Recognition-directed assembly of salt-binding [2]rotaxanes

Deetz, Martin J.; Shukla, R. C.; Smith, Bradley D.

doi:10.1016/s0040-4020(01)01108-5

Cited by 49 publications

(31 citation statements)

References 32 publications

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“…Recently, Deetz et al described the synthesis of four isomeric rotaxanes exhibiting coconformational exchange upon salt binding. 41 Kern and co-workers reported a molecular machinelike copper rotaxane observed by X-ray absorption spectroscopy experiments. 42 Glink and co-workers described temperature-controlled (-140 to +50 °C) molecular shuttles using rotaxanes.…”

Section: Introductionmentioning

confidence: 98%

“…The construction of molecular shuttles in which the ring shifts between two or more “stations” on the linear chain in response to external stimuli is one promising target for prototype molecular devices. ,,,,,− Numerous examples have been reported. Recently, Deetz et al described the synthesis of four isomeric rotaxanes exhibiting coconformational exchange upon salt binding . Kern and co-workers reported a molecular machinelike copper rotaxane observed by X-ray absorption spectroscopy experiments .…”

Section: Introductionmentioning

confidence: 99%

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Modeling of a Rotaxane-Based Molecular Device

Zheng

Sohlberg

2003

J. Phys. Chem. A

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A computational procedure is presented for investigating photoinduced switchable rotaxanes and demonstrated for a known system. This procedure starts with the generation of >10 4 chemically reasonable rotaxane coconformations based on an empirical intramolecular potential-energy function. Each of the structures is then assigned by its gross structural features (coiled or extended) and by the position of the ring along the shaft. Single-point energy calculations at the semiempirical (AM1) level are then carried out for each structure in the singlet (ground), triplet, and anionic doublet states. The structural features are then correlated with energy for each state. What emerges is a profile of the structure-energy relationship that captures the salient features of the system that endow it with devicelike character. The full geometry optimization of a subset of the coconformations demonstrates that the procedure based on single-point calculations is sufficient to obtain a profile of the relationship of the structural features to energy that is consistent with experiments at a greatly reduced computational cost.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Modeling of a Rotaxane-Based Molecular Device

Zheng

Sohlberg

2003

J. Phys. Chem. A

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“…Rotaxanes and catenanes have for some time been the subject of intense study [1][2][3][4][5][6][7] both because of their fascinating architectures, [8][9][10][11][12][13][14][15][16][17][18] and because they may have useful properties as molecular-level switches and sensors. [5,[19][20][21][22][23][24][25] Our approach has been to bring together neutral electron-rich components such as crown ether 1 (the "donor") and electron-poor components such as pyromellitic diimide 2 (the "acceptor") to create highly colored donor-acceptor systems that are neutral, chemically robust, and capable of postsynthetic modification.…”

Section: In Memory Of Norma Stoddartmentioning

confidence: 99%

Lithium‐Templated Synthesis of a Donor–Acceptor Pseudorotaxane and Catenane

et al. 2004

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“…For instance, the protons H b (see Figure 1), which give a signal at 8.43 ppm when free in chloroform solution, are no longer chemically equivalent when incorporated into the rotaxane, where two doublets at 8.64 and 8.55 ppm are observed. 11 Moreover, the roomtemperature 1 H NMR spectrum of the rotaxane in chloroform is well resolved and exhibits no dynamic behavior after cooling, which can be ascribed to the predominance of a specific co-conformation (i.e., the relative orientation of the component parts of an interlocked molecule). In contrast, the 1 H NMR spectrum of the rotaxane in dimethyl sulfoxide (DMSO) shows broad signals for the axle protons at room temperature, which nevertheless sharpen considerably upon addition of 5 molar equiv of KPF 6 .…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Study of [2]Rotaxanes: Influence of Solvation and Cation on Co-conformation

et al. 2003

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The conformational preference of a [2]rotaxane system has been examined by molecular dynamics simulations. The rotaxane wheel consists of two bridged binding components: a cis-dibenzo-18-crown-6 ether and a 1,3-phenyldicarboxamide, and the penetrating axle consists of a central isophthaloyl unit with phenyltrityl capping groups. The influence of solvation on the co-conformation of the [2]rotaxane was evaluated by comparing the conformational flexibility in two solvents: chloroform and dimethyl sulfoxide. Attention was also paid to the effect of cation binding on the dynamical properties of the [2]rotaxane. The conformational stability of the [2]rotaxane was calculated using a MM/PB-SA strategy, and the occurrence of specific motions was examined by essential dynamics analysis. The changes in the co-conformational properties in the two solvents and upon cation binding are discussed in light of the available NMR data. The results indicate that in chloroform solution the [2]rotaxane system exists as a mixture of co-conformational states including some that have hydrogen bonds between axle C=O and wheel NH groups. Analysis of the simulations allow us to hypothesize that the [2]rotaxane's circumrotation motion can occur as the result of a dynamic process that combines a preliminary axle sliding step that breaks these hydrogen bonds and a conformational change in the ester group more distant from the wheel. In contrast, no hydrogen-bonded co-conformation was found in dimethyl sulfoxide, which appears to be due to the preferential formation of hydrogen bonds between the wheel NH groups with solvent molecules. Moreover, the axle experiences notable changes in anisotropic shielding, which would explain why the NMR signals are broadened in this solvent. Insertion of a sodium cation into the crown ether reduces co-conformational flexibility due to an interaction of the axle with the cation. Overall, the results reveal how both solvent and ionic atmosphere can influence the co-conformational preferences of rotaxanes.

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Recognition-directed assembly of salt-binding [2]rotaxanes

Cited by 49 publications

References 32 publications

Modeling of a Rotaxane-Based Molecular Device

Modeling of a Rotaxane-Based Molecular Device

Lithium‐Templated Synthesis of a Donor–Acceptor Pseudorotaxane and Catenane

Molecular Dynamics Study of [2]Rotaxanes: Influence of Solvation and Cation on Co-conformation

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