Design, stabilization, and efficiency of organometallic "electron reservoirs". 19-Electron sandwiches .eta.5-C5R5FeI-.eta.6-C6R'6, a key class active in redox catalysis

Astruc, Didier; Hamon, Jean‐René; Althoff, Gisela; Román, Enrique; Batail, Patrick; Michaud, Pascal; Mariot, Jean Pierre; Varret, F.; Cozak, Daniel

doi:10.1021/ja00512a071

Cited by 126 publications

(76 citation statements)

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“…Monoelectronic reductants such as ferrocene, ethynylferrocene, decamethylferrocene, and the electron-reservoir sandwich complex [Fe I (η 5 -C 5 H 5 )(η 6 -C 6 Me 6 )], which has 19 valence electrons on the iron valence shell, 33,84 have also been used for the first time for the reduction of HAuCl 4 to AuNPs (Figure 3). Their outer-sphere reduction mechanism 67 implied a much slower reduction than that involving the inner-sphere reductant NaBH 4 , and the size of the dendrimerstabilized AuNPs formed (between 7 and 38 nm) was directly related to the standard oxidation potentials of the Fe I and Fe II reductants.…”

Section: Recognition Of Transition-metal Cations and Oxo-anions Usingmentioning

confidence: 99%

Click Dendrimers and Triazole-Related Aspects: Catalysts, Mechanism, Synthesis, and Functions. A Bridge between Dendritic Architectures and Nanomaterials

et al. 2011

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One of the primary recent improvements in molecular chemistry is the now decade-old concept of click chemistry. Typically performed as copper-catalyzed azide-alkyne (CuAAC) Huisgen-type 1,3-cycloadditions, this reaction has many applications in biomedicine and materials science. The application of this chemistry in dendrimer synthesis beyond the zeroth generation and in nanoparticle functionalization requires stoichiometric use of the most common click catalyst, CuSO(4)·5H(2)O with sodium ascorbate. Efforts to develop milder reaction conditions for these substrates have led to the design of polydentate nitrogen ligands. Along these lines, we have described a new, efficient, practical, and easy-to-synthesize catalytic complex, [Cu(I)(hexabenzyltren)]Br, 1 [tren = tris(2-aminoethyl)amine], for the synthesis of relatively large dendrimers and functional gold nanoparticles (AuNPs). This efficient catalyst can be used alone in 0.1% mol amounts for nondendritic click reactions or with the sodium-ascorbate additive, which inhibits aerobic catalyst oxidation. Alternatively, catalytic quantities of the air-stable compounds hexabenzyltren and CuBr added to the click reaction medium can provide analogously satisfactory results. Based on this catalyst as a core, we have also designed and synthesized analogous Cu(I)-centered dendritic catalysts that are much less air-sensitive than 1 and are soluble in organic solvents or in water (depending on the nature of the terminal groups). These multivalent catalysts facilitate efficient click chemistry and exert positive dendritic effects that mimic enzyme activity. We propose a monometallic CuAAC click mechanism for this process. Although the primary use of click chemistry with dendrimers has been to decorate dendrimers with a large number of molecules for medicinal or materials purposes, we are specifically interested in the formation of intradendritic [1,2,3]-triazole heterocycles that coordinate to transition-metal ions via their nitrogen atoms. We describe applications including molecular recognition of anions and cations and the stabilization of transition metal nanoparticles according to a principle pioneered by Crooks with poly(amido amine) (PAMAM) dendrimers, and in particular, the control of structural and reactivity parameters in which the intradendritic [1,2,3]-triazoles and peripheral tripodal tri(ethylene glycol) termini play key roles in the click-dendrimer mediated synthesis and stabilization of gold nanoparticles (AuNPs). By varying these parameters, we have stabilized water-soluble, weakly liganded AuNPs between 1.8 and 50 nm in size and have shown large differences in behavior between AuNPs and PdNPs. Overall, the new catalyst design and the possibilities of click dendrimer chemistry introduce a bridge between dendritic architectures and the world of nanomaterials for multiple applications.

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Section: Recognition Of Transition-metal Cations and Oxo-anions Usingmentioning

confidence: 99%

Click Dendrimers and Triazole-Related Aspects: Catalysts, Mechanism, Synthesis, and Functions. A Bridge between Dendritic Architectures and Nanomaterials

et al. 2011

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“…Both of the new triblock copolymers contain two cationic adjacent FbX and CcX blocks as the second and third block, respectively, and the neutral Fc or Fc* block is located at one end of the triblock copolymer chain as the first block ( Scheme ). All these sandwich units present redox stabilities, this property being eventually enforced by ring permethylation in electron‐reservoir systems . The electrochemical properties and redox cascades in the copolymers will also be analyzed in this article using cyclic voltammetry (CV).…”

Section: Introductionmentioning

confidence: 99%

Living ROMP Synthesis and Redox Properties of Triblock Metallocopolymers Containing Side‐Chain Iron and Cobalt Sandwich Complexes

Ciganda

Castel

et al. 2018

Macro Chemistry & Physics

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Metalloblock copolymers are intensively researched because of their multifunctionalities and potential applications in biomedicine and materials science. In addition, metal fragments with redox stabilities are of interest toward conductors, sensors, and batteries. Here, Grubb’s third‐generation metathesis catalyst is efficiently used in ring‐opening metathesis polymerization (ROMP) reactions leading to the synthesis of two triblock metallopolymers in which each block contains a redox‐reversible iron or cobalt sandwich site. For each metallocopolymer, among six possibilities, only one involving a precise order of introduction of blocks is efficient with the completion of 25 units per block. Cyclic voltammetry measurements show the respective ability of the metal centers to exchange electrons with the electrode, with some electron transfer paths being marred by the positive charges and ligand bulk. Overall, these systems provide a cascade of chemically reversible electron transfers, their number being reasonably estimated using the empirical Bard–Anson model within approximately 20% of the number of redox sites determined by 1H NMR.

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“…Dendrimer construction is based on branching iteration, a principle reported by Vögtle's group and our group in the late 1970's [6]. Here we would like to review the organo-iron-mediated dendrimer construction based on the CpFe þ -induced activation of arenes that we have initiated in the late 1970's [7], with emphasis on recent results on the reactions involving the useful 1 / 3 connectivity.…”

Section: Introductionmentioning

confidence: 99%

Organo-iron mediated synthesis of functional dendrimers with 1 → 3 connectivity

Astruc

Ruiz

2011

Journal of Organometallic Chemistry

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Design, stabilization, and efficiency of organometallic "electron reservoirs". 19-Electron sandwiches .eta.5-C5R5FeI-.eta.6-C6R'6, a key class active in redox catalysis

Cited by 126 publications

References 0 publications

Click Dendrimers and Triazole-Related Aspects: Catalysts, Mechanism, Synthesis, and Functions. A Bridge between Dendritic Architectures and Nanomaterials

Click Dendrimers and Triazole-Related Aspects: Catalysts, Mechanism, Synthesis, and Functions. A Bridge between Dendritic Architectures and Nanomaterials

Living ROMP Synthesis and Redox Properties of Triblock Metallocopolymers Containing Side‐Chain Iron and Cobalt Sandwich Complexes

Organo-iron mediated synthesis of functional dendrimers with 1 → 3 connectivity

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