The crystal structure of a mononuclear PrIII complex with cucurbit[6]uril

A new mononuclear complex, penta-aqua-(cucurbit[6]uril-κ2 O,O')(nitrato-κ2 O,O')praseodymium(III) dinitrate 9.56-hydrate, [Pr(NO3)(CB6)(H2O)5](NO3)2·9.56H2O (1), was obtained as outcome of the hydro-thermal reaction between the macrocyclic ligand cucurbit[6]uril (CB6, C36H36N24O12) with a tenfold excess of Pr(NO3)3·6H2O. Complex 1 crystallizes in the P21/n space group with two crystallographically independent but chemically identical [Pr(CB6)(NO3)(H2O)5]2+ complex cations, four nitrate counter-anions and 19.12 inter-stitial water mol-ecules per asymmetric unit. The nona-coordinated PrIII in 1 are located in the PrO9 coordination environment formed by two carbonyl O atoms from bidentate cucurbit[6]uril units, two oxygen atoms from the bidentate nitrate anion and five water mol-ecules. Considering the differences in Pr-O bond distances and O-Pr-O angles in the coordination spheres, the coordination polyhedrons of the two PrIII atoms can be described as distorted spherical capped square anti-prismatic and muffin polyhedral.

Supramolecular Assembly of Tetramethylcucurbit[6]uril and 2-Picolylamine

The supramolecular assembly of symmetrical tetramethylcucurbit[6]uril (TMeQ[6]) and 2-picolylamine (AMPy) has been investigated via various techniques, including ultraviolet-visible (UV-vis) and nuclear magnetic resonance spectroscopy, isothermal titration calorimetry (ITC), and X-ray crystallography. The results indicated that TMeQ[6] could encapsulate the AMPy guest molecule to form a stable inclusion complex. The rotational restriction of the guest in the cavity of TMeQ[6] resulted in a large negative value of entropy. The X-ray crystal structure of the 1:1 inclusion complex between TMeQ[6] and AMPy revealed that AMPy exists in the elliptical cavity of TMeQ[6].

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.

Potential Applications of Cucurbit[n]urils and Their Derivatives in the Capture of Hazardous Chemicals

Cucurbit[n]urils (Q[n]s) are a relatively young family of macrocycles, consisting of glycoluril units bridged by methylene groups, and their unique structures have attracted extensive attention from chemists in recent decades. Due to the presence of a rigid hydrophobic inner cavity and two polar outer portals lined with carbonyl groups, Q[n]s not only encapsulate guest species into the cavity, but also coordinate with metal ions/clusters. Considerable achievements have been obtained in the fields of Q[n]s-based host-guest chemistry, coordination chemistry, as well as the combination of host-guest and coordination chemistry. Furthermore, the outer surface of Q[n]s has been demonstrated to be capable of interacting with definite species to generate supramolecular architectures in recent years. With more in-depth research into Q[n]s, their application studies have also emerged as a hot topic. This Minireview focuses on recent advances in the potential applications of solid-state materials based on Q[n]s and their derivatives for the capture and adsorption of hazardous chemicals from a solution or a gas mixture.

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.

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.

Study on the Binding Interaction of the α,α',δ,δ'-Tetramethylcucurbit[6]uril With Biogenic Amines in Solution and the Solid State

1H NMR spectroscopy and MALDI-TOF mass spectrometry were utilized to examine the binding interaction of α,α',δ,δ'-tetramethylcucurbit[6]uril (TMeQ[6]) and six biogenic amines (spermine, spermidine, 2-phenethylamine, tyramine, histamine, and tryptamine). Their 1H NMR spectra both at pD = 7 and pD = 3 revealed that four biogenic amines (spermine, spermidine, 2-phenethylamine, and histamine) can fit in the TMeQ[6] cavity, respectively, and other biogenic amines were located outside of the TMeQ[6] portal. In addition, a solid-state evaluation with single-crystal X-ray diffraction analysis showed the binding interaction of spermine, spermidine, 2-phenethylamine, and tyramine with TMeQ[6].

Coordination and Supramolecular Assemblies of Fully Substituted Cyclopentanocucurbit[6]uril with Lanthanide Cations in the Presence of Tetrachlorozincate Anions, and Their Potential Applications

Coordination and supramolecular assemblies of a fully substituted cyclopentanocucurbit[6]uril (CyP₆Q[6]) with a series of lanthanide cations (Ln³⁺) have been investigated in the presence of tetrachlorozincate anion ([ZnCl₄]^2-). X-ray single-crystal diffraction analysis has revealed that the interaction of CyP₆Q[6] and a series of Ln³⁺cations unexpectedly results in the formation of at least seven different CyP₆Q[6]-based coordination complex adduct and supramolecular assemblies groups, including with (1) La³⁺, Ce³⁺cations; (2) Pr³⁺, Nd³⁺cations; (3) Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺ with P1̅ or P1 space group, in which CyP₆Q[6] molecules coordinate alternatively with Ln³⁺cations and form linear coordination polymers; (4) CyP₆Q[6] molecules interact alternatively with [Ho(H₂O)₈]³⁺ aqueous complexes and form linear supramolecular chains; CyP₆Q[6] molecules can assemble two different Ln³⁺ free porous supramolecular assemblies from CyP₆Q[6]-Ln(NO₃)₃-ZnCl₂-HCl systems, Ln = Tm, Yb, and Lu; however, no solid crystals were obtained from system containing Er³⁺cation. Thus, these differences could lead CyP₆Q[6] to be useful in not only the isolation of lighter lanthanides from their heavier lanthanides but also special selectivity for different volatile organic compounds.

A molecular basis to rare earth separations for recycling: tuning the TriNOx ligand properties for improved performance

A methoxy-substituted tripodal hydroxylamine ligand, H₃TriNOx^OMe, was synthesized and coordinated to rare earth cations for separation purposes.

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).