Toward supramolecular polymers incorporating double cavity cucurbituril hosts

We describe the synthesis of a series of guests (1-6) containing two adamantylammonium ions separated by xylylene spacing groups and their complexation properties toward double cavity cucurbituril host bis-ns-CB[10]. We observed the preferential formation of 1:1, 2:2, and oligomeric complexes rather than the desired n:n supramolecular polymers. Guest 7, which contains a longer biphenyl spacer successfully precludes the formation of the 1:1 complex but results in the formation of the 2:2 complex (bis-ns-CB[10]₂·7₂) rather than supramolecular polymer. Guest 8, which contains adamantylammonium, p-xylylene diammonium, and hexanediammonium ion binding regions is shown to reversibly form 2:2 and 1:2 complexes (bis-ns-CB[10]₂·8₂ and bis-ns-CB[10]·8₂) in response to changes in host:guest stoichiometry. Lastly, this equilibrium can be manipulated by the addition of exogenous CB[6], which selectively targets the hexanediammonium ion binding region of 8 and delivers the penta-molecular complex bis-ns-CB[10]·8₂·CB[6]₂.     

Mechanically interlocked molecules incorporating cucurbituril and their supramolecular assemblies

Mechanically interlocked molecules incorporating cucurbituril (CB[6]) as a molecular 'bead' and their supramolecular assemblies are described. An efficient synthesis of 1D, 2D and 3D polyrotaxanes with high structural regularity and molecular necklaces has been achieved by a combination of self-assembly and coordination chemistry. The functional aspects of these interlocked molecules and their supramolecular assemblies, including molecular machines and switches based on [2]rotaxanes, a 2D polyrotaxane with large cavities and channels, pseudorotaxane-terminated dendrimers, and interaction of pseudorotaxanes containing polyamines and CB[6] with DNA are also described.     

Transition metal ion directed bimetallic macrocyclic complexes

Template condensation of 1,4-phenylenediamine, formaldehyde, 1,3-diaminopropane and benzil in a 1:4:4:2, molar ratio results in the formation of a new series of binuclear decaazamacrocyclic complexes: dichloro/nitrato [1-phenyl bis(8,9-diphenyl-1,3,7,10,14 pentaazacyclo-pentadeca-7,9-diene) metal (II)], [M₂LX₄](M = MnII, Co^II, Ni^II, CuII and Zn^II, X = Cl or NO₃), which were characterised by i.r., ¹H-n.m.r., e.p.r., u.v–vis. spectral studies, conductivity and magnetic susceptibility measurements. All the complexes show octahedral geometry.     

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.     

Gold nanoparticles in organic capsules: a supramolecular assembly of gold nanoparticles and cucurbituril

Gold nanoparticles (相似文献   

Transition and post-transition metal ion chemistry of dibenzo-substituted,mixed-donor macrocycles incorporating five donor atoms

The transition and post-transition metal ion chemistry of a wide range of potentially pentadentate dibenzo-substituted macrocyclic ligands incorporating nitrogen, oxygen and/or sulfur donors is reviewed and shown to result in a diverse range of structural types. Aspects of metal ion recognition, bulk membrane transport, systems incorporating appended chromophores, a sulfate binding system, induced Cu(I)/Cu(II) redox switching, coordination polymers, and unsymmetric macrocyclic ligand systems are all discussed.     

葫芦脲：分子识别与组装

综述了葫芦脲这一类合成受体的最新研究进展，包括葫芦脲的分子设计与合成 ，离子和分子识别，键合的热力学性质，分子组装及其功能的最新研究概况。     

Encapsulation of transition metal catalysts by ligand-template directed assembly

Encapsulated transition metal catalysts are presented that are formed by templated self-assembly processes of simple building blocks such as porphyrins and pyridylphosphine and phosphite ligands, using selective metal-ligand interactions. These ligand assemblies coordinate to transition metals, leading to a new class of transition metal catalysts. The assembled catalyst systems were characterized using NMR and UV-vis spectroscopy and were identified under catalytic conditions using high-pressure infrared spectroscopy. Tris-3-pyridylphosphine binds three mesophenyl zinc(II) porphyrin units and consequently forms an assembly with the phosphorus donor atom completely encapsulated. The encapsulated phosphines lead exclusively to monoligated transition metal complexes, and in the rhodium-catalyzed hydroformylation of 1-octene the encapsulation of the catalysts resulted in a 10-fold increase in activity. In addition, the branched aldehyde was formed preferentially (l/b = 0.6), a selectivity that is highly unusual for this substrate, which is attributed to the encapsulation of the transition metal catalysts. An encapsulated rhodium catalyst based on ruthenium(II) porphyrins and tris-meta-pyridyl phosphine resulted in an even larger selectivity for the branched product (l/b = 0.4). These encapsulated catalysts can be prepared easily, and various template ligands and porphyrins, such as tris-3-pyridyl phosphite and ruthenium(II) porphyrins, have been explored, leading to catalysts with different properties.     

Specific ion and ph effects on supramolecular assembly of mesostructured V-Mg oxides

Mesostructured V-Mg oxides were synthesized using the surfactant cetyltrimethylammonium bromide (CTAB) as template, V2O5, V(acac)3 (vanadium acetylacetonate), or NH4VO3 as vanadium source, and Mg(NO3)2, MgCl2, MgSO4, (MgCO3)4.Mg(OH)2, Mg(CH3CO2)2, or Mg(C2H5O)2 as magnesium source. The factors that influence the formation of mesostructured V-Mg oxides, such as the pH, the natures of magnesium and vanadium sources, and the ionic strength, were identified. The formation of mesophases could be related to the presence of anionic vanadium species, to the electrostatic interactions between the oppositely charged vanadates and micellar headgroups, and to the nature of the counterion of Mg2+ in the magnesium source. The main role was played by the pH and only when the pH allowed the formation of vanadates was a mesostructure generated. The counterions of Mg2+ also played a role, which could be explained via specific ion effects and the formation of complexes between them and the vanadium-containing species, which are attracted by the headgroups of the micellar templates.     

Sequential metal ion assembly in cyclic phenylazomethine

[reaction: see text] Cyclic phenylazomethines with methylene spacers (CPA-M) are obtained by dehydration of diamine with diketone. During the titration of CPA-M 4mer with FeCl(3), we observe two consecutive isosbestic points in the UV-vis spectra. We conclude that complexation occurs in two consecutive steps. Our analysis suggests that the stepwise metal ion assembly is caused by a difference in the basicity of the imine conformers. Metal ion binding first occurs at the Z imines followed by coordination to the E imine. Finally, metal ion assembly in this compound can be controlled electrochemically.     

Triangles and tetrahedra: metal directed self-assembly of metallo-supramolecular structures incorporating bis-beta-diketonato ligands

The interaction of six aryl-linked bis-beta-diketones, including a new naphthylene linked species, with copper(II), iron(III) and, in one instance gallium(III), has been investigated with the aim of obtaining metallo-supramolecular assemblies exhibiting different geometries. New examples of two assembly types incorporating the above bis-beta-diketones (L) were generated. The first type is represented by a range of molecular triangles of formula [Cu(3)(L-H(2))(3)](solvent)(n) while the second is given by a corresponding selection of less-common neutral molecular tetrahedra of formula [Fe(4)(L-H(2))(6)](solvent)(n) as well as [Ga(4)(L-H(2))(6)].8.5THF.0.5H(2)O; an example of each type has been characterised by X-ray crystallography. A magnetochemical investigation of [Fe(4)(-H(2))(6)].6THF is reported. The susceptibility is Curie like and consistent with very weak coupling occurring between the iron(III) d(5)(high spin) centres. The X-ray structures of two trinuclear copper(II) as well as a tetranuclear iron(III) and a tetranuclear gallium(III) assembly confirm their discrete triangular and tetrahedral geometries, respectively. The structure of the gallium(III) species is closely related to that of the corresponding iron(III) species. The tetrahedral structures provide rare examples of such assemblies encapsulating guest solvent molecules--in each case tetrahydrofuran is incorporated in the central cavity.     

Controlled assembly of zero-, one-, two-, and three-dimensional metal chalcogenide structures

A room-temperature solution route to the controlled synthesis of 0-, 1-, 2-, and 3-D assemblies of molecularly linked metal chalcogenide clusters using essentially identical building blocks is reported. The solvating, ligating, and reducing abilities of hydrazine at room temperature have been exploited to simultaneously dissolve metal chalcogenides and organize the resulting building blocks into frameworks of increasing dimensionalities. Control of the product dimensionality was achieved by varying the reactant ratios and the amount of hydrazine solvent employed in the reaction. The products have been characterized by single-crystal X-ray diffraction, Raman spectroscopy, and magnetic susceptibility.     

Ligand-template directed assembly: an efficient approach for the supramolecular encapsulation of transition-metal catalysts

Supramolecular encapsulation of small guest molecules inside well-defined cavities of molecular capsules has witnessed broad attention because of the unusual behaviour of these systems. The molecular capsules generally consist of rigid complementary building blocks that are held together by multiple, complementary non-covalent interactions. Interestingly, it has been shown that chemical transformations can take place inside these capsules and in some examples the reaction is accelerated, while in other cases otherwise instable intermediates could be isolated in the capsulated form. Many reactions of interest require a transition-metal (TM) catalyst, and the creation of new capsules in which such catalysts are implemented within the structure is thus required for the development of resourceful type of catalyst systems for these processes. In this concept article we will discuss new strategies to arrive at such systems, with a focus on a ligand-templated approach. In this approach, multifunctional ligands are used as templates for the encapsulation process by supramolecular building blocks and concomitantly for the formation of TM complexes that are active in catalytic processes. The obtained encapsulated transition-metal catalysts show unusual reactivity and selectivity behaviour that will be discussed in detail.     

Janus scorpionates: supramolecular tectons for the directed assembly of hard-soft alkali metallopolymer chains

A new scorpionate ligand [HB(mtda)3-] containing mercaptothiadiazolyl (mtda) heterocyclic rings with both hard nitrogen donors and soft sulfur donors has been prepared. This new ligand, the Janus scorpionate, is a hybrid of a tris(pyrazolyl)borate and a tris(mercaptoimidazolyl)borate. The differential hard/soft character of the dissimilar donor groups in this bridging ligand was exploited for the controlled solid-state organization of homometallic and heterometallic alkali metal coordination polymers. Remarkably, in the case of sodium, coordination polymers with both acentric (with NaS3N3H kernels) and centric (with alternating NaN6 and NaS6H2 kernels) chains are found in the same crystal (where the centricity is defined by the relative orientations of the B-H bonds of the ligands along the lattice). For the homometallic potassium congener, the larger cation size, compared to sodium, induced significant distortions and favored a polar arrangement of ligands in the resulting coordination polymer chain. An examination of the solid-state structure of the mixed alkali metal salt system revealed that synergistic binding of smaller sodium cations to the nitrogen portion and of the larger potassium cations to the sulfur portion of the ligand minimizes the ligand distortions relative to the homometallic coordination polymer counterparts, a design feature of the ligand that likely assists in thermodynamically driving the self-assembly of the heterometallic chains. The effect of alkali metal complexation on the solution properties of the ligand was studied by comparing NMR chemical shifts, B-H stretching frequencies, and electrochemical properties with those of the noncoordinating tetrabutylammonium salt of the scorpionate. The similarity of these data regardless of cation indicates that the salts are likely dissociated in solution rather than maintaining their solid-state polymeric structures. This data is augmented by the ESI(+/-) mass spectral data for a series of mixed alkali metal tris(mercaptothiadiazolyl)borates that also indicate that dissociation occurs in solution.     

Ionic hydrogen bonds controlling two-dimensional supramolecular systems at a metal surface

Hydrogen-bond formation between ionic adsorbates on an Ag(111) surface under ultrahigh vacuum was studied by scanning tunneling microscopy/spectroscopy (STM/STS), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and molecular dynamics calculations. The adsorbate, 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA), self-assembles at low temperatures (250-300 K) into the known open honeycomb motif through neutral hydrogen bonds formed between carboxyl groups, whereas annealing at 420 K leads to a densely packed quartet structure consisting of flat-lying molecules with one deprotonated carboxyl group per molecule. The resulting charged carboxylate groups form intermolecular ionic hydrogen bonds with enhanced strength compared to the neutral hydrogen bonds; this represents an alternative supramolecular bonding motif in 2D supramolecular organization.     

Transition metal ion complexes of 2-methylsulfinylpyridine n-oxide

Transition metal ion complexes in which 2-methylsulfinylpyridine N-oxide acts as a bidentate ligand have been prepared and characterized by molar conductivity measurements as well as IR and electronic spectra. Crystal field parameters are calculated for the Cr(III), Co(II) and Ni(II) solids based on octahedral symmetry from solid state spectra. Optical electronegativity calculations indicate that the charge transfer bands are metal-ligand in nature.     

Coexistence of one- and two-dimensional supramolecular assemblies of terephthalic acid on Pd(111) due to self-limiting deprotonation

The adsorption of terephthalic acid [C(6)H(4)(COOH)(2), TPA] on a Pd(111) surface has been investigated by means of scanning tunneling microscopy (STM), x-ray photoelectron spectroscopy, and near-edge x-ray absorption fine structure spectroscopy under ultrahigh vacuum conditions at room temperature. We find the coexistence of one- (1D) and two-dimensional (2D) molecular ordering. Our analysis indicates that the 1D phase consists of intact TPA chains stabilized by a dimerization of the self-complementary carboxyl groups, whereas in the 2D phase, consisting of deprotonated entities, the molecules form lateral ionic hydrogen bonds. The supramolecular growth dynamics and the resulting structures are explained by a self-limiting deprotonation process mediated by the catalytic activity of the Pd surface. Our models for the molecular ordering are supported by molecular mechanics calculations and a simulation of high resolution STM images.     

A multi-color and white-light emissive cucurbituril/ terpyridine/ lanthanide supramolecular nanofiber

The enhanced lanthanide white-emission in solid by cucurbituril-based supramolecular assembly may provide a new strategy for smart light-emitting materials.