Copper Catalyst Activation Driven by Photoinduced Electron Transfer: A Prototype Photolatent Click Catalyst

Harmand, Lydie; Cadet, Sarah; Kauffmann, Brice; Scarpantonio, Luca; Batat, Pinar; Jonušauskas, Gediminas; McClenaghan, Nathan D.; Lastécouères, Dominique; Vincent, Jean‐Marc

doi:10.1002/ange.201203014

Cited by 15 publications

(16 citation statements)

References 47 publications

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“…The presence of the tetradentate tren ligand in 1 might limit the over‐reduction process, by lowering the reduction potential of the Cu II /Cu I and Cu I /Cu 0 , compared with copper salts. The E 1/2 of the Cu II /Cu I couple for 1 measured in acetonitrile was found at a rather low value of −0.34 V vs. SCE 5. Nonetheless, we observed that prolonged irradiation of 1 leads to Cu I to Cu 0 reduction and the formation of copper NPs.…”

Section: Resultsmentioning

confidence: 52%

“…Interestingly, this shows that the reaction medium is not limited to good H‐donating solvents. Indeed, the photoreduction of 1 in CH 2 Cl 2 in the absence of the reactant is sluggish, as approximately 75 % of 1 is reduced after 3 h irradiation 5. However, as described above for the photoreduction in water, under the reaction conditions, the alkyne may serve as a sacrificial reductant.…”

Section: Resultsmentioning

confidence: 87%

“…[17] In our preliminary account we reported the synthesis and characterization of the copper(II) complex [Cu(t-BuBz 3 tren)ketoprofenate]ketoprofenate 1 and its non-photoactivable structural analogue [Cu(t-BuBz 3 tren)acetate]acetate 2. [5] The precatalyst (compound 1) was obtained in 90 % yield by treating the tBuBz 3 tren ligand in methanol with the copper(II)-carboxylate complex [Cu 2 (ketoprofenate) 4 www.chemeurj.org profen in water. The precipitate that immediately forms is filtered and dried affording 3 as a green powder in 97 % yield.…”

Section: Resultsmentioning

confidence: 99%

“…Rather surprisingly, photoinduced electron transfer (PET) to a metal cation as a way to activate a catalyst has been largely unexplored. We recently reported the synthesis, preliminary sensitized photoreduction studies and catalytic activity of [Cu( t BuBz 3 tren)ketoprofenate]ketoprofenate complex 1 (Figure 1), a prototype photolatent catalyst whose activation is driven by a PET process 5. The copper(I)‐catalyzed alkyne–azide cycloaddition (CuAAC) is an example of a reaction for which the catalyst is inactive in its oxidized cupric state but active in its reduced cuprous form 6.…”

Section: Introductionmentioning

confidence: 99%

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A Photoreducible Copper(II)‐Tren Complex of Practical Value: Generation of a Highly Reactive Click Catalyst

Harmand

Lambert

Scarpantonio

et al. 2013

Chemistry A European J

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A detailed study on the photoreduction of the copper(II) precatalyst 1 to generate a highly reactive cuprous species for the copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) click reaction is presented. For the photoactive catalyst described herein, the activation is driven by a photoinduced electron transfer (PET) process harnessing a benzophenone-like ketoprofenate chromophore as a photosensitizer, which is equally the counterion. The solvent is shown to play a major role in the Cu(II) to Cu(I) reduction process as the final electron source, and the influence of the solvent nature on the photoreduction efficiency has been studied. Particular attention was paid to the use of water as a potential solvent, aqueous media being particularly appealing for CuAAC processes. The ability to solubilize the copper-tren complexes in water through the formation of inclusion complexes with β-CDs is demonstrated. Data is also provided on the fate of the copper(I)-tren catalytic species when reacting with O2, O2 being used to switch off the catalysis. These data show that partial oxidation of the secondary benzylamine groups of the ligand to benzylimines occurs. Preliminary results show that when prolonged irradiation times are employed a Cu(I) to Cu(0) over-reduction process takes place, leading to the formation of copper nanoparticles (NPs). Finally, the main objective of this work being the development of photoactivable catalysts of practical value for the CuAAC, the catalytic, photolatent, and recycling properties of 1 in water and organic solvents are reported.

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Section: Resultsmentioning

confidence: 52%

Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Photoreducible Copper(II)‐Tren Complex of Practical Value: Generation of a Highly Reactive Click Catalyst

Harmand

Lambert

Scarpantonio

et al. 2013

Chemistry A European J

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“…Thus,for example,crosslinking reactions (such as network formation), [7] surfacemodification methods (such as self-assembled monolayers [8] or polymeric surfaces), [9] or the generation of self-healing materials [10] have been enabled as ac onsequence of its high substrate tolerance as well as its solvent insensitivity usually under low temperatures.Besides the known large number of homogeneous and heterogeneous Cu I -based catalysts,e specially latent catalytic "click" systems have been designed, for example,those which can be triggered by aspecific stimulus. Thus,asite-specific activation of the "click" reaction by triggers such as light, [11] pressure, [8a, 12] or as imple heterogeneous ball-milling procedure [13] have been achieved. However,ah omogeneous mechanochemical "click" system has not yet been developed to the best of our knowledge ( Figure 1).…”

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confidence: 99%

A Mechanochemically Triggered “Click” Catalyst

Michael

Binder

2015

Angewandte Chemie

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Click" chemistry represents one of the most powerful approaches for linking molecules in chemistry and materials science.T riggering this reaction by mechanical force would enable site-and stress-specific "click" reactionsah itherto unreported observation. We introduce the design and realization of ahomogeneous Cu catalyst able to activate through mechanical force when attached to suitable polymer chains,a cting as al ever to transmit the force to the central catalytic system. Activation of the subsequent copper-catalyzed "click" reaction (CuAAC) is achieved either by ultrasonication or mechanical pressing of ap olymeric material, using af luorogenic dye to detect the activation of the catalyst. Based on an N-heterocyclic copper(I) carbene with attached polymeric chains of different flexibility,t he force is transmitted to the central catalyst, therebyactivating aCuAACinsolution and in the solid state.

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Benzophenone vs. Copper/Benzophenone in Light‐Promoted Atom Transfer Radical Additions (ATRAs): Highly Effective Iodoperfluoroalkylation of Alkenes/Alkynes and Mechanistic Studies

et al. 2016

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Iodoperfluooralkylation of terminal alkenesa nd alkynes is effectively photo-promoted by benzophenone 2 (BP) or the photoreducible copper(II) complex 1.I np articular,B Pa t1mol%i n methanol upon3 65 nm irradiationw ith al ow-pressure mercury lamp (type TLC = thin layer chromatography, 6W)r esults in af ast reaction with excellent reactiony ields.C omplex 1 and BP 2 exhibited very similarr eactivity,s uggestingt hat the reactions involving 1 are likely to be governed by the benzophenone photoactivation processes,r athert han copper(I)/(II) redox processes.M echanistic investigations using transient absorption spectroscopy revealed that ad eactivation pathway of the benzophenone triplet( 3 BP*) is via its reactionw ith the methanol solvent. We propose that the generated radicals, in particular CCH 2 OH, play ak ey role in the initiation step formingR f C by reactingw ith R f I, R f C then entering ar adical chain cycle. 1 HNMR studies provided evidence that as ubstantial amount (~7% NMR yield) of the hemiacetal CH 3 OCH 2 OH is formed, i.e., the possible by-product of the reaction between CCH 2 OH and R f I. Finally,D FT calculations indicatet hat at riplet-triplete nergy transfer (TTET) process from 3 BP* to perfluorooctyl iodide (C 8 F 17 I) is unlikely or should be rather slow under the reaction conditions,c onsistent with the transient absorption studies.

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Copper Catalyst Activation Driven by Photoinduced Electron Transfer: A Prototype Photolatent Click Catalyst

Cited by 15 publications

References 47 publications

A Photoreducible Copper(II)‐Tren Complex of Practical Value: Generation of a Highly Reactive Click Catalyst

A Photoreducible Copper(II)‐Tren Complex of Practical Value: Generation of a Highly Reactive Click Catalyst

A Mechanochemically Triggered “Click” Catalyst

Benzophenone vs. Copper/Benzophenone in Light‐Promoted Atom Transfer Radical Additions (ATRAs): Highly Effective Iodoperfluoroalkylation of Alkenes/Alkynes and Mechanistic Studies

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