Dendrimers constitute a class of polymers with unique properties and applications resulting from the presence of internal voids and of a large number of functionalities on the surface. The development of a macromolecular chemistry within the cavities of dendrimers is illustrated here. Two examples of construction of six dendrimer units within the cascade structure of a main dendrimer are reported. The preparation of these multidendritic systems involves the regioselective modification of the framework of the central dendrimer to create internal reactive centers, followed by the stepwise synthesis of the six dendritic macromolecules.

The synthesis of dendrimers including PN−PS linkages specifically placed at some generations within the dendrimeric architecture allows the grafting of several types of functional groups at site- and depth-specific locations in the internal layers. The synthesis is carried out up to the fourth generation starting from a difunctional core, or up to the third generation starting from a hexafunctional core. These dendrimers include 2, 6, or 18 PN−PS groups, depending on the type of core and the generation considered. The functional groups are introduced by several types of reactions. First, the strong polarization of the PN−PS linkage induces a facile reactivity with various alkyl triflates such as methyl, allyl, and propargyl triflates, leading to the formation of functionalized phosphonium salts [PNP−S−R]+. The alkylation induces a weakening of the P−S bond which is cleaved with P(NMe2)3, leading to the formation of internal aminophosphite groups [PN−P:]. These highly reactive tricoordinated phosphorus atoms are alkylated by methyl or allyl iodide, leading to a second series of functionalized dendrimers including phosphonium salts at some precise internal layers. A third series of internally functionalized dendrimers is obtained by the Staudinger reaction of functionalized azides with the aminophosphite internal groups. Isothiocyanate, aldehyde, and primary amine derivatives have been grafted regiospecifically in this way [PN−PN−R]. The reactivity of the aldehyde internal functions leading to the grafting of azides or crown-ethers is also described.

The construction of dendritic and polydendritic macromolecules which incorporate PNÀPS, PNÀPNÀPS, and ÀPR 2 ligands in selected generations within the cascade structure is reported. Complexation of these internal units with [AuCl(tht)] allows the regioselective grafting of up to 90 gold atoms in different layers. The X-ray structure of a first-generation dinuclear complex is described.