Chemistry Reference
In-Depth Information
ruthenium core was coupled to one extended dendron and protected smaller bipyr-
idine units leading to desymmetrized dendrimers, as demonstrated in Chapter 7.
The size, shape, and polyphenylene density of the G3 Ru(bipy)
3
-cored dendrimer
(
Ru(bpy)
3
-G3
) were compared with those of the related G3 species with a TPM core
(
) [13]. Diffusion NMR measurements revealed a hydrodynamic radius of
2.5 nm for dendrimer
TPM-G3
Ru(bpy)
3
-G3
, which is slightly larger than that determined for
the
species (2.2 nm). This finding indicated a decrease in the large voids
between branches, as the physical radii were almost identical. Whereas the tetrahedral
dendrimer
TPM-G3
distributed 144 phenylene rings within the hydrodynamic
volume, the density of the
TPM-G3
was increased to 216 aromatic rings.
Another intriguing aspect, which is still under consideration, is the interaction of
the core with the counter ions, their distance, and the influence of the counter ions on
the structure of the Ru-dendrimers or other charge-carrying cores.
Ru(bipy)
3
-G3
5.5 FUNCTIONALIZED SCAFFOLD OF POLYPHENYLENE
DENDRIMERS
Functionalization of the scaffold can serve several purposes, for example, multiplying
the number of dyes in a defined environment and distances, or fine-tuning of charge or
energy transfer to a functional core. As opposed to core functionalities, functiona-
lization of the scaffold needs to be introduced by the CP unit, which has been
established for the growth reaction and needs to be verified further to carry the desired
function, and also possess the TIPS-ethynyl groups for growth reactions. Sketching
the accessibility of such CP units the Knoevenagel condensation of difunctionalized
benzils
(Scheme 5.12).
The most common way is the functionalization that has been introduced either in the
a
38
with the disubstituted acetones
39
results in product
40
position of the CP units, as presented by the two guiding structures
dibromotetraphenyl-CPs
or in the
b
41
(
b
-substituted) and
42
,(
a
-substituted), which can also
easily be converted to their diborolanes, as
26
(Scheme 5.7).
SCHEME 5.12
Functionalized CP units
40
and some typically used dibromoderivatives
41
(
b
-substituted CP) and
42
(
a
-substituted CP).
