Synthesis of Large [2]Rotaxanes. The Relationship between the Size of the Blocking Group and the Stability of the Rotaxane

Saito, Shinichi; Takahashi, Eiko; Wakatsuki, Kouta; Inoue, Kazuhiko; Orikasa, Tomoko; Sakai, Kenta; Yamasaki, Ryu; Mutoh, Yuichiro; Kasama, Takeshi

doi:10.1021/jo302800t

Cited by 29 publications

(13 citation statements)

References 53 publications

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“…After finding that a 3,3-dimethylindoline squaraine dye can be encapsulated by a tetralactam macrocycle, the next step was to determine if the gem -dimethyl groups were large enough to block rotaxane threading or unthreading. ,− We decided to prepare a rotaxane that encapsulated the symmetrical 3,3-dimethylindoline squaraine 2 with proximal gem -dimethyl groups on either side of the central C 4 O 2 core. This was achieved in two synthetic steps.…”

Section: Resultsmentioning

confidence: 80%

Synthesis and Structure of 3,3-Dimethylindoline Squaraine Rotaxanes

et al. 2017

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Squaraine rotaxanes are mechanically interlocked molecules comprised of a dumbbell shaped squaraine dye inside a tetralactam macrocycle. Previous squaraine rotaxanes have employed planar squaraine dyes with 4-aminophenyl, 2-aminothiophene, or N-amino units appended to the central C4O2 core. Here we describe two rotaxanes that encapsulate a 3,3-dimethylindoline squaraine inside a tetralactam with anthracene sidewalls. The rotaxanes were prepared by a templated clipping reaction and an X-ray crystal structure shows that the squaraine gem-dimethyl groups force a relatively wide separation between the macrocycle anthracene sidewalls. The decreased interaction between the encapsulated squaraine and the anthracene sidewalls leads to a smaller red shift of the squaraine absorption and emission bands. Solution-state studies show that the gem-dimethyl groups in 3,3-dimethylindoline squaraine dyes are large enough to prevent macrocycle threading or rotaxane unthreading. One of the new rotaxanes emits an orange light (560–650 nm), and there is a 10-fold enhancement in the squaraine fluorescence quantum yield upon encapsulation as a rotaxane. This orange-emitting dye completes the palette of known squaraine rotaxane fluorophores whose emission profiles span the color range from green to near-infrared.

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Section: Resultsmentioning

confidence: 80%

Synthesis and Structure of 3,3-Dimethylindoline Squaraine Rotaxanes

et al. 2017

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“…Saito group has estimated the relationship between the stability of the rotaxanes and the structure/size of the ring/axle components by using the same synthetic strategy, as mentioned above ( Scheme 4 ). 9 A series of phenanthroline based [2]rotaxanes 14a–d with difference in the size of macrocyclic component as well as in nature of blocking groups were synthesized. Rotaxane 14c, with small macrocycle 11a ( n = 6) and having tris(4-cyclohexylbiphenyl)methyl group as blocking group was highly stable and the dissociation of the ring and axle components did not proceed under elevated temperature.…”

Section: Introductionmentioning

confidence: 99%

Phenanthroline based rotaxanes: recent developments in syntheses and applications

2022

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“…The fundamental feature of a "normal" rotaxane is the fact that the stoppers prevent the ring from slipping off the axle. However, from a mathematical-topological point of view, a rotaxane is topologically not special because by deformation (shrinking of the stoppers or enlargement of the ring), the ring may slip off-as it does in pseudorotaxanes [7][8][9]. Figure 1 (right) shows a sketch of a "real" knotaxane.…”

Section: Introductionmentioning

confidence: 99%

Towards a Real Knotaxane

Duden

Lüning

2020

Chemistry

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Two classes of mechanically interlocked molecules, [3]rotaxanes and knotted [1]rotaxanes, were the subject of this investigation. The necessary building blocks, alkyne-terminated axles containing two ammonium ions and azide-terminated stoppers, and azide-containing substituted macrocycles, have been synthesized and characterized. Different [3]rotaxanes were synthesized by copper-catalyzed “click” reactions between the azide stoppers and [3]pseudorotaxanes formed from the dialkyne axles and crown ethers (DB24C8). Methylation of the triazoles formed by the “click” reaction introduced a second binding site, and switching via deprotonation/protonation was investigated. In preliminary tests for the synthesis of a knotted [1]rotaxane, pseudorotaxanes were formed from azide-containing substituted macrocycles and dialkyne substituted diammonium axles, and copper-catalyzed “click” reactions were carried out. Mass spectral analyses showed successful double “click” reactions between two modified macrocycles and one axle. Whether a knotted [1]rotaxane was formed could not be determined.

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Synthesis of Large [2]Rotaxanes. The Relationship between the Size of the Blocking Group and the Stability of the Rotaxane

Cited by 29 publications

References 53 publications

Synthesis and Structure of 3,3-Dimethylindoline Squaraine Rotaxanes

Synthesis and Structure of 3,3-Dimethylindoline Squaraine Rotaxanes

Phenanthroline based rotaxanes: recent developments in syntheses and applications

Towards a Real Knotaxane

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