Symbiotic Control in Mechanical Bond Formation

Wang, Yuping; Sun, Jiazeng; Liu, Zhichang; Nassar, Majed S.; Botros, Youssry Y.

doi:10.1002/anie.201605454

Cited by 24 publications

(22 citation statements)

References 53 publications

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“…This behavior was already suggested to occur in other types of supramolecular systems involving π-dimerization of viologens. 45,46 Interestingly, similar behaviors were also reported for supramolecular polymers based on perylene diimide derivatives showing that this phenomenon could be extended to other types of π-conjugated units. 47 High light intensity could be focalized on the samples upon conducting the irradiation through the objective of the microscope.…”

Section: Resultssupporting

confidence: 67%

Photoredox Processes in the Aggregation and Gelation of Electron-Responsive Supramolecular Polymers Based on Viologen

et al. 2022

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Viologen-based ditopic bis-pyridinyl-triazole bidentate ligands self-assemble in the presence of palladium ions into supramolecular polymers whose structure is imposed by the directed formation of coordination bonds. Light-irradiation of these electron-responsive supramolecular materials triggers a photo-induced electron transfer yielding isolated π-radicals and dimers of radicals. The photoreduction events and the associated dimerization steps trigger a large-scale reorganization occurring within the supramolecular network yielding aggregates or gels depending on the irradiation conditions (power, duration). Detailed electrochemical, spectro-electrochemical and photochemical analyses were conducted to understand the mechanisms at stakes in these light-induced aggregation and gelation.

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Section: Resultssupporting

confidence: 67%

Photoredox Processes in the Aggregation and Gelation of Electron-Responsive Supramolecular Polymers Based on Viologen

et al. 2022

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“…The para-substituted tetrafluorophenylene building block 3, which was prepared according to literature procedures, 23 ring and the alkyne-functionalized stopper precursor 6, by employing (Scheme 1b) a Cu-mediated synthetic methodology in a threading-followed-by-stoppering protocol developed recently by us. 21 Briefly, the azide-functionalized, dumbbell precursor 5•2PF6 and CBPQT•4PF6 were dissolved in MeCN in a 1:1 molar ratio under an atmosphere of Ar, followed by the addition of an excess of Cu 0 dust (diam < 425 µm). Upon stirring the reaction mixture for 20 min, the BIPY 2+ units in both On the other hand, their counterparts, such as protons a', b' and c', experience significant changes in chemical shift on account of their being much closer to the ring component.…”

Section: Resultsmentioning

confidence: 99%

“…In order to meet these two requirements, we have introduced triazole units which act (i) as the pelectron-rich recognition sites for CBPQT 4+ and, at the same time, (ii) as the means of templating the synthesis of the tristable [2]rotaxane by the copper(I) catalyzed azide-alkyne cycloaddition 21 (CuAAC). Finally, for the p-electron-deficient sites, tetrafluorinated phenylene (Ar F ) units are introduced 16 in the knowledge that the changes in the chemical environments of these Ar F units can be monitored by 19 F NMR spectroscopy, an additional tool which would provide us with clearcut evidence for the location of the ring component in both the fully oxidized and neutral states.…”

Section: Introductionmentioning

confidence: 99%

Neighboring Component Effect in a Tri-stable [2]Rotaxane

et al. 2018

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The redox properties of cyclobis(paraquat-p-phenylene) cyclophane (CBPQT 4+) renders it a uniquely variable source of recognition in the context of mechanically interlocked molecules, through aromatic donor-acceptor interactions in its fully oxidized state (CPBQT 4+) and radicalpairing interactions in its partially reduced state (CBPQT 2(•+)). Although it is expected that the fully reduced neutral state (CBPQT (0)) might behave as a p-donating recognition unit, resulting in a dramatic change in its binding properties when compared with the other two redox states, its role in rotaxanes has not yet been investigated. To address this challenge, we report herein the synthesis of a tristable [2]rotaxane in which a CBPQT 4+ ring is mechanically interlocked with a dumbbell component containing five recognition sites¾(i) one, a bipyridinium radical cation (BIPY (•+)) located centrally along the axis of the dumbbell, straddled by (ii) two tetrafluorophenylene units linked to (iii) two triazole rings. In addition to the selective recognition between (iv) the CBPQT 4+ ring and the triazole units, and (v) the CBPQT 2(•+) ring and the reduced BIPY (•+) unit in the dumbbell component, investigations in solution have now confirmed the presence of additional noncovalent bonding interactions between the CBPQT (0) ring, acting as a donor in its neutral state towards the two tetrafluorophenylene acceptors in the dumbbell component. The unveiling of this piece of molecular recognition in a [2]rotaxane is reminiscent of the existence in much simpler, covalently linked, organic molecules of neighboring group participation (anchimeric assistance giving way to transannular interactions) in small-, medium-, and large-membered rings. ACS Paragon Plus Environment Journal of the American Chemical Society Recently, we reported 16 that, although a 1:1 inclusion complex between the fully reduced pelectron-rich cyclobis(paraquet-p-phenylene) (CBPQT (0)) ring and the p-electron-deficient guest 1,4-dicyanobenzene (DCB) can be isolated as a solid-state superstructure, the binding constant for this host-guest complex in (toluene) solution is too small to be measured by the usual techniques.

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“…The use − of radical-pairing interactions − to template the formation of catenanes and rotaxanes has been a significant recent development − in the field of functional MIMs, not only offering a facile means to their synthesis but also imbuing the products with distinct electronic properties , and stimulus responsive motion. ,, This research began with the discovery , that the dicationic diradical state of cyclobis(paraquat- p -phenylene), CBPQT 2(+•) , and the monocationic monoradical state of methyl viologen, MV +• , form a strongly associated tricationic trisradical complex [CBPQT⊂MV] 3(+•) . Variations of this host–guest complex have been used (Scheme ) to template − the formation of a variety of MIMs, such as the [2]rotaxane CBPQT-RV-[2]R 6+ and the homo[2]catenane bis -CBPQT-[2]C (7+)(1•) . The restricted motion of the interlocked cyclophanes in bis -CBPQT-[2]C (7+)(1•) results in this MIM exhibiting an air-stable radical state, while reduction and oxidation of CBPQT-RV-[2]R 6+ toggle between strong attraction and repulsion of its viologen components .…”

Section: Introductionmentioning

confidence: 99%

Shuttling Rates, Electronic States, and Hysteresis in a Ring-in-Ring Rotaxane

Lipke

Roy

et al. 2018

ACS Cent. Sci.

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The trisradical recognition motif between a 4,4′-bipyridinium radical cation and a cyclo-bis-4,4′-bipyridinium diradical dication has been employed previously in rotaxanes to control their nanomechanical and electronic properties. Herein, we describe the synthesis and characterization of a redox-active ring-in-ring [2]rotaxane BBR·8PF6 that employs a tetraradical variant of this recognition motif. A square-shaped bis-4,4′-bipyridinium cyclophane is mechanically interlocked around the dumbbell component of this rotaxane, and the dumbbell itself incorporates a smaller bis-4,4′-bipyridinium cyclophane into its covalently bonded structure. This small cyclophane serves as a significant impediment to the shuttling of the larger ring across the dumbbell component of BBR8+, whereas reduction to the tetraradical tetracationic state BBR4(+•) results in strong association of the two cyclophanes driven by two radical-pairing interactions. In these respects, BBR·8PF6 exhibits qualitatively similar behavior to its predecessors that interconvert between hexacationic and trisradical tricationic states. The rigid preorganization of two bipyridinium groups within the dumbbell of BBR·8PF6 confers, however, two distinct properties upon this rotaxane: (1) the rate of shuttling is reduced significantly relative to those of its predecessors, resulting in marked electrochemical hysteresis observed by cyclic voltammetry for switching between the BBR8+/BBR4(+•) states, and (2) the formally tetraradical form of the rotaxane, BBR4(+•), exhibits a diamagnetic ground state, which, as a result of the slow shuttling motions within BBR4(+•), has a long enough lifetime to be characterized by 1H NMR spectroscopy.

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Symbiotic Control in Mechanical Bond Formation

Cited by 24 publications

References 53 publications

Photoredox Processes in the Aggregation and Gelation of Electron-Responsive Supramolecular Polymers Based on Viologen

Photoredox Processes in the Aggregation and Gelation of Electron-Responsive Supramolecular Polymers Based on Viologen

Neighboring Component Effect in a Tri-stable [2]Rotaxane

Shuttling Rates, Electronic States, and Hysteresis in a Ring-in-Ring Rotaxane

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