Guest 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. 

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],... 

Very recently, a novel and versatile method has been reported for the construction of stable, zero-valent metal quantum dots, using dendrimers as well-defined nano-template/containers. The concept involves the use of dendrimers as hosts to preorganize small molecules or metal ions, followed by a simple in situ reaction, which immobilizes and incarcerates these nanodomains (Figure 17) [89]. The size, shape, size distribution, and surface functionality of the dendritic nanocomposites are determined and controlled by the architecture. Dendrimer-based nanocomposites display unique physical and chemical properties as a consequence of the atomic/molecular level interactions between the guest and host components within the dendrimer as well as the dendrimer interaction with various solvents and media. 

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... 

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. 

Baars MWPL, Meijer EW (2000) Host-Guest Chemistry of Dendritic Molecules. 210 131-182 Balazs G, Johnson BP, Scheer M (2003) Complexes with a Metal-Phosphorus Triple Bond. 232 1-23... 

In 1994 we published the first chiral dendrimers built from chiral cores and achiral branches [ 1,89], see for instance dendrimer 57 with a core from hydroxy-butanoic acid and diphenyl-acetaldehyde and with twelve nitro-groups at the periphery (Fig. 21). As had already been observed with starburst dendrimers, compound 57 formed stable clathrates with many polar solvent molecules, and it could actually only be isolated and characterized as a complex [2 (57- EtO-Ac (8 H20))]. Because no enantioselective guest-host complex formation could be found, and since compounds of type 57 were poorly soluble, and could thus not be easily handled, we have moved on and developed other systems to investigate how the chirality of the core might be influencing the structure of achiral dendritic elongation units. 

Figure 16.14 To investigate hydrogen bonding in dendrimers Zimmerman and Moore [187] prepared dendritic wedges (A-B = CH20 or C=C) functionalized with anthypyridine units at the focal point that function as hosts for benzamidinium guest molecules...

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