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Structure of dendrimers and dendrons

Dendrimers (from the Greek dendron - the tree) are chemical compounds whose structure is branched out from a branching core like a tree . Dendrimers consist of branches of repeating units, thus resulting in a radial symmetry . Assuming a core, these must contain branches, otherwise a chain is created. There can be a branch to two or more connection points. Since dendrimers are monodisperse due to their clearly defined structure , they belong to the cascade polymers and thus differ from the other polymers . The branches are built up in layers called generations. When viewed in cross-section, the comparison of the tree can be made, this time with its annual rings . A dendrimer always consists of a core to which dendrons are attached. Dendrons are regularly branched macromolecules.

Donald Tomalia is one of the pioneers in dendrimer development .

Synthesis strategies

Divergent synthesis

The divergent synthesis of dendrimers begins with a core with n binding sites to which n units are bound. To prevent the units from polymerizing, they each contain only one active group, which forms the new bond. The functional groups that are to serve as new binding sites in the second synthesis step must therefore first be protected or masked and only activated after the first synthesis step. In summary, in the divergent synthesis, the dendrimers grow step by step from the core to the periphery.

Convergent synthesis

In convergent synthesis, the dendrons are first synthesized from the periphery to their attachment point and then attached to the core. Here, units are required that have several functional groups with the same reactivity and one protected or masked group. This method has the decisive advantage that defective dendrimers can easily be separated from the desired ones, since in this case a defective dendrimer differs from the desired one by a whole dendron. In divergent synthesis it happens that only a single group is missing in the periphery, such a dendrimer then does not differ from the desired ones due to its polarity, size or shape and therefore cannot be removed (by chromatography or similar). .

An example to illustrate this

Has the initiator core z. B. three reactive groups and you get a branching to two new reactive groups through a synthesis sequence, you get six reactive groups in the first step (generation 0) . In the next generation there are already twelve etc.

An exponential growth of the terminal groups is therefore observed . This leads to very large, complex molecules in just a few synthetic steps. These cannot be arbitrarily large because the packing of the terminal groups is becoming increasingly dense. The macroscopic structure approaches a sphere .

The use of dendrimers is based on the one hand on the multiple functionalization of the surface and on the other hand on the possibility of using the different chemical surroundings of the interior, which leads to molecular capsules.


  • Hans-Bernhard Mekelburger, Wilfried Jaworek, Fritz Vögtle: Dendrimers, Arboroles and Cascade Molecules: The start of new materials every generation. In: Angewandte Chemie. 104, 12, 1992, pp. 1609-1614, doi : 10.1002 / ange.19921041206 .
  • Donald Tomalia, H. Durst: Genealogically directed synthesis: Starburst / cascade dendrimers and hyperbranched structures. In: Topics in Current Chemistry. 1993, pp. 193-313, doi : 10.1007 / BFb0111285 .
  • Donald A. Tomalia, Adel M. Naylor, William A. Goddard III: Starburst dendrimers: control of size, shape, surface chemistry, topology and flexibility in the transition from atoms to macroscopic matter. In: Angewandte Chemie. 102, 2, 1990, pp. 119-157, doi : 10.1002 / anie.19901020204 .
  • Jörg Issberner, Rolf Moors, Fritz Vögtle: Dendrimers: from generations to functionalities and functions . In: Angewandte Chemie. 106, 23-24, 1994, pp. 2507-2514, doi : 10.1002 / anie.19941062308 .
  • Marco Fischer, Fritz Vögtle : Dendrimers: from design to application - a progress report . In: Angewandte Chemie. 111, 7, 1999, pp. 934-955, doi : 10.1002 / (SICI) 1521-3757 (19990401) 111: 7 <934 :: AID-ANGE934> 3.0.CO; 2-4 .