Redox metallodendrimers

Thus, these giant redox metallodendrimers exhibit a breathing mechanism controlled by the redox potential. 

Covalent coupling A pre-existing metal complex is coupled covalently with den-drons and is thus surrounded by a dendritic shell. Appropriate examples are the redox-active metallodendrimers of Kaifer et al. [117] or the dendritic porphyrin/ metal complexes prepared and characterised by Diederich et al. [118] and Aida et al. [119]. 

In another study also, electrochemical impedance technique has been shown to be a useful method for a DNA biosensor using a multinuclear nickel(II) salicylaldimine metallodendrimer platform [164], Both the preparation of the dendrimer-modified GCE surface and the immobilization of DNA have been effectively done by simple drop-coating procedures. The metallodendrimer is electroactive exhibiting two redox couples in phosphate buffer solution. The impedance study demonstrated that the DNA biosensor responded well to 5 nM of target DNA by displaying a decrease in charge transfer resistance in phosphate buffer solution and increase in charge transfer resistance in the presence of the [Fe(CN)6]3/4" redox probe. 

Star and dendrimer core molecules were prepared by the peralkylation or allylation of cyclopentadienyliron complexes containing methyl-substituted arenes.298,301,302,304-311,333 The preparation of water-soluble metallodendrimers containing six cationic cyclopentadienyliron moieties, 281, has also been reported.301 Dendrimer 281 was tested for potential use as a redox catalyst for the cationic reduction of nitrates and nitrites to ammonia. 

Metallodendrimers have attracted widespread interest for various sensing applications, such as ion detection, gas sensing, and redox-active switches, because of their polyvalent characteristics.220 Several recent examples of successful sensors using the metallodendrimers have appeared. 

METALLODENDRIMERS WITH REDOX-STABLE METALLOCENE TERMINALS 451... 

B. Anion Recognition by Metallodendrimers Assembled by Hydrogen Bonding Between a Redox-Active Dendronic Phenol and Dendritic Primary Amines... 

For the formation of metallodendrimers of precise nature, a second favorable position in the overall structure for complexation can obviously be at the periphery. Excellent examples of such systems have been reported that include a silicon dendrimer decorated with 243 ferrocenyl units at the periphery with stable redox activity [58]. Catalytic activity of dendrimers with metals located at the periphery has also proven to be of great interest as it has been recently reviewed by several authors [59,60]. Placing photoactive centers at this specific location can nonetheless be more intricate in this case, as demonstrated by the limited number of reported examples. 

Metallodendrimers that contain peripheral ferrocene groups have been prepared by means of a variety of different methodologies. From tetraallylsilane as the initiator core, novel silane dendrimers (e.g., 229), in which reactive Si-Gl end groups are present, were constructed. The reaction with lithioferrocene or / -aminoethylferrocene afforded the corresponding tetraferrocenyl dendrimers 230 and 231 that represented the first examples of well-defined and well-characterized, redox-active macromolecules of this type (Scheme 21). ... 

Cyclic voltammetric studies of these metallodendrimers showed one reversible oxidation wave characteristic of independent, non-interacting redox centers. Also, the use of these materials for modification of electrode surfaces was... 

Cyclic voltammetric studies of these metallodendrimers showed one reversible oxidation wave, characteristic of independent, non-interacting redox centers. Also, the use of these materials for the modification of electrode surfaces was explored [37-39]. The researchers found that platinum, glass, and carbon-disk electrodes modified by electrodeposited films of these dendrimers are extremely durable and reproducible, with no detected loss of electroactivity even after their use in different electrolyte solutions or after standing for long periods in air. Studies on the thermodynamics and kinetics of adsorption of these redox-active dendrimers onto Pt electrodes by means of electrochemical and electrochemical quartz crystal microbalance techniques were conducted. These showed the adsorption processes to be activation-controlled rather than diffusion-controDed, and to be dependent on... 

Ferrocene dendrimers are also of interest for reasons other than their redox activity. For example, metallodendrimer 8.26 possesses planar chiral ferrocene units that make the bidentate phosphine ligation sites of potential interest for applications in asymmetric catalysis. Indeed, asymmetric hydrogenations of dimethyl ita-conate catalyzed by Rh complexes of 8.26 showed impressive enantiomeric excess values of 98% [47]. 

The synthesis of a water-soluhle metallodendrimer containing six cationic cyclopentadienyliron moieties was also reported (249). This dendrimer was examined as a redox catalyst for the cathodic reduction of nitrates and nitrites to ammonia. Star-shaped polyaromatic ether complexes of cyclopentadienyliron were recently reported hy Ahd-El-Aziz and co-workers (250). These complexes contained up to 15 cationic cyclopentadienyliron moieties pendent to aromatic rings in the star branches (111). Electrochemical analysis of these star polymers showed that the iron centers underwent reversible reduction processes. 

Dendrimers and their Use as Supramolecular Redox Sensors for the Recognition of Small Inorganic Anions, J. Am. Chem. Soc. 119,2588,1997 b) C. Valerio et al. - A Polycationic Metallodendrimer with... 

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