Chemistry Reference
In-Depth Information
a
b
c
Fig. 10 (a) Illustration of different H-bonded supramolecular architectures. (b) First C
60
-based
supramolecular dimer. (c) Chemical structures of supramolecular dimers of C
60
4.1 H-Bonded Fullerene Assemblies
H-bonds are, perhaps, the best studied non-covalent interactions. Although they are
weak interactions, with binding energies in the range of ~ 5 kcal/mol, hydrogen
bonds are also selective and directional [
117
]. When molecules interact by forming
two or more hydrogen bonds, secondary electrostatic interactions can give rise to
dramatic differences in the stability of the supramolecular complexes. The combi-
nation of different non-covalent interactions, such as ionic,
interactions, etc.,
with hydrogen bonds allows one to modulate the affinity between the interacting
molecules, giving rise to a wide spread of supramolecular architectures (Fig.
10
).
The importance of hydrogen bonds in determining the geometry and, overall, the
function of biomolecules such as DNA, RNA, proteins, tobacco mosaic virus, and
so forth is well known. Another natural example comes from the photosynthetic
apparatus, in which a highly ordered supramolecular array of electron-donors
(chlorophylls) and electron-acceptors (quinones) harvests and converts sunlight
into chemical potential energy through cascades of short-range electron transfer
steps [
118
]. Inspired by the natural photosynthetic event, intramolecular photoin-
duced electron transfer processes have been thoroughly studied in different cova-
lent and non-covalent systems formed by donor and acceptor electroactive moieties
for their implementation in molecular electronic devices [
119
,
120
]. In this context,
fullerene C
60
has probably been the most studied electroactive entity owing to its
unique electron-acceptor properties and low reorganization energy in electron
transfer processes.
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