Silicon-based dendrimers

Perrier RJ (2001) Direct Conversion of 5,6-Unsaturated Hexopyranosyl Compounds to Functionalized Glycohexanones. 215 277-291 Frey H, Schlenk C (2000) Silicon-Based Dendrimers. 210 69-129 Forster S (2003) Amphiphilic Block Copolymers for Templating Applications. 226 1-28 Frullano L, Rohovec J, Peters JA, Geraldes CFGC (2002) Structures of MRI Contrast Agents in Solution. 221 25-60... 

Ferrier RJ (2001) Direct Conversion of 5,6-Unsaturated Hexopyranosyl Compounds to Functionalized Glycohexanones. 215 277-291 Frey H, Schlenk C (2000) Silicon-Based Dendrimers. 210 69-129... 

Son, D. Y. Silicon-Based Dendrimers and Hyperbranched Polymers. In Chemistry of Organic Silicon Compounds-, Rappoport, Z., Apeloig, Y., Eds. Wiley Chichester, 2001 Vol. 3, pp 745-803. 

C. Organotransition Metal Silicon-Based Dendrimers Exhibiting... 

This review summarizes pioneering relevant works of expert groups on oiganomet-allic dendritic mactomolecules, together with our initial effmts in this developing field. Throughout the chapter, the synthetic aspects are especially emphasized. Likewise, we describe in detail the redox properties exhibited by a new family of silicon-based ferrocenyl-containing dendrimers and we also mention some of their relevant applications. 

On the basis of the results described here, extension of these syntheses to higher generations, as well as work aimed at more detailed studies with respect to the electrochemical properties and valuable applications of these silicon-based ferro-cenyl dendrimers, clearly represent interesting areas of future research. 

Scheme 3. Synthesis of phenyl-terminated silicon-based dendrimers and functionalization of the branches with Cr(CO)j units.

Scheme 12. Construction of silicon-based dendrimers using ferrocenyl-containing dendrons.

Silicon-based dendrimers 8 and 9 (Fc = ferrocenyl) also showed oxidative precipitation onto electrodes to give idealized electrochemistry as films.181 Specifically, the peak current was linear with scan rate and the potential difference between the anodic and cathodic waves was small (AE = 10 mV at a scan rate of 100 mV/s).182 This latter observation indicated that the rate of electron transfer was rapid. For molecule 9, the surface coverage was measured as = 2 x 10 10 mol/cm2. These molecules were also explored as mediators in amperometric biosensors.183 In contrast, molecule 10 showed two redox peaks, indicative of interaction between the two ferrocenyl units at each peripheral site. 181 When oxidation of one of the two interacting redox units results in some electron sharing between the two units (Robin-Day class II mixed valence species), the second oxidation is naturally... 

As shown below in Section 4.1.9 (silicon-based dendrimers), there are meanwhile many examples of carbohydrate-coated dendrimers (glycodendrimers) [48], not least because these terminal groups confer better solubility upon the molecules because they are, so-to-speak, sugar coated . 

Van Koten et al. successfully prepared silicon-based dendrimers with a polyca-tionic branching shell. The dendrimer type shown in Fig. 4.37 consists of a non-polar core (tetraarylsilane) bearing an ionic layer which, in turn, is surrounded by a less polar polyether shell [67]. Such dendrimers are predestined for potential inclusion of anionic guests - with anion exchange - in the positively charged host scaffold. 

Siloxanes, prepared in 1989 as representatives of silicon-based dendritic molecules ( silicodendrimers ), were the first dendrimers to contain heteroatoms other than the usual ones (N, O, S, halogens) [68]. As with the phosphodendri-mers (Section 4.1.10), their readily modifiable architecture and their pronounced thermostability hold promise of applications, for example, in the form of carbo-silanes as liquid-crystalline materials and catalyst supports. They can be subdivided into a number of basic types and their properties are presented below with the aid of characteristic representatives ... 

Repetitive silicon-based transformations were then employed for dendritic construction. Palladium-catalyzed silane hydroxylation of the core 71 afforded triol 73, which was then treated with three equivalents of monochloropolysiloxane 72 to generate the hexa-hydrido, first generation dendrimer 74. Further application of the Pd-mediated hydroxylation, followed by attachment of monochloro-monomer 72, led to the second (75) and third (76) generation polysiloxane cascades. 

Tonic Dendrimers and Related Materials [R. Engel, Chapt. 3, pp. 73-99]. Silicon-based Stars, Dendrimers, and Hyperbranched Polymers [L. J. Mathias, T. W. Carothers, Chapt. 4, pp. 101-121]. 

In this review, complete coverage of the syntheses and applications of silicon-based dendrimers and hyperbranched polymers will be provided. For organizational purposes, dendrimers and hyperbranched polymers will be reviewed in separate sections, and each section will be further divided according to polymer class. For this review, the various classes will be defined according to the branch backbone substituents as follows ... 

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