Künstliche molekulare Maschinen

Balzani, Vincenzo; Credi, Alberto; Raymo, Françisco M.; Stoddart, J. Fraser

doi:10.1002/1521-3757(20001002)112:19<3484::aid-ange3484>3.0.co;2-o

Cited by 551 publications

(110 citation statements)

References 484 publications

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“…We have been involved in using the self-assembly of pyridine-appended ligands in the presence of cis-protected Pd II /Pt II ions to obtain [2]catenanes. [7] In contrast to the cyclization in which covalent bond formation is the key step, our method is much easier since self-assembly directs to catenane formation in quantitative yields by simply combining suitably designed ligand/ligands with coordinatively unsaturated metal ions (e.g., [Pd(en)(NO 3 ) 2 ]) under suitable conditions.…”

Section: Introductionsupporting

confidence: 55%

“…[1] Further, the use of these interlocked molecules in material research as building blocks for the construction of molecular scale machines and nanomaterials, [2] biological research for the study of DNA replication, [3] and many other applications are subjects of considerable current interest. Various promising synthetic methods exist in literature for the synthesis of catenanes including metal- [4] and organic-templating [5,6] strategies, and self-assembly strategies.…”

Section: Introductionmentioning

confidence: 99%

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DOSY Study on Dynamic Catenation: Self-Assembly of a [3]Catenane as a Meta-Stable Compound from Twelve Simple Components

et al. 2001

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Synthesis of [2]catenane 6 has been successfully achieved by the combination of Pd complex 1 and pyridines 2 and 3 at a molar ratio of 2:1:1 in D20. A mixture of square molecule 4 (prepared from 1 and 2) and macrocycle 5 (obtained from 1 and 3), in which the final ratio of 1, 2, and 3 was kept 2:1:1 reorganizes in D2O/CD3OD (1:1) to form 6 within one day. However, the same mixture in D2O shows the formation of novel [3]catenane 7 along with the [2]catenane. In order to make 7, the theoretical ratio of components 1, 2, and 3 should be 3:1:2. Thus, deliberately maintaining such ratio of the above-mentioned molecules, a higher proportion of the [3]catenane is observed in D2O as found from 1H NMR spectra of the system. Reorganization of the twelve components to form [3]catenane is supported by studies with the DOSY method. This method is a first attempt to separate, from a mixture, either catenanes or any other supramolecular self-assembly structures. CSI-MS studies further support the assigned catenane super structures 6 and 7. All the results indicate that the [2]catenane is thermodynamically the most stable structure, while the [3]catenane is a meta-stable self-assembly.

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Section: Introductionsupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

DOSY Study on Dynamic Catenation: Self-Assembly of a [3]Catenane as a Meta-Stable Compound from Twelve Simple Components

et al. 2001

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“…[2] However, the iodination of alkanes has been a particularly elusive reaction and still remains as an active research area. [3] The endothermic nature of the overall process has been invoked to explain the failure of a radicalchain approach to accomplish this reaction. [4,5] While performing b-scission reactions of cycloalkanols, [6] we noticed that (diacetoxyiodo)benzene [PhI(OAc) 2 ] [7] gave rise to a mixture of compounds, where iodocyclohexane (2 b) was found as the major product, resulting from an activation of the cyclohexane used as solvent.…”

mentioning

confidence: 99%

Activation of Alkanes upon Reaction with PhI(OAc)2-I2

Barluenga

González‐Bobes

González

2002

Angew. Chem. Int. Ed.

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“…[1] This possibility gives rise to a new class of potential artificial molecular machines, [2] thus adding to the possibilities based on rotaxanes and catenanes. [3,4] Movement of metal ions, which takes place following a predetermined pathway, can be induced by different stimuli, such as a variation of the redox potential, [5,6] or a pH change. [7] The use of pH as the stimulus is especially convenient as it involves a rather mild perturbation and does not cause degradation of the system, and hence its operation can be repeated at will, indefinitely.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Signal Amplification by a Fluorescent Indicator of a pH-Driven Intramolecular Translocation of a Copper(II) Ion

Amendola

Fabbrizzi

Mangano

et al. 2002

Angew. Chem. Int. Ed.

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The translocation of a metal ion in a reversible and repeatable manner from one compartment to the other within a ditopic ligand could lead to mechanical work at the molecular level. [1] This possibility gives rise to a new class of potential artificial molecular machines, [2] thus adding to the possibilities based on rotaxanes and catenanes. [3,4] Movement of metal ions, which takes place following a predetermined pathway, can be induced by different stimuli, such as a variation of the redox potential, [5,6] or a pH change. [7] The use of pH as the stimulus is especially convenient as it involves a rather mild perturbation and does not cause degradation of the system, and hence its operation can be repeated at will, indefinitely. This situation is not always the case with the more drastic and destructive processes which involve an auxiliary oxidation and reduction reaction. The essential requirements for the occurrence of a pH-driven metal translocation process are that 1) one of the two coordinating compartments (A) also shows a distinct acid ± base behavior (for example, through the AH n >A nÀ nH equilibrium), and that 2) the coordinating tendencies of the two compartments decrease along the series A nÀ ) B ) AH n , where B is the second compartment that does not display acid ± base behavior, at least in the investigated pH interval. Thus, at a pH value in which AH n dominates, the metal ion stays in compartment B. On the other hand, when the pH value is increased and AH n deprotonates, the metal ion moves to the more appealing compartment A nÀ . The metal ion moves back to B on decreasing the pH value. In the case of transition metal ions, a change in the compartment typically modifies the stereochemistry and the ligand field experienced by the cation, thus altering its electronic structure and spectral features. Ultimately, the displacement of the metal ion is signaled by a color change of the solution. We show here that the position of the metal ion in the ditopic system can be determined by the powerful signal of a fluorescent indicator (which is present at a very low concentration) provided that the indicator is able to interact selectively with the metal ion.The envisaged ditopic ligand 1 contains two distinct tetradentate compartments: A and B. The donor set of A consists of two secondary amine and two secondary amide nitrogen atoms. As the amide group itself possesses poor or no coordinating tendencies, the neutral form AH 2 is expected to display minimum binding tendencies towards the chosen metal ion, Cu II . On the other hand, at neutral or slightly alkaline pH values, the amide group deprotonates in the presence of divalent late-transition-metal ions to give rise to a very strong donor group: thus, the doubly deprotonated A 2À compartment is expected to establish especially intense metal ± ligand interactions and give rise to a very stable complex with a square geometry. Compartment B is constituted by two 2,2'-bipyridine (bpy) fragments, which display fairly good binding tendencies towards Cu II...

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Künstliche molekulare Maschinen

Cited by 551 publications

References 484 publications

DOSY Study on Dynamic Catenation: Self-Assembly of a [3]Catenane as a Meta-Stable Compound from Twelve Simple Components

DOSY Study on Dynamic Catenation: Self-Assembly of a [3]Catenane as a Meta-Stable Compound from Twelve Simple Components

Activation of Alkanes upon Reaction with PhI(OAc)2-I2

Signal Amplification by a Fluorescent Indicator of a pH-Driven Intramolecular Translocation of a Copper(II) Ion

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