Switch in Catalyst State: Single Bifunctional Bi-state Catalyst for Two Different Reactions
TL;DR: A molecular switch which responds to acid-base stimuli and serves as a bi-state catalyst for two different reactions, used in an assisted tandem catalysis set up involving dehydrogenative coupling of an amine and then hydrogenation of the resulting imine product by switching between the respective states of the catalyst.
Abstract: Disclosed here is a molecular switch which responds to acid-base stimuli and serves as a bi-state catalyst for two different reactions. The two states of the switch serve as a highly active and poorly active catalyst for two catalytic reactions (namely a hydrogenation and a dehydrogenative coupling) but in a complementary manner. The system was used in an assisted tandem catalysis set-up involving dehydrogenative coupling of an amine and then hydrogenation of the resulting imine product by switching between the respective states of the catalyst.
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TL;DR: Multicatalysis is an emerging field targeting the development of efficient catalytic transformations to quickly convert relatively simple starting materials into more complex value-added products.
Abstract: Multicatalysis is an emerging field targeting the development of efficient catalytic transformations to quickly convert relatively simple starting materials into more complex value-added products. ...
109 citations
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
TL;DR: Dissipative catalysis by synthetic molecular machines has implications for the future design of networks that feature communication and signaling between the components.
Abstract: We report on catalysis by a fuel-induced transient state of a synthetic molecular machine. A [2]rotaxane molecular shuttle containing secondary ammonium/amine and thiourea stations is converted between catalytically inactive and active states by pulses of a chemical fuel (trichloroacetic acid), which is itself decomposed by the machine and/or the presence of additional base. The ON-state of the rotaxane catalyzes the reduction of a nitrostyrene by transfer hydrogenation. By varying the amount of fuel added, the lifetime of the rotaxane ON-state can be regulated and temporal control of catalysis achieved. The system can be pulsed with chemical fuel several times in succession, with each pulse activating catalysis for a time period determined by the amount of fuel added. Dissipative catalysis by synthetic molecular machines has implications for the future design of networks that feature communication and signaling between the components.
91 citations
TL;DR: The aminocatalysis and anion-binding catalysis sites of the dual-function rotaxane catalyst can be sequentially concealed or revealed, enabling catalysis of both steps of a tandem reaction process.
Abstract: The “off” state for aminocatalysis by a switchable [2]rotaxane is shown to correspond to an “on” state for anion-binding catalysis. Conversely, the aminocatalysis “on” state of the dual-function rotaxane is inactive in anion-binding catalysis. Switching between the different states is achieved through the stimuli-induced change of position of the macrocycle on the rotaxane thread. The anion-binding catalysis results from a pair of triazolium groups that act together to CH-hydrogen-bond to halide anions when the macrocycle is located on an alternative (ammonium) binding site, stabilizing the in situ generation of benzhydryl cation and oxonium ion intermediates from activated alkyl halides. The aminocatalysis and anion-binding catalysis sites of the dual-function rotaxane catalyst can be sequentially concealed or revealed, enabling catalysis of both steps of a tandem reaction process.
76 citations
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.
56 citations
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1,225 citations
TL;DR: In this article, a taxonomy of one-pot, coupled catalytic transformations is presented, which distinguishes between onepot, domino/cascade, and tandem catalysis, and the proposed taxonomy is illustrated with examples drawn from olefin metathesis and hydroformylation chemistry.
805 citations
TL;DR: It is found that a robust nanoparticulate electrocatalytic material, H(2-CoCat, can be electrochemically prepared from cobalt salts in a phosphate buffer and can be converted on anodic equilibration into the previously described amorphous cobalt oxide film (O(2)-CoCat or CoPi) catalysing O(2) evolution.
Abstract: The future of energy supply depends on innovative breakthroughs regarding the design of cheap, sustainable and efficient systems for the conversion and storage of renewable energy sources. The production of hydrogen through water splitting seems a promising and appealing solution. We found that a robust nanoparticulate electrocatalytic material, H(2)-CoCat, can be electrochemically prepared from cobalt salts in a phosphate buffer. This material consists of metallic cobalt coated with a cobalt-oxo/hydroxo-phosphate layer in contact with the electrolyte and mediates H(2) evolution from neutral aqueous buffer at modest overpotentials. Remarkably, it can be converted on anodic equilibration into the previously described amorphous cobalt oxide film (O(2)-CoCat or CoPi) catalysing O(2) evolution. The switch between the two catalytic forms is fully reversible and corresponds to a local interconversion between two morphologies and compositions at the surface of the electrode. After deposition, the noble-metal-free coating thus functions as a robust, bifunctional and switchable catalyst.
740 citations
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
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