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Molecular Recognition of C60 with -Cyclodextrin.

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[ I ] A. Clcailield. R . H. Blessing. 1. A. S t y e s . J Inorg. IL1tc1.(~/wnr1968.30. 2249:
S. Y:imanak:i. M. Tanaka. ibrd. 1979. 41. 45.
[2] N . .I. Clayden. J. Ciirrn. So<. Driifon Truns. 1987. 1877; A. Christensen. E. K.
Aiidciwn. I . G K Anderscn. G. Alberti. N . Niclsen. M. S. Lehinmn. Ai.to
S u t r d . 1990, 44. 865
/norg. C%enr. 1976. /S, 2811; S. Yamanaka. K. Sakamoto. M.
Hattori. J PliJ.\. Chcwi. 1984. 88. 2067.
141 G Alhci-ti. hl. C;isciola. R. K. Biswds. fnorg. C'hrnl. Acrrr 1992. 201. 207: G.
Alherti. U . Costantino. R. Vivani. R. K . Bisaas. Rruct. Polym. 1992, 17. 245;
G Alherti. R . Vivani. R. K . Biswas. S.Murcia-Mascarhs, ibid. 1993, 19. 1 : G.
iola. R . Vibani. R. K. Biswas. I ~ ( J
Ckem.
Y ~ 1993,
.
32. 4250.
ostantino. R . Vivani. P. Zappelli. Af7gm. ( ' h w f . 1993. 105.
I3Yh. , ~ I I , F C ~<,/win.
II.
I t r t . Ed. Etrgi. 1993, 32. 1357.
rti, S Murcia-Mascarbs, R. Vivani. Mufcr. Chrn?.P h w . 1993. 3% 187.
('hair.
(31 S. Xiinanakn.
\rilucs ( N M R . elemental analysis) were used for the determination of
[9]
[lo]
[I I ]
[12]
the lirst reflection in the X-ray
powdcr dill'raction patterns.
G . Albei-ti. hi. G Bernasconi. M. Casciola. Retrt.t. P / J / w ~ 1989.
.
fi. 245.
G. t l o n a t h . K . Kawazoe. J. Chiwi. Eng. Jpn. 1983, 16. 470.
Stirtiice iirciis \$ere investieated by BET analysis. The presence of mesopores
uah cxcluded hy the rcversihil~tyof the adsorption isotherms. Information on
the ~ o l i i m euf ihc micropores was derived from both the t-plot and the Horv;irh Kawiime analysis: the samples were previously degassed at l o - ' Torr.
Crystalline -,-ZrP I was used 21s a nonporous reference material.
C;. Alhcrti. U . Co\tantino. R. Vikani. P Zappclli. Mnr. Krs. So<. LY>wp.Proc.
1991. 23.3. 95.
rugbyball C,, (7 A diameter at the equator, 8 8, between poles),
y-CyD can accommodate both C,, and C,, .
Here we report the first preparation of the stable, watersoluble C,,jy-CyD (1 :2) complex ("bicapped buckminsterfullerene") and the spectral investigation for elucidation of the
molecular recognition of C,, by y-CyD.
The synthesis of the stable complex (samples A, B, and C) (see
Experimental[6' 'I) has the following features: 1 ) efficient formation of the complex by expelling C,, from toluene solution into
the aqueous y-CyD solution, utilizing the anomalously large
solubility decrease of C,, in toluene at 118'C,'8.91 and
2) strengthening of the interaction between C,, and y C y D by
dehydration of the hydrated complex by heating under vacuum.
The obtained samples A, B, and C can be stored in crystalline
form without decomposition. However, they differ in their stability in aqueous solution. At room temperature, sample A commences to eliminate C,, from the complex in solution after 10 h.
On the other hand samples B and C are stable in aqueous solution at least for one and three days, respectively. These samplea.
and sample C in particular, can therefore be employed to investigate the molecular recognition of C,, with y-CyD.
Although X-ray diffraction of the C,,/;'-CyD (1 :2) complex
:';IX[(
126' for sample C) has not yet been accomplished because of difficulty in growing single
crystals for this purpose, a bicapped
structure (Fig. 1) is deduced on the
basis of the 'H and 13C N M R and
elemental analyses.
Evidence for molecular recognition is obtained from the C D spectra
(Fig. 2) for the C,,/y-CyD complex
(samples A, B, and C) in aqueous
solution (pH 6.8, 25:C). Since C,,
is chromophoric but achiral and
y-CyD is chiral but nonchromophoric. this indicates induction
Fig. I . Modcl o f the C , i
i-C?D ( I : ? ) cc)Wlcx (hiof chirality by the host (pCyD) in
capped buckminsterfullerene).
the guest (C6,,). It is worth noting
that increasing dehydration gives
rise to more intense negative (in particular at 230 nm) and positive (in particular at 258 nm) C D bands which suggests increas-
+
Molecular Recognition of C,, with
y-Cyclodextrin **
Zen-ichi Yoshida," Hideko Takekuma, Shin-ichi
Takekuma, and Yoshiharu M a t s u b a r a
Based on the superaromaticity concept we predicted that C,,
was a soccerball-type
Since C,, has been available
on a preparative scale,[1h1one of our big concerns associated
with biomimetic studies on enzymes[2331 has been the molecular
recognition of C,,, at active sites in the hydrophobic pocket of
enzymes and the resulting biological functions.[41
Very recently such an exciting example was reported for the
inhibition of HIV-1 protease by C,, derivatives;['] we were interested in the fundamental problem of how C,, interacts with
the cylindrical hydrophobic cavity of y-cyclodextrin (i'-CyD) in
the complex formed on recognition of C,, by y-CyD in water.
Such ;I host-guest interaction is generally investigated in the
equilibrium system in solution. in which, however, other complexes of different compositions can exist. To avoid this problem, the stable inclusion complex of defined composition should
be studied. For this reason we have tried to prepare a stable
C,,,?;-CyD complex; an unstable complex of nondefined composition has already been reported.[,' The preliminary examination of the complex formation in the two phase solution system
(fullerenes in toluene, y-CyD in water) demonstrated that, firstly. among x-, p- and ;.-cyclodextrins only y-CyD formed the
complex and. secondly, ;.-CyD recognized only C,, in the solution of C,,, and C,,. The latter observation is particularly interesting because. judging froin the cavity size of p C y D (9 8, circular opening) and the size of soccerball C,, (7 8, diameter) and
t11.0 r
.
.
.
1
.
. . . . . . . .
Prof. Dr. Z. Yoshida. H. Takekuma. Prof. Dr. S. Takekuma,
Prof. Dr. Y Matsubard
Departmciit of Applied Chemistry. Faculty of Science and Engineering
Kinki Universit>
3-4-1. Kouakae, Higashi-Osaka 577 (Japan)
Telelkr . Int. code + (6) 727-4301
[*"I This \ ~ o i - kwas partially supported by the Ministry of Education. Science and
('ulture (<;rant-in-Aids for Scientific Research No. 05453131).
I
t
At:
0
-12.5
["I
/
1 90
A [nml
-
340
Fig. 2. CD spectra of the C,,h-CyD complex in aqueous solution at 25 C' ( p H 6.8.
concentration: 1.0 m g m L - ' cach. length of the cell: 1 mm): a ) sample A (without
freeze-drying): i,,, [nm] = 212.4. 255.2, 287.4. 305.6. 326.2; h) sample B (after
freeze-drying): E.,
[nm] = 201.4, 211.8, 219.6, 229.6, 238.4 sh, 249.8. 257.6. 265.8.
276.2sh. 286.2. 307.6.326.0;~) sample C (after freeze-dryingand diyingat 55 C for
24 h): J.,, [nm] =195.6, 207.0, 216.0. 230.5. 246.0, 257.9, 268.8 sh. 287.3. 307.6,
321.2.
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ing interaction due to orbital steering between C,, and the functional groups (active sites -0-and OH) of y-CyD as these become increasingly exposed.
This interaction (recognition) is elucidated by N M R spectroscopy. The chemical shifts of the ' H N M R spectrum
(500 MHz) and 13C N M R spectrum (125 MHz) for y-CyD and
the C,,/:'-CyD complex (sample C) are shown in Fables 1 and 2,
Table 1 . 'H NMR (500 MHz. D,O) chemical shifts 6 for the protons of the glucose
units in ;-CyD and C,,+CyD [a] complex.
H-I
H-2
H-3
6
H-4
H-5
H-6a
structures of y-CyD and C,, indicate that the ether oxygen atom
and the strongly hydrogen-bonded oxygen atom at C3 (C3O H . . OH-C2) between adjacent glucose units are favorably
situated for charge transfer to C,, .[I6,
Since the characteristic
NIR and ESR spectra['8s191of the anions of C,, were not observed, the amount of the charge transfer is considered to be
smaller than one elementary charge.
The specific interaction due to such a charge transfer in addition to size and shape recognition between C,, and biological
systems (for example, enzymes like HIV-1 protease where the
active site is a cdrboxylate n-donor'" 201) should presumably be
reflected in the specific biological functions of C,, .
H-6b
Experimentul Procedure
5.155
3.698
3.980
3.631
3.907
3.915
3.910
;'-CyD
C,,,/-,-CyD
5.084
3.634
4.220
3.611
3.823
3.980
3.975
difl'erence -0.071 -0.064 +0.240 -0.020 -0.084
+0.065 +0.065
[a] Sample C. [h] J(1.2) = 4.0 Hr, J(2.3) = J(3.4) = J(4.5) =10.0 Hz, .1(5.6a) =
J(5.6b) = 3.0 Hz. J(6a.hb) =15.0 Hz. J(4.6a) = J(4,6b) =1.0 Hz.
Table 2 "C NMR (125 MHz) chemical shifts & for the C atoms in C,
glucose unit of ;-CyD and C,,,b-CyD [a] complex.
c,,
C," [bl
143.23
-,-CyD [c]
C,,+CyD [c] 144.05
difference
+0.82
C-I
c-2
6
C-3
102.64
104.59
+1.95
72.76
73.55
+0.79
73.92
74.21
+0.29
and in the
C-4
C-5
C-6
81.43
83.38
73.30
73.64
+0.34
61.23
61.45
+0.22
+1.95
[a] Sample C. [b] In [DJbenrene. [c] In D,O
respectively. From the substantially low-field shifts of 6 = 0.24
for C3-H,[I0."1 6 = 1.95 for C1 and 6 = 1.95 for C4. we conclude that the specific interaction leading to chirality induction
and the stability of the complex is the charge transfer from the
n-donor (the hydroxy oxygen atom bound to C, and the ether
oxygen between adjacent glucose units) to C,,, as shown in
Figure 3. The reasons are following: 1) C,, does not behave as
Fig. 3. Mode of interaction in the C,,p;-CyD complex based on the HGS stereochemical molecular model (HGS = Hinomoto Gouseijnshi Seisakujo) and X-ray
crystal structure of 7-CyD and C6".
a n base like benzene but as an extremely strong electron acceptor (electron affinity: 2.7 eV),['*. and ether oxygen and alcoholic oxygen functions are known to serve as the n-donor in
charge-transfer complex formation with iodine (electron affinity: 2.5 eV);[1412) intermolecular hydrogen bonding between
OH groups and n-electron systems is not observed even for
electronegative, substituted benzenes (like benzonitrile) and
alkenes (like acrylonitrile);" 'I 3) molecular models and X-ray
1598
;(;
VCH Verlug.geseNsthq/l mhH, D-69451 Weinheim, lYY4
The mixture of two liquid phases consisting o f a solution of ;'-CyD (67 mg. 52 pmol)
in water (10 mL) and a solution ofC,, (or C,,:C,, mixture, 92:8) (20 mg) in toluene
(10 mL) was refluxed at 118'C for 30 h under vigorous magnetic stirring. After
cooling to room temperature, the aqueous layer containing precipitated C,,:y-CyD
complex mas centrifuged. The purple crystals were washed with cold water (10 mL)
and dried in vacuo (sample A). The obtained crystals were dissolved in warm
(50 60 C ) water (200mL), and filtered to remove the insoluble materials (C6"
eliminated from unstable complexes). The filtrate was freeze-dried to give 40 mg of
stable C,&;-CyD complex (sample B, HPLC purity >99.8%). These crystals were
then recrystallized from water and dried at 55°C for 24 h to provide the purple
plates (sample C,the most stable complex). A similar result was obtained by using
an efficient rreeie-dry system (e.g. Lahconco LL-6). Sample C : M.p z 2 9 0 C:
[or]iO: + 1 2 6 ' ( c = 0.1 inwater)(co~npare[a]:,~(r-CyD):+177 , ( c = 0.1 i n water)]:
U V V I S (water): 2.,,x[nm] (logs) = 214 (5.10), 231 sh (4.83). 260 (5.08). 332 (4.63).
408 (3.24). 493 sh (2.73). 536 (2.81). 574 sh (2.70). 601 (2.73). 629 sh (2.46): IR
(KBr): P[cm-l] (hands that are not assigned to g y D or C6J =1641. 1430 sh.
1410. 1369. 1335. 1101 sh. 1078. 1026, 937, 731. 581. 527; C. H analysis for
C,,,H,,,O,,
(Cc90.2 j'-CyD '15 H,O): calcd. C . 52.26; H. 5.30; found: C , 52.23 H.
4.88. The 1 :2 composition of C,,, and ;'-CyD was confirmed from the ratio of the
aieas of the corresponding '.'C NMR spectral peaks to C,, and j K y D (analytical
mode: single pulse with heterogated decoupling without NOE). The ' H and I3C
N M R spectral data of this complex suggest a symmetric structure for C,,,;g-CyD
(1 :2) complex (see Figure 1). because the signals for the two j-CyD units were not
split.
Received: March 17, 1994 [Z 6767 IE]
German version: Anger. Chvm. 1994. 106, 1658
[I] a) Z. Yoshida. E. Osawa, Aroniutiuty, Kagakudojin, Kyoto, 1970, p. 74 (in
Japanese); b) W. Kritschmer, L. D. Lamb. K. Fostiropoulos, D. R. Huffman,
Nuture (London) 1990, 347, 354.
[2] a) Z. Yoshida. M. Kato, J Am. Chem. Soc. 1954, 76, 311; h) Nippon Kuguku
Zadri 1954, 7S, 109.
[ 3 ] Z. Yoshida, in BrofnimefrcCliemistrj (Eds.: D. Dolphin, C. Mckenna, Y. Murakami, I. Tabushi), American Chemical Society. Washington, 1980, p. 307.
[4] Recently we detected herbicide activity with Ca0.
[ S ] S. H Friedman, D. L. Decamp, R. P. Sijbesma, G. Srdanov, F. Wudl, G. L.
Kenyon. J Am. Chem. Soc. 1993, 115, 6506.
[6] Our procedure of heating of an aqueous solution of sample A to obtain pure
C,, as crystals is considered to he a better purification method for C,, from
toluene extract of soots than the method proposed by Wennerstrom et al. [7].
[7] T Andersson, K. Nilsson. M. Sundahl. G. Westman. 0. Wennerstrom, J.
Chem. Soc. Cliem. Commun. 1992, 604.
[8] R. S. Ruoff, R. Malhotra. D. L. Huestis, D. S. Tse, D. C. Lorents, Nature
(London) 1993. 362. 140.
[9] Efficient complex formation is demonstrated by a color change (purple to
colorless) of the toluene layer after refluxing.
[lo] The low-field shift is not to the ring current of Cbo; its value is negligible
because the diamagnetic and paramagnetic ring currents cancel [I 11.
1111 R. C. Haddon. Science 1993, 261, 1545.
[12] Z. Yoshida, Perroredi ( T o k j o ) 1992. 15, 396.
[I31 Z. Yoshida. I. Dogane, H. Ikehira, T. Endo. Chem. Phys. Lett. 1992,201,4816.
[14] P. A . D. de Maine. J Cliem. P l z w 1957. 26, 1192.
[ 151 a) Z. Yoshida. E. Osawa, J. P h m Cliem. 1964. 68.2895, b) J Am. C/?em.Sot.
1965. 37. 1467; c) Nippon KuguAu Zasshr 1966.87, 509; d) E. Osawa, T. Kato,
Z. Yoshida, J Org. Chenr. 1967. 32.2803; e) Z. Yoshida, N. Ishibe, H. Ozoe. J.
Am Chem. SOC. 1972, 94.4948.
[16] The cyclodextrin macrocycle IS stabilized by intramolecular hydrogen bonds
0 3 - H . . ' 0 2 between secondary OH groups of adjacent glucose units.
[17] a) K. Lindner. W. Saenger, Biorheni. B i o p h . ~ .Rrs. Commun. 1980, 92, 93.3;
b) J. M. Maclennan, J. J. Stcaowski, ibid. 1980, 92, 926; Review: c) W Saenger,
A n g r u . Chem. 1980. 92. 343. Anreir. Cheni. Int. Ed. EnRl. 1980, 19. 344.
l)S70-0833iY4!1515-ISYHd /O.UO+ .25/U
A i z g e ~Chem. I n / . Ed, Engl. 1994, 33. No. 15/16
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[18] a J T . Kato. T.Kodama. M. Oyama. S. Okazaki. T. Shida. T. Nakagawa, Y
Matsui. S. Suzuki, H. Shiromaru. K. Yamauchi. Y Achiba. Chrm. P h w . Leu.
1991. 186. 35; b) M. A. Greaney, S. M. Gorun. J P h p Clirm. 1991, 95, 7142.
1191 D. R . Lawson, D. L. Feldheim. C. A. Foss. P. K . Dorhout. C. M. Elliot, J
E/ec o-o~ham.. k c . 1992, 139. L68.
[30] M. V. Hosur. T N . Bhat. D. J. Kempf, E. T. Baldwin, B. Liu, S. Gulnik, N. E.
Widcburg. D. W. Norbeck. K . Appelt. J. W Erickson. J Am. Chen?. Sor. 1994.
f 16. 847.
Macropolyhedral Boron-Containing Cluster
Chemistry : Isolation and Characterization
of the First Macropolyhedral Thiaborane,
the arachno-Type [9,9’-S,B,,H,,] - Ion**
TomQSJelinek, John D. Kennedy,* Bohumil Stibr, and
Mark Thornton-Pett
VIII
VI1
Scheme 2.
comprise the eight-vertex lz~pho(S,B,} system (VII),[201the
nine-vertex arachno {S,B,} system (VIII),’20. and the elevenvertex nido JS,B,} system ( I x ) , ~ ~ ~ ~
There is current interest in large macromolecular units based
o n assemblies of heteroborane clusters with twelve vertices and
fewer.[231 The individual clusters of reported assemblies are
however generally linked together by a single two-electron twocenter
bond, or by a single common atom, generally of a
metallic element. An alternative approach to large boron-based
molecules is to use larger contiguous heteroborane building
blocks that are based upon the fusion of smaller polyhedral
clusters rather than upon clusters that are joined by single linkages. Here there is value in the discovery and delineation of new
intercluster bonding modes that will facilitate the development of this new area of “macropolyhedral” heteroborane
chemistry.
We now report our preliminary results on the isolation and
characterization of the presently unique large nineteen-vertex
macropolyhedral dithiaborane anion, [S,B,,H
(cluster connectivity as in X, Scheme 2). This is the first structurally characterized macropolyhedral heteroborane, and it also demonstrates
for the first time a structure in which two arachno-type subclusters are fused to form a boron macropolyhedron. Previous
macropolyhedral structures have been limited to fusions among
nido- and closo-type clusters.
The [S,B,,H,,]- ion, isolated in 48 ‘YOyield as its [PPh4]+ salt,
is obtained by the action of elemental sulfur on a solution of the
~nti-[B,,H,,]~- ion (formed from anli-B,,H,, and NaH in
THF),124*
251 followed by chromatographic separation of the
products. It was identified and characterized by X-ray diffraction
analysis (Fig. 1) and NMR spectroscopy (Fig. 2). The principal
other product is the known[3-12,181 nido-[7-SBi,H, ,I- ion
(45 Y o ) identified
,
by NMR spectroscopy. The formation of the
[S,B,,H,,]~ ion from the unti-(B,,} skeleton involves a marked
change in structure: incorporation of the two sulfur atoms is
accompanied by loss of one boron center and there is an interesting reduction in the intimacy of the intercluster fusion. From
two boron atoms held in common in [B,,H,,]2~ there is a conversion to a somewhat more open structure that has one boron
atom in common and has the interboron linkage B(8)-B(8’)
(Scheme 3 ; open circles represent BH units).
The structure of this [B2B17H,,]- ion (Fig. 1 ) derives formally
from the fusion, with two common vertices. between a ten-vertex
aruchno (SB,} cluster and an eleven-vertex araclino {SB,,) cluster, although a useful alternative model consistent with the inherent twofold symmetry consists of two ten-vertex crrarhno
(SB,} clusters fused with one common boron atom (B(9)) and
with one additional intercluster link (B(8)- B(8‘)). The aruchno
nature of the two {SB,} subclusters is readily apparent: a ) the
similarity of the NMR properties with those of the aruchno
I
The structural variety of polyhedral boron hydride chemistry
is in principle also available to any combinations of main-group
elements that have the same numbers of valence electrons. However, heteroborane chemistry, other than that of the carbaboranes,“] is surprisingly limited. Apart from the carboboranes,
the best-exemplified and most diverse main-group polyhedral
heteroboranes are the thiaboranes. However, only seven basic
contiguous monothiaborane building blocks are available (cluster geometries I-VI, Scheme
Ill
1
IV
V
v1
Scheme 1
These comprise the nine-vertex nido[’] and a r ~ c h n o ~{ ~SB,}
-~]
systems (I and 11, respectively), the ten-vertex closo {SB,} system
(1 V) ,[3.7 1 11 the ten-vertex nidol4. 1 1 - 1 4 1 and
{SB,) systems (both of gross geometry III), the eleven-vertex nido
{SB,,) system (V),I37 1 2 . I s ] and the twelve-vertex closo {SB,,)
system (VI) .I3.
91 In contrast to the very extensive known
dicarbaborane chemistry,[’] only three dithiaborane building
blocks (geometries VII-IX, Scheme 2) are known.[20-221These
-
“3
”3
[*] Dr. S. D. Kennedy, Dr. M. Thornton-Pctt
School of Chemistry of the University of Leeds
Leeds 1.S2 9ST ( U K )
Telefax: Int. code + (532)336565
Dr. T. Selinek. Dr. B. Stibr
Institute of Inorganic Chemistry of the Academy of Sciences
of the C x c h Republic
[**I Contribution no. 44 from the Rei-Leeds Anglo-Czech Polyhedral Collaboration (ACPCJ.We thank the Royal Society (London), The AcademyofSciences
ofthe Czech Republic (grant no. 43204). and Borax Research Ltd for support.
and Dr. R. A. Walker and Dr. D. M. WagnerovL for helpful cooperation. The
work hy T. Selinek was carried out in the Leeds laboratories during the tenure
or a Royal Society Fellowship.
IX
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