A novel two-dimensional polyrotaxane network self-assembled by heterowheel [4]pseudorotaxane

A novel heterowheel pseudorotaxane comprised of one guest, one cucurbit[7]uril and two cucurbit[6]urils was synthesised and characterised by ¹H NMR, single crystal X-ray diffraction analysis and thermogravimetric analysis. Single crystal X-ray diffraction analysis demonstrates that the heterowheel pseudorotaxane self-assembles into two-dimensional polyrotaxane network with the aid of water molecules and hydrogen bonds. Every four heterowheel pseudorotaxanes self-assemble into a parallelogram, which is the basic unit of the 2D network.     

Encapsulation of a Porous Organic Cage into the Pores of a Metal–Organic Framework for Enhanced CO2 Separation

We present a facile approach to encapsulate functional porous organic cages (POCs) into a robust MOF by an incipient‐wetness impregnation method. Porous cucurbit[6]uril (CB6) cages with high CO₂ affinity were successfully encapsulated into the nanospace of Cr‐based MIL‐101 while retaining the crystal framework, morphology, and high stability of MIL‐101. The encapsulated CB6 amount is controllable. Importantly, as the CB6 molecule with intrinsic micropores is smaller than the inner mesopores of MIL‐101, more affinity sites for CO₂ are created in the resulting CB6@MIL‐101 composites, leading to enhanced CO₂ uptake capacity and CO₂/N₂, CO₂/CH₄ separation performance at low pressures. This POC@MOF encapsulation strategy provides a facile route to introduce functional POCs into stable MOFs for various potential applications.     

A new type of pseudorotaxanes based on cucurbit[6]uril and bis-cyanopyridyl alkane compounds

Using bis-cyanopyridyl alkane compounds as guests, three cucurbit[6]uril-based new pseudorotaxanes (2a, 2b and 2c) were synthesised and characterised. The crystal structures for 2a and 2c have been determined and discussed. In addition, formation constants and thermodynamic parameters in aqueous solution, as well as thermal decomposition behaviour in solid state, have been studied by ¹H NMR and TGA techniques, respectively.     

Synthesis and crystal structures of supramolecular adducts of molybdenum and tungsten selenide aqua complexes with macrocyclic cavitand cucurbituril

The supramolecular compounds {[W₃Se₄Cl₃(H₂O)₆]₂[PyHC₃₆H₃₆N₂₄O₁₂]}Cl₃·18H₂O (1) and {[Cl₃SnMo₃Se₄Cl₃(H₂O)₆][Cl₃SnMo₃Se₄Cl₂(H₂O)₇](C₃₆H₃₆N₂₄O₁₂)}Cl·26H₂O (2) were isolated from solutions of the selenium-containing tungsten and molybdenum clusters [W₃Se₄(H₂O)₉]⁴⁺ and [Cl₃SnMo₃Se₄(H₂O)₉]³⁺, respectively, and organic cavitand cucurbituril. X-ray diffraction analysis demonstrated that the macrocylcic cucurbituril molecule is coordinated on both sides by the cluster cations through the formation of complementary hydrogen bonds. Compound 1 has a chain structure stabilized by Se...Se interactions between the adjacent cluster cores. In compound 2, the bridging ₂-selenium atoms of the cluster fragment Mo₃Se₄ are coordinated to the tin atom of the SnCl₃ ^– ligand, thus losing the ability to be involved in Se...Se interactions.     

Overcoming dissipation in the calculation of standard binding free energies by ligand extraction

This article addresses calculations of the standard free energy of binding from molecular simulations in which a bound ligand is extracted from its binding site by steered molecular dynamics (MD) simulations or equilibrium umbrella sampling (US). Host–guest systems are used as test beds to examine the requirements for obtaining the reversible work of ligand extraction. We find that, for both steered MD and US, marked irreversibilities can occur when the guest molecule crosses an energy barrier and suddenly jumps to a new position, causing dissipation of energy stored in the stretched molecule(s). For flexible molecules, this occurs even when a stiff pulling spring is used, and it is difficult to suppress in calculations where the spring is attached to the molecules by single, fixed attachment points. We, therefore, introduce and test a method, fluctuation‐guided pulling, which adaptively adjusts the spring's attachment points based on the guest's atomic fluctuations relative to the host. This adaptive approach is found to substantially improve the reversibility of both steered MD and US calculations for the present systems. The results are then used to estimate standard binding free energies within a comprehensive framework, termed attach‐pull‐release, which recognizes that the standard free energy of binding must include not only the pulling work itself, but also the work of attaching and then releasing the spring, where the release work includes an accounting of the standard concentration to which the ligand is discharged. © 2013 Wiley Periodicals, Inc.     

甘脲和羟基葫芦[6]脲气相色谱固定相的制备及其色谱分离性能比较研究

甘脲是羟基葫芦[6]脲(HOCB6)的前体, 本文设计了一种在酸性条件下均匀涂渍固定液的新方法, 首次将甘脲和羟基葫芦[6]脲用作气相色谱固定相. 将甘脲和HOCB6填装成气相色谱填充柱后, 以烷烃、卤代烃、芳香烃、醇、酮、酯、酸、胺等物质为探针, 用复杂样品花露水对它们的色谱分离性能进行了比较研究. 结果表明, 甘脲和HOCB6 都是良好的气相色谱固定相, 热稳定性高, 柱性能稳定. 两种固定相对以上溶质探针都有较好的分离能力, HOCB6固定相(PSP)与甘脲固定相(GSP)相比较, 总体上具有更好的分离选择性, 对难分离的芳香族位置异构体(如二甲苯、甲基苯胺)具有良好的分离能力, 显示出较高的立体选择性, 对花露水中的高沸点组分有较好的分离效果. 上述研究也表明, 由于溶质在载气中传质比葫芦脲内腔快得多, 全包结尽管有利于提高分离选择性, 但展宽后的柱效不理想; 适当的高柱温既保留了部分包结作用, 同时存在端口协同作用, 能兼顾高选择性和高柱效.     

新型金属轮烷自组装体系的表征及配位平衡研究

由cucurbituril和精胺盐酸盐生成的类轮烷，与水合烷基钴肟发生自组装反应后，在水溶液中形成了一种新型的金属轮烷。本文通过 ¹H NMR，ESI-MS，UV-vis方法进行了表征并对该金属轮烷生成的配位反应进行了热力学研究。     

Syntheses and crystal structures of SmIII and ThIV complexes with macrocyclic cavitand cucurbituril

Slow evaporation of solutions of samarium nitrate and thorium chloride in hydrochloric acid containing the macrocyclic cavitand cucurbituril (C₃₆H₃₆N₂₄O₁₂) afforded crystals of the [{Sm(H₂O)₅(NO₃)}₂(C₃₆H₃₆N₂₄O₁₂)](NO₃)₄·6.5H₂O and [{Th(H₂O)₅Cl}₂(C₃₆H₃₆N₂₄O₁₂)]Cl₆·13H₂O complexes, respectively. The [Sm(C₃₆H₃₆N₂₄O₁₂)(H₂O)₅(SO₄)][Sm(H₂O)₅(SO₄)₂]·17H₂O complex was generated upon heating (130 °C) of a mixture of samarium sulfate, cucurbituril, and water in a sealed tube. X-ray diffraction analysis demonstrated that the metal atoms in these complexes are bound to the portal oxygen atoms of the cucurbituril molecules. In addition, the portal oxygen atoms of cucurbituril are linked to the coordinated H₂O molecules via hydrogen bonds.