Reversible conversion between a pleated oligo-tetrathiafulvalene radical foldamer and folded donor–acceptor [3]pseudorotaxane under redox conditions

Zhan, Tian‐Guang; Wu, Lin; Zhao, Zhixiong; Zhou, Zhi-Bei; Yun, Meng-Yan; Wei, Jie; Zheng, Si-Tai; Yin, Huanhuan; Zhang, Kang‐Da

doi:10.1039/c7cc02526b

Cited by 9 publications

(3 citation statements)

References 48 publications

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“…Molecular machines and switches with three components are well represented by [3]pseudorotaxanes (9)(10)(11)(12)(13)(14), [3]catenanes (15)(16)(17)(18), and [3]rotaxanes (19)(20)(21)(22)(23)(24)(25). Examples include unidirectional motion of two small rings around a larger ring (15) and muscle-like contraction of two rings along a dumbbell in a [3] rotaxane (20).…”

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confidence: 99%

Inchworm movement of two rings switching onto a thread by biased Brownian diffusion represent a three-body problem

Benson

Fatila

Liu

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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The coordinated motion of many individual components underpins the operation of all machines. However, despite generations of experience in engineering, understanding the motion of three or more coupled components remains a challenge, known since the time of Newton as the "three-body problem." Here, we describe, quantify, and simulate a molecular three-body problem of threading two molecular rings onto a linear molecular thread. Specifically, we use voltage-triggered reduction of a tetrazine-based thread to capture two cyanostar macrocycles and form a [3]pseudorotaxane product. As a consequence of the noncovalent coupling between the cyanostar rings, we find the threading occurs by an unexpected and rare inchworm-like motion where one ring follows the other. The mechanism was derived from controls, analysis of cyclic voltammetry (CV) traces, and Brownian dynamics simulations. CVs from two noncovalently interacting rings match that of two covalently linked rings designed to thread via the inchworm pathway, and they deviate considerably from the CV of a macrocycle designed to thread via a stepwise pathway. Time-dependent electrochemistry provides estimates of rate constants for threading. Experimentally derived parameters (energy wells, barriers, diffusion coefficients) helped determine likely pathways of motion with rate-kinetics and Brownian dynamics simulations. Simulations verified intercomponent coupling could be separated into ring-thread interactions for kinetics, and ring-ring interactions for thermodynamics to reduce the three-body problem to a two-body one. Our findings provide a basis for high-throughput design of molecular machinery with multiple components undergoing coupled motion.

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confidence: 99%

Inchworm movement of two rings switching onto a thread by biased Brownian diffusion represent a three-body problem

Benson

Fatila

Liu

et al. 2018

Proc. Natl. Acad. Sci. U.S.A.

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“…Under reducing conditions, however, the V⋅ + units fold and form a π‐radical stack that is intercalated by the two CBPQT 2( ⋅ +) rings to establish favorable radical‐pairing interactions. Folding can also be observed [219] in a TTF‐containing oligopseudorotaxane, in which threading of two CBPQT 4+ rings can be controlled by redox chemistry.…”

Section: Molecular Switchesmentioning

confidence: 99%

The Story of the Little Blue Box: A Tribute to Siegfried Hünig

Chen

Stoddart

2022

Angewandte Chemie

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The tetracationic cyclophane, cyclobis(paraquat-p-phenylene), also known as the little blue box, constitutes a modular receptor that has facilitated the discovery of many host-guest complexes and mechanically interlocked molecules during the past 35 years. Its versatility in binding small π-donors in its tetracationic state, as well as forming trisradical tricationic complexes with viologen radical cations in its doubly reduced bisradical dicationic state, renders it valuable for the construction of various stimuli-responsive materials. Since the first reports in 1988, the little blue box has been featured in over 500 publications in the literature. All this research activity would not have been possible without the seminal contributions carried out by Siegfried Hünig, who not only pioneered the syntheses of viologencontaining cyclophanes, but also revealed their rich redox chemistry in addition to their ability to undergo intramolecular π-dimerization. This Review describes how his pioneering research led to the design and synthesis of the little blue box, and how this redox-active host evolved into the key component of molecular shuttles, switches, and machines.

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“…To provide structural stability to these otherwise labile adducts at room temperature, [TTF] 2 •+ and [TTF •+ ] 2 have previously been encapsulated within molecular or supramolecular hosts. Prominent examples include cucurbit[8]uril, coordination cages, rotaxanes, and catenanes. − Alternatively, multiple TTF units can be covalently linked by bridging units. − …”

Section: Introductionmentioning

confidence: 99%

Redox-Driven Folding, Unfolding, and Refolding of Bis(tetrathiafulvalene) Molecular Switch

et al. 2019

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We report redox-driven folding, unfolding, and refolding motions of a synthetic molecular system, in which two tetrathiafulvalene (TTF) units are tethered onto a conformationally rigid yet torsionally flexible π-conjugated backbone. Upon oneelectron oxidation, this molecular switch undergoes swiveling motions from a fully relaxed and freely rotating Z-shaped conformation to a compact folded conformation stabilizing πstacked radical species. Subsequent one-electron oxidation produces dicationic intermediates, which either engage in intimate π−π interactions or transition to an open structure. Further oxidation, however, brings the molecule back to the initial conformation to minimize the repulsion between doubly-charged TTF units. Intriguingly, the reaction coordinates of this redox-driven structural change have strong dependence on the environment, such as the solvent (THF vs CH 2 Cl 2 ) and supporting electrolyte (PF 6 − vs B(C 6 F 5 ) 4 − ). With a proper design, factors that are typically considered as "secondary effects" could dictate the solution dynamics and reaction pathways of structural folding and unfolding, all driven by controlled delivery of electrons.

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Reversible conversion between a pleated oligo-tetrathiafulvalene radical foldamer and folded donor–acceptor [3]pseudorotaxane under redox conditions

Cited by 9 publications

References 48 publications

Inchworm movement of two rings switching onto a thread by biased Brownian diffusion represent a three-body problem

Inchworm movement of two rings switching onto a thread by biased Brownian diffusion represent a three-body problem

The Story of the Little Blue Box: A Tribute to Siegfried Hünig

Redox-Driven Folding, Unfolding, and Refolding of Bis(tetrathiafulvalene) Molecular Switch

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