Dendrimer Host-Guest Chemistry

A novel approach to guest inclusion by dendrimers is the use of molecular imprinting . We will look at molecular imprinted polymers in more detail in Section 14.3. Generally the imprinting technique involves assembly of a covalent polymer - in this case dendrimer - about the target guest which acts 

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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... 

Keywords. Rotaxane dendrimers. Host-guest interaction, Recognition, Self-assembly, Supra-molecular chemistry... 

If the periphery of a POPAM dendrimer bears azobenzene units then dye molecules can be included as guests in the dendrimer scaffold (see also host/ guest chemistry in Section 6.2.3) [23]. Here the E- and Z-isomers (or their enriched versions) differ in their capacity for accommodating guest molecules. In principle, guest molecule inclusion can be controlled (switched) in this way (Fig. 5.21). 

The initial focus in dendrimer research was largely on their synthesis, but recently more importance has been given towards their functional aspects [23]. The successful blending of dendrimer chemistry with several contemporary themes such as host-guest chemistry [24], metallo-organic chemistry [25], luminescent materials [26], catalysis [20a], medicinal chemistry [18d] and polymers [27] has contributed enormously over the years to a rich chemistry with potential applications. As a detailed survey of this area is beyond the scope of this chapter, we will restrict ourselves to two topics involving these molecules (a) dendritic self-assembly [28] and (b) metallodendrimers [25,26]. 

Baars MWPL,Meijer EW (2000) Host-Guest Chemistry of Dendritic Molecules. 210 131-182 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... 

Dendrimers are of interest in a variety of contexts, such as host-guest chemistry and catalysis in which the dendritic core region, which is often highly porous, can exhibit interesting host behaviour, while the densely packed outer layer acts... 

Multivalency in the gas phase host-guest chemistry of dendrimers... 

This chapter presents a selective glimpse of this dynamic family of spherical macromolecnles for newcomers to the topic in order to help them better appreciate the field that has been extensively reviewed elsewhere. This chapter is divided into several parts to emphasize the structmal diversity and their potential applications. First, a study of the internal structure of the dendritic architecture, emphasizing the different types, followed by a study of their interactions with other molecules or atoms, such as in the case of host-guest chemistry, molecular recognition, or encapsulation inside the dendrimer. Finally, there is a small section that will address the intermolecular interactions of dendrimers and dendrons to either themselves or other nano-objects. In this past quarter century, tens of thousands of papers have been published producing a wide variety of different dendritic architectures with varied structural components capable of novel supramolecular interactions. Therefore, only an overview describing their structure with representative examples and practical purposes will be discussed, when appropriate. 

Figure 6 Host-guest chemistry (a) Representation of the self-assanbly of a hoUow dendrimer host, metal ions guest. (Reproduced with pamission from Ref. 50. American Chemical Society, 2008.) (b) pH-Dependent encapsulation of pyrene in PPI-core PAMAM-shell dendrimers. (Reproduced with permission from Ref. 63. Amaican Chanical Society, 2009.)...

Porphyrins and phthalocyanines can be used as core, branches, and terminal groups of dendrimers that have been extensively used as bio-inspired models or mimics of natural systems such as hemoproteins and chlorophyll in photosynthesis, but also in host-guest chemistry, biosensors, photodynamic therapy, and catalysis. Aida et al. demonstrated the amplitude of this field in a review of 2009 [98]. In the following paragraphs, some historical backgrounds will be presented before focusing in a topic specifically concerned on the porphyrin-dendrimer electrochemistry and photoinduced electron transfer processes. 

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