Type III-B rotaxane dendrimers

Ho, Watson K.‐W.; Lee, Siu‐Fung; Wong, Chi Hin; Zhu, Xiaoming; Kwan, Chak‐Shing; Chak, Chun‐Pong; Mendes, Paula M.; Chen, Cheng; Leung, Ken Cham‐Fai

doi:10.1039/c3cc46759g

Cited by 31 publications

(20 citation statements)

References 22 publications

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“…The earliest example of first generation (G1) T3B-RD was reported by Vögtle colleagues 23 . We reported the first facile synthesis of prototypical G2 type III-B rotaxane dendrons in 2013 24 . The preparation of higher generation T3B-RD has not been deciphered since then.…”

Section: Introductionmentioning

confidence: 99%

Higher-generation type III-B rotaxane dendrimers with controlling particle size in three-dimensional molecular switching

et al. 2018

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Type III-B rotaxane dendrimers (T3B-RDs) are hyperbranched macromolecules with mechanical bonds on every branching unit. Here we demonstrate the design, synthesis, and characterization of first to third (G1–G3), and up to the fourth (G4) generation (MW > 22,000 Da) of pure organic T3B-RDs and dendrons through the copper-catalyzed alkyne–azide cycloaddition (CuAAC) reaction. By utilizing multiple molecular shuttling of the mechanical bonds within the sphere-like macromolecule, a collective three-dimensional contract-extend molecular motion is demonstrated by diffusion ordered spectroscopy (DOSY) and atomic force microscopy (AFM). The discrete T3B-RDs are further observed and characterized by AFM, dynamic light scattering (DLS), and mass spectrometry (MS). The binding of chlorambucil and pH-triggered switching of the T3B-RDs are also characterized by 1H-NMR spectroscopy.

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Section: Introductionmentioning

confidence: 99%

Higher-generation type III-B rotaxane dendrimers with controlling particle size in three-dimensional molecular switching

et al. 2018

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“…With a view to extending this approach towards more complex dendritic-type systems [ 61 , 67 , 68 ], we herein report the use of a triyne ( 6 ) in a similar manner, allowing the stepwise, high-yielding synthesis of [2]- and [3]rotaxanes. Disappointingly, due to the steric crowding which allows us to conduct this protecting-group free synthesis, the attempted formation of [4]rotaxanes proceeded in severely diminished yields.…”

Section: Introductionmentioning

confidence: 99%

Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes

2017

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Despite significant advances in the last three decades towards high yielding syntheses of rotaxanes, the preparation of systems constructed from more than two components remains a challenge. Herein we build upon our previous report of an active template copper-catalyzed azide-alkyne cycloaddition (CuAAC) rotaxane synthesis with a diyne in which, following the formation of the first mechanical bond, the steric bulk of the macrocycle tempers the reactivity of the second alkyne unit. We have now extended this approach to the use of 1,3,5-triethynylbenzene in order to successively prepare [2]-, [3]- and [4]rotaxanes without the need for protecting group chemistry. Whilst the first two iterations proceeded in good yield, the steric shielding that affords this selectivity also significantly reduces the efficacy of the active template (AT)-CuAAC reaction of the third alkyne towards the preparation of [4]rotaxanes, resulting in severely diminished yields.

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“…Herein, we employ a slippage approach in one pot ( Figure 1 ) to yield a thermodynamically stable [ 2 ]pseudorotaxane [ 29 , 30 ] by mixing an ammonium thread (dumbbell) 1 -H·PF 6 with dibenzo[ 24 ]crown-8 ( DB24C8 ). Benzo-crown ether DB24C8 is capable to recognize with secondary ammonium ions by virtue of [N + –H···O] and [N + –C–H···O] hydrogen bonds, electrostatic interactions, and augmented with some aromatic π-π interactions [ 31 , 32 , 33 , 34 , 35 , 36 ].…”

Section: Resultsmentioning

confidence: 99%

“…CH 2 Cl 2 was freshly distilled from CaH 2 . Cyclohexanemethylamine ( 3 ) and dibenzo[ 24 ]crown-8 ( DB24C8 ) were commercially available from Sigma-Aldrich (St. Louis, MO, USA) while the starting compound ( 2 ) was synthesized according to the literature procedures [ 39 ]. The synthetic scheme of new compounds is shown in Scheme 1 .…”

Section: Methodsmentioning

confidence: 99%

“…The construction of rotaxane-like assemblies has recently relied upon thermodynamic, templated reactions with enhanced efficiencies [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. The term “slippage” has been coined [ 25 , 26 , 27 , 28 ] for pseudorotaxane synthesis that employs thermodynamic threading of macrocycle to a “dumbbell”.…”

Section: Introductionmentioning

confidence: 99%

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Revisiting the Formation and Tunable Dissociation of a [2]Pseudorotaxane Formed by Slippage Approach

Leung

Lau

Wong

2015

IJMS

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A new [2]pseudorotaxane DB24C8⊃1-H·PF6 with dibenzo[24]crown-8 (DB24C8) crown ether-dibenzylammonium (1-H·PF6) binding which was formed by slippage approach at different solvents and temperature, had been isolated and characterized by NMR spectroscopy and mass spectrometry. The [2]pseudorotaxane DB24C8⊃1-H·PF6 was stable at room temperature. The dissociation rate of [2]pseudorotaxane DB24C8⊃1-H·PF6 could be tuned by using different stimuli such as triethylamine (TEA)/diisopropylethylamine (DIPEA) and dimethyl sulfoxide (DMSO). In particular, the dissociation of [2]pseudorotaxane DB24C8⊃1-H·PF6 by an excess of TEA/DIPEA base mixture possessed a long and sustained, complete dissociation over 60 days. Other stimuli by DMSO possessed a relatively fast dissociation over 24 h.

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Type III-B rotaxane dendrimers

Cited by 31 publications

References 22 publications

Higher-generation type III-B rotaxane dendrimers with controlling particle size in three-dimensional molecular switching

Higher-generation type III-B rotaxane dendrimers with controlling particle size in three-dimensional molecular switching

Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes

Revisiting the Formation and Tunable Dissociation of a [2]Pseudorotaxane Formed by Slippage Approach

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