Chemistry Reference
In-Depth Information
SCHEME 5.17
Polypyridyl dendrimer
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.
properties of the stiff dendrimers, binding only 3-4 dyes each, for the first- and
second-generation dendrimers.
The other example for
a
-functionalized CP units is a dendrimer with pyridine in the
scaffold based on
with protected dienophile functions. By varying the building
blocks at the last step of dendrimer construction, one could design molecules
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possessing either phenyl- or pyridyl-decorated outer shells (Scheme 5.17) [66,67].
The pyridine then could serve as ligation site for metal ions. Therefore, these stiff
polyphenylene dendrimers with embedded pyridyls were used as a matrix for
encapsulation of Pd nanoparticles [67]. The fourth-generation poly(phenylenepyr-
idyl) dendrimer with a phenyl-decorated periphery and pyridine-containing interior
was found to serve as a powerful template for metal-nanoparticle formation, resulting
in excellent nanoparticle stability with catalytic function. Further, these special
functionalized dendrimers exhibited very strong sensitivity toward the explosive
triacetonetriperoxide (TATP), which will shortly be outlined in Chapter 8 [68].
5.6 FUNCTIONALIZED SURFACES
Functionalization at the surface is the most simple and flexible route to obtain
functionalized dendrimers and it offers the highest flexibility to control the type,
number, and position of the substituents.
There are two possibilities to achieve functionalized surfaces of polyphenylene
dendrimers. The first and most straightforward one is to introduce any functional
cyclopentadienone unit “a priory” as endcapping reagent in the dendrimer synthesis
of desired generation just as discussed above for pyridyls. Since the Diels-Alder
reaction takes place at high temperatures only, an important requirement of the
functional groups is their thermal stability, which in some cases necessitates
