Dendritic Polymer Applications Catalysts

Utrecht University, Debye Institute, Utrecht, The Netherlands 

Metallodendrimers can be constructed via binding of groups with suitable donor atoms (e.g., polydentate ligands) on either the periphery or the core of the dendrimer and the subsequent complexation/coordination of these ligands to an appropriate metal salt. Ultimately, this binding can involve the formation of a direct a bond linkage (i.e., a M-C bond). This chapter describes various 

Dendrimers and Other Dendritic Polymers. Edited by Jean M. J. Frechet and Donald A. Tomalia 2001 John Wiley Sons Ltd 

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Kleij AW, Klein Gebbink RJM, van Koten G (2002) Dendritic polymer application catalysts. In Frechet J, Tomalia D (eds) Dendrimers and other dendritic polymers. Wiley, New York... 

Whether dendritic catalysis can compete successfully in commercial applications with other strategies that allow recycling of the catalyst remains to be seen. Dendrimer supports are still relatively expensive, but for applications that do not require the well-defined structure of the dendrimer support, hy-perbranched polymers can offer a cheaper alternative. A recent novel strategy in this research area that might provide the added value required to make the step towards commercial applications involves the noncovalent functionalization of dendritic support with catalysts (Fig. 1). This offers several advantages above the traditional covalent approaches. In this chapter we will review the progress in the area of supramolecular dendritic catalysis. 

Dendritic polymers can be covalently functionalized with organometallic complexes to obtain a dendritic catalyst with molecularly defined catalytic sites [5-7]. Moreover, a considerable number of reports on the applicability of functionalized dendrimers in catalysis have led to the idea of a dendritic effect on the catalyst activity/selectivity, which can either be positive or... 

Another application of hyperbranched polymers as supports for catalysts is their use as backbones for the covalent attachment of organometallic fragments. NCN-pincer complexes (NCN-pincer = 2,6-bis[(dimethylamino)-methyl] phenyl anion) are attractive building blocks for catalytic reactions [20,21], Covalent introduction of the transition-metal complexes can also be of interest for visualization and imaging of dendritic polymers by transmission electron microscopy (TEM). 

The book also covers the solution properties of the regular star polymers. This class of materials has been known for many years to polymer chemists however, rapid development has occurred only ce tiie proposal of the idea of dendritic polymers in the mid-1980s. The characteristics of tiie polymers discussed here include the size and shape of the molecules, their biological activities, their low viscosity in solution, their substrate-holding properties inside the molecule, etc. The unique properties of these polymers attract many chemists, not only in polymer chemistiy but also in organic chemistry, biochemistry, medicine, oiganometaUic chemistry, catalyst chemistry, and so on, for these new materials are e q)ected to find applications in many... 

The structural perfection of a dendritic support is not required for every application in catalysis, and hyperbranched polymers provide interesting and cheap alternatives as catalyst supports [37]. These hyperbranched polymers are obtained from a simple one-pot synthesis, yielding globular polymeric structures with broad weight distributions compared to their dendritic analogues. 

As cheaper and readily accessible alternatives to regular dendrimers, hyper-branched polymers are increasingly being used as catalyst platforms. Rainer Haag has been one of the leaders in this field. He and C. Hajji provide an overview of an area for which commercial applications are most likely. Finally, all of these catalysis-related topics are complemented by a review of metallo-dendritic exoreceptors for the redox recognition of oxo-anions and halides, written by D. Astruc. This field offers new perspectives both for catalytic transformation and the development of molecular sensors. 

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