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Olefin cross metathesis is used for the functionalization of polyolefin dendrimers, polymers and gold nanoparticles by using the second-generation Grubbs catalyst. The studies have shown that cross metathesis can be an excellent strategy for achieving an iterative divergent dendrimer construction.

The Pd catalysis of C-C bond formation is explored from the angle of nanoparticles (NPs) to determine whether they are homogeneous or heterogeneous precatalysts and whether they are intentionally preformed or generated from a Pd derivative such as Pd[(OAc).sub.2]. The Pd-catalyzed C-C bond-forming reactions proceed at high temperatures with the formation of Pd nanoparticle (NP) intermediates that leach catalytically active Pd atoms whether the Pd source is molecular or heterogeneous.

Hexasubstitution of apical triflate ligands in the octahedral clusters [M](sub 2) [Mo(sub 6X(sub 8)(CF(sub 3)SO(sub 3)(sub 6)] (M=n-Bu(sub 4)N or Cs, X=Br or I) and monosubstitution in [n-Bu(sub 4)N](sub 2)Mo(sub 6)Br(sub 13)(CF(sub 3)SO (sub 3)] was carried out in tetrahydrofuran with simple pyridines and then extended to organometallic pyridines. The organometallic pyridines yielded cluster-cored stars, and dendronic polyallyl and polyferrocenylpyridiens yielded cluster-coated polyallyl and polyferrocenyl dendrimers and dendrons.

Measurement of the redox potentials ([E.sub.1/2]) of ferrocene (1), decamethylferrocene (2), decamethylcobaltocene (3), and [[Fe.sup.I][Cp.sup.*]([η.sub.6]-[C.sub.6][Me.sub.6])] (4) ([Cp.sup.*] = [η.sup.5]-[C.sub.5][Me.sub.5]) in DMF, C[H.sub.3]CN, THE DME, C[H.sub.2][Cl.sub.2], and DMSO were recorded vs. the saturated calomel electrode (SCE), showing that the [E.sub.1/2] value of 1 was more solvent dependent than those of 2-4, and that the difference in [E.sub.1/2] values among 2-4 was solvent independent, unlike those found between 1 and 2-4. This shows that 2-4 are much more reliable internal references for determining redox potentials than 1, but using data from this article, one can convert the literature values reported vs. 1 into values vs. 2, 3, or 4. The electrochemistry of 1 and 2 is all the more inhibited by polyamine dendrimers as the dendrimer generation is higher. On the other hand, ferrocenes or other iron sandwich compounds containing hydroxy groups can reestablish reversible cyclic voltammograms. It is shown, using a tetra(ferrocenylmethylamine), that this phenomenon is due to hydrogen bonding between the amido and phenol groups rather than bonding of hydroxy groups to the electrode surface. Key words: ferrocene, reference, electrochemistry, metallocene, sandwich complex, iron, dendrimer, passivation, hydrogen bond. Utilisant une electrode de calomel saturee (ECS) et operant dans le DMF, le C[H.sub.3]CN, le THF, le DME, le C[H.sub.2][Cl.sub.2] et de DMSO, on a mesure les potentiels redox ([E.sub.1/2]) du ferrocene (1), du decamethyl ferrocene (2), du decamethylcobaltocene (3) et du [[Fe.sup.I][Cp.sup.*]([η.sup.6]-[C.sub.6][Me.sub.6])] (4) ([Cp.sup.*] = [η.sup.5]-[C.sub.5][Me.sub.5]). Les resultats obtenus montrent que la valeur [E.sub.1/2] du compose 1 est plus influencee par le solvant que celles des composes 2-4 et que la difference entre les valeurs de [E.sub.1/2] entre les composes 2-4 est independante du solvant, ce qui n'est pas le cas pour celles observees entre le compose 1 et les composes 2-4. Ces observations montrent que, par comparaison avec le compose 1, les composes 2-4 sont des references internes beaucoup plus fiables pour determiner les potentiels redox. Il est toutefois possible, en utilisant les donnees de cet article, de convertir les valeurs obtenues par rapport a la reference 1 et rapportees anterieurement dans la litterature en valeurs par rapport aux references 2, 3 ou 4. L'electrochimie des composes 1 et 2 est d'autant plus inhibee par les dendrimeres polyamides que la generation de dendrimere est elevee. Par ailleurs, les ferrocenes et les autres composes sandwichs contenant des groupes hydroxyles peuvent retablir les voltamperogrammes cycliques reversibles. On a demontre, a l'aide de tetra(ferrocenylmethylamine), que ce phenomene est du a une liaison hydrogene entre les groupes amido et phenol plutot qu'a une liaison des groupes hydroxyles a la surface de l'electrode. Mots cles : ferrocene, reference, electrochimie, metallocene, complexe sandwich, fer, dendrimere, passivation, liaison hydrogene. [Traduit par la Redaction], Introduction The determination of standard redox potentials of compounds is a 'Holy Graal' in electrochemistry. The average of the cathodic and anodic peak potentials ([E.sub.1/2] = ([E.sub.pa] + [E.sub.pc])/2) in [...]

Large dendrimers are synthesized using a tripodal branching unit that multiplies the branch number by 3 at each generation up to a diameter of 13 nm. Thus, the feasibility of the synthesis of giant dendrimers, far beyond the dense-packing limit opens a new scope of supramolecular chemistry involving dendritic structures.

Tri-and nonaferrocenyl thiol dendrons have been synthesized and used to assemble dendronized gold nanoparticles either by the ligand-substitution method from dodecanethiolate-gold nanoparticles (AB(sub 3) units) or Brust-type direct synthesis from a 1:1 mixture of dodecanethiol and dendronized thiol (AB(sub 9) units). The fabrication of modified electrodes is very successful only with the dendronized nanoparticles that contain the triamidoferrocenyl and nonaferrocenyl dendrons.

The stereoelectronic effects of Cp permethylactin and Cp acetylation are quite significant. Results emphasize the crucial role for recognition by the amidoferrocenium form of the H-bonding.

This review focuses on the field of dendrimers and their catalytic applications which spreads into different areas of inorganic, organic, materials, polymer and biological chemistry. The results obtained in this area have been analyzed and discussed.

Research demonstrates the syntheses of the 24-nitrile dendrimers and the octaferrocene compounds using polychlorocarbonylated compounds, such as octachlorocarbonyl derivative, with amines. Data indicate that the chlorocarbonylation of di-, hexa, and octabenzyl cores is a remarkable regiospecific reaction.

An extremely sensitive 17e complex is synthesized using either any of two neutral precursors by one-electron oxidation using (FeIIICp2)+PF6-. The complex is characterized using elemental analysis, ESR and Mossbauer spectroscopic techniques. It is also characterized by its one-electron reduction to an isostructural FeII complex using another electron-reservoir complex.

An added salt shapes the behavior of an ion pair in a chemical reaction, whether it is an electron transfer (ET) process or an electrophilic/ nucleophilic one. Depending on the solvent's polarity, the nature of interacting ions and the dissociation kinetics of the geminate ions, the new ions affect the extent and selectivity of the reaction. This is specially true with contact ion pairs found in low dielectric constant solvents, where they act as catalysts. Of special interest is their effect on photolytic ET reactions, which may find application in energy storage devices.

Water-soluble arene-cored 'clicked' and non-'clicked' dendrimers terminated by 27, 81 and 243 triethyleneglycol (TEG) tethers are prepared and have formed dendrimer-encapculated gold nanoparticles (DEAuNPs) and dendrimer-stabilized gold nanoparticles (DSAuNPs). The active role of the 'clicked' traizole rings, dendrimer generation, stoichiometry of Au precursor and nature of the reductant and of the solvent are delineated, which has led to DSAuNPs with the G0 dendrimer and smaller DEAuNPs with the G1 and G2 dendrimers.

The article discusses a new visisble-light photolysis approach, which can be used for the simple synthesis of the various functional mono- and biferrocenes.

A series of large glycodendrimers containing 27, 81, and 243 terminal modified xylose branches from the first ([G.sub.1]-27) to the third generation ([G.sub.3]-243) are prepared from 2E-azidoethyl 2,3,4-tri-O-acetyl-[beta]-D-xylopyranoside and alkynyl-terminated dendrimers by ' click' chemistry, which is used to obtain large glycodendrimers. The size progression in the series is shown by using both DOSY NMR and size exclusion chromatography (SEC) and the size measured by dynamic light scattering for the dendrimer [G.sub.3]-243 is close to that obtained by the DOSY NMR method.

Redox-active ferrocenyl-terminated dendrimers were used to design and construct robust and active interfaces exhibiting the inherent properties of the dendrimers that are preserved. The experimental findings demonstrated that the fast and efficient charge-transfer communication between the dendrimers inside the layer is influenced by the dendrimer generation.

A study of the movement of electrons around the peripheries of dendrimers and between their redox termini and electrodes through analysis of the electrochemistry of dendrimers presenting metallocenes (and other transition metal sandwich complexes) as terminal groups is presented. The observations and conclusions of the study are discussed.

X-ray structural and [super 1]H NMR studies of mono-, bis- and tris-1,2,3-ferrocenyltriazoles formed by 'click' reactions of ethynylferrocene with azido derivatives and reversible coordination to M[Cl.sub.2] in dimethylsulfoxide (DMSO) (where M = Pd, Pt) is reported. The results provide insights into the fragility of the ligand binding related to the steric effect of the disubstituted [Pd.sup.II] complex for which equilibrium are observed between the DMSO, nitriles, and triazole ligands.

A singe-step synthesis involving visible-light photolysis of the complex [CpFe([[eta].sup.6]-toluene)][P[F.sub.6]] was used to obtain multinuclear and dendritic iron-nitrile piano-stool cationic complexes. The piano-stool iron complexes and dendrimers are robust and present high stability to air and moisture and showed single fully reversible redox waves in CV except for the para-substituted dinitrilediiron complex.

The standard electron-reservoir complex can be conveniently used with air to deprotonate weak acids, via the intermediacy of superoxide radical anion [O.sub.2.sup..-). This is exemplified with the deprotonation of imidazolium salts, generating N-heterocyclic (NHC) carbenes.

Two families of five metallodendrimers are assembled by hydrogen bonding between primary amino groups of DSM dendrimers and the OH group of phenol dendrons. These supramolecular ferrocenyl dendrimers disclose the classic single reversible ferrocenyl/ferrocenium wave in cyclic voltammetry due to the weakness of electrostatic factor.

A variety of structures, properties, and applications of gold nanoparticles are described. They are assembly, supramolecular chemistry, quantum-size-related properties, and their applications toward biology, catalysis, and nanotechnology.

The recognition of anions such as H2PO4- is of interest in the biological and environmental contexts and is investigated using a variety of endoreceptors while the recognition of small anions using metallodendrimers and gold nanoparticles as exoreceptors. Because topological effects were found to be essential factors in studies, assembling redox-active metallodendrimes by multiple H-bonding to possibly benefit from positive dendritic effects was envisaged.

Research into the catalysis of metallodendrimers, using the electron-reservoir complex [Fe(I)Cp(C6Me6)], is described.

The synthesis of large dendrimers through a one-pot organoiron-mediated reaction involving eight successive steps of four different kinds was investigated. The organoiron synthesis resulted in a new tripodal dendron. The new dendron was observed to have a synthetic potential for the fast divergent and convergent syntheses of polyallyl dendrons and dendrimers. Moreover, the convergent synthesis of the nona-allyl dendron was successfully achieved by the reaction of a free phenol derivative with the tri-iodalkyl derivative.

Experimentation in the use of the benzylic C-H activation system to attach redox catalysts onto star molecules and dimers led to a triple C-H/N-H activation under ambient conditions. The reaction led to heterobifunctionalization of the catalyst and both its solubilization in water and its attachment to star molecules without loss of catalytic activity. The chemistry of the reaction suggests further applications of the concept of electron reservoirs in redox catalysts.

The synthesis of ferrocene dendrimers and the dendritic effect for the recognition of small inorganic ions were studied. Monitoring the titration of ferrocene dendrimer using cyclic voltammetry (CV) is better than H nuclear magnetic resonance. The dendritic effect refers to the ability of a dendrimer to gain good recognition of anions and sensing by CV as the dendritic generation increases. The highest soluble generation has the best effect and selectivity because it creates the largest open cavities.

A special salt effect in which intramolecular electron transfer (ET) between the two iron redox centers of the fulvalene-bridged diradical is induced by Na+ upon ligand exchange is reported. Moreover, the ET reaction can be switched to intermolecular ET by controlling the donicity of the incoming ligand. To illustrate the application of this finding, electronic communication between the two metal centers mediated by across a delocalized hydrocarbon ligand was induced and modulated.