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1.
The self‐assembly of nanostructures is dominated by a limited number of strong coordination elements. Herein, we show that metal–acetylene π‐coordination of a tripodal ligand (L) with acetylene spacers gave an M3L2 double‐propeller motif (M=CuI or AgI), which dimerized into an M6L4 interlocked cage (M=CuI). Higher (M3L2)n oligomers were also selectively obtained: an M12L8 truncated tetrahedron (M=CuI) and an M18L12 truncated trigonal prism (M=AgI), both of which contain the same double‐propeller motif. The higher oligomers exhibit multiply entangled facial structures that are classified as a trefoil knot and a Solomon link. The inner cavities of the structures encapsulate counteranions, revealing a potential new strategy towards the synthesis of functional hollow structures that is powered by molecular entanglements.  相似文献   

2.
The self-assembly of nanostructures is dominated by a limited number of strong coordination elements. Herein, we show that metal–acetylene π-coordination of a tripodal ligand (L) with acetylene spacers gave an M3L2 double-propeller motif (M=CuI or AgI), which dimerized into an M6L4 interlocked cage (M=CuI). Higher (M3L2)n oligomers were also selectively obtained: an M12L8 truncated tetrahedron (M=CuI) and an M18L12 truncated trigonal prism (M=AgI), both of which contain the same double-propeller motif. The higher oligomers exhibit multiply entangled facial structures that are classified as a trefoil knot and a Solomon link. The inner cavities of the structures encapsulate counteranions, revealing a potential new strategy towards the synthesis of functional hollow structures that is powered by molecular entanglements.  相似文献   

3.
The dynamic solution equilibria between molecular Borromean rings (BRs) and Solomon knots (SKs), assembled from transition metal‐templated macrocycles, consisting of exo‐bidentate bipyridyl and endo‐tridentate diiminopyridyl ligands, have been examined with respect to the choice of the metal template and reaction conditions employed in the synthesis of the metalated BRs, otherwise known as Borromeates. Three new Borromeates, their syntheses templated by CuII, CoII, and MnII, have been characterized extensively (two by X‐ray crystallography) to the extent that the metal centers in the assemblies have been shown to be distanced sufficiently from each other not to communicate. The solid‐state structure of the CoII–Borromeate reveals that six MeOH molecules, arranged in a [O? H???O] hydrogen bonded, chair‐like conformation, are located within its oxophilic central cavity. When a mixture of CuII and ZnII is used as the source of templation, there exists a dynamic equilibrium, in MeOH at room temperature, between a mixed‐metal BR and a SK, from which the latter has been fractionally crystallized. By employing appropriate synthetic protocols with ZnII or CdII as the template, significant amounts of SKs are formed alongside BRs. Modified crystallization conditions resulted in the isolation of both an all‐zinc BR and an all‐zinc SK, crystals of which can be separated manually, leading to the full characterization of the all‐zinc SK by 1H NMR spectroscopy and X‐ray crystallography. This doubly interlocked [2]catenate has been identified retrospectively in recorded spectra, where it was attributed previously to a Borromeate with a ZnII cation coordinated to the oxophilic interior walls of the ensemble. Interestingly, these ZnII‐templated assemblies do not interconvert in MeOH at room temperature, indicating the significant influence of both the metal template and solvent on the solution equilibria. It would also appear that d10 metal ions favor SK formation—no evidence of CuII‐, CoII‐, or MnII‐templated SKs has been found, yet a 1:0.9 ratio of BR:SK has been identified by 1H NMR spectroscopy when CdII is used as the template.  相似文献   

4.
A molecular Solomon link was synthesized through the assembly of an interwoven molecular grid consisting of four bis(benzimidazolepyridyl)benzthiazolo[5,4‐d]thiazole ligands and four zinc(II), iron(II), or cobalt(II) cations, followed by ring‐closing olefin metathesis. NMR spectroscopy, mass spectrometry, and X‐ray crystallography confirmed the doubly interlocked topology, and subsequent demetalation afforded the wholly organic Solomon link. The synthesis, in which each metal ion defines the crossing point of two ligand strands, suggests that interwoven molecular grids should be useful scaffolds for the rational construction of other topologically complex structures.  相似文献   

5.
Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) was utilized to study dendritic macromolecules with various architectures, such as dendrons, dendrimers and hyperbranched polyesters prepared from bis‐(hydroxymethyl)propionic acid (Bis‐MPA) and a series of hyperbranched polyethers based on 3‐ethyl‐3(hydroxymethyl)oxetane. The measurements were performed on spin‐coated thin films of the branched molecules (D) onto silicon, chemically etched copper foil and silver‐coated wafers. They showed weak signatures of molecular ions by proton capture (D + H)+ in the high mass range of the spectra (m/z > 400). On the contrary, cationization of the intact molecules with alkali or transition metal ions such as Na+, Cu+ or Ag+ was observed. High‐intensity quasi‐molecular ions (D + M)+ (with M = Na+, Cu+ or Ag+) allowed the studied polymers to be identified. The whole molecular species were observed for Bis‐MPA dendrons and dendrimers up to 3000 Da for hydroxyl or acetonide‐terminated derivatives. The success of the so‐called cationization experiments with metal substrates compared with analysis of molecular adsorbates on silicon is highlighted. The ToF‐SIMS sensitivity appeared useful to provide information about the molecular end‐groups or to highlight incomplete reaction occurring during some deprotection step of the synthesis. Only uncationized fragments of low masses were detected for the hyperbranched polyesters. This result suggested the effect of molecular asymmetry and/or flattening of the molecules on the substrates, which hampered the molecule lift‐off efficiency. Nevertheless, the hyperbranched polyethers were characterized based on the peak distribution of intensities, which allowed estimation of their molecular weight average. This work was intended to illustrate the capabilities of ToF‐SIMS to analyse dendritic polymers on surfaces. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

6.
We report on multicomponent self‐sorting to form open circular helicates of different sizes from a primary monoamine, FeII ions, and dialdehyde ligand strands that differ in length and structure by only two oxygen atoms. The corresponding closed circular helicates that are formed from a diamine—a molecular Solomon link and a pentafoil knot—also self‐sort, but up to two of the Solomon‐link‐forming ligand strands can be accommodated within the pentafoil knot structure and are either incorporated or omitted depending on the stage that the components are mixed.  相似文献   

7.
A new electrochemical sensing platform was designed for sensitive detection of copper(II) (Cu2+) based on click conjugation of two short oligonucleotides by using methylene blue‐functionalized hairpin DNA as the template. The analyte (Cu2+) was in situ reduced to Cu+ by sodium ascorbate, which catalyzed the click conjugation between two single‐stranded oligonucleotides one was labelled with a 5′‐alkyne and the other with 3′‐azide group via the Cu+‐catalyzed azide‐alkyne cycloaddition. The newly formed long‐chain oligonucleotide induced the conformational change of hairpin DNA to open the hairpin, resulting in methylene blue far away from the electrode for the decrease of redox current. Under optimal conditions, the decrease in the electronic signal was directly proportional to target Cu2+ concentration, and allowed the detection of Cu2+ at a concentration as low as 1.23 nM. Our strategy also displayed high selectivity for Cu2+ against other metal ions owing to the highly specific Cu+‐catalyzed click chemistry reaction, and was applicable for monitoring of Cu2+ in drinking water with satisfactory results.  相似文献   

8.
A multiply interlocked catenane with a novel molecular topology was synthesized; a phthalocyanine bearing four peripheral crown ethers was quadruply interlocked with a cofacial porphyrin dimer bridged with four alkylammonium chains. The supramolecular conjugate has two nanospaces surrounded by a porphyrin, a phthalocyanine, and four alkyl chains to accommodate guest molecules. Because the phthalocyanine can move along the alkyl chains, it acts as an adjustable wall, thus permitting the invasion of large molecules into the nanospaces without spoiling the affinity of the association. The dynamic molecular invasion allowed the intercalation of dianionic porphyrins into both nanospaces with high affinity. A photometric titration experiment revealed the two‐step inclusion phenomenon. The multiply interlocked catenane complexed with three Cu2+ ions, and the spin–spin interaction was switched off by the intercalation of dianionic porphyrins.  相似文献   

9.
Linearly arranged metal atoms that are embedded in discrete molecules have fascinated scientists across various disciplines for decades; this is attributed to their potential use in microelectronic devices on a submicroscopic scale. Luminescent oligonuclear Group 11 metal complexes are of particular interest for applications in molecular light‐emitting devices. Herein, we describe the synthesis and characterization of a rare, homoleptic, and neutral linearly arranged tetranuclear CuI complex that is helically bent, thus representing a molecular coil in the solid state. This tetracuprous arrangement dimerizes into a unique octanuclear assembly bearing a linear array of six CuI centers with two additional bridging cuprous ions that constitute a central pseudo‐rhombic CuI4 cluster. The crystal structure determinations of both complexes reveal close d10???d10 contacts between all cuprous ions that are adjacent to each other. The dynamic behavior in solution, DFT calculations, and the luminescence properties of these remarkable complexes are also discussed.  相似文献   

10.
The gas phase reactions of metal ions (Al+, Cu+) with amine molecules [CH3NH2=MA, (CH3)2NH=DMA] were investigated using a laser ablation‐molecular beam method. The directly associated product complex ions,Al+‐MA and Al+‐DMA, and the dehydrogenation product ions, Cu+(CH2NH) and Cu+(C2H5N), as well as hydrated ion Cu+(NC2H5·H2O), have been obtained and recorded from the reactions of the metal ions and organic amine molecules, and density functional theory (B3LYP) calculations have been performed to reveal the optimized geometry, energetics, and reaction mechanism of the title reactions with basis set 6‐311+G(d,p) adopted.  相似文献   

11.
A molecular Solomon link was synthesized in high yield through the template‐free, coordination‐driven self‐assembly of a carbazole‐functionalized donor and a tetracene‐based dinuclear ruthenium(II) acceptor. The doubly interlocked topology was realized by a strategically chosen ligand which was capable of participating in multiple CH ??? π and π–π interactions, as evidenced from single‐crystal X‐ray analysis and computational studies. This method is the first example of a two‐component self‐assembly of a molecular Solomon link using a directional bonding approach. The donor alone was not responsible for the construction of the Solomon link, and was confirmed by its noncatenane self‐assemblies obtained with other similar ruthenium(II) acceptors.  相似文献   

12.
The deposition of Cu2+ and Zn2+ from aqueous solution has been investigated by a combination of classical molecular dynamics, density functional theory, and a theory developed by the authors. For both cases, the reaction proceeds through two one‐electron steps. The monovalent ions can get close to the electrode surface without losing hydration energy, while the divalent ions, which have a stronger solvation sheath, cannot. The 4s orbital of Cu interacts strongly with the sp band and more weakly with the d band of the copper surface, while the Zn 4s orbital couples only to the sp band of Zn. At the equilibrium potential for the overall reaction, the energy of the intermediate Cu+ ion is only a little higher than that of the divalent ion, so that the first electron transfer can occur in an outer‐sphere mode. In contrast, the energy of the Zn+ ion lies too high for a simple outer‐sphere reaction to be favorable; in accord with experimental data this suggests that this step is affected by anions.  相似文献   

13.
The molecular steps involved in the self‐assembly of Cu3(BTC)2 (BTC=1,3,5‐benzenetricarboxylic acid) metal–organic frameworks that enclose Keggin‐type H3PW12O40 heteropolyacid molecules were unraveled by using solution 17O, 31P, and 183W NMR spectroscopy, small‐angle X‐ray scattering, near‐IR spectroscopy, and dynamic light scattering. In aqueous solution, complexation of Cu2+ ions with Keggin‐type heteropolyacids was observed. Cu2+ ions are arranged around the Keggin structure so that linking through benzenetricarboxylate groups results in the formation of the Cu3(BTC)2 MOF structure HKUST‐1. This is a unique instance in which a templating mechanism that relies on specific molecular‐level matching and leads to explicit nanoscale building units can be observed in situ during formation of the synthetic nanoporous material.  相似文献   

14.
Using density functional theory calculations, we investigated the structural, energetic, electronic, and optical properties of recently synthesized duplex DNA containing metal‐mediated base pairs. The studied duplex DNA consists of three imidazole (Im) units linked through metal (Im‐M‐Im, M=metal) and four flanking A:T base pairs (two on each side). We examined the role of artificial base pairing in the presence of two distinctive metal ions, diamagnetic Ag+ and magnetic Cu2+ ions, on the stability of duplex DNA. We found that metal‐mediated base pairs form stable duplex DNA by direct metal ion coordination to the Im bases. Our results suggest a higher binding stability of base pairing mediated by Cu2+ ions than by Ag+ ions, which is attributed to a larger extent of orbital hybridization. We furthermore found that DNA modified with Im‐Ag+‐Im shows the low‐energy optical absorption characteristic of π–π*orbital transition of WC A:T base pairs. On the other hand, we found that the low‐energy optical absorption peaks for DNA modified with Im‐Cu2+‐Im originate from spin–spin interactions. Additionally, this complex exhibits weak ferromagnetic coupling between Cu2+ ions and strong spin polarization, which could be used for memory devices. Moreover, analyzing the role of counter ions (Na+) and the presence of explicit water molecules on the structural stability and electronic properties of the DNA duplex modified with Im‐Ag+‐Im, we found that the impact of these two factors is negligible. Our results are fruitful for understanding the experimental data and suggest a potential route for constructing effective metal‐mediated base pairs in duplex DNA for optoelectronic applications.  相似文献   

15.
A facile and efficient two‐step synthesis of p‐substituted tris(2‐pyridylmethyl)amine (TPMA) ligands to form Cu complexes with the highest activity to date in atom transfer radical polymerization (ATRP) is presented. In the divergent synthesis, p‐Cl substituents in tris(4‐chloro‐2‐pyridylmethyl)amine (TPMA3Cl) were replaced in one step and high yield by electron‐donating cyclic amines (pyrrolidine (TPMAPYR), piperidine (TPMAPIP), and morpholine (TPMAMOR)) by nucleophilic aromatic substitution. The [CuII(TPMANR2)Br]+ complexes exhibited larger energy gaps between frontier molecular orbitals and >0.2 V more negative reduction potentials than [CuII(TPMA)Br]+, indicating >3 orders of magnitude higher ATRP activity. [CuI(TPMAPYR)]+ exhibited the highest reported activity for Br‐capped acrylate chain ends in DMF, and moderate activity toward C?F bonds at room temperature. ATRP of n‐butyl acrylate using only 10–25 part per million loadings of [CuII(TPMANR2)Br]+ exhibited excellent control.  相似文献   

16.
Cu4P4X4Fe2 (X = Cl, Br) cages are formed upon reactions of octaethyl‐1,1′‐diphosphaferrocene (odpf) with the respective CuI halide in CH2Cl2/CH3CN solvent mixtures. These cages have adamantoid Cu4X4P2 cores with two planar anelated CuP2Fe rings as the flaps. Both complexes 1 and 2 feature tri‐ and tetracoordinate CuI ions and an additional acetonitrile solvent molecule in the crystal. In 1 , the solvent molecule is coordinated to one copper ion whereas it remains uncoordinated in 2 . The tricoordinate CuI ions show a slight pyramidalization at the metal atom and somewhat short contacts to the other tricoordinate CuI ion in 2 or the Cu3‐triangle in 1 . NMR spectroscopy revealed easy decoordination of the acetonitrile ligand from 1 and a dynamic “windshield‐wiper”‐type process that interconverts the differently coordinated phospholide rings of each odpf ligand and the tri‐ and tetracoordinate CuI ions.  相似文献   

17.
Herein, two new groups of isomeric bimetallic nickel(II) and copper(II) complexes containing pyrazine or pyrimidine rings are synthesized and examined. The complexes exhibit liquid‐crystalline columnar phases in a broad temperature range. For the copper(II) complexes, super‐exchange coupling between two CuII ions is observed. For the pyrimidine derivative in which the paramagnetic CuII ions are separated only by three atoms, an antiferromagnetic spin alignment is detected. When the distance between CuII ions increases to four atoms in the pyrazine derivative, the magnetic interaction becomes significantly weaker.  相似文献   

18.
Half a century after Schill and Lüttringhaus carried out the first directed synthesis of a [2]catenane, a plethora of strategies now exist for the construction of molecular Hopf links (singly interlocked rings), the simplest type of catenane. The precision and effectiveness with which suitable templates and/or noncovalent interactions can arrange building blocks has also enabled the synthesis of intricate and often beautiful higher order interlocked systems, including Solomon links, Borromean rings, and a Star of David catenane. This Review outlines the diverse strategies that exist for synthesizing catenanes in the 21st century and examines their emerging applications and the challenges that still exist for the synthesis of more complex topologies.  相似文献   

19.
The CXCR4 chemokine receptor is implicated in a number of diseases including HIV infection and cancer development and metastasis. Previous studies have demonstrated that configurationally restricted bis‐tetraazamacrocyclic metal complexes are high‐affinity CXCR4 antagonists. Here, we present the synthesis of Cu2+ and Zn2+ acetate complexes of six cross‐bridged tetraazamacrocycles to mimic their coordination interaction with the aspartate side chains known to bind them to CXCR4. X‐ray crystal structures for three new Cu2+ acetate complexes and two new Zn2+ acetate complexes demonstrate metal‐ion‐dependent differences in the mode of binding the acetate ligand concomitantly with the requisite cis‐V‐configured cross‐bridged tetraazamacrocyle. Concurrent density functional theory molecular modelling studies produced an energetic rationale for the unexpected [Zn(OAc)(H2O)]+ coordination motif present in all of the Zn2+ cross‐bridged tetraazamacrocycle crystal structures, which differs from the chelating acetate [Zn(OAc)]+ structures of known unbridged and side‐bridged tetraazamacrocyclic Zn2+‐containing CXCR4 antagonists.  相似文献   

20.
Two large rings, 66‐ (m‐66 ) and 78‐membered ( m‐78 ) rings, each one incorporating two pairs of transition‐metal‐complexing units, have been prepared. The coordinating fragments are alternating bi‐ and tridentate chelating groups, namely, 2,9‐diphenyl‐1,10‐phenanthroline (dpp) and 2,2′,2′,6′′‐terpyridine (terpy) respectively. Both macrocycles form molecular figures‐of‐eight in the presence of FeII, affording a classical bis‐terpy complex as the central core. The larger m‐78 ring can accommodate a four‐coordinate CuI center with the formation of a {Cu(dpp)2}+ central complex and a highly twisted figure‐of‐eight backbone, whereas m‐66 is too small to coordinate CuI. Macrocycle m‐78 thus affords stable complexes with both FeII and CuI; the ligand around the metal changes from (terpy)2 to (dpp)2. This bimodal coordination situation allows for a large amplitude rearrangement of the organic backbone. When coordinated to preferentially octahedrally coordinated FeII or CuII, the height of the molecule along the coordinating axis of the tridentate terpy ligands is only about 11 Å, whereas the height of the molecule along the same vertical axis is several times as large for the tetrahedral CuI complex. Chemically or electrochemically driven contraction and extension motions along a defined axis make this figure‐of‐eight particularly promising as a new class of molecular machine prototype for use as a constitutive element in muscle‐like dynamic systems.  相似文献   

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