Supramolecular dendrimers

Dendrimers can be constructed from chemical species other than purely organic monomers. For example, they can be built up from metal branching centres such as ruthenium or osmium with multidentate ligands. The resulting molecules are known as metallodendrimers. Such molecules can retain their structure by a variety of mechanisms, including complexation, hydrogen bonding and ionic interactions. 

Generation Relative molar mass Number of NH terminal groups 

An example of this type of dendrimer is the polynuclear species that can be prepared from 2,3-bis(2-pyridyl)pyrazine as bridging ligands, bipyridines as terminal bgands, and either Ru(II) or Os(II) as the metal centre. 

Polynuclear dendrimer complexes of this type can undergo redox reactions at the metal centre and have luminescent properties. They have been proposed as molecular photochemical devices, although no practical examples have yet been produced. 

Co-ordination chemistry is not the only possible approach to the successful preparation of supramolecular dendrimers. Other examples include hydrogen-bonded dendrimers, which have been prepared using tetracar-boxylic acid moieties as the linking species, and others have been prepared where the hydrogen bonds were developed using melamine and cyanuric acid at the focal point (i.e. the point towards which convergent synthesis is directed). 

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Smith DK, Diederich F (2000) Supramolecular Dendrimer Chemistry - A Journey Through the Branched Architecture. 210 183-227 Stec WJ, see Guga P (2002) 220 169-200 Steudel R (2003) Aqueous Sulfur Sols. 230 153-166 Steudel R (2003) Liquid Sulfur. 230 80-116... 

Percec, V. et al. Synthesis and retrostructural analysis of hbraries of AB3 and constitutional isomeric AB2 phenyl propyl ether-based supramolecular dendrimers, J. Am. Chem. Soc., 128, 3324, 2005. 

Percec, V., Cho, W.D., Mosier, P.E., Ungar, G., and Yeardley, D.J.P. (1998) Structural analysis of cylindrical and spherical supramolecular dendrimers quantifies the concept of monodendron shape control by generation number./. Am. Chem. Soc. 120, 11061-11070. 

Fig. 6a,b. Height micrographs obtained by tapping mode SFM from monolayers of a spherical b cylindrical molecules adsorbed on mica [84]. Top self-assembly of monodendron side groups into spherical and cylindrical supramolecular dendrimers. The process depends on the degree of polymerization of the polystyrene main chain... 

Percec V, Cho WD, Ungar G. Increasing the diameter of cylindrical and spherical supramolecular dendrimers by decreasing the solid angle of their monodendrons via periphery functionalization. J Am Chem Soc 2000 122 10273-10281. 

Further supramolecular dendrimer syntheses and syntheses of dendrimers with metal complex or polyglycerol structure will be found in the literature [45, 39b]. 

Fig. 6.11 Su pramolecular self-assembly of supramolecular dendrimers (according to Hirsch et al.)...

Cook, A. G., Baumeister, U., Tschierske, C., Supramolecular dendrimers Unusual mesophases of ionic liquid crystals derived from protonation of DAB dendrimers with facial amphiphilic carboxylic acids. J. Mater. Chem. 2005, 15, 1708-1721. 

Figure 14.9 (a) Supramolecular dendrimer based on L-lysine derived dendrons assembled by an... 

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