Chemistry Reference
In-Depth Information
N
O
O
NH
N
O
39
Fig. 15 Chemical structure and solid-state crystal structure of hydrogen-bonding barbiturate
fullerene 39 highlighting the close van der Waals contacts between fullerenes in the H-bonding
ribbon. (Reprinted with permission from [
137
]. Copyright 2010 American Chemical Society.)
An appealing topic in molecular electronics is the use of supramolecular
interactions to control the assembly of the electron donors and acceptors in order
to obtain highly ordered supramolecular entities with specific functions. In this
context, Bassani et al. reported the hierarchical self-assembly of a barbituric acid
appended fullerene and a thiophene oligomer substituted with a melamine moiety to
build a photovoltaic device. They found that the photocurrent is 2.5-fold greater in
this device than in analogous ones constructed with fullerene C
60
and the oligomer
without the H-bonding units, which is attributable to higher order at the molecular
level [
137
].
Recently, trying to take advantage of the ability of supramolecular assembly to
control the electronic interactions between the fullerene units, OFET devices
were constructed with derivative 39, which combines the solubilizing 3,4-
ditertbutylbenzene group with the barbituric acid motif [
138
]. The fabricated
OFET devices showed a mobility approximately two orders of magnitude lower
than the devices constructed with pristine fullerene, owing to the anisotropy of the
electrical conductivity of the crystals of 39 (Fig.
15
).
4.2 On Concave-Convex Interactions
We have just seen some examples of supramolecular associates of fullerene
derivatives based on hydrogen bonding. All of these rely on the previous covalent
modification of the fullerene to introduce adequate chemical groups. Pristine
fullerenes, on the other hand, are unfunctionalized, approximately spherical
polyenes. From the point of view of their supramolecular chemistry this means
