Chemistry Reference
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Fig. 17 Chemical structure of the “buckycatcher” and solid state structure of its complex with
C
60
. Note that the fullerene unit is disordered in the crystal. Reprinted with permission from [
144
]
Fig. 18 Chemical structure of some CPPAs and general structure of CPPs. The solid state
structure of the [10]CPP·C
60
associate is also shown
et al. in 1996 [
145
]. The diameter of the cavity of 41 is 1.33 nm as found in its solid
state structure, a close to perfect fit for C
60
. Consequently, the ability of 41 to
associate with [60] fullerene was investigated through UV-vis titrations, the analy-
sis of which afforded a binding constant of log
K
a
¼
4.2 in benzene at room
temperature [
146
]. In order to increase the depth of the cavity, and in turn increase
interactions between host and fullerene, macrocycles 42-44 (Fig.
18
) were
synthesized [
147
]. In these carbon nanorings at least two of the
p
-phenylene
moieties are substituted by naphthalene units. This structural optimization bore
fruit, as all of the newly synthesized hosts form complexes of remarkable stability
with both C
60
and C
70
. In fact, the binding constants in benzene were log
K
a
>
5as
estimated through fluorescence quenching experiments.
Cycloparaphenylenes (CPPs, 45 in Fig.
18
), in which the phenyl units are
connected directly, have also been synthesized [
148
], and their association with
fullerenes investigated. In particular, [10]CPP presents a concave cavity of 1.34 nm
in diameter, ideally suited to associate with C
60
. Indeed, it does so with a remark-
able association constant of log
K
a
¼
6.4 in toluene at room temperature [
149
].
These experiments have been followed up by the group of Jasti, who have reported
