Photoswitchable catalysis based on the isomerisation of double bonds

Dorel, Ruth; Feringa, Ben L.

doi:10.1039/c9cc01891c

Cited by 142 publications

(94 citation statements)

References 84 publications

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“…Actually, it is difficult to think of a supramolecular system and function that has not be controlled or regulated by an azobenzene moiety . Noticeable applications range from classical supramolecular devices (recognition, self‐assembly, transport, sensing, catalysis, etc .) to photoresponsive architectures, passing through responsive materials and polymer science, energy‐related technologies, molecular machines, and biology .…”

Section: Introductionmentioning

confidence: 99%

Configurational Selection in Azobenzene‐Based Supramolecular Systems Through Dual‐Stimuli Processes

Tecilla

Bonifazi

2020

ChemistryOpen

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Azobenzene is one of the most studied light-controlled molecular switches and it has been incorporated in a large variety of supramolecular systems to control their structural and functional properties. Given the peculiar isomeric distribution at the photoexcited state (PSS), azobenzene derivatives have been used as photoactive framework to build metastable supramolecular systems that are out of the thermodynamic equilibrium. This could be achieved exploiting the peculiar E/Z photoisomerization process that can lead to isomeric ratios that are unreachable in thermal equilibrium conditions. The challenge in the field is to find molecular architectures that, under given external circumstances, lead to a given isomeric ratio in a reversible and predictable manner, ensuring an ultimate control of the configurational distribution and system composition. By reviewing early and recent works in the field, this review aims at describing photoswitchable systems that, containing an azobenzene dye, display a controlled configurational equilibrium by means of a molecular recognition event. Specifically, examples include programmed photoactive molecular architectures binding cations, anions and H-bonded neutral guests. In these systems the non-covalent molecular recognition adds onto the thermal and light stimuli, equipping the supramolecular architecture with an additional external trigger to select the desired configuration composition.[a] Prof. P. Tecilla

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Section: Introductionmentioning

confidence: 99%

Configurational Selection in Azobenzene‐Based Supramolecular Systems Through Dual‐Stimuli Processes

Tecilla

Bonifazi

2020

ChemistryOpen

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“…Photoswitchable catalysis has been realized following several approaches using a variety of photochromic systems. Feringa et al recently published a review including systems based on double bond isomerizations [1]. An earlier review from the same group summarized light and redox responsive catalytic systems including azobenzenes, diarylethenes, spiropyranes, and stilbenes [2].…”

Section: Introductionmentioning

confidence: 99%

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

Ludwig¹,

Helberg²,

Zipse³

et al. 2020

Beilstein J. Org. Chem.

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We present the synthesis and the photochemical and catalytic switching properties of an azopyridine as a photoswitchable ligand, covalently attached to a Ni(II)-porphyrin. Upon irradiation with 530 nm (green light), the azopyridine switches to the cis configuration and coordinates with the Ni2+ ion. Light of 435 nm (violet) isomerizes the ligand back to the trans configuration, which decoordinates for steric reasons. This so-called record player design has been used previously to switch the spin state of Ni2+ between singlet and triplet. We now use the coordination/decoordination process to switch the catalytic activity of the dimethylaminopyridine (DMAP) unit. DMAP is a known catalyst in the nitroaldol (Henry) reaction. Upon coordination to the Ni2+ ion, the basicity of the pyridine lone pair is attenuated and hence the catalytic activity is reduced. Decoordination restores the catalytic activity. The rate constants in the two switching states differ by a factor of 2.2, and the catalytic switching is reversible.

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“…The facile cis ‐ trans isomerization of the azo group, usually achieved upon photoirradiation, thereby leading to salient luminescent changes, has attracted considerable attention in recent years. Substituted azobenzenes can thus work as photoswitches that can further be harnessed as artificial molecular machines, photoresponsive materials, as well as (bio)sensors and actuators Moreover, the photoswitchable double bonds can be incorporated into active catalysts, and the azo group has shown a directing effect in organocatalysis . In addition, the term azolog space has been introduced to denote azologation of chemical groups (i.e.…”

Section: Introductionmentioning

confidence: 99%

Thermal and Photochemical Switching of Chiral Sugar Azoalkenes: A Mechanistic Interrogation

et al. 2020

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This manuscript describes a thorough study on the thermal and photochemical evolution of carbohydrate-based azoalkenes, which have been proposed as putative intermediates en route to other heterocyclic derivatives and nucleoside analogues. These substances represent new protagonists in the azo chemical space, under intense study due to reversible photoswitching of this functional group suitable for designing artificial nanomachines and responsive materials. Although structurally simple azadienes derived from monosaccharides have long been known, the dynamics of such species in solution and solid phase remains poorly characterized. Herein, we [a] Dr. Scheme 2. Thermal and photochemical behavior of sugar 1,2-diaza-1,3-butadienes.Here, we look back at monosaccharidic 1,2-diaza-1,3-butadienes, describing structural and configurational aspects in detail and focusing on their unexplored photophysical properties. The O-acylated sugar chain imparts chirality but also conformational flexibility, accompanied by enhanced hydrophobicity. It is well established that reversible trans-to-cis photoisomerization of the azobenzene motif can be tuned by shifts at shorter and longer wavelengths, respectively (the latter induced by thermal relaxation too). We show the dual lability of the C=C and N=N bonds in thermal and photochemical isomerizations (Scheme 2), often under mild conditions (sunlight suffices), and assessing the mechanistic aspects by both experiment and theoretical calculations. Overall, this dynamic behavior paves the way to a new class of chiral switches derived from cheap and abundant natural products.

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Photoswitchable catalysis based on the isomerisation of double bonds

Cited by 142 publications

References 84 publications

Configurational Selection in Azobenzene‐Based Supramolecular Systems Through Dual‐Stimuli Processes

Configurational Selection in Azobenzene‐Based Supramolecular Systems Through Dual‐Stimuli Processes

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

Thermal and Photochemical Switching of Chiral Sugar Azoalkenes: A Mechanistic Interrogation

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