular assemblies and its efficient detection of chloramphenicol

By introducing 4,4′-naphthalenedisulfonic acid (4,4′-H2BPs) as a structure-induced agent, four novel cucurbit[6]uril-based supramolecular assemblies have been successfully prepared in the cucurbit[6]uril (Q[6]) system with light rare-earth elements (La3+, Ce3+, Pr3+, Nd3+) under hydrothermal conditions. Crystal structure analysis shows that the assemblies 1 (La3+), 2 (Ce3+), 3 (Pr3+) are isomorphism 3D frameworks, where Q[6] can directly coordinate with light rare-earth metal ions to form 1D −Ln(III)- Q[6]-Ln(III)- chains, while the 4 (Nd3+) presents 3D structures stacking by the unit of Q[6]@Nd3+@Q[6]@Nd3+@Q[6], respectively. In these structures, 4,4′-H2BPs ligands all can act as an organic counter anion and bridging via the outer-surface interaction of cucurbit[n]uril (OSIQ) in the system, which is the main driving force from low-dimensional to high-dimensional. Meanwhile, the fluorescence sensing performance of the two assemblies for antibiotics was investigated, and the results showed that assembly 1 could be used as a promising fluorescent sensor material to detect chloramphenicol (CAP).

Selective removal of Cr2O72- in aqueous solution by nonporous pure crystals of cucurbit[6]uril.

Cucurbit[6]uril (Q[6]) could serve as a selective absorbent for the toxic anion Cr2O72-, which was demonstrated by the results of UV-vis, ICP, XPS, SEM, and EDS experiments. Single-crystal X-ray diffraction analysis revealed that capture capacity could be attributed to the outer-surface interactions of cucurbit[n]uril between Cr2O72- and the outer surface of Q[6].

Effect of tetrachloro cadmium (II)/cobalt (II) ions modulation on organic-macrocyclic adaptive assembly based on cucurbit[6]uril and p-nitrophenol

Adaptive pore channels provide many possibilities for constructing functional supramolecular assemblies, making macrocyclic-based assemblies available for a variety of functions. To investigate the effect of ions modulation on the structure and properties of organic-macrocyclic adaptive assemblies, two supramolecular assemblies based on cucurbit[6]uril (Q[6]) and p-nitrophenol (PNP) are constructed through the outer-surface interactions of cucurbit[n]urils (Q[n]s): assembly 1 (Q[6]-PNP) and assembly 2 (Q[6]-PNP-[CdCl4]2−-[CoCl4]2−). The structural characteristics and the difference in the ability of the two assemblies to capture PNP molecules are investigated by X-ray crystallography, UV–vis spectroscopy, etc. It is found that after [CdCl4]2−, [CoCl4]2− are added as structure-directing agents, many honeycomb-like hexagonal pores are formed in assembly 2, but its ability to capture PNP molecules is only one-third of that of assembly 1. This indicates that ions modulation may reduce the ability of macromolecules to capture organic molecules, but the assembly 2 modulated by tetrachloro cadmium (II) /cobalt (II) ions has many honeycomb-like pores, which also provides new insights for the construction of more supramolecular assemblies with functionality based on Q[n]s.

Supramolecular Self-assemblies of inverted cucurbit[6]uril with 1,5-pentanediamine

In this study, single crystal X-ray diffraction and 1H NMR spectroscopy were used to examine the interaction of the guest 1,5-pentanediamine with inverted cucurbit[6]uril (iQ[6]) in the presence of [ZnCl4]2− anion. The results show that [ZnCl4]2− and [Zn(H2O)Cl3]− anions form a honeycomb framework structure, and iQ[6] forms a 1:1 complex with 1,5-pentanediamine. Inverted cucurbit[6]uril forms molecular chains via outer surface interactions, which in turn fill in the honeycomb framework structure. The amino groups at both ends of the 1,5-pentanediamine guest are situated at the entrance of the central cavity, while the alkyl chain part resides in the central cavity of the iQ[6].

Preparation and Biomedical Applications of Cucurbit[n]uril-Based Supramolecular Hydrogels.

The cucurbit[n]uril supramolecular hydrogels are driven by weak intermolecular interactions, of which exhibit good stimuli responsiveness and excellent self-healing properties. According to the composition of the gelling factor, supramolecular hydrogels comprise Q[n]-cross-linked small molecules and Q[n]-cross-linked polymers. According to different driving forces, hydrogels are driven by the outer-surface interaction, the host-guest inclusion interaction, and the host-guest exclusion interaction. Host-guest interactions are widely used in the construction of self-healing hydrogels, which can spontaneously recover after being damaged, thereby prolonging their service life. The smart Q[n]s-based supramolecular hydrogel composed is a kind of adjustable and low-toxicity soft material. By designing the structure of the hydrogel or modifying the fluorescent properties, etc., it can be widely used in biomedicine. In this review, we mainly focus on the preparation of Q[n]-based hydrogels and their biomedical applications including cell encapsulation for biocatalysis, biosensors for high sensitivity, 3D printing for potential tissue engineering, drug release for sustained delivery, and interfacial adhesion for self-healing materials. In addition, we also presented the current challenges and prospects in this field.

Self-assembly of symmetric tetramethylcucurbit[6]uril with phosphomolybdic acid: A stable anode material with lithium-storage properties

Here, a new hybrid material was prepared by the self-assembly of symmetric tetramethylcucurbit [6]uril (TMeQ [6]) and Keggin-type phosphomolybdic acid (PMA). The driving force of TMeQ [6] and PMA self-assembly was the outer-surface interactions of cucurbit[n]uril, i.e., electrostatic interactions between the positively-charged electric outer surface of TMeQ [6] and the PMA anion. The TMeQ [6]-PMA hybrid was stable and maintained the redox properties of PMA. As an electrode material, it could undergo multi-electron redox reactions and showed good structural stability and electrochemical performance. Moreover, the porous structure of the TMeQ [6]-PMA hybrid gave it a large specific surface area and the ability to store Li/Li+, which gives it potential application prospects as an anode material in lithium-ion batteries.

A cucurbit[8]uril-based supramolecular polymer constructed via outer surface interactions: Use as a sensor, in cellular imaging and beyond

In recent years, most of the constructions on cucurbit[n]uril-based supramolecular polymers have been based on host–guest chemistry, however, this limits the choice of host and guest. Herein, we present a newly designed supramolecular polymer, namely Q[8]@PEG-HPTS formed by utilizing outer surface Q[8] interactions. In aqueous solution, the supramolecular polymer Q[8]@PEG-HPTS was obtained quickly and simply by mixing Q[8] with PEG-HPTS, where after, a variety of characterization techniques were employed to confirm the structure of the Q[8]@PEG-HPTS. The ability of this system to selectively recognize metal ions as well as pesticide molecules was also investigated; selectivity was observed for Fe3+ and paraquat. The biocompatibility and excellent fluorescence properties associated with the constituents of the supramolecular polymer allowed for the imaging of HeLa cells. This system could image and trace the nucleus through the cytoplasm, indicating that it could enter and internalize HeLa cells. Finally, by continuously adjusting the ratio between Q[8] and PEG-HPTS, a Q[8]@PEG-HPTS hydrogel was obtained. This hydrogel exhibited a stimulated temperature response, and opens up further possibilities for exploring the applications of such supramolecular polymers.

Q[8]-based frameworks exhibiting clustering-triggered emission and responses to organic molecules

The outer surface interaction of cucurbit[n]urils (Q[n]s) is an important supramolecular interaction that results from the positive electrostatic potential on the outer surface of Q[n]s. It cannot only result in the formation of various novel Q[n]-based supramolecular frameworks, but can also lead to clustering emission of Q[n]s. In this work, three different Q[8]-based supramolecular frameworks, assembled through the outer surface interaction of Q[n]s (OSIQ), were prepared according to the literature. The solid-state clustering-triggered emission (CTE) characteristics of the frameworks were also determined. Moreover, investigation of their adsorption properties showed that the solid-state CTE of the three Q[8]-based supramolecular frameworks was quenched in the presence of certain chemicals and that they exhibited high selectivity for pyridine. Framework B exhibited the highest adsorption of pyridine.

Cucurbit[6]uril-based supramolecular frameworks formed through outer surface interactions and application for iodine adsorption

The interaction between the outer surface of cucurbit[6]uril (Q[6]) and methyl triphenyl phosphorus iodide (MTPI) has been studied in the presence of [CdCl4]2-. The MTPI is connected to four neighboring Q[6]s through weak interactions such as C-H···π and C-H···O, whilst the [CdCl4]2- is connected with the portal carbonyl oxygen, glycoside urea methylene and a bridging methylene of a Q[6] molecule via ion–dipole interactions. These interactions were evident from a single crystal X-ray diffraction study of Q[6]-MTPI-[CdCl4]2-. Furthermore, this complex exhibits a porous structure, which can be described as a Q[6]-based supramolecular framework (QSF), and its ability to adsorb iodine was also investigated.

CdS-Based Catalysts Derived from TMeQ[6]/[CdxCly]n--Based Frameworks for Oxidation Benzylamine.

The anion-induced outer surface interaction of Q[n]s is an important driving force in the construction of Q[n]-based supramolecular frameworks. In this work, a symmetric tetramethyl-substituted cucurbit[6]uril (TMeQ[6]) is selected as the basic structural block. Using the anion-induced outer surface interaction of Q[n]s derived from [CdxCly]n- anions formed by Cd2+ cations in a HCl medium, four different TMeQ[6]-[CdxCly]n--based supramolecular frameworks are constructed. Three of the most common TMeQ[6]-[CdxCly]n--based supramolecular frameworks are selected for further vulcanization, and three different CdS/TMeQ[6]-based framework catalysts with different structures and properties are obtained. The catalytic activities of these three CdS/TMeQ[6]-based framework catalysts are investigated by the coupling photocatalytic reaction of aminobenzyl, and the results showed that the catalytic activities of the three catalysts are all higher than that of pure CdS. Therefore, this work establishes that it is possible to establish a method for synthesizing the Q[n]-based framework-supported catalysts by first synthesizing TMeQ[6]-[CdxCly]n--based supramolecular frameworks and then forming Q[n]-based framework supported catalysts by sulfurization or reduction.

Clustering emission of cucurbit[n]urils in the solid- and solution-state induced by the outer surface interactions of cucurbit[n]urils

Atypical luminescent compounds that do not contain conventional chromophores emit light due to clustering and have important basic research value and a broad range of potential applications. To date, most atypical luminescent compounds are small molecules or polymers containing groups such as cyano, carbonyl and hydroxyl. In this work, driven by some sporadic and accidental luminescence phenomena observed for cucurbit[n]urils (Q[n]s), the luminescent properties and mechanism of Q[n]s in the solid- and solution-state were systematically studied and the clustering emission of Q[n]s confirmed. Our experiments have revealed that the self-induced outer-surface interactions of Q[n]s (OSIQ) are the most important driving force resulting in the clustering emission of Q[n]s. Substances that can weaken the effect of self-induced OSIQ, such as the presence of various aromatic compounds and anions, may weaken or quench the clustering emission of Q[n]s. This not only reveals the new characteristics and mechanism of the clustering emission of Q[n]s, but also provides new insights on how to utilize the clustering emission of Q[n]s and construct new types of macrocyclic luminescence systems.

Capture and Release of [PdCl4]2– by TMeQ[6]-Based Supramolecular Frameworks Assembled via the Outer Surface Interaction of Q[n

Capture and Release of [PdCl₄]^2– by TMeQ[6]-Based Supramolecular Frameworks Assembled via the Outer Surface Interaction of Q[<i>n</i>

Study on the interactions between melamine-cored Schiff bases with cucurbit[n]urils of different sizes and its application in detecting silver ions.

Three different complexes, TMeQ[6]-TBT, Q[7]-TBT, and Q[8]-TBT are constructed by three different cucurbiturils and synthesized by guest melamine-cored Schiff bases (TBT) through outer-surface interaction and host–guest interactions. TBT forms a TMeQ[6]-TBT complex with TMeQ[6] through outer-surface interaction, while Q[7]-TBT and Q[8]-TBT form complexes with Q[7,8] through host–guest interactions. Among them, Q[7]-TBT is selected as a UV detector for the detection of silver ions (Ag+). This work makes full use of the characteristics of each cucurbituril and melamine-cored Schiff base to construct a series of complexes and these are applied to metal detection.

Q[8]/SC[6]A-based framework constructed via OSIQ for metal ion capture

Since the outer surface interaction of Q[n]s (OSIQ, including self-, anion- and aromatic-induced OSIQs) was proposed in 2014, it has become the most important research area in our group to construct various Q[n]-based supramolecular frameworks via the OSIQ strategy. Herein, we report a novel supramolecular framework constructed using cucurbit[8]uril (Q[8]) and 4-sulfocalix[6]arene (SC[6]A). This Q[8]/SC[6]A-based supramolecular framework is a product via the perfect combination of self-, anion- and aromatic-induced OSIQs. This framework has the characteristics of easy preparation and high stability with the most important feature being the sequence selective capture of specific metal cations, such as common alkali- and alkaline earth metal ions, and renewability. Thus, this framework may be used in seawater desalination, potassium ion enrichment, radioactive cesium ion pollution source treatment, Gruinard's treatment or water softening and other applications.

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 [ZnCl4]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

Supramolecular self-assemblies of perhydroxycucurbit[5]uril with Keggin-type heteropolyacids

We report the preparation and single crystal X-ray diffraction analysis of three supramolecular self-assemblies based on perhydroxycucurbit[5]uril {(HO)10Q[5]}, Keggin-type heteropolyacids (HPAs), and potassium or barium cations. Crystallographic data revealed that all 3D self-assemblies are constructed by a stack of 2D layered structures composed of (HO)10Q[5]/K+ or (HO)10Q[5]/Ba2+ complexes cations and HPAs anions. Although there are differences in 2D layered structures, all the driving force comes from the outer surface interactions of (HO)10Q[5] including: (1) typical hydrogen bonding by hydroxyl groups and atypical hydrogen bonding by methylene on the outer surface of (HO)10Q[5]; (2) dipole interaction between the positively charged methylene or carbonyl carbon atoms of (HO)10Q[5] and the negatively charged oxygen atoms of the HPAs; (3) The electrostatic interaction between the (HO)10Q[5]/metal cations and the HPAs anions plays a main role in self-assembling.

Supramolecular Frameworks Constructed by Exclusion Complexes of Symmetric Dicyclohexanocucurbit[6]uril with Benzene Ring-Containing Guests

Supramolecular interactions between symmetric dicyclohexanocucurbit[6]uril (CyH2Q[6]) and five benzene ring-containing guests have been studied by various techniques, such as X-ray crystallography, 1H NMR spectroscopy, mass spectrometry, and quantum chemistry calculations. X-ray crystallography shows that the exclusion complexes of CyH2Q[6] with guests generate supramolecular assemblies with multidimensional and multilevel frameworks. The supramolecular interactions include portal interactions between the negatively electrostatic potential portals of CyH2Q[6] and the terminal groups of the guests, and the outer-surface interaction between the positively electrostatic potential outer surface of the CyH2Q[6] and the benzene ring of the guests. In aqueous solution, the experimental data and quantum chemistry calculation results show that all the guests prefer exo binding with CyH2Q[6].

Cucurbit[n]uril-Based Supramolecular Frameworks Assembled through Outer-Surface Interactions.

Porous materials, especially metal-organic frameworks, covalent organic frameworks, and supramolecular organic frameworks, are widely used in heterogeneous catalysis, adsorption, and ion exchange. Cucurbit[n]urils (Q[n]s) suitable building units for porous materials because they possess cavities with neutral electrostatic potential, portal carbonyls with negative electrostatic potential, and outer surfaces with positive electrostatic potential, which may result in the formation of Q[n]-based supramolecular frameworks (QSFs) assembled through the interaction of guests within Q[n]s, the coordination of Q[n]s with metal ions, and outer-surface interaction of Q[n]s (OSIQ). This review summarizes the various QSFs assembled via OSIQs. The QSFs can be classified as being assembled by 1) self-induced OSIQ, 2) anion-induced OSIQ, and 3) aromatic-induced OSIQ. The design and construction of QSFs with novel structures and specific functional properties may establish a new research direction in Q[n] chemistry.