Dendritic host molecule

Inclusion of guest species in dendritic host molecules 6.2.3.1 Dendrimers with multiple receptor units... 

The possibilities for encapsulating guest molecules in dendritic hosts were first proposed by Maciejewski in 1982 [143], In 1990, Tomalia presented evidence for unimolecular encapsulation of guest molecules in dendrimers and pointed out that it was one of the possible future research areas in dendrimer chemistry [164],... 

The field in which the interaction between the dendritic host and the guest molecule(s) can be classified as electrostatic is very elaborate and therefore the focus in this section will be on the interaction of organic acids with dendrimers. 

While the previous sections have largely addressed variation of the dendrimer periphery by covalent transfunctionalisation, an alternative concept is based on modification of the dendrimer surface by non-covalent interactions [18]. Selective interactions of guest molecules with dendritic hosts depend upon the nature of both the dendrimer core and the dendrimer shell. 

A light-controlled dendritic box was investigated in analogous fourth-generation POPAM dendrimers whose periphery alternately bore azobenzene and naphthyl moieties. Measurements of photoisomerisation at a wavelength of 365 nm in dichloromethane showed that not all azobenzene units in the E form are transformed into the Z form, but that, for example, four units remain in the E form and some 28 units isomerise to the Z form. At pH 7, six eosin molecules per host molecule were taken up by this mixture of isomers. On the other hand, the dendrimer having all azobenzene groups in the E form takes... 

Huskens et al. exploited host-guest interactions between dendritic guest molecules and CD-modified nanoparticles for the formation of organic/metal nanoparticle multilayers on a PDMS stamp (Fig. 13.15).88 The multilayer stacks were transferred to a complementary host surface, while no materials remained on the protruding areas of the PDMS stamp. These multilayers showed a well-defined thickness control of 2 nm per bilayer. 

Supramolecular hyperbranched polymers have been developed that utilize molecular recognition to facilitate selective binding of a guest molecule or molecules by a (dendritic) host or self-assembly that involves numerous weak noncovalent interactions to generate large functional assemblies. Examples of both these classes of supramolecular hyperbranched polymers are examined in the following sections. 

Rose Bengal and 8-10 molecules of p-nitrobenzoic acid could be encapsulated in each dendritic host. To achieve selective liberation of p-nitrobenzoic acid, the dendritic box was penetrated by hydrolysis of the iBOC and dialysis of the reaction mixture. In this way aU p-nitrobenzoic acids were dissolved in the mixture while guests Rose Bengal remained encapsulated. Hydrolysis of the outer shell released Rose Bengal after dialysis [25],... 

Dendrimers ([3] dendrimers and other dendritic polymers [4]) are repeatedly branched molecules that can contain selected functional groups in predetermined sites of their multiarmed structure. In spite of their large structures, that usually make dendrimers attractive as host molecules, suitably designed dendrimers can be involved as guests in molecular recognition phenomena (for some recent examples, see [5-12]). In such cases, the host species does not interact with the whole... 

Baars MWPL, Meijer EW (2000) Host-Guest Chemistry of Dendritic Molecules. 210 131-182 Balczewski P, see Mikoloajczyk M (2003) 223 161-214 Ballauff M (2001) Structure of Dendrimers in Dilute Solution. 212 177-194 Baltzer L (1999) Functionalization and Properties of Designed Folded Polypeptides. 202 39-76 Balzani V, Ceroni P, Maestri M, Saudan C, Vicinelli V (2003) Luminescent Dendrimers. Recent Advances. 228 159-191 Barre L, see Lasne M-C (2002) 222 201-258 Bartlett RJ, see Sun J-Q (1999) 203 121-145... 

Because of their proximity, the various functional groups of a dendrimer may easily interact with one another. Interaction can also occur between dendrimer units and molecules hosted in the dendritic cavities or associated to the dendrimer surface. 

Quantitative analysis of the results obtained has shown that a single eosin guest is sufficient to completely quench the fluorescence of any excited dansyl unit of the hosting dendrimer. Fluorescence lifetime measurements indicated that the dye molecules can occupy two different sites (or two families of substantially different sites) in the interior of the dendritic structure. 

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