Construction of cucurbit[7]uril based tubular nanochannels incorporating associated [CdCl4]2- and lanthanide ions

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 [Cd_xCl_y]^n- anions formed by Cd²⁺ cations in a HCl medium, four different TMeQ[6]-[Cd_xCl_y]^n--based supramolecular frameworks are constructed. Three of the most common TMeQ[6]-[Cd_xCl_y]^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]-[Cd_xCl_y]^n--based supramolecular frameworks and then forming Q[n]-based framework supported catalysts by sulfurization or reduction.

Cucurbit[8]uril-Assisted Nucleophilic Reaction: A Unique Supramolecular Approach for Cyanide Detection and Removal from Aqueous Solution

A unique supramolecular approach of preparing and using a cucurbit[8]uril (Q[8])-based dynamic host-guest assembly for cyanide sensing in and removal from water has been successfully developed. The dicyanovinyl-attached cationic guest (1) was designed as the fluorescent response moiety for the detection of the cyanide anion via a nucleophilic addition reaction in the assist of the Q[8]-based 2:2 quaternary complexes. Furthermore, the reaction of cyanide with 1 further switched the Q[8]-based host-guest assemblies from the 2:2 complexes to the 1:1 supramolecular polymers that precipitate in water. Thus, the macrocyclic-based dynamic host-guest assembly has potential use in applications for solving the problem of toxic anion pollutants present in aqueous environments.

Elucidating dissociation activation energies in host-guest assemblies featuring fast exchange dynamics

The ability to mediate the kinetic properties and dissociation activation energies (E _a) of bound guests by controlling the characteristics of "supramolecular lids" in host-guest molecular systems is essential for both their design and performance. While the synthesis of such systems is well advanced, the experimental quantification of their kinetic parameters, particularly in systems experiencing fast association and dissociation dynamics, has been very difficult or impossible with the established methods at hand. Here, we demonstrate the utility of the NMR-based guest exchange saturation transfer (GEST) approach for quantifying the dissociation exchange rates (k _out) and activation energy (E _a,out) in host-guest systems featuring fast dissociation dynamics. Our assessment of the effect of different monovalent cations on the extracted E _a,out in cucurbit[7]uril:guest systems with very fast k _out highlights their role as "supramolecular lids" in mediating a guest's dissociation E _a. We envision that GEST could be further extended to study kinetic parameters in other supramolecular systems characterized by fast kinetic properties and to design novel switchable host-guest assemblies.

Thorium(iv) and uranium(vi) compounds of cucurbit[10]uril: from a one-dimensional nanotube to a supramolecular framework

Cucurbit[10]uril {Q[10]} has the largest portal size and cavity in the series of Q[n] (n = 5-10) molecules. In contrast to its rich host-guest chemistry, its coordination chemistry is underdeveloped with only limited metal ions being investigated so far. In this work, we initiated the study of Q[10] complexes with Th(iv) and U(vi) ions in HCl solutions via a self-assembly approach. The coordination of Th(iv) ions with Q[10] led to the formation of a compound, {Th4(Cl)16(H2O)20(Q[10])}·nH2O (Q[10]-Th), with a unique nano-tubular structure, while U(vi) ions facilitated the formation of a compound, [(UO2)2(Cl)4(H2O)6]·(Q[10])2·HCl·nH2O (Q[10]-U), with a Q[10]-based supramolecular framework structure via intermolecular outer-surface and second-shell interactions. The structural and spectroscopic aspects of the two compounds together with their optical and thermal properties have been investigated. The successful preparation and characterization of the first two Q[10] compounds with Th(iv)/U(vi) ions highlighted the potential for further exploration of Q[10] coordination chemistry with actinide ions.

Yttrium and lanthanide (Ln = La and Gd) complexes with cucurbit[10]uril: crystals transforming from supramolecular frameworks to coordination nanotubes

Yttrium and lanthanide complexes with cucurbit[10]uril have been investigated with crystals transforming from supramolecular structures to coordination nanotubes being revealed.

Lanthanoid Heteroleptic Complexes with Cucurbit[5]uril and Dicarboxylate Ligands: From Discrete Structures to One-Dimensional and Two-Dimensional Polymers

Lanthanoid heteroleptic complexes with cucurbit[5]uril {Q[5]} and two dicarboxylate ligands, e.g., diglycolic acid (H₂DGC) and glutaric acid (H₂GT), have been investigated with six new compounds featuring a tetrametallic and dimetallic discrete structures, a one-dimensional (1D) polymer, and three two-dimensional (2D) polymers with a unique honeycomb-type topology being synthesized and structurally characterized. [La₄(Q[5])₃(DGC)₂(NO₃)₂(H₂O)₁₂][La(DGC)(H₂O)₆]·7NO₃· nH₂O (1) has a tetrametallic structure constructed with three bis-bidentate Q[5] ligands linking two [La(DGC)(H₂O)₂]⁺ species in the middle and two [La(H₂O)₄(NO₃)]²⁺ species at both ends. [Ce₂(Q[5])(DGC)(NO₃)(H₂O)₁₀]·3NO₃·4H₂O (2) has a dimetallic structure built up with a bis-bidentate Q[5] ligand linking [Ce(DGC)(H₂O)₃(NO₃)] and [Ce(H₂O)₇]³⁺ on each side of the Q[5] portals. [Ce₃(Q[5])₃(DGC)₂(H₂O)₉][Ce(DGC)(H₂O)₆]₂·7NO₃· nH₂O (3) has a 1D polymeric structure built up with bis-bidentate Q[5] ligands in-turn linking one [Ce(H₂O)₆]³⁺ and two [Ce(DGC)(H₂O)₆]¹⁺ cationic species. [Ln₂(Q[5])₂(GT)(H₂O)₆]·4NO₃· nH₂O [Ln = La (4), Ce (5) and Nd (6)] have similar 2D polymeric structures built up with two types of 9-fold coordinated Ln polyhedra linked by Q[5] via bis-bidentate carbonyl groups on both sides forming 1D chains which are further connected by bridging GT^2- ligands to form 2D polymers with a unique honeycomb-type topology. Their vibrational modes and electronic structures have also been investigated.

Porous supramolecular assemblies and functional properties of perhydroxylated cucurbit[6]uril and polyoxometallates

(HO)₁₂Q[6] and POMs were used as basic building blocks, and interactions yielded two novel types of supramolecular assemblies at different HCl concentrations.

Thorium(IV) and Uranium(IV) Complexes with Cucurbit[5]uril

Tetravalent thorium and uranium complexes with cucurbit[5]uril (Q[5]) were investigated with eight new complexes being synthesized and structurally characterized. [Th(Q[5])(OH)(H₂O)₂]₆·18NO₃· nH₂O (1) has a hexagonal nanowheel structure with each of the six Th⁴⁺ ions being cap-coordinated by a Q[5] and monodentate-coordinated to the nearby Q[5]. [Th(Q[5])(HCOO)(H₂O)₄][Th(NO₃)₅(H₂O)₂]₂[Th(NO₃)₃(HCOO)(H₂O)₂]_0.5·NO₃· nH₂O (2) has a heteroleptic mononuclear structure with a Th⁴⁺ ion cap-coordinated on one side of the Q[5] portal and monodentate-coordinated to a formate anion inside the Q[5] cavity. [KTh_1.5(Q[5])Cl(NO₃)₃][Th(NO₃)₅(H₂O)₂]·2NO₃·2.5H₂O (3) has a heterometallic structure with both Th⁴⁺ and K⁺ ions each occupying one side of the two Q[5] portals forming a capsule. [CsTh(Q[5])Cl(NO₃)₂(H₂O)₃]·2NO₃· nH₂O (4) has a heterometallic 1D polymeric structure with both Th⁴⁺ and Cs⁺ ions each occupying one side of the two Q[5] portals, forming monomers which are linked together by sharing two water molecules and one carbonyl oxygen atom between Th⁴⁺ and Cs⁺ ions. [Th(Q[5])Cl(H₂O)][CdCl₃][CdCl₄]·0.5HCl·4H₂O (5), [Th(Q[5])Cl(H₂O)][Ru₂OCl₉(H₂O)]·0.5HCl·9.5H₂O (6), [Th(Q[5])Cl(H₂O)][IrCl₆]_1.5·3H₂O (7), and [U(Q[5])Cl(H₂O)][ZnCl₃(H₂O)][(ZnCl₄)]·8H₂O (8) have similar 1D polymeric structures with Th⁴⁺/U⁴⁺ ions cap-coordinated on one side of a Q[5] and bidentate coordinated to the nearby Q[5]. The transition metal chlorides act as anions for charge compensation as well as structure inducers via cation-anion interactions forming various anion patterns around the 1D polymers. Actinide contraction has been observed in the early actinide series.

The chaotropic effect as an orthogonal assembly motif for multi-responsive dodecaborate-cucurbituril supramolecular networks

In aqueous solution, host-guest complexation is frequently driven by the hydrophobic effect, which also constitutes a popular approach in the design of supramolecular assemblies. Herein, we report an orthogonal assembly motif, the chaotropic effect, which exploits the tendency of chaotropic anions to associate with hydrophobic surfaces.

Highly selective absorption of polychloromethanes in perhydroxylated cucurbit[6]uril-based supramolecular assemblies

Two perhydroxylated cucurbit[6]uril-based porous assemblies have been obtained by the crystallization of perhydroxylated cucurbit[6]uril {(HO)₁₂Q[6]} from aqueous HCl solutions of different concentrations, which exhibit highly selective absorption of polychloromethanes.

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.

Synthesis and Structure of the Inclusion Complex {NdQ[5]K@Q[10](H₂O)₄}·4NO₃·20H₂O

Heating a mixture of Nd(NO₃)₃·6H₂O, KCl, Q[10] and Q[5] in HCl for 10 min affords the inclusion complex {NdQ[5]K@Q[10](H₂O)₄}·4NO₃·20H₂O. The structure of the inclusion complex has been investigated by single crystal X-ray diffraction and by X-ray Photoelectron spectroscopy (XPS).

Adducts of aqua complexes of Ln3+with hexahydroxyhexamethylcucurbit[6]uril: potential application in the isolation of heavy lanthanides

The interactions between a series of Ln³⁺and HHQ[6] were investigated. X-ray crystallography analysis revealed that HHQ[6] selectively interacts with certain Ln ions. The experimental results point to a possible means of isolating lighter or heavier Ln cations.

Supramolecular assemblies constructed from inverted cucurbit[7]uril and lanthanide cations: synthesis, structure and sorption properties

The interaction of a series of lanthanide cations (Ln³⁺) with inverted cucurbit[7]uril (iQ[7]) in the presence of [ZnCl₄]²⁻ anions as a structure-directing agent have been investigated.

Interaction of a symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril with Ln3+: potential applications for isolation of lanthanides

Interaction of a symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (TMeQ[6]) with a series of lanthanide cations (Ln³⁺) was investigated in neutral water and acidic solution.

Interaction of Ln3+ with Methyl-Substituted Cucurbit[n]urils (n=5,6) Derived from 3α-Methyl Glycoluril

The interactions between a series of lanthanide cations (Ln³⁺ ) and methyl-substituted cucurbiturils (SPMeQ[5] and SHMeQ[6]) derived from a 3α-methyl glycoluril have been investigated. Single-crystal X-ray diffraction analysis revealed that both SPMeQ[5] and SHMeQ[6] selectively interact with certain lanthanide ions. SPMeQ[5] forms coordination capsules in the presence of [CdCl₄ ]^2- . The Ln³⁺ cations that interact are the four light lanthanides, La³⁺ , Ce³⁺ , Pr³⁺ , and Nd³⁺ , whereas the remaining lanthanide cations remain in solution. SHMeQ[6] formed adducts of SHMeQ[6] with aqua complexes of lanthanide cations ([Ln(H₂ O)₈ ]³⁺ ); for SHMeQ[6]-Ln(NO₃ )₃ -CdCl₂ -HCl systems (Ln=Gd-Lu), no solid crystals were obtained from systems that contained La, Ce, Pr, Nd, Sm, or Eu. Whereas solid crystals of adducts of SHMeQ[6] with aqua complexes of lanthanide cations (Ln=Sm-Lu) formed SHMeQ[6]-Ln(NO₃ )₃ systems in neutral solution, no solid crystals were obtained from systems that contained La, Ce, Pr, or Nd. These results suggest that SPMeQ[5]- and SHMeQ[6]-Ln(NO₃ )₃ systems could be useful for the selective isolation of these lighter or heavier lanthanide cations from mixtures. Energy-dispersive spectrometry indicated that the lighter or heavier lanthanide cations could be isolated from their heavier or lighter counterparts through interaction with SPMeQ[5] and SHMeQ[6].

Host–guest interactions in an inverted cucurbit[7]uril with α,ω-alkyldiammonium guests

Host–guest interactions in an aqueous solution of an inverted cucurbit[7]uril (iQ[7]) with α,ω-alkyldiammonium guests (H₃N(CH₂)_xNH₃Cl₂, x = 2, 4, 6, 8, 10, and 12 named 1–6) were investigated by nuclear magnetic resonance (NMR) and isothermal titration calorimetry (ITC).

Unexpected crystallization of the metastable tubular coordination polymer of cucurbit[6]uril with magnesium ions which spontaneously transforms into a discrete coordination complex

We report on the kinetic crystallization of the tubular coordination polymer constructed from cucurbit[6]uril and magnesium ions. The metastable phase spontaneously converts into a thermodynamically favored discrete coordination complex.

Coordination of Ln3+ in ortho-tetramethyl-substituted cucurbituril supramolecular assemblies formed in the presence of cadmium nitrate: potential applications for isolation of heavier lanthanides

Coordination in supramolecular assemblies was investigated by reacting a series of lanthanide cations (Ln³⁺) and a new alkyl-substituted cucurbituril, (o-TMeQ[6]).

Cucurbit[n]uril-based coordination chemistry: from simple coordination complexes to novel poly-dimensional coordination polymers

Cucurbit[n]urils are a family of molecular container hosts bearing a rigid hydrophobic cavity and two identical carbonyl fringed portals. They have attracted much attention in supramolecular chemistry because of their superior molecular recognition properties in aqueous media. This review highlights the recent advances and challenges in the field of cucurbit[n]uril-based coordination chemistry. It not only presents progress in the knowledge of such macrocyclic compounds, which range from simple to complicated architectures, but also presents new routes of synthesis and their advantages in hybrid porous solids. The concept of structure "inducer" for their structural design to achieve predictable structures and controlled pores is described. The large pore sizes and hydrophobic cavities of these compounds that lead to unprecedented properties and potential applications are also discussed.