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Journal ArticleDOI

Recent developments on artificial switchable catalysis

07 Feb 2018-Tetrahedron Letters (Pergamon)-Vol. 59, Iss: 6, pp 487-495
TL;DR: In this paper, the significance of this young but burgeoning field was emphasized with the help of these latest examples, and some recent developments in the field of artificial switchable catalysis achieved during the last couple of years.
About: This article is published in Tetrahedron Letters.The article was published on 2018-02-07. It has received 56 citations till now.
Citations
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TL;DR: In this article, the authors describe polymers as one of the largest and most important materials we use in daily life and their popularity has stemmed from their wide range of material properties combined with their low cost of manufacturing.
Abstract: Polymers have become one of the largest and most important materials we use in daily life. Their popularity has stemmed from their wide range of material properties combined with their low cost of ...

160 citations

Book
13 Jan 2021
TL;DR: In this paper, the effects of organic functional groups on structure, host-guest chemistry and applications of functional metal-organic frameworks (FMOFs) in order to be able to synthesize functional MOFs for specific purposes through an in depth analysis of the literature.
Abstract: Owing to their three dimensionality and high porosity, metal-organic frameworks (MOFs) have attracted the attention of scientists especially chemists and material engineers. The frameworks of this subclass of hybrid materials are made of inorganic metal ions/clusters and organic bridging ligands. Special connections between these two building blocks of MOFs lead to a theoretically unlimited number of frameworks. Unlike other porous materials, MOFs benefit from characteristics such as high crystallinity and regularity, high porosity and surface area, hybrid organic-inorganic nature, moderate to high chemical and thermal stability, and decorable pores with different functional groups. Decorating MOFs with functions is possible through functionalization of organic linkers, inorganic building blocks, and void cavities of the framework. Tunability of MOFs with organic linkers is of particular importance due to the unlimited possibility to design functional or multi-functional organic linkers as well as distinctive chemical properties of organic functional groups (OFGs). The purpose of this review is to gain deeper insight into the effects of organic functional groups on structure, host-guest chemistry and applications of functional metal-organic frameworks (FMOFs) in order to be able to synthesize functional MOFs for specific purposes through an in depth analysis of the literature.

117 citations

Journal ArticleDOI
TL;DR: C cucurbit[8]uril as a molecular host has emerged in the chemical literature as a reliable strategy for the creation of dynamic chemical systems, owing to its ability to form homo- and heteroternary complexes in aqueous media with appropriate molecular switches as guests.
Abstract: The use of cucurbit[8]uril as a molecular host has emerged in the chemical literature as a reliable strategy for the creation of dynamic chemical systems, owing to its ability to form homo- and heteroternary complexes in aqueous media with appropriate molecular switches as guests. In this manner, CB[8]-based supramolecular switches can be designed in a predictable and modular fashion, through the selection of appropriate guests able to condition the redox, photochemical, or pH-triggered behavior of tailored multicomponent systems. Furthermore, CB[8] allows the implementation of dual/triple and linear/orthogonal stimuli-dependent properties into these molecular devices by a careful selection of the guests. This versatility in their design gives these supramolecular switches great potential for the rational development of new materials, in which their function is not only determined by the custom-made stimuli-responsiveness, but also by the transient aggregation/disaggregation of homo- or heteromeric building blocks.

110 citations

Journal ArticleDOI
TL;DR: This Feature Article summarises the key developments accomplished over the past years through the incorporation of photoswitchable double bonds into the structure of catalytically competent molecules and shows some perspectives on the remaining challenges and possibilities arising from this, yet still somehow immature, exciting area of research.

93 citations

Journal ArticleDOI
TL;DR: This work reports the development of a new system to achieve visible-light-controlled metathesis by merging olefin meetathesis and photoredox catalysis, and applications of this system in synthesis, as well as in polymer patterning and photolithography with spatially resolved ring-opening metatheses polymerization.
Abstract: Olefin metathesis is now one of the most efficient ways to create new carbon–carbon bonds. While most efforts focused on the development of ever-more efficient catalysts, a particular attention has recently been devoted to developing latent metathesis catalysts, inactive species that need an external stimulus to become active. This furnishes an increased control over the reaction which is crucial for applications in materials science. Here, we report our work on the development of a new system to achieve visible-light-controlled metathesis by merging olefin metathesis and photoredox catalysis. The combination of a ruthenium metathesis catalyst bearing two N-heterocyclic carbenes with an oxidizing pyrylium photocatalyst affords excellent temporal and spatial resolution using only visible light as stimulus. Applications of this system in synthesis, as well as in polymer patterning and photolithography with spatially resolved ring-opening metathesis polymerization, are described.

65 citations

References
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Journal ArticleDOI
TL;DR: The latest generations of sophisticated synthetic molecular machine systems in which the controlled motion of subcomponents is used to perform complex tasks are discussed, paving the way to applications and the realization of a new era of “molecular nanotechnology”.
Abstract: The widespread use of molecular machines in biology has long suggested that great rewards could come from bridging the gap between synthetic molecular systems and the machines of the macroscopic world. In the last two decades, it has proved possible to design synthetic molecular systems with architectures where triggered large amplitude positional changes of submolecular components occur. Perhaps the best way to appreciate the technological potential of controlled molecular-level motion is to recognize that nanomotors and molecular-level machines lie at the heart of every significant biological process. Over billions of years of evolution, nature has not repeatedly chosen this solution for performing complex tasks without good reason. When mankind learns how to build artificial structures that can control and exploit molecular level motion and interface their effects directly with other molecular-level substructures and the outside world, it will potentially impact on every aspect of functional molecule and materials design. An improved understanding of physics and biology will surely follow. The first steps on the long path to the invention of artificial molecular machines were arguably taken in 1827 when the Scottish botanist Robert Brown observed the haphazard motion of tiny particles under his microscope.1,2 The explanation for Brownian motion, that it is caused by bombardment of the particles by molecules as a consequence of the kinetic theory of matter, was later provided by Einstein, followed by experimental verification by Perrin.3,4 The random thermal motion of molecules and its implications for the laws of thermodynamics in turn inspired Gedankenexperiments (“thought experiments”) that explored the interplay (and apparent paradoxes) of Brownian motion and the Second Law of Thermodynamics. Richard Feynman’s famous 1959 lecture “There’s plenty of room at the bottom” outlined some of the promise that manmade molecular machines might hold.5,6 However, Feynman’s talk came at a time before chemists had the necessary synthetic and analytical tools to make molecular machines. While interest among synthetic chemists began to grow in the 1970s and 1980s, progress accelerated in the 1990s, particularly with the invention of methods to make mechanically interlocked molecular systems (catenanes and rotaxanes) and control and switch the relative positions of their components.7−24 Here, we review triggered large-amplitude motions in molecular structures and the changes in properties these can produce. We concentrate on conformational and configurational changes in wholly covalently bonded molecules and on catenanes and rotaxanes in which switching is brought about by various stimuli (light, electrochemistry, pH, heat, solvent polarity, cation or anion binding, allosteric effects, temperature, reversible covalent bond formation, etc.). Finally, we discuss the latest generations of sophisticated synthetic molecular machine systems in which the controlled motion of subcomponents is used to perform complex tasks, paving the way to applications and the realization of a new era of “molecular nanotechnology”. 1.1. The Language Used To Describe Molecular Machines Terminology needs to be properly and appropriately defined and these meanings used consistently to effectively convey scientific concepts. Nowhere is the need for accurate scientific language more apparent than in the field of molecular machines. Much of the terminology used to describe molecular-level machines has its origins in observations made by biologists and physicists, and their findings and descriptions have often been misinterpreted and misunderstood by chemists. In 2007 we formalized definitions of some common terms used in the field (e.g., “machine”, “switch”, “motor”, “ratchet”, etc.) so that chemists could use them in a manner consistent with the meanings understood by biologists and physicists who study molecular-level machines.14 The word “machine” implies a mechanical movement that accomplishes a useful task. This Review concentrates on systems where a stimulus triggers the controlled, relatively large amplitude (or directional) motion of one molecular or submolecular component relative to another that can potentially result in a net task being performed. Molecular machines can be further categorized into various classes such as “motors” and “switches” whose behavior differs significantly.14 For example, in a rotaxane-based “switch”, the change in position of a macrocycle on the thread of the rotaxane influences the system only as a function of state. Returning the components of a molecular switch to their original position undoes any work done, and so a switch cannot be used repetitively and progressively to do work. A “motor”, on the other hand, influences a system as a function of trajectory, meaning that when the components of a molecular motor return to their original positions, for example, after a 360° directional rotation, any work that has been done is not undone unless the motor is subsequently rotated by 360° in the reverse direction. This difference in behavior is significant; no “switch-based” molecular machine can be used to progressively perform work in the way that biological motors can, such as those from the kinesin, myosin, and dynein superfamilies, unless the switch is part of a larger ratchet mechanism.14

1,434 citations

Journal ArticleDOI
TL;DR: How being able to template the formation of mechanically interlocked molecules has led to the design and synthesis of shuttles, switches, and machines at the nanoscale is described.
Abstract: Chemistry welcomes a new bond: The mechanical bond has endowed molecules with component parts whose movements can be controlled and monitored. In his Nobel Lecture, J. F. Stoddart describes how being able to template the formation of mechanically interlocked molecules has led to the design and synthesis of shuttles, switches, and machines at the nanoscale.

615 citations

Journal ArticleDOI
TL;DR: The creation of interlocking ring molecules is so important in relation to the molecular machinery area that the first part of this work will be devoted to the dynamic properties of such systems and to the compounds for which motions can be directed in a controlled manner from the outside.
Abstract: To a large extent, the field of "molecular machines" started after several groups were able to prepare, reasonably easily, interlocking ring compounds (named catenanes for compounds consisting of interlocking rings and rotaxanes for rings threaded by molecular filaments or axes). Important families of molecular machines not belonging to the interlocking world were also designed, prepared, and studied but, for most of them, their elaboration was more recent than that of catenanes or rotaxanes. Since the creation of interlocking ring molecules is so important in relation to the molecular machinery area, we will start with this aspect of our work. The second part will naturally be devoted to the dynamic properties of such systems and to the compounds for which motions can be directed in a controlled manner from the outside, that is, molecular machines. We will restrict our discussion to a very limited number of examples which we consider as particularly representative of the field.

539 citations

Journal ArticleDOI
TL;DR: The state-of-art in artificial switchable catalysis is outlined, classifying systems according to the trigger used to achieve control over the catalytic activity and stereochemical or other structural outcomes of the reaction.
Abstract: Catalysis is key to the effective and efficient transformation of readily available building blocks into high value functional molecules and materials. For many years research in this field has largely focussed on the invention of new catalysts and the optimization of their performance to achieve high conversions and/or selectivities. However, inspired by Nature, chemists are beginning to turn their attention to the development of catalysts whose activity in different chemical processes can be switched by an external stimulus. Potential applications include using the states of multiple switchable catalysts to control sequences of transformations, producing different products from a pool of building blocks according to the order and type of stimuli applied. Here we outline the state-of-art in artificial switchable catalysis, classifying systems according to the trigger used to achieve control over the catalytic activity and stereochemical or other structural outcomes of the reaction.

490 citations

Journal ArticleDOI
TL;DR: This Review addresses the implementation of the information encoded in nucleic acids to develop DNA switches to tailor switchable DNA hydrogels, for the controlled drug-release and for the activation of switchable enzyme cascades.
Abstract: The base sequence of nucleic acid encodes structural and functional properties into the biopolymer. Structural information includes the formation of duplexes, G-quadruplexes, i-motif, and cooperatively stabilized assemblies. Functional information encoded in the base sequence involves the strand-displacement process, the recognition properties by aptamers, and the catalytic functions of DNAzymes. This Review addresses the implementation of the information encoded in nucleic acids to develop DNA switches. A DNA switch is a supramolecular nucleic acid assembly that undergoes cyclic, switchable, transitions between two distinct states in the presence of appropriate triggers and counter triggers, such as pH value, metal ions/ligands, photonic and electrical stimuli. Applications of switchable DNA systems to tailor switchable DNA hydrogels, for the controlled drug-release and for the activation of switchable enzyme cascades, are described, and future perspectives of the systems are addressed.

375 citations