Dendrimers phosphorus

Keywords Dendrimer, phosphorus, multiplurifunctionalization, complexation, dipole moments. 

Polyether dendrimers, phosphorus-containing dendrimers, and polyurethane dendritic wedges also have been characterized by MALDI-TOF. 

Among all types of dendrimers, phosphorus-containing dendrimers [4] that are dendrimers having one phosphorus atom at each branching point play more and more an important role. In this chapter, we will focus on their use as catalysts, for materials, and in biology. Besides our own work, a few other groups have reported the synthesis of phosphorus-containing dendrimers. We can mentioned in particular the first example of any type of phosphoms dendrimers (poly(phosphonium)... 

Majoral J-P, Caminade A-M (2003) What to do with Phosphorus in Dendrimer Chemistry. 223 111-159... 

What To Do With Phosphorus in Dendrimer Chemistry J.-P. Majoral A.-M. Caminade... 

Divergent Approaches to Phosphorus-Containing Dendrimers and their Functionalization... 

Dubois et al. [184] reported the synthesis of phosphorus based dendrimers terminated with multivalent palladium complexes. Iterative free radical addition... 

Although the first publication on dendrimers appeared in 1978 [ 1 ] it is only in 1990 that the first report on phosphorus-containing dendrimers was published [2] i.e. after numerous papers devoted to the synthesis of organic dendrimers and practically at the same time than the description of a silicon containing dendrimer. 

The aim of this review is to present the state-of-the-art concerning the synthesis and the chemical properties of phosphorus-containing dendrimers with emphasis made on the specificity introduced by phosphorus. 

Most of the methods of synthesis reported above present some limitations and constraints lack of solubility for polycationic phosphorus-containing dendrimers from generation 3 [2], dendrimers of weak molecular weight [4], difficulties to overcome cross Unking reactions [6], possibility only to incorporate phosphorus groups on the surface of dendrimers [3], etc. 

All these drawbacks can be avoided by using a simple and general strategy for the synthesis of neutral phosphorus dendrimers elaborated up to generation 12, in which the core and subsequent branching points are pentavalent phosphorus atoms. 

All the experiments are conducted on aldehyde terminal functions. Depending on the solubility of the resulting phosphorylated dendrimers, anchorage of phosphorus moieties has been carried out on generation 1 (6 phosphate or phosphinite groups) and up to generation 5 [(96 aminophosphate (Fig. 6, Scheme 15), amino phosphite or functionalized phosphonate groups)] [17b]. 

Fig. 6. Dendrimers of generation 5 with 96 various terminal phosphorus groups...

Another specific monosubstitution which does not occur on phosphorus but on the substituents linked to phosphorus consists of a Mannich type reaction between Ph2PCH2OH and dendrimers bearing NH groups in a position relative to the terminal phosphorus atoms (Scheme 22). This reaction only occurs on one of the two NH chain ends, and no disubstitution takes place here [21]. 

At this stage two strategies (one of them outlined in Scheme 37) can be developed to start the construction of dendrimers within the cascade structure of 88-[G3]. Each of them allows the synthesis of six internal dendrimers of generation 4 into the internal voids of 88- [G3]. 31P NMR constitutes an extraordinary and unique tool for monitoring the construction of these controlled polydendritic structures (see Fig. 9 for illustration). Chemical shifts of phosphorus groups are different from one generation to another and the intensities of signals are of... 

Even if only a few methods of synthesis of phosphorus-containing dendrimers are reported up to date, it is clear that these macromolecules now constitute a well known class of polymers whose studies appear to be an emerging field of research. 

The contribution of phosphorus in the area of dendrimer chemistry is essential for many reasons. 

Phosphorus dendrimers are among the largest dendrimers reported till now (generation 12, molecular weight higher than 3 000000). 

A variety of phosphorus cores can be used. These cores can be di-, tri-, tetra-or hexafunctionalized, enhancing the possibilities to prepare dendrimers of various forms at least for the lower generations ( cauliflower , bow-tie , bolaform, ball shaped). 

Phosphorus also permits the postmodification of the backbone of dendrimers. Indeed charges, and also various functional groups, can be selectively introduced into the internal voids. Such a transformation can be performed where and when required. 

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