Chemistry Reference
In-Depth Information
connected to Behera's amine, its second- and third-generation analogs. An important
question that we must address is: Why stop at the third generation? Our answer is
based on two considerations. First, we wanted to work with well-defined molecules.
The third-generation dendrimer has 27 esters (or carboxylic acids) on the surface and
the fourth-generation analog would have 81 groups on the surface. In the latter case, it
becomes statistically much more difficult to guarantee that we are dealing with a
single molecular species, without any significant dispersion in the molecular weight.
Our mass spectroscopic data indicates that it is possible to prepare third-generation
dendrimers of this kind without detectable molecular weight distribution. Further-
more, we have observed in all cases very clear trends of molecular properties from the
first to the third generation, which has made it essentially unnecessary to reach the
fourth-generation dendrimers.
Figure 7.3 shows all the dendrimers that we have prepared with this general
structure. Dendrimers
are fluorescent as a result of the covalent
incorporation of dansyl and pyrene groups at their focal points. Dendrimers
1-3
and
4-6
7-24
are electroactive, that is, they undergo electrochemical reactions at accessible
FIGURE 7.3
Structures of all dendrimers prepared using Newkome dendrons.
