在四氯合锌离子诱导下反式六元瓜环与碱金属离子构筑的配位超分子自组装体

在盐酸介质中,通过四氯合锌离子诱导,碱金属离子能与反式六元瓜环端口羰基氧原子直接配位构筑形成超分子自组装体。单晶结构表明在HCl介质中,四氯合锌离子形成“蜂巢结构”,而且在[ZnCl₄]^2-诱导作用下,碱金属离子和反式六元瓜环端口羰基氧直接配位形成一维超分子自组装体而填充在“蜂巢结构”中。     

在四氯合锌离子诱导下反式六元瓜环与碱金属离子构筑的配位超分子自组装体

在盐酸介质中,通过四氯合锌离子诱导,碱金属离子能与反式六元瓜环端口羰基氧原子直接配位构筑形成超分子自组装体。单晶结构表明在HCl介质中,四氯合锌离子形成"蜂巢结构",而且在[ZnCl₄]^2-诱导作用下,碱金属离子和反式六元瓜环端口羰基氧直接配位形成一维超分子自组装体而填充在"蜂巢结构"中。     

Self‐Assembly of Anionic Porphyrins and Alkaline or Alkaline Earth Metal Ions Mediated by Cucurbit[7,8]uril

Nanoscaled coordination polymers based on biologically prevalent ions have potential applications in drug delivery and biomedical imaging. Herein, coordination polymer nanoparticles of anionic porphyrins, including meso‐tetra(4‐carboxyphenyl)‐porphyrin (H₂TCPP^4?) and meso‐tetra(4‐sulfonatophenyl)‐porphyrin (H₂TPPS^4?), and alkaline or alkaline earth metal cations, such as K⁺ and Ca²⁺, were constructed in aqueous solution in the presence of cucurbit[7]uril (CB7) or cucurbit[8]uril (CB8). UV/Vis absorption and fluorescence spectroscopy, dynamic light scattering (DLS), scanning electron spectroscopy (SEM), and atomic force microscopy (AFM) were applied to explore the assembly and particle formation of porphyrin anions and metal cations mediated by CBn. The particle size depends on the kinds of CBn and metal cations and their concentrations. The uptake of H₂TPPS^4? particles by tumor cells (A549 cells) was found to be more efficient than H₂TPPS^4? at 37 °C, showing the application potential of such assembled particles in biology and medicine.     

Complex Formation between Cucurbit[n]urils and Alkali, Alkaline Earth and Ammonium Ions in Aqueous Solution

The complex formation between cucurbit[5]uril, decamethylcucurbit[5]uril and cucurbit[6]uril and alkali, alkaline earth and ammonium cations is examined. The solubility of these ligands is rather small in aqueous solution. In the presence of salts the solubility normally increases due to the formation of complexes. The total concentration of the ligands can be easily measured from the total organic carbon content of the salt solutions saturated with the ligand. From these results it is possible to calculate the stability constants of the complexes formed even without the knowledge of the exact solubility of the ligand.     

Efficient Preparation of Separable Pseudo[n]rotaxanes by Selective Threading of Oligoalkylammonium Salts with Cucurbit[7]uril

A salty solution : Well‐defined pseudo[n]rotaxanes (n=2, 3, 4, 5) were prepared as pure compounds through threading of oligoalkylammonium salts with cucurbit[7]uril (CB[7]) and by subsequent counterion exchange. A unique self‐assembling mode was observed (see graphic).

     

Supramolecular Inhibition of Amyloid Fibrillation by Cucurbit[7]uril

Amyloid fibrils are insoluble protein aggregates comprised of highly ordered β‐sheet structures and they are involved in the pathology of amyloidoses, such as Alzheimer’s disease. A supramolecular strategy is presented for inhibiting amyloid fibrillation by using cucurbit[7]uril (CB[7]). CB[7] prevents the fibrillation of insulin and β‐amyloid by capturing phenylalanine (Phe) residues, which are crucial to the hydrophobic interactions formed during amyloid fibrillation. These results suggest that the Phe‐specific binding of CB[7] can modulate the intermolecular interaction of amyloid proteins and prevent the transition from monomeric to multimeric states. CB[7] thus has potential for the development of a therapeutic strategy for amyloidosis.     

Cucurbit[8]uril/cucurbit[7]uril controlled off/on fluorescence of the acridizinium and 9-aminoacridizinium cations in aqueous solution

The blue fluorescence of acridizinium bromide (ADZ+) and the green fluorescence of 9-aminoacridizinium bromide (AADZ+) in aqueous solutions can be almost entirely switched off upon the double inclusion of these guests in the cavity of cucurbit[8]uril (CB[8]) owing to the formation of a nonfluorescent, noncovalent dimer complex, and then fluorescence can be effectively restored by adding cucurbit[7]uril (CB[7]) to the complex because it competitively extracts the fluorophores out of the CB[8] cavity.     

Switching Properties of a Spiropyran–Cucurbit[7]uril Supramolecular Assembly: Usefulness of the Anchor Approach

A nitrospiropyran, which was modified with a cadaverine‐derived anchor, was investigated with respect to its thermally induced isomerizations, hydrolytic stability of the merocyanine form, and photochromic ring closure. The host–guest complexation of the anchor by the cucurbit[7]uril macrocycle, evidenced by absorption titration, NMR spectroscopy, and electrospray ionization mass spectrometry, produced significant improvements of the switching properties of the photochrome: 1) appearance of the merocyanine form about 70 times faster, 2) practically unlimited hydrolytic stability of the merocyanine (two and a half days without any measureable decay), and 3) fast, clean, and fatigue‐resistant photoinduced ring closure back to the spiro form. The importance of an adequate molecular design of the anchor was demonstrated by including control experiments with spiropyrans with a shorter linker or without such structural asset.     

Supramolecular Complexation of N‐Alkyl‐ and N,N′‐Dialkylpiperazines with Cucurbit[6]uril in Aqueous Solution and in the Solid State

Water seeds : Complex stoichiometry/composition and degree of oligomerization (oligomeric supramolecular complex formation) of cucurbit[6]uril (CB[6]) with N‐alkyl‐ and N,N′‐dialkylpiperazine were investigated in aqueous solutions by means of isothermal titration calorimetry (ITC), ESI‐MS, NMR and light scattering measurements.

     

Metal Ion Modulated Torsion Angle in a Ditopic Oligothiophene Ligand: Toward Supramolecular Control of π Conjugation

A π‐conjugated oligomer bearing two 15‐crown‐5‐containing styryl moieties connected at the inner β positions of the terminal thiophene nuclei can adopt either a U or a Z shape depending on the structures of its complexes with magnesium and barium ions. We show that barium cations lead to the formation of a mononuclear complex in solution, which causes the system to fold into the U shape. Magnesium ions lead to the same effect at low concentration, but force the ligand to adopt the Z‐shaped geometry at high concentrations favoring formation of a binuclear complex. These geometrical reorganizations in solution are accompanied by profound changes in spectroscopic properties, which can be rationalized in terms of variations in the extent of electron delocalization along the oligothiophene backbone. The effects are analyzed by mass spectrometry and ¹H NMR, UV/Vis absorption, and fluorescence spectroscopy in the steady‐state and time‐resolved regimes. The experimental results are compared to data calculated by using MOPAC2007 with the PM6 Hamiltonian including the COSMO solvation model.     

碱土金属在Q[5]-CdCl_2体系中配位超分子自组装体的构筑(英文)

通过X射线单晶衍射仪的结构表征技术,研究了碱土金属在五元瓜环-四氯镉酸根体系中的配位超分子自组装体的构筑。晶体结构表明:[CdCl4]2-的存在,能够使得碱土金属与五元瓜环形成分子胶囊。研究结构还发现,在这样的体系即使没有[CdCl4]2-或"蜂巢效应"存在,由于瓜环的外壁作用也能够促使这种结构形成。     

Reversible Shape‐Morphing and Fluorescence‐Switching in Supramolecular Nanomaterials Consisting of Amphiphilic Cyanostilbene and Cucurbit[7]uril

We demonstrate a reversible shape‐morphing with concurrent fluorescence switching in the nanomaterials which are complexed with cucurbit[7]uril (CB[7]) in water. The cyanostilbene derivative alone forms ribbon‐like two‐dimensional (2D) nanocrystals with bright yellow excimeric emission in water (λ_em=540 nm, Φ_F=42 %). Upon CB[7] addition, however, the ribbon‐like 2D nanocrystals immediately transform to spherical nanoparticles with significant fluorescence quenching and blue‐shifting (λ_em=490 nm, Φ_F=1 %) through the supramolecular complexation of the cyanostilbene and CB[7]. Based on this reversible fluorescence switching and shape morphing, we could demonstrate a novel strategy of turn‐on fluorescence sensing of spermine and also monitoring of lysine decarboxylase activity.     

Controlling the Size and Morphology of Supramolecular Assemblies of Viologen–Resorcin[4]arene Cavitands

A novel class of self‐assembling nanoparticles is formed with viologen–resorcin[4]arene cavitands; the association model is strongly controlled by their hydrophobicity. Interestingly, the cavitand assemblies are designed through click chemistry to form self‐assembled noncovalently connected aggregates through counterion displacement. The iodide and benzoate ions are utilized as strongly polarizable counterions to induce cavitand self‐assembly. The counterion‐mediated decrease in hydrophilicity of the viologen–resorcin[4]arenes is the underlying trigger to induce particle formation. These particles can be used as nanocontainers and find their applications in delivery systems.