From being an aesthetic molecular object to a building block for the construction of molecular machines, catenanes and related mechanically interlocked molecules (MIMs) continue to attract immense ...interest in many research areas. Catenane chemistry is closely tied to that of rotaxanes and knots, and involves concepts like mechanical bonds, chemical topology and co-conformation that are unique to these molecules. Yet, because of their different topological structures and mechanical bond properties, there are some fundamental differences between the chemistry of catenanes and that of rotaxanes and knots although the boundary is sometimes blurred. Clearly distinguishing these differences, in aspects of bonding, structure, synthesis and properties, between catenanes and other MIMs is therefore of fundamental importance to understand their chemistry and explore the new opportunities from mechanical bonds.
Catenane chemistry is closely associated with that of rotaxane and knot, and this perspective highlights their similarities and differences in various aspects including synthesis, structure and properties.
A new demetallation method for Cu(I)‐bound catenanes that contain a strong binding bis(phenanthroline) cavity using the bidentate ethylenediamine is reported. Cu(I) extraction using the organic ...diamine is mild, convenient and efficient, and the metal can be removed from the kinetically stable catenane complexes in various solvents within 5 minutes, offering an alternative strategy to the use of toxic cyanide in competing for the Cu(I) coordination.
In contrast to the conventional use of the strong and monodentate cyanide ligand, kinetically stable Cu+‐catenane complexes can be demetallated by the bidentate ethylenediamine within 5 minutes in various common organic solvents. The procedure is mild, safe, convenient and efficient, providing the metal‐free catenane in good yields.
Catalytic activity of copper(
i
) complexes supported by phenanthroline-containing catenane ligands towards a new C(sp
3
)-O dehydrogenative cross-coupling of phenols and bromodicarbonyls is ...reported. As the phenanthrolines are interlocked by the strong and flexible mechanical bond in the catenane, the active catalyst with an open copper coordination site can be revealed only transiently and the stable, coordinatively saturated Cu(
i
) pre-catalyst is quickly regenerated after substrate transformation. Compared with a control Cu(
i
) complex supported by non-interlocked phenanthrolines, the catenane-supported Cu(
i
) is highly efficient with a broad substrate scope, and can be applied in gram-scale transformations without a significant loss of the catalytic activity. This work demonstrates the advantages of the catenane ligands that provide a dynamic and responsive copper coordination sphere, highlighting the potential of the mechanical bond as a design element in transition metal catalyst development.
The use of a catenane-supported copper(
i
) complex for the cross dehydrogenative C-O coupling of phenols and bromodicarbonyls is described.
The chemistry of mechanically interlocked molecules (MIMs) such as catenane and rotaxane is full of new opportunities for the presence of a mechanical bond, and the efficient synthesis of these ...molecules is therefore of fundamental importance in realizing their unique properties and functions. While many different types of preorganizing interactions and covalent bond formation strategies have been exploited in MIMs synthesis, the use of cucurbit6uril (CB6) in simultaneously templating macrocycle interlocking and catalyzing the covalent formation of the interlocked components is particularly advantageous in accessing high‐order catenanes and rotaxanes. In this review, catenane and rotaxane obtained from CB6‐catalyzed azide‐alkyne cycloaddition will be discussed, with special emphasis on the synthetic strategies employed for obtaining complex nrotaxanes and ncatenanes, as well as their properties and functions.
In this review, the use of cucurbit6uril in mediating click reactions for the efficient synthesis of rotaxanes and catenanes in various structures as well as their properties and functions are discussed.
Aqueous soluble and stable Cu(I) molecular catalysts featuring a catenane ligand composed of two dicationic, mutually repelling but mechanically interlocked macrocycles are reported. The ligand ...interlocking not only fine‐tunes the coordination sphere and kinetically stabilizes the Cu(I) against air oxidation and disproportionation, but also buries the hydrophobic portions of the ligands and prevents their dissociation which are necessary for their good water solubility and a sustained activity. These catenane Cu(I) complexes can catalyze the oxidative C−C coupling of indoles and tetrahydroisoquinolines in water, using H2O2 as a green oxidant with a good substrate scope. The successful use of catenane ligands in exploiting aqueous Cu(I) catalysis thus highlights the many unexplored potential of mechanical bond as a design element for exploring transition metal catalysis under challenging conditions.
Copper(I) molecular catalysts that are water soluble and stable against oxidative degradation are obtained by the strategic use of multiply charged catenane ligands. By using the new catalysts, oxidative C−C cross‐coupling is realized in water using H2O2 as a green and convenient oxidant, highlighting the potential of ligand interlocking in leveraging transition metal catalysis under challenging conditions.
A pair of radial 5catenanes, with either an isomeric cyclic ‐AABB‐ or ‐ABAB‐ type sequence of the interlocked β‐cyclodextrin (β‐CD) and cucurbit6uril (CB6) units, has been efficiently synthesized. ...Because of a marked difference in the binding strength and interlocking sequence of the peripheral macrocycles, interesting sequence‐dependent properties, characteristic of mechanically bonded macrocycles, were realized. Variable‐temperature 1H NMR studies showed that the ‐ABAB‐ isomer has a more independent β‐CD dynamic, whereas the β‐CD motions in the ‐AABB‐ isomer are coupled. Dynamics of the pH‐insensitive β‐CD can also be further modulated upon base‐triggered mobilization of the CB6. These unique properties of the mechanical bond expressed in a sequence‐specific fashion and the transmission of the control on the macrocycle dynamics from one interlocked component to another, highlight the potential of similar complex heteroncatenanes in the design of advanced, multicomponent molecular machines.
Lock on: A pair of radial 5catenane isomers with different sequences of the peripheral macrocycles, β‐cyclodextrin and cucurbit6uril units, was obtained in high yield. Given the marked difference in binding strength and interlocking sequence of the peripheral macrocycles, interesting sequence‐dependent properties, characteristic of mechanically bonded macrocycles, were realized.
A branched 8catenane from an efficient one‐pot synthesis (72 % HPLC yield, 59 % isolated yield) featuring the simultaneous use of three kinds of templates and cucurbit6uril‐mediated azide–alkyne ...cycloaddition (CBAAC) for ring‐closing is reported. Design and assembly of the 8catenane precursors are unexpectedly complex that can involve cooperating, competing and non‐influencing interactions. Due to the branched structure, dynamics of the 8catenane can be modulated in different extent by rigidifying/loosening the mechanical bonds at different regions by using solvent polarity, acid‐base and metal ions as the stimuli. This work not only highlights the importance of understanding the delicate interplay of the weak and non‐obvious supramolecular interactions in the synthesis of high‐order ncatenane, but also demonstrates a complex control of dynamics and flexibility for exploiting ncatenanes applications.
A branched 8catenane was synthesized from a one‐pot procedure with good efficiency. Rigidifying/loosening the mechanical bond in the core, middle or periphery of the 8catenane resulted in, respectively a large, middle and small degree of change in the catenane dynamics and flexibility.
For more than 150 years, it is known that occupational overexposure of manganese (Mn) causes movement disorders resembling Parkinson's disease (PD) and PD‐like syndromes. However, the mechanisms of ...Mn toxicity are still poorly understood. Here, we demonstrate that Mn dose‐ and time‐dependently blocks the protein translation of amyloid precursor protein (APP) and heavy‐chain Ferritin (H‐Ferritin), both iron homeostatic proteins with neuroprotective features. APP and H‐Ferritin are post‐transcriptionally regulated by iron responsive proteins, which bind to homologous iron responsive elements (IREs) located in the 5′‐untranslated regions (5′‐UTRs) within their mRNA transcripts. Using reporter assays, we demonstrate that Mn exposure repressed the 5′‐UTR‐activity of APP and H‐Ferritin, presumably via increased iron responsive proteins‐iron responsive elements binding, ultimately blocking their protein translation. Using two specific Fe2+‐specific probes (RhoNox‐1 and IP‐1) and ion chromatography inductively coupled plasma mass spectrometry (IC‐ICP‐MS), we show that loss of the protective axis of APP and H‐Ferritin resulted in unchecked accumulation of redox‐active ferrous iron (Fe2+) fueling neurotoxic oxidative stress. Enforced APP expression partially attenuated Mn‐induced generation of cellular and lipid reactive oxygen species and neurotoxicity. Lastly, we could validate the Mn‐mediated suppression of APP and H‐Ferritin in two rodent in vivo models (C57BL6/N mice and RjHan:SD rats) mimicking acute and chronic Mn exposure. Together, these results suggest that Mn‐induced neurotoxicity is partly attributable to the translational inhibition of APP and H‐Ferritin resulting in impaired iron metabolism and exacerbated neurotoxic oxidative stress.
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For more than 150 years, it is known that occupational overexposure of manganese (Mn) causes movement disorders resembling Parkinson's disease (PD) and PD‐like syndromes. Here, we demonstrate that Mn exposure results in suppression of amyloid precursor protein (APP) and H‐Ferritin in vitro and in vivo. On the molecular level, it could be shown that Mn inhibits the protein translation via repressing the 5’‐UTR activity of both proteins. Mn‐mediated suppression of both iron‐regulating proteins results in an accumulation of redox‐active iron (Fe2+) that fuels neurotoxic cellular oxidative stress and lipidperoxidation. APP overexpression significantly attenuate Mn‐induced oxidative stress and neurotoxicity. The implications that Mn exposure results in a translational suppression of APP and H‐Ferritin links a disturbed iron homeostasis with Mn‐induced oxidative neurotoxicity.
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Copper is a required metal nutrient for life, but global or local alterations in its homeostasis are linked to diseases spanning genetic and metabolic disorders to cancer and neurodegeneration. ...Technologies that enable longitudinal in vivo monitoring of dynamic copper pools can help meet the need to study the complex interplay between copper status, health, and disease in the same living organism over time. Here, we present the synthesis, characterization, and in vivo imaging applications of Copper-Caged Luciferin-1 (CCL-1), a bioluminescent reporter for tissue-specific copper visualization in living animals. CCL-1 uses a selective copper(I)-dependent oxidative cleavage reaction to release D-luciferin for subsequent bioluminescent reaction with firefly luciferase. The probe can detect physiological changes in labile Cu⁺ levels in live cells and mice under situations of copper deficiency or overload. Application of CCL-1 to mice with liver-specific luciferase expression in a diet-induced model of nonalcoholic fatty liver disease reveals onset of hepatic copper deficiency and altered expression levels of central copper trafficking proteins that accompany symptoms of glucose intolerance and weight gain. The data connect copper dysregulation to metabolic liver disease and provide a starting point for expanding the toolbox of reactivity-based chemical reporters for cell-and tissue-specific in vivo imaging.
As a major class of mechanically interlocked molecules, not only are catenanes topologically intriguing targets that challenge the chemical synthesis to the efficient formation of mechanical bonds, ...but also the mechanical properties arising from the topology offer unique and attractive features for the development of novel functional molecular materials. Despite advancements in templated methods for different types of interlocked architectures, ncatenane possessing multiple numbers of interlocked macrocycles still remains a difficult synthetic target with very few reported examples. If the unique mechanical properties of catenanes are to be fully exploited, reliable, controllable, and efficient strategies for accessing ncatenanes will be necessary. In this Viewpoint, challenges, considerations, and strategies to ncatenanes are discussed.
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![Radial Hetero[5]catenanes: ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1433-7851/small "Radial Hetero[5]catenanes: Peripheral Isomer Sequences of the Interlocked Macrocycles")
