Chemistry Reference
In-Depth Information
dendrimer size, electron transfer is progressively more difficult. Practically no
electron transfer from the fullerene singlet occurs for
in CH
2
Cl
2
, whereas some
of it is still detected in the more polar PhCN. These trends can be rationalized by
considering increasingly compact dendrimer structures in more polar solvents [76].
This implies that the actual polarity experienced by the involved electron transfer
partners, particularly the central OPV, is no longer that of the bulk solvent. This
strongly affects electron transfer thermodynamics that, being reasonably located in
the normal region of theMarcus parabola, becomes less exergonic and thus slower and
less competitive toward intrinsic deactivation of the fullerene singlet state. This
dendritic effect is in line with the molecular dynamics studies that suggest that the
central OPV unit is more and more protected by the dendritic branches when
the generation number is increased. Actually, the calculated structure of
62
shows
that the two dendrons of third generation are able to fully cover the central OPV core.
62
6.4 CONCLUSIONS
Dendrimer chemistry and fullerenes crossed each other to give rise to a new
interdisciplinary field in which the imagination of chemists has allowed to design
and construct unprecedented molecular and supramolecular fullerene-based na-
noarchitectures. Substantial research efforts have been carried out to organize such
compounds onto surface as well as in liquid crystals. Owing to their special
photophysical properties, fullerene-based dendrimers are also good candidates for
evidencing dendritic effects or to produce original photoactive molecular devices.
Despite some remarkable recent achievements, it is clear that the examples discussed
herein represent only the first steps toward the design of fullerene-containing
macromolecules that can display functionality at the macroscopic level. More
research in this area is clearly needed to fully explore the possibilities offered by
these materials, for example, in nanotechnology or in photovoltaics.
ACKOWLEDGMENTS
This research was supported by the CNRS. All my coworkers and collaborators are
acknowledged for their outstanding contributions, their names are cited in the
references. I further thank Profs. D. Astruc, T. Aida, and R. Deschenaux for having
kindly provided the original files of Figures 6.4, 6.8 and 6.13, respectively.
REFERENCES
[1] G. R. Newkome, C. N. Moorefield, F. Vogtle, Dendrimers and Dendrons: Concepts,
Syntheses, Applications, VCH, Weinheim,
2001
.
[2] J.-F. Nierengarten, Chem. Eur. J.
2000
, 6, 3667-3670.
[3] M. Holler, J.-F. Nierengarten, Aust. J. Chem.
2009
, 62, 605-623.
