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The 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 Au(III) or Ag(I) gives nanosnake-shaped networks (observed by transmission electron microscopy and atomic force microscopy) of this mixed-valent Fe(II)Fe(III) 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 Fe(II)Fe(III) and Fe(III)Fe(III) polymer states, respectively, ATP(2-) via the outer ferrocenyl units of the polymer and Pd(II) via the inner Fc units; this recognition works well in dichloromethane, but also to a lesser extent in water with NaCl as the electrolyte.

Simple 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., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A magnetically separable ruthenium catalyst was synthesized through immobilizing a pentamethylcyclopentadienyl ruthenium complex on iron oxide nanoparticles. The catalyst is highly active and selective for the synthesis of 1,5-disubstituted 1,2,3-trizoles via cycloaddition of alkynes and organic azides and can be recycled at least 5 times.

The derivatization of macromolecules with redox-stable groups is a challenge for molecular electronics applications. The large majority of redox-derivatized macromolecules involve ferrocenes, and there are only a few reports with cobalticinium. We report here the first click derivatization of macromolecules with the cobalticinium redox group using ethynylcobalticinium hexafluorophosphate, 1. Cu(I) catalysis was used for these selective click metallodendrimer syntheses starting from 1 and providing the tripodal dendron 3 that contains three 1,2,3-triazolylcobalticinium termini and a phenol focal point and the dendrimers of generations 0, 1, and 2 containing 9, 27, and 81 triazolylcobalticinium units for the dendrimers 4, 5, and 6, respectively. Atomic force microscopy (AFM) statistical studies provided the progression of height upon increase of dendrimer generation. Cyclic voltammetry studies in MeCN and dimethylformamide (DMF) show the solvent-dependent reversibility of the Co(III/II) wave (18e/19e) and generation dependent reversibility of the Co(II/I) (19e/20e) wave in DMF. The H2PO4(-) anion is only recognized by the largest metallodendrimer 6 by a significant cathodic shift of the Co(III/II) wave.

In this Concept article, we summarize and discuss recent reports on dendritic molecular electrochromic batteries. Giant dendrimers containing 3(n+2) terminal tethers (n = generation number) and terminated by first-raw late-transition-metal metallocenes, permethyl metallocenes and other sandwich complexes were shown to be redox robust. Indeed, they can be oxidized and reduced without decomposition and exist under two stable oxidation states (Fe(III/II), Co(III/II)). Thus, a pre-determined number of electrons (up to 14,000) per dendrimer can be exchanged. Cyclic voltammetry showed a remarkable complete reversibility even up to 14,000 Fe and Co termini in metallodendrimers, indicating fast electron hoping among the redox sites and between dendrimers on a carbon surface covered by arylcarboxylate groups. The dendrimer sizes were measured by dynamic light scattering in solution and by AFM (subsequent to flattening in the condensed state also indicating that these metallodendrimers aggregate to form discrete nanoparticles of dendrimers, as atoms do). The metallodendrimer size varies considerably between the two redox forms due to tether extension of the cationic dendrimers upon oxidation, and a breathing mechanism was shown by atomic and electric force microscopy (AFM and EFM). When the redox potential is very negative, the reduced form is an electron-reservoir system that can deliver a large number of electrons per dendrimer to various reducible substrates. These systems are thus potential dendritic molecular batteries with two different colors for the two redox forms (electrochromic behavior).

A new, very simple, and general method for the synthesis of functional and heterodifunctional 1,1'-ferrocenes is reported using the visible-light photolysis of a simple 100-W desk lamp with the easily available complexes [(eta(5)-C(5)H(4)R)Fe(eta(6)-toluene)][PF(6)] (R = Me, Cl, COMe, CO(2)H, CO(2)Me, CO(2)CH(2)CCH, CONHCH(2)Ph) and a substituted cyclopentadienyl salt MC(5)H(4)R' (M = Li, Na, R' = H, COMe, CO(2)Me, SiMe(2)CH(2)Cl, PPh(2)) under ambient conditions. All the reactions give high yields except when the side chain contains a strong ligand competing with the Cp anion complexation.

"Click" dendrimers containing 1,2,3-triazolyl ligands that coordinate to PdII(OAc)2 have been synthesized in view of catalytic applications. Five of these dendrimers contain ferrocenyl termini directly attached to the triazole ligand in order to monitor the number of PdII that are introduced into the dendrimers by cyclic voltammetry. Reduction of the PdII-triazole dendrimers by using NaBH4 or methanol yields Pd nanoparticles (PdNPs) that are stabilized either by several dendrimers (G0, DSN) or by encapsulation inside a dendrimer (G1 and G2: DEN), as confirmed by TEM. Relative to PAMAM-DENs (PAMAM=poly(amidoamine)), the "click" DSNs and DENs show a remarkable efficiency and stability for olefin hydrogenation under ambient conditions of various substrates. The influence of the reductant of PdII bound to the dendrimers is dramatic, reduction with methanol leading to much higher catalytic activity than reduction with NaBH4. The most active NPs are shown to be those derived from dendrimer G1, and variation of its termini groups (ferrocenyl, alkyl, phenyl) allowed us to clearly delineate, optimize, and rationalize the role of the dendrimer frameworks on the catalytic efficiencies. Finally, hydrogenation of various substrates catalyzed by these PdNPs shows remarkable selectivity features.

Covalent assembly between gold-thiolate nanoparticles (AuNPs) and the cluster [Fe(eta(5)-C(5)H(5))(mu(3)-CO)](4), 1, can be achieved either by direct Brust-Schriffin-type synthesis using a mixture of undecanethiol and a thiol functionalized with , or by substitution of undecanethiolate ligands in AuNPs by thiolate ligands functionalized with ; cyclic voltammetry of these AuNPs functionalized with allows us to recognize and titrate the oxo-anions H(2)PO(4)(-) and ATP(2-).

Two families of five metallodendrimers have been assembled by hydrogen bonding between the primary amino groups of DSM dendrimers G(n)-DAB-dendr-(NH(2))x (n = 1-5; x = 4, 8, 16, 32, 64) and the OH group of phenol dendrons containing a triallyl or a triferrocenylalkyl tripod in para position. These H-bonded dendrimers noted G(1)-DAB-12Fc, G(2)-DAB-24Fc, G(3)-DAB-48Fc, G(4)-DAB-96Fc, and G(5)-DAB-192Fc have been characterized as resulting from fast, reversible hydrogen bonding by the single broad signal observed in (1)H NMR for the three NH(2) + OH protons whose location depends on the concentration. The cyclic voltammograms (CVs) show a single reversible ferrocenyl wave due to the equivalence of these groups and the fast rotation of the supramolecular ensemble compared to the CV time scale. A new CV wave appears at less anodic potential upon addition of H(2)PO(4)(-) or adenosine-triphosphate (ATP(2)(-)) anion as a tetrabutylammonium salt as with previously studied ferrocenyl dendrimers. In addition, other specific and remarkable features are the fact that the new CV wave is much less intense than the initial one and the dramatically sudden disappearance of the initial CV wave at the equivalent point indicating the formation of a large supramolecular assembly with the hydrogenophosphate groups. Finally, the variation of the number of equivalent anions with the generation number to reach the equivalent point also suggests that the competition between the amino- and amido group for the interaction with hydrogenophosphate depends on the generation number. Recognition by these supramolecular dendrimers of H(2)PO(4)(-) and ATP(2)(-) follows the model of the relatively strong-interaction type in the Kaifer-Echegoyen model, which allows access to the ratio of association constants K(+)/K(0). A positive dendritic effect is found for the recognition of H(2)PO(4)(-) (i.e., the difference of potentials DeltaE(1/2) between the initial CV wave and the new one and the K(+)/K(0) value increase as the generation number increases) whereas the dendritic effect is slightly negative for the recognition of ATP(2)(-).

A series of bis(tert-butylphosphine)- and bis(cyclohexylphosphine)-functionalized Pd(II) monomers and polyamino (DAB) dendritic catalysts were synthesized and investigated for Sonogashira carbon-carbon coupling reactions in a copper-free procedure. The influence of phosphine substituents (tBu versus Cy) on the reaction kinetics was investigated by a GPC technique to monitor the reactions. The dendritic catalysts containing the cyclohexylphosphine ligands could be recovered and reused without loss of efficiency until the fifth cycle. The dendritic Pd(II) catalysts show a negative dendritic effect, that is, the catalyst efficiency decreases as the dendrimer generation increases.

A family of five metallodendrimers with pentamethylamidoferrocenyl termini were synthesized from the DSM dendrimers G(n)-DAB-dend-(NH(2))(x) (x=4, 8, 16, 32, 64) and characterized by standard techniques, including prominent molecular peaks (broad for x=64) in their MALDI-TOF mass spectra. Oxidation of G(4)-DAB-dend-(NHCOFc*)(x) (Fc*=C(5)H(4)FeCp*, Cp*=eta(5)-C(5)Me(5)) with SbCl(5) in CH(2)Cl(2) yields the stable 17-electron pentamethylferrocenium analogue, which can be characterized by ESR and Mössbauer spectroscopy and reduced back to the initial Fe(II) dendrimer, the cycle being carried out without decomposition. The cyclic voltammograms (CVs) of all dendrimers, recorded in CH(2)Cl(2) or DMF, show a fully reversible ferrocenyl wave without adsorption. They are much cleaner than those of the parent ferrocenyl analogues previously synthesized and studied by Cuadrado et al. These properties allow much easier recognition and titration of H(2)PO(4) (-) and ATP(2-) by CV with the permethylated series than with the parent series. On the other hand, permethylation reduces the difference between the potentials recorded before and after titration. This is not crucial for H(2)PO(4) (-) and ATP(2-), but it is for HSO(4) (-), because of the weak interaction in this case. Thus recognition and titration in CH(2)Cl(2) proceeds best with the parent series, and a positive dendritic effect is revealed by the appearance of a new wave whose difference in potential relative to the initial wave increases with increasing generation number. In DMF, recognition and titration are only possible with the permethylated series and are subject to a dramatic dendritic effect. Indeed, the titration is followed by only a shift of the initial wave with G(1) and by the appearance of a new wave with G(2) and G(3). In conclusion, the permethylated dendrimers allow excellent recognition and titration of the oxoanions by CV due to the stereoelectronic stabilization of the 17-electron form and their hydrophobic effect. The magnitude of the recognition and positive dendritic effects is very sensitive to the dendrimer structure and to the nature of the solvent. The recognition is of the strong-interaction type (square scheme) between these dendrimers and ATP(2-) with a stoichiometry of 0.5 equiv ATP(2-) per ferrocenyl branch.