Opposing substitution in cucurbit[6]urils forms ellipsoid cavities: the symmetrical dicyclohexanocucurbit[6]uril is no exception highlighted by inclusion and exclusion complexes

The symmetrical dicyclohexanocucurbit[6]uril has been synthesised by the controlled condensation of the diether of cyclohexanoglycoluril (1) and the dimer of glycoluril (2). The symmetrical dicyclohexanocucurbit[6]uril, (CyH)₂Q[6], characterised by the ¹H NMR spectroscopy, ESMS and further confirmed by single crystal X-ray diffraction of a cobalt aqua exclusion complex, which demonstrates an ellipsoid cavity. Within a cucurbit[6]uril ellipsoid cavity, an inclusion complex of 5,5′-dimethyl-2,2′-bipyridine adopts a preferred orientation, aligning with the longest axis. The ellipsoid cavity is further supported by semiempirical AM1 gas phase calculations.

Preferential orientation of a guest within the ellipsoid cavity of the symmetrical dicyclohexanocucurbit[6]uril     

Cucurbit[5]uril, Decamethylcucurbit[5]uril and Cucurbit[6]uril. Synthesis, Solubility and Amine Complex Formation

A simple way to prepare cucurbit[5]uril is described. The macrocycles of the cucurbituril type are nearly insoluble in water. The solubilities of cucurbit[5]uril, decamethylcucurbit[5]uril and cucurbit[6]uril in hydrochloric acid, formic acid and acetic acid of different concentrations have been investigated. Due to the formation of complexes between cucurbit[n]urils and protons the solubility increases in aqueous acids. The macrocyclic ligands are able to form complexes with several organic compounds. Thus, the complex formation of the cucurbituril macrocycles with different amines has beenstudied by means of calorimetric titrations. The reaction enthalpy gives noevidence of the formation of inclusion or exclusion complexes. ¹H-NMR measurements show that in the case of cucurbit[5]uril and cucurbit[6]uril the organic guest compound is included within the hydrophobic cavity. Decamethylcucurbit[5]uril forms only exclusion complexes with organicamines. This was confirmed by the crystal structure of the decamethylcucurbit[5]uril-1,6-diaminohexane complex.     

六元瓜环与磺基水杨酸主客体配合物的晶体结构

合成了六元瓜环与磺基水杨酸主客体配合物,并测定了其单晶结构.晶体结构表明六元瓜环包结了3个水分子,磺基水杨酸位于六元瓜环的外侧,且与水分子通过氢键与六元瓜环相连,瓜环之间通过端口的羰基O原子、磺基水杨酸以及水分子间的氢键作用形成一维超分子.     

Metal ion-assisted assembly of one-dimensional polyrotaxanes incorporating cucurbit[6]uril

Three cucurbit[6]uril (CB[6])-based polyrotaxanes [Cu(H₂ C6N4)(CB[6])]Cl₄·12H₂O (1), [Co(H₂ C6N4)(CB[6])]Cl₄·14H₂O (2) and [Ag(C6N4)(CB[6])]NO₃·7H₂O (3) are prepared using N,N′-bis(4-pyridylmethyl)-1,6-hexanediamine (C6N4) threading into CB[6]'s and metal ions' assistance. Single-crystal X-ray diffraction analyses reveal that polyrotaxanes 1, 2 and 3 all have 1D chain structure where 1 and 2 are linear and 3 has two shapes, linear and sawtooth, respectively. The effects of guest molecules, metal and counter ions as well as intermolecular weak interactions on the architectures of polyrotaxanes are discussed.     

Synthesis and crystal structures of PrIII and NdIII complexes with the macrocyclic cavitand cucurbit[6]uril

The [{Pr(NO₃)₂(H₂O)₃}{Pr(NO₃)(H₂O)₄} (C₃₆H₃₆N₂₄O₁₂)](NO₃)₃·4H₂O and [{Nd(NO₃)(H₂O)₄} ₂(NO₃@C₃₆H₃₆N₂₄O₁₂)][Nd(NO₃)₆] complexes were prepared by heating a mixture of lanthanide nitrates, cucurbit[6]uril, and water in a sealed tube. X-ray diffraction study demonstrated that the metal atoms in the former complex are linked to the macrocycle through tridentate coordination of the portal oxygen atoms of cucurbit[6]uril to the praseodymium(III) cation. The neodymium(III) complex is the first example of lanthanide compounds with cucurbit[6]uril belonging to coordination polymers. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1511–1517, September, 2006.     

对称四甲基六元瓜环与2-苄基咪唑啉盐酸盐自组装包合物的晶体结构

以2-苄基-咪唑啉盐酸盐(Benid)为客体,对称四甲基六元瓜环(TMeQ[6])为主体,在水溶液中形成自组装包合物(TMeQ[6]-Benid)的晶体.X-射线单晶衍射实验表明,Benid-TMeQ[6]为单斜晶系,空间群P21,晶胞参数:a=1.18633(5) nm,b=2.06145(6) nm,c=1.35163(5) nm,α=90.00°,β=96.102(2)°,γ=90.00°,V=3.28676 nm3,Z=2,Mr=1626.95,Dc=1.569 g·cm-3,μ=0.169 mm-1,R1=0.0739,Wr2=0.1412.通过多种非共价键弱相互作用,主客体以1:1的包结比形成自组装包合物,客体的苯环被包结在主体的空腔内.1H NMR结果进一步证实了在溶液中也是同样的包结模式,包结稳定常数为7.23×105 mol-1·L.     

Crystal structure of a La(III) complex with macrocyclic cavitand cucurbit[6]uril

Slow evaporation in air of a lanthanum nitrate solution containing macrocyclic cavitand cucurbit[6]uril yields a complex of the composition of [La(H₂O)₆(X@C₃₆H₃₆N₂₄O₁₂)(NO₃)](NO₃)₂· 6.96H₂O (X = 0.5C₅H₅N + 0.5H₂O). The complex is structurally characterized using single crystal X-ray diffraction. Lanthanum atoms are coordinated with oxygen atoms of carbonyl groups of cucurbit[6]uril portals. The compound crystallizes in the orthorhombic crystal system, space group Pnn2, unit cell parameters (150 K): a = 11.997(2) Å, b = 17.093(3) Å, c = 14.133(3) Å, V = 2899.3(10) ų, Z = 2. Lanthanum atoms are disordered, alternative positions being related by the two-fold axis. The complex has an island structure. A pyridine molecule occupies an internal cavity of one half of cucurbit[6]uril molecules, while a water molecule occupies the other.     

Complexation behavior of cucurbit[6]uril with short polypeptides

The binding properties of cucurbit[6]uril towards various peptides have been investigated in acidic aqueous solution. Stability constants and thermodynamic values of the complex formation between following peptides: glycyl-l-alanine, l-leucyl-l-valine, glycyl-l-asparagine, l-leucyl-l-phenylalanine, l-leucyl-l-tryptophan, glycyl-l-histidine, l-glutathione reduced (γ-l-glutamyl-l-cysteinyl-glycine, GSH), and dl-leucyl-glycyl-dl-phenylalanine) with cucurbit[6]uril in aqueous formic acid (50%, v/v) have been calculated from calorimetric titrations. From these results it can be seen that the peptides form exclusion complexes with cucurbit[6]uril. Due to the polar peptide bond they are not included within the hydrophobic cavity of cucurbit[6]uril. The complex formation is favoured by entropic contributions. The release of water molecules from the polar amino groups of the peptides and the carbonyl groups of cucurbituril are responsible.     

含有葫芦[6]脲的新型准轮烷的合成

通过葫芦[6]脲(CB[6])与两个质子化的1,4-丁二胺在水溶液中于室温下进行超分子自组装, 得到一种新型的准轮烷. 通过¹H NMR, 质谱和¹H ROESY NMR对其结构进行了表征, 证实CB[6]位于质子化1,4-丁二胺的脂肪链上, 通过非共价键与1,4-丁二胺结合, 并且主体(CB[6])与客体的结合的物质的量之比为2∶1.     

Use of the macrocyclic ligand cucurbit[6]uril for isolation of tetranuclear lanthanide aquahydroxo-carboxylate complexes from aqueous solutions

The tetranuclear lanthanide complexes {[Ln₄(μ₃-OH)₄(μ₂-OH)₂(C₅NH₄COO)₂ (H₂O)₄-(C₃₆H₃₆N₂₄O₁₂)₂][Ln(H₂O)₈]_1.5[Ln(H₂O)₆(NO₃)₂]_0.5} (NO₃)₉·nH₂O (Ln = Ho, Gd, or Er) were prepared by heating (130 °C) aqueous solutions of lanthanide nitrates, cucurbit[6]uril (C₃₆H₃₆N₂₄O₁₂), and 4-cyanopyridine. The tetradentate coordination of the macrocyclic cucurbit[6]uril ligands through the portals leads to the formation of sandwich compounds, in which the tetranuclear hydroxo complex is located between two macrocyclic molecules. The polynuclear complexes are additionally stabilized by the chelating effect of the isonicotinate ligands generated by hydrolysis of 4-cyanopyridine. In the complexes, the aromatic moiety of the isonicotinate ion is encapsulated into the hydrophobic inner cavity of cucurbit[6]uril. In the absence of cucurbit[6]uril, the reaction with 4-cyanopyridine produces only the polymeric complexes [Nd(C₅NH₄COO)₃(H₂O)₂] and [Ln(C₅NH₄COO)₂(H₂O)₄]NO₃ (Ln = Pr, Sm, or Gd), whose structures were established by X-ray diffraction. In water and aqueous solutions of nonionic and cationic surfactants, irreversible changes of the tetranuclear fragment of the complex (Ln = Gd) were observed after storage for two days, whereas the anionic surfactant stabilizes the complexes. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1885–1894, November, 2006.     

Inclusion complex of riboflavin with cucurbit[7]uril: study in solution and solid state

The aqueous solution of riboflavin and cucurbit[7]uril complex has been studied based on fluorescence and ¹H NMR spectroscopic results. Upon addition of cucurbit[7]uril, the fluorescence intensity of riboflavin was quenched and a slight red shift was observed for the maximum emission peak. These results indicated that the cucurbit[7]uril–riboflavin complex was formed at a 1:1 mole ratio. The temperature-dependent inclusion constants were calculated, from which ΔH and ΔS values were calculated. Meanwhile, rationale of the interaction mechanism was also discussed based on ¹H NMR results. The solid inclusion complex was prepared from co-evaporation method and characterised by differential thermal analysis and fluorescence lifetime analysis methods. The experimental results indicated that riboflavin and cucurbit[7]uril formed stable host–guest inclusion complex in both solution and solid states.     

New lanthanide-based complexes constructed from cucurbit[6]uril: Synthesis,structures and properties

Three lanthanide-based complexes, {Gd₂(H₂O)₁₀(CB[6])₂}·CB[6]·6Cl·12H₂O (1), {[Gd₂(H₂O)₈CB[6]₂]·(CuCl₄)·4Cl·46H₂O}_n (2), and {Dy₂(NO₃)₂(H₂O)₁₀(CB[6])}·4NO₃·14H₂O (3) (CB[6] = cucurbit[6]uril), were prepared with cucurbit[6]uril (CB[6]). These complexes were characterized by single-crystal X-ray diffraction, elemental analysis, FT-IR spectroscopy, UV–Vis spectroscopy, thermogravimetric analysis and magnetization measurements. Crystallographic results showed that 1 and 3 are dinuclear and crystallize in the triclinic space group Pī, whereas 2 is a 1-D zigzag supramolecular chain that crystallizes in the monoclinic system in C2/c. The results indicated that temperature has a big effect on the supramolecular assemblies and a different structure inducer also leads to the formation of different coordination polymers. Frequency dependence in the ac susceptibility signals was observed in 3.     

Supramolecular assembly of cucurbit[6]uril and N-butyl-4-pyrrolidinopyridine

The nature of the supramolecular host–guest complex involving 4-pyrrolidinopyridine (BuPC4) and cucurbit[6]uril (Q[6]) has been investigated by NMR and UV spectroscopy, MALDI-TOF mass spectrometry, X-ray crystallography and isothermal titration calorimetry. The results revealed that the alkyl chain of the guest BuPC4 is located inside the cavity of the Q[6] host, whereas the other section of the BuPC4 guest remains outside of the portal.     

Synthesis and crystal structures of supramolecular compounds of polynuclear aluminum(III) aqua hydroxo complexes with cucurbit[6]uril

Supramolecular compounds of the di-, trideca-, and triacontanuclear aluminum aqua hydroxo complexes, viz., [Al₂(OH)₂(H₂O)₈]⁴⁺, [Al₁₂(AlO₄)(OH)₂₄(H₂O)₁₂]⁷⁺, and [Al₃₀O₈(OH)₅₆(H₂O)₂₆]¹⁸⁺, respectively, with the organic macrocyclic cavitand cucurbit[6]uril (C₃₆H₃₆N₂₄O₁₂) were prepared by evaporation of aqueous solutions of aluminum nitrate and cucurbit[6]uril after the addition of pyridine, ammonia, KOH, or NaOH at pH 3.1–3.8. X-ray diffraction study demonstrated that the aqua hydroxo complexes are linked to the macrocycle through hydrogen bonds between the hydroxo and aqua ligands of the polycations and the portal oxygen atoms of cucurbit[6]uril. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 261—268, February, 2006.     

六元瓜环／1，2-乙二胺的超分子化合物结构及相互作用模式

合成了六元瓜环与链状烷基二胺（1,2-乙二胺）形成的超分子化合物．采用X射线衍射技术测定了其晶体结构,并得到元素分析、热重、红外光谱的佐证,揭示了主客体相互作用的模式．还采用^1HNMR技术研究了溶液中六元瓜环与乙二胺的超分子相互作用．研究表明,在不同的环境下瓜环与客体采取相异的超分子作用模式,晶体结构中显示一个六元瓜环的两个端口通过离子偶极作用以不同的作用模式分别跟两个乙二胺客体分子形成一个三单元组成的超分子作用实体;而在溶液中瓜环与乙二胺的相互作用模式与晶体中的不同．     

Synthesis and crystal structure of a supramolecular adduct of the aqua nitrato complex of gadolinium [Gd(NO<Subscript>3</Subscript>)(H<Subscript>2</Subscript>O)<Subscript>7</Subscript>]<Superscript>2+</Superscript> with macrocyclic cavitand cucurbit[6]uril

A supramolecular adduct of gadolinium aqua nitrato complex and cucurbit[6]uril { [Gd(NO₃)(H₂O)₇](C₅H₅N)@(C₃₆H₃₆N₂₄O₁₂)}(NO₃)₂·10H₂O is obtained by slow diffusion of methanol into an aqueous solution containing gadolinium nitrate, pyridine, and cucurbit[6]uril. According to single crystal X-ray diffraction data, water molecules coordinated to metal atom make hydrogen bonds to polarized carbonyl groups of the macrocycle. The heptaaquanitratogadolinium(III) [Gd(NO₃)(H₂O)₇]²⁺ cation is structurally characterized for the first time. Crystal system is triclinic, space group \(P\overline 1 \), a = 12.3137(4) Å, b = 14.2334(5) Å, c = 19.5629(6) Å; α = 80.850(1)°, β = 86.879(1)°, γ = 68.855(1)°; V = 3157.15(18) ų, Z = 2. Oriented hydrogen-bonded chains of alternating cucurbit[6]uril molecules and gadolinium aqua cations form in the crystal structure.     

Characterization of host-guest complexes of cucurbit[n]uril (n = 6, 7) by electrospray ionization mass spectrometry

When an intramolecular cavity exists in a molecule, it can trap another chemical species to form a host-guest complex. We examine the formation of such an inclusion complex with cucurbit[n]uril (CBn, n = 6, 7) as the host to trap alkali metal or ammonium ions as the guest, by electrospray ionization mass spectrometry (ESI-MS). The results show that the inclusion complexes are formed between the three-dimensional cylinder of CBn hosts and the guest cations. Selectivity of the complex formation is dependent both on (1) ion-dipole interactions between the cylindrical portal of the CBn hosts and the guest cations and (2) the hydrophobic interactions at the inner cavity of CBn.     

A hemicyanine and cucurbit[n]uril inclusion complex: competitive guest binding of cucurbit[7]uril and cucurbit[8]uril

The interaction between the hemicyanine indole derivative H and the cucubit[n]urils Q[7] and Q[8] has been studied using ¹H NMR and UV spectroscopy as well as by fluorescence experiments. Competitive studies on the inclusion of H by Q[7] and Q[8] have also been conducted, and reveal that on changing the size of the Q[n] cavity, the binding behaviour can be very different.     

六元瓜环、对称四甲基六元瓜环与2,2'-(1,8-辛烷)-二异喹啉二溴化物的自组装模式

利用核磁共振波谱、 紫外吸收光谱、 荧光光谱和单晶X射线衍射分析等考察了六元瓜环(Q[6])及对称四甲基六元瓜环(TMeQ[6])与2,2'-(1,8-辛烷)-二异喹啉二溴化物的相互作用. 实验结果表明, 客体分子分别与这2种瓜环自组装形成相似的1∶1包结配合物, 但晶体结构分析结果表明两个体系在主客体分子间作用力诱导下形成了不同的空间堆积模式, 其包结常数分别为K_K8-Q[6]=4.18×10⁷ L/mol, K_K8-TMeQ[6]=6.11×10⁷ L/mol.     

瓜环与哌嗪衍生物主客体配合物的研究(英)

本文采用核磁共振技术研究瓜环与哌嗪衍生物主客体配合物的结构特征。¹H核磁共振谱证实八元瓜环能与一些哌嗪衍生物形成稳定的双客体主客体配合物,六元瓜环与一些哌嗪衍生物形成稳定的1∶1主客体配合物。而五、七元瓜环和哌嗪衍生物则未表现出明显地相互作用。形成的自组装主客体配合物得到质谱的进一步证实。