Ingéniérie des nanomatériaux redox métallocèniques

Dendrimers and polymers containing transition metals such as iron, cobalt andrhodium can serve in the fabrication of useful nanomaterials for catalysis, molecularrecognition and molecular electronics. For their construction, ionic bonds, clickchemistry: CuAAC and hydroamination, ROMP and radical polymerization were usedand allowed the formation of new types of metallocenyl polyélectrolytes. Thesynthesis of new gold, silver and palladium nanoparticles from these metallopolymersand metallodendrimers has been developed, leading to specific and well-definedarchitectures. These supramolecular assemblies and molecular engineering opensthe way towards the application of organometallic chemistry in the design of newstructured nanoparticle-containing nanomaterials using the redox properties ofmetallomacromolecules.Les dendrimères et polymères contenant des métaux de transition comme le fer, lecobalt et le rhodium peuvent servir à la fabrication des nanomatériaux utiles à lacatalyse, la reconnaissance moléculaire et l’électronique moléculaire. Pour leurconstruction, des liaisons ioniques, de la chimie click : CuAAC et hydroamination, lapolymérisation ROMP et la polymérisation radicalaire ont été utilisés et ont permis laformation de nouveaux types de polyélectrolytes metallocéniques. La synthèse denouvelles nanoparticules d’or, d’argent et de palladium à partir de cesmétallopolymères et métallodendrimères ont été mises au point, conduisant à desréseaux à architecture spécifique bien définie. Ces assemblages supramoléculaireset ingénierie moléculaire ouvrent la voie vers l’application de la chimieorganométallique dans la conception de nouveaux nanomatériaux nanoparticulairesstructurés à l’aide des propriétés rédox des métallomacromolécules

Engineering of redox metallocenic nanomaterials

Les dendrimères et polymères contenant des métaux de transition comme le fer, lecobalt et le rhodium peuvent servir à la fabrication des nanomatériaux utiles à lacatalyse, la reconnaissance moléculaire et l’électronique moléculaire. Pour leurconstruction, des liaisons ioniques, de la chimie click : CuAAC et hydroamination, lapolymérisation ROMP et la polymérisation radicalaire ont été utilisés et ont permis laformation de nouveaux types de polyélectrolytes metallocéniques. La synthèse denouvelles nanoparticules d’or, d’argent et de palladium à partir de cesmétallopolymères et métallodendrimères ont été mises au point, conduisant à desréseaux à architecture spécifique bien définie. Ces assemblages supramoléculaireset ingénierie moléculaire ouvrent la voie vers l’application de la chimieorganométallique dans la conception de nouveaux nanomatériaux nanoparticulairesstructurés à l’aide des propriétés rédox des métallomacromolécules.Dendrimers and polymers containing transition metals such as iron, cobalt andrhodium can serve in the fabrication of useful nanomaterials for catalysis, molecularrecognition and molecular electronics. For their construction, ionic bonds, clickchemistry: CuAAC and hydroamination, ROMP and radical polymerization were usedand allowed the formation of new types of metallocenyl polyélectrolytes. Thesynthesis of new gold, silver and palladium nanoparticles from these metallopolymersand metallodendrimers has been developed, leading to specific and well-definedarchitectures. These supramolecular assemblies and molecular engineering opensthe way towards the application of organometallic chemistry in the design of newstructured nanoparticle-containing nanomaterials using the redox properties ofmetallomacromolecules

ROMP Synthesis of Cobalticenium–Enamine Polyelectrolytes

The synthesis of redox-robust polyelectrolyte polymers has long been investigated. Two simple methods of synthesis of well-defined cobalticenium-containing polymers are presented using both the norbornene ring-opening-metathesis polymerization (ROMP) method initiated by a third-generation Grubbs catalyst and the mild uncatalyzed hydroamination of the easily available ethynyl cobalticenium hexafluorophosphate salt. In the first strategy, a norbornene monomer functionalized with an enamine-cobalticenium group is polymerized by ROMP, whereas in the second one a norbornene derivative functionalized with a secondary amine group is polymerized by ROMP using the same catalyst followed by hydroamination of ethynyl cobalticenium. The structures of the polymers have been established by ¹H, ¹³C NMR, and DOSY NMR, IR, UV–vis spectroscopy, mass spectrometry, elemental analysis, and cyclic voltammetry. The number of units in the polymers have been determined for various polymer lengths using end-group analysis by ¹H NMR using the diffusion coefficient determined by DOSY NMR and by cyclic voltammetry upon comparing the relative intensities of a monomer reference and the cobalticenium polymers

Catalytically-active palladium nanoparticles stabilized by triazolylbiferrocenyl-containing polymers

International audienceFour different triazolylbiferrocenyl-containing polymers were used for the stabilization of palladium nanoparticles (PdNPs) upon reducing triazole-coordinated Pd(II) both in organic solvents and in water. The resulting PdNPs were active in the Suzuki-Miyaura coupling of bromoaromatics even with down to only 20 ppm of Pd. The comparison between the four different polymer-stabilized PdNPs allows concluding that a flexible polyethylene glycol moiety in the linear triazolylbiferrocenyl polymer permits a better stabilization of the PdNPs than polymers containing triazolylbiferrocenyl side chains with a rigid styrene or succinimide moieties

Spin crossover polymer composites, polymers and related soft materials

International audienceWe review the synthesis, properties and applications of spin crossover polymer composites, polymers and some related ‘soft’ materials. These materials have received recently much attention because they provide an efficient way for the processing of spin crossover complexes in various shapes at various size scales and can give rise also to unique physical properties. First, we discuss in detail the state of the art of the elaboration of spin crossover polymer composites, using either inorganic complex precursors in solution or preformed spin crossover powder. A particular attention is paid on the influence of the polymer matrix on the spin crossover properties and on the use of ‘active’ polymers for development of synergies between the properties of the matrix and the load. Polymer composite devices for applications in the fields of artificial muscles, energy harvesting and thermochromic sensors are also highlighted. Then, more recent works, in which organic polymeric chains are used as ligands for the transition metal ions are presented. Finally, we overview various related ‘soft’ spin crossover compounds including spin crossover dendrimers, gels, liquid crystals and Langmuir Blodgett films with particular emphasis on compounds with supramolecular interactions of alkyl chains

Rhodicenium Salts: From Basic Chemistry to Polyelectrolyte and Dendritic Macromolecules

A new, facile synthesis of rhodicenium chloride is described, leading to the synthesis of rhodicenium tetraarylborate, the first rhodicenium salt that is soluble in less polar solvents. This opens the route to further chemistry that was prevented by the insolubility of the formerly available rhodicenium salts. This strategy has been extended to the synthesis of water-soluble polyelectrolyte and dendritic macromolecular cobaltocenium and rhodicenium salts

Click Chemistry of an Ethynylarene Iron Complex: Syntheses, Properties, and Redox Chemistry of Cationic Bimetallic and Dendritic Iron-Sandwich Complexes

The functionalization of dendrimers and other macromolecules with cationic redox-active organometallics remains a target toward metal-containing dendrimers and polymers that can serve in particular as polyelectrolytes and multielectron redox reagents. Along this line, we report the click functionalization of organometallics and dendrimers with a redox-active ethynylarene iron complex, [FeCp­(η⁶-ethynylmesitylene)]­[PF₆], <b>3</b>, easily available from [FeCp­(η⁶-mesitylene)]­[PF₆], <b>1</b>. Complex <b>3</b> reacts with azidomethylferrocene upon catalysis by copper sulfate and sodium ascorbate (CuAAC reaction) to give a bimetallic complex that is reduced on the mesitylene ligand to a mixture of isomeric cyclohexadienyl complexes. Complex <b>3</b> also reacts according to the same click reaction with zeroth- and first-generation metallodendrimers containing, respectively, 9 and 27 azido termini to provide new polar polycationic metallodendrimers that are reversibly reduced, on the electrochemical time scale, to 19-electron Fe^I species

Uncatalyzed hydroamination of electrophilic organometallic alkynes: fundamental, theoretical, and applied aspects.

International audienceSimple reactions of the most used functional groups allowing two molecular fragments to link under mild, sustainable conditions are among the crucial tools of molecular chemistry with multiple applications in materials science, nanomedicine, and organic synthesis as already exemplified by peptide synthesis and "click" chemistry. We are concerned with redox organometallic compounds that can potentially be used as biosensors and redox catalysts and report an uncatalyzed reaction between primary and secondary amines with organometallic electrophilic alkynes that is free of side products and fully "green". A strategy is first proposed to synthesize alkynyl organometallic precursors upon addition of electrophilic aromatic ligands of cationic complexes followed by endo hydride abstraction. Electrophilic alkynylated cyclopentadienyl or arene ligands of Fe, Ru, and Co complexes subsequently react with amines to yield trans-enamines that are conjugated with the organometallic group. The difference in reactivities of the various complexes is rationalized from the two-step reaction mechanism that was elucidated through DFT calculations. Applications are illustrated by the facile reaction of ethynylcobalticenium hexafluorophosphate with aminated silica nanoparticles. Spectroscopic, nonlinear-optical and electrochemical data, as well as DFT and TDDFT calculations, indicate a strong push-pull conjugation in these cobalticenium- and Fe- and Ru-arene-enamine complexes due to planarity or near-planarity between the organometallic and trans-enamine groups involving fulvalene iminium and cyclohexadienylidene iminium mesomeric forms

Synthesis and redox activity of “clicked” triazolylbiferrocenyl polymers, network encapsulation of gold and silver nanoparticles and anion sensing

International audienceThe design of redox-robust polymers is called for in view of interactions with nanoparticles and surfaces toward applications in nanonetwork design, sensing, and catalysis. Redox-robust triazolylbiferrocenyl (trzBiFc) polymers have been synthesized with the organometallic group in the side chain by ring-opening metathesis polymerization using Grubbs-III catalyst or radical polymerization and with the organometallic group in the main chain by Cu(I) azide alkyne cycloaddition (CuAAC) catalyzed by [Cu(I)(hexabenzyltren)]Br. Oxidation of the trzBiFc polymers with ferricenium hexafluorophosphate yields the stable 35-electron class-II mixed-valent biferrocenium polymer. Oxidation of these polymers with AuIII or AgI gives nanosnake-shaped networks (observed by transmission electron microscopy and atomic force microscopy) of this mixed-valent FeIIFeIII polymer with encapsulated metal nanoparticles (NPs) when the organoiron group is located on the side chain. The factors that are suggested to be synergistically responsible for the NP stabilization and network formation are the polymer bulk, the trz coordination, the nearby cationic charge of trzBiFc, and the inter-BiFc distance. For instance, reduction of such an oxidized trzBiFc-AuNP polymer to the neutral trzBiFc-AuNP polymer with NaBH4 destroys the network, and the product flocculates. The polymers easily provide modified electrodes that sense, via the oxidized FeIIFeIII and FeIIIFeIII polymer states, respectively, ATP2– via the outer ferrocenyl units of the polymer and PdII via the inner Fc units; this recognition works well in dichloromethane, but also to a lesser extent in water with NaCl as the electrolyte

Poly(Biferrocenylethynyl)arene and Bis(biferrocenyl)diynyl Complexes and Their Redox Chemistry

Orange linear bis-, star tris-, and dendritic tetra-biferrocenes linked by rigid ethynylaryl and diynyl spacers were synthesized through Sonogashira coupling and homocoupling reactions and oxidized to robust blue biferrocenium complexes. The proximity of the two ferrocenyl units to each other in the biferrocenyl units introduces electrostatic and electronic effects that are observed by cyclic voltammetry and are responsible for mixed-valence stabilization and localization. The use of the polyfluorinated electrolyte [<i>n</i>-Bu₄N]­[BAr₄^F] {Ar^F = 3,5-bis­(trifluoro­methyl)­phenyl} allows observing considerable enhancement of these effects and separation of electrochemical waves representing the two ferrocenyl groups of the biferrocenyl unit. The electrostatic effect is also selectively observed with the latter electrolyte between the two central ferrocenyl units of bis­(biferro­cenyl)­diyne. Oxidation of all of these poly­(biferro­cenyl) complexes using a ferricinium salt yields blue, robust biferrocenium complexes. Their localized mixed-valent electronic structure was demonstrated at both Mössbauer and infrared time scales even with the counteranion (BAr₄^F) that provokes the maximum electrostatic effect and very much enhances the difference between the two oxidation potentials. Their near-infrared spectra show the intervalent charge transfer and are similar to those previously recorded for biferrocenium and derivatives, confirming the class-II mixed valence. The biferrocene units around the arene linker are completely electronically independent in the neutral and cationic complexes. In conclusion, from a practical standpoint, the easy oxidation of these stiff electrochromic nanosystems and the largely increased robustness of their oxidized form compared to ferricinium make their potential use as electrochromes considerably more attractive than that of simple ferrocene derivatives