Cored dendrimer, synthesis

Ionic interactions have been used to prepare lanthanide-core dendrimers. This has been achieved using a convergent synthesis, in which polyether den-drons with a carboxylic acid group at the focal point were assembled around a lanathanide cation. This involved a metathetical reaction with compounds such as Er(OAc)3, Tb(OAc)3 or Eu(OAc)3 to introduce the appropriate lanthanide ion. 

This chapter shows that the synthetic and analytical problems associated with the synthesis of the title dendrimers are not outrageously more complex than for small core dendrimers and that the difficulties can be overcome. It draws a comprehensive picture of what has been done in the field of dendrimers with polymeric cores putting emphasis first on synthetic issues and then on experiments investigating the aggregation behavior of these intruiging macromolecules both in the solid state and on surfaces. Finally, experiments will be described which show that some of these dendrimers can be considered cylindrical molecular objects. The macromolecules treated in this chapter may be... 

Each step in dendrimer synthesis occurs independent of the other steps therefore, a dendrimer can take on the characteristics defined by the chemical properties of the monomers used to construct it. Dendrimers thus can have almost limitless properties depending on the methods and materials used for their synthesis. Characteristics can include hydrophilic or hydrophobic regions, the presence of functional groups or reactive groups, metal chelating properties, core/shell dissimilarity, electrical conductivity, hemispherical divergence, biospecific affinity, photoactivity, or the dendrimers can be selectively cleavable at particular points within their structure. 

S-C Lo, EB Namdas, PL Burn, and IDW Samuel, Synthesis and properties of highly efficient electroluminescent green phosphorescent iridium cored dendrimers, Macromolecules, 36 9721-9730, 2003. 

Meijer and co-workers also used a divergent dendrimer synthesis to prepare AB diblock structures (Figure 7.13B) in which the polystyrene linear block is used to initiate growth of the polypropylene imine) dendritic block [45], An amino end group had to be introduced in the polystyrene as a core for subsequent growth of the dendritic fragment via an iterative protocol of sequential... 

Figure 3.13 Synthesis of gold nanoparticle-cored dendrimers using Frechet-type dendrons.

It should be re-stated and emphasized that dendrimers are large collections of atoms that are systematically organized around a reference point (core) by means of branched connectivity (usually covalent). As such, the synthetic strategies leading to the construction (Aufbau) of these molecular assemblies can be examined and experimentally manipulated. We described earlier the Aufbau steps leading to dendrimer synthesis which include the following stages ... 

Finally, a two stage dendrimer synthesis [117] was demonstrated by preconstructing a lower generation dendrimer using the convergent dendron/diver-gent anchor method as shown in Scheme 13. Secondly, coupling pre-formed dendrons to this multi-valent hyperbranched/dendrimer core produced a... 

Alternatively, initiator cores have been tethered to solid support (Merrifield resins [83]). Using protein synthesis procedures that avoid the workup difficulties involved in handling large excesses of reagents, one can readily control dendrimer growth. Unfortunately, only noncleavable linkers have been examined to date with these PAMAM dendrimers. The use of initiator cores possessing cleavable linkers should make dendrimer synthesis and isolation very facile. This was demonstrated for mono-dendrons derived from poly(lysines) as reported by Tam et al. [105-107] (Fig. 26). 

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