Chemistry Reference
In-Depth Information
both the size and the degree of branching vary with the generation of the dendrimer.
The largest networks were obtained with
44-G
4
(Figure 16.12) [55].
Another important field of research in materials chemistry consists in modifying
the surface of an existing material by the deposition of organic thin films. Various
techniques were already applied using phosphorus dendrimers; the first examples that
we will see consists of obtaining modified electrodes, using dendrimers possessing
electroactive groups in their structure. Dendrimers
0-4) possess bithio-
phene terminal groups that are electropolymerizable, leading to electrodes irrevers-
iblymodified by a dark blue filmon the anode. This film is an electroactive conjugated
polydendritic polymer, which remains electroactive in aqueous media, particularly
when elaborated from the highest generations [56]. On the other hand, the electro-
deposition of dendrimers
45-G
n
(n
¼
46-G
3
, possessing 24 TTF-crown ethers as terminal groups,
is fully reversible. This dendrimer modified electrode is usable for the electrochemical
sensing of a metal cation (i.e., Ba
2
þ
), as shown in Figure 16.13 (upper part), which
displays the changes of the electrochemical response upon increasing concentrations
of Ba
2
þ
[57]. However, one of the most popular electroactive derivatives is certainly
ferrocene, thanks to its robustness and its full electrochemical reversibility in many
cases. It has been linked very often to dendrimers, generally as terminal groups [58].
In the particular case of phosphorus dendrimers, we have grafted ferrocene derivatives
as terminal groups, but also as core and in the interior; in all cases a blue film was
reversibly deposited onto the electrode [59]. The most original examples are shown in
Figure 16.13: ferrocenes functionalized by aldehydes were grafted as terminal groups
FIGURE 16.13
Various types of electrochemically active phosphorus dendrimers.
