Communication
À n+
3
of the guest with a bulky substituent, which penetrated one of
assigned to the [5ꢁC Àn·NO ] species (n=2, 3, and 4, re-
60
the four openings (Figure 5c). The pyridyl signal H of the cap-
spectively; Figures 6e and S36 in the Supporting Information).
Peaks derived from other host–guest complexes and the
h
sule split into four signals from 9.07 to 9.68 ppm after binding
1
f-C . The formation of 1:1 host–guest complex 4ꢁf-C was
empty capsules were not observed. In the H NMR spectrum,
60
60
clearly elucidated by the ESI-TOF MS spectrum, in which prom-
two sets of the pyridyl signals (Hh-j and Hh’-j’) and the pendant
inent signals were observed at m/z 2173.6, 1427.8, and 1055.6,
methoxyethoxy signals (HA-C and HA’-C’) of 5ꢁC were clearly
60
À n+
assigned to the [4ꢁf-C Àn·NO ] species (n=2, 3, and 4, re-
observed (Figures 6c and S31 in the Supporting Information).
Because each of capsules 2 and 4 can quantitatively encapsu-
late one molecule of C , the 5ꢁC structure is a thermody-
60
3
spectively; Figure S30 in the Supporting Information). The
three-dimensional host–guest structures of 4ꢁC70 and 4ꢁf-C
60
60
60
obtained by force-field calculations are in good agreement
with the NMR and MS data (Figures 5a and S44 in the Support-
namically favored product over the other possible
M L L’ ꢁC structures (n=0, 1, 3, and 4). The 5ꢁC com-
2
n
4Àn
60
60
[
12]
ing Information). In contrast, the encapsulation of C70 and f-
plex, in principle, is able to generate two geometrical isomers,
[
14]
C60 by capsule 2 was not observed under various conditions.
Unexpectedly, we found the guest-induced reorganization
cis- and trans-isomers, based on the coordination geometry of
[15]
II
the square-planar Pd center. Force-field calculations indicated
of expanded capsule 4 and original capsule 2 in the presence
of fullerene C , leading to the sole formation of new capsule 5
that the structure of the cis-isomer, which is an unusual
“Janus”-like capsule, is much more favorable than that of the
60
À1
(Figure 6a). When capsules 4 and 2 (in a 1:1 ratio) were com-
trans-isomer (DE=À22.2 kcalmol ; Table S2 in the Supporting
[10,12]
Information).
In addition, the combination of a 1:1 mixture
of capsules 2 and 4 with the monofunctionalized C60 (f-C ) led
60
to the selective formation of a 5ꢁf-C60 complex (Figures S48
and 49 in the Supporting Information).
The strong encapsulation of the fullerene derivatives and
the selective rearrangement of the host frameworks most
probably stem from efficient host–guest aromatic–aromatic in-
teractions. Thus, neither host–guest interaction, nor frame rear-
rangement was observed by the treatment of the capsules
with aliphatic and small aromatic guests (e.g., 1-acetyladaman-
tane and [2.2]paracyclophane) as well as anionic guests (e.g.,
sodium tetraphenylborate) under the same conditions.
In summary, we presented the anisotropic expansion of
a spherical M L coordination capsule with a polyaromatic an-
2
4
thracene shell through the simple elongation of the organic
ligand. The expanded M L’ capsule provides a large elliptical
2
4
cavity surrounded by polyaromatic frameworks with four open-
ings and thereby encapsulates elliptical fullerene C70 as well as
monosubstituted fullerene C . More importantly, the guest-in-
60
duced reorganization of the expanded M L’ capsule and the
2
4
original M L capsule occurs in the presence of C or mono-
2
4
60
substituted C , which exclusively gives multicomponent
60
M L L’ capsule. The preparation of new expanded M’ L’ cap-
2
2
2
2
4
sules by using a variety of metal ions (M’) and the guest-in-
duced frame rearrangement of the M’ L’ capsule and previ-
2
4
Figure 6. a) Schematic representation of the C60-induced reorganization of
[8]
1
ously reported M’2L4 capsules
are currently under
capsules 2 and 4 (R=H). H NMR spectra (500 MHz, CD
mixture of M
L’4Àn (n=0–4; RT); and c) 5ꢁC60 (508C). ESI-TOF MS spectra
CH
CN, RT) of d) the complex mixture and e) 5ꢁC60
3
CN) of b) a complex
2
L
n
investigation.
(
3
.
Acknowledgements
1
bined in DMSO at 1008C for 3 h, the complicated H NMR and
ESI-TOF MS spectra of products were obtained (Figure 6b,d),
which indicates the generation of a mixture of M L , M L L’ ,
This work was supported by the Japan Society for the Promo-
tion of Science (JSPS) through a “Funding Program for Next-
Generation World-Leading Researchers (NEXT Program)” and
by the Japanese Ministry of Education, Culture, Sports, Science
and Technology (MEXT) through Grants-in-Aid for Scientific Re-
search on Innovative Areas “Soft Molecular Systems”. We thank
Dr. Norifumi Kishi (RIKEN) and Dr. Ken-ichi Sano (Nippon Inst.
of Tech.) for helpful discussions and generous support of this
work.
2
4
2
3
1
M L L’ , M L L’ , and M L’ capsules. On the other hand, addi-
2
2
2
2
1
3
2
4
tion of fullerene C60 to the complex mixture in acetonitrile fol-
lowed by stirring the mixture at 808C for three hours resulted
in the quantitative formation of the 5ꢁC complex with the
60
[
16]
composition of Pd ·1 ·3 ꢁC . The ESI-TOF MS analysis of the
2
2
2
60
resultant solution showed a simple spectrum, in which promi-
nent signals were observed at m/z 2044.0, 1342.0, and 991.0,
Chem. Eur. J. 2015, 21, 4200 – 4204
4203
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim