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C60 From Soot to Superconductors.

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Zum Vergleich wurde auch die chemische Synthese eines
Proteins mit sich wiederholenden Nonapeptideinheiten in
relativ aufwendiger Weise gemif3 Schema 1 durchgefiihrt['].
Die Gesamtausbeute nach 18 Stufen betrug bei dem konventionellen Verfahren lediglich 11 YO.Durch Gelpermeationschromatographic wurde das Vorliegen einer polydispersen
Mischung mit ntir relativ geringer mittlerer Molekiilmasse
von ca. 10000 ermittelt.
Nach den neuesten Befunden['] scheint der Zugang zu
Proteinen mit repetierenden Aminosauresequenzen durch
biotechnologische Methoden besonders aussichtsreich zu
sein. Die groBen Anstrengungen, solche relativ einfach aufgebauten Materialen bereitzustellen, rechtfertigen sich besonders dadurch, daf3 Anwendungen irn Bereich der Medizin
schon jetzt erkennbar sind. So konnten z. B. Blockcokondensate aus repetierenden Arninosauresequenzen als SeideAnaloga und Sequenzen. die eine hohe Bindungsfahigkeit zu
Zelloberflachen aufweisen, zur .,Verklebung" von einzelnen
Zellen zu grofiercn Aggregaten, wie es z. B. bei Brandverletzungen notwendig ist, genutzt werden. Die Verkniipfung von
Hart- und Weichsegmenten von entsprechend repetierend
aufgebauten Aminosiuresequenzen wird als Ursache fur die
hohe Elastizitat von Spinnweben angesehen. Die nun biotechnologisch zuglnglichen Materialien sollten bei blockartiger Verkniipfung ihnliche Eigenschaften aufweisen und in
Form von Folien zur Wundabdeckung oder als Beschichtungsmaterial von Implantaten besonders interessant seinf'].
Der von Tirrell et al. gewiesene Weg zum Aufbau von
Proteinen, die wenige. immer wiederkehrende AminosiureEinheiten enthalten und die eine exakt festgelegte Molekiilmasse haben, hat sich gegeniiber klassischen Methoden beziiglich Aufwand und Ergebnis a k iiberlegen erwiesen. Damit werden dem Polymer- und Proteinchemiker neue Materialien in die Hand gegeben, die sich durch chemische und
enzymatische Prozesse weiter umwandeln lassen sollten. z. B.
in Block- oder Pfropfcokondensate. SchlieMich bleibt abzuwarten, inwieweit die Strukturvielfalt der monodispersen
Proteine. z. B. durch fluorierte Aminosiuren im Nihrmedium, noch zu vergroDern ist.
[ I ] H.S. Creel. M J. Fournier. T L Mason. D . A . Tirrell. .Mu~r,,r?ioli,i.uIc.s24
(1991) 1213
[ 2 ] H . D. Jakubke. P. Kuhl. A Konnecke, Angc."'. Chcwi. 97(1985) 79: ArigRcw.
Chenr I n / . Ed. Engl. 24 (1985) 8 5 .
131 E. Bayer. Angiw. Cheni. 103 (199 I ) I 17: Angrit. Chew I n / , Ed. €rig/. 30
(1991) 113.
[4] H. Rehse. H. Ritter. Mukrornol Chmt. /89(198X) 529: M. Gorrnanns. H.
Ritter. hid.. im Druck.
[5] K Fritrsche. R. W. Lenz. R . C . Fuller. Mukroniol. Clieni IYI (1990) 1957:
C. Abe. Y. Tairna. Y Nakamura. Y. Doi. PO/!??I.Comrmrrr. 31 (1990) 404.
161 K. P. McGrath. D . A. Tirrell. M Kawai. T. L. Mason, M . J. Fournier. EIOrwhnol. Prog. 6 (1990) 188.
171 D. A. Tirrell. Amherst, M A , USA. personliche Mitteilunp.
C h 0 :From Soot to Superconductors
By Franyois Diederich* and Robert L. Wherren
In 1990, a team of astronomers led by Krarschmer and
Hufjinan['] reported that the new allotrope of carbon C,,
(buckminsterfullerene, so named after Buckminster Fuller.
an architect renowned for his geodesic domes)''] can be produced in macroscopic quantities through resistive heating of
graphite under inert atmosphere. In an Angewandfe Chemie
Highlight article in January 1991. Fraser Stoddarr summarized the early results in the vigorous worldwide research
efforts that were triggered by this surprising development.[31
Only half a year later, a series of exciting new findings require that yet another Highlight article be written (closing
date May 20, 1991).
X-ray Crystal Structure Analysis of Osrnylated C,,
Although the icosahedral-cage structure of C,, was
strongly suggested by 13C NMR[31,IR[3-61,Ramanf6].and
photoelectron spectroscopy.f71as well as by scanning tunneling microscopy (STM) imaging,['- ''] the ultimate confirmation and detailed parameters of the soccerball-shaped
framework had to await X-ray crystallography. However,
rapid isotropic rotational motion of the orderly packed
spherical molecules in the crystal to temperatures down to
Prof. Dr. F. Diedertch. Prof R. L. Whetten
Department of Chemistry and Biochemistry
University o f California. Los Angeles. C A 90024-1569 (USA)
A n g w . C h e m 1113 ( 1 9 > 1 ) N r . d
100 K'' '*' I have so far prevented a successful high resolution X-ray crystal structure analysis. To break the symmetry
of C,, and prevent its rapid spinning in the crystal. Howkin.s
et al. prepared by osmylation [Eq. (a)] a remarkable 1 : I
C,,-osmium tetraoxide adduct.[l3<I4l The crystal structure
of this adduct was subsequently solved by the Berkeley
group and clearly confirms the soccerball structure of C,,,
composed of 20 six-membered rings fused to 12 five-rnembered rings (Fig. l).1141All tricoordinate carbon atoms of
C,, are pyramidalized and lie at an average distance of
3.512(3) 8, from the center of the sphere. The unfunctionalized five- and six-membered rings are all planar within
f 0.05 A. The two bond lengths in these rings are 1.388(9)A
for the fusion between two six-membered rings and
1.432(5) 8, for the fusion between a six- and a five-membered
ring. Values of 1.40 ( f 0.01 5 ) A and 1.45 ( 0.01 5 ) 8, were
determined for the two bond lengths in C,, by solid-state
13C NMR,[lSl
LTH ~~rluRsResellsclrulr
mhfl. W-6940 Weinheini. 1991
0044-X249:91~0606-169SR 3 SO
+ 2.5 0
69 5
Superconductivity of Alkali-Metal-Doped C,,
Fig. I . Structure of the C,,,-osmium tctraoxidc-di(p-ipri-hutylpyridine)adduct i n the crystal 1161.
Reactivity of' C,,
The chemiitry of C,, promises to develop rapidly in the
coming months. Initial reactivity studies with this fully delocalized closed-shell molecule" might have been of limited
success since they probably relied too much on analogy to
the chemistry of polycyclic aromatic hydrocarbons. However. C,, differs in many aspects from these planar molecules
and shows "ambiguous'*['H1aromatic character. The C,,
structural framework is highly stable. Ion-beam collision experiments. in which Cf, or Cfo collide with silicon or graphite surfaces at speeds up to 50000 km per hour ( & 250 eV
impact energy) show high inelasticity of the ions. but no
evidence for impact-induced fragmentation.['y1This behavior differs from those of any other molecule or similar-sized
cluster ions that have been tested. including benzene and
naphthalene ions, which show fragmentation under these
drastic conditions. The electronic properties predicted by
Elser and Htrddon[201were confirmed. C,, possesses a vanishingly small n-electron ring-current magnetic susceptibility
z, far below 1 hat of graphite or benzene, resulting from accidental cancellation of the diamagnetic and paramagnetic
contribution< to x.['*. 2 ' 1 Electrochemical studies showed
that C,, is :3 very strong oxidizing agent. comparable to
methyl viologen and flavin chromophores. and its first reduction potential ( E = - 180 mV in T H F against Ag/AgCI)
is at least 1 'd more positive than those of most polycyclic
aromatic hydrocarbons.[3.4. This electron-deficient character of C,, determines much of the chemistry that is currently being pursued. C,, does not react with electrophiles or
as a diene in Diels-Alder and other cycloadditions. Rather,
it is easily reduced and reacts readily with nucleophilic
a g e n t ~ . [ ' ~ In
. ~ an
~ I exploratory investigation, Oluh et al. obtained deep red-brown solutions of diamagnetic polyanions
of C,, upon reaction with lithium in
alkylation with methyl iodide led to polymethylated C,,;
according to mass spectrometric analysis, one or more (all
the way up to 24) methyl groups were covalently added to the
sphere. Wudl et al. observed multiple additions of amine
nucleophiles to C,,, and were able to prepare polyaminated
derivatives that are soluble in water.[241In sharp contrast to
rigid aromatic polycycles. C,,, upon excitation, exhibits no
significant fluorescence or phosphorescence despite a richly
structured optical spectrum in the red and violet reg i o n ~ ; [ ~ luminescence
observed for neat C,, films is
probably due to solid-state interactions between spheres.[z8]
Besides being a strong oxidizing agent, C,, is a potent sensitizer of singlet oxygen and, therefore, should be handled with
Recent reports from A T & T Bell Laboratories on the conductivity and superconductivity of C,, are breakthrough results with potentially significant technological implications.[2'. 301 Today. doped C,, is the molecular superconductor with by far the highest onset temperature of superconductivity T,. It is not difficult to predict in view ofextremely
rapid developments that the following information might
well be outdated when this article is published.
Earlier, the Wudl group used C,,'s high electron affinity to
prepare a crystalline semiconducting (10-5-10-7 S c m - ' )
Ph,P@/C?, salt by bulk e l e ~ t r o l y s i s . Hddon
~ ~ ' ~ et al. found
that C,, films doped with alkali-metal vapor become organic
metals that exhibit conductivities at ambient temperature
comparable to those of n-type doped polyacetylene
(100 S c m - l for Rb/C,, and 500 S c m - ' for K/Cho).1291
Doping is presumed to occur in the tetrahedral interstices
between C,, molecules. Soon after. a report from the same
laboratory appeared on the superconductivity of potassiumdoped C,,, both in forms of thin films and polycrystalline
The powder samples showed a well-defined. yet
small (circa 1 YO).diamagnetic shielding (Meissner effect)
with an onset temperature T, of 18 K. The C,, group at the
University of California in Los Angeles (UCLA) subsequently characterized the composition of the stable superconductive phase as K,C,,. and T, = 19.3 K.[321Controlled
sample preparation raised the Meissner effect to above 40%
of the perfect diamagnetic shielding. which is a high value for
a powder sample. This should probably be regarded as a
stoichiometric compound ( K ~
C rather
~ than
~ a )doped
molecular solid. The UCLA group also found that Rb,C,,
shows an even higher onset temperature for superconductivity
(q = 30 K ) ; diamagnetic shielding was 7 % at the time of
manuscript preparation.[321 An onset temperature of T
= 28 K for a Rb-doped C,, sample was measured by the Bell
Theoretical models for the superconductivity
of doped fullerenes are already a ~ p e a r i n g . 1 ~ ~ 1
The Fullerene and Heterofullerene Family
Buckminsterfullerene (C,,,) and C,,, whose ellipsoidalcage structure with D,,-symmetry is now firmly supported
by a variety of spectroscopic method^,[^.^-^. 22.3 s I are both
major, but not the only products that can be isolated from
the toluene-soluble fraction of the fluffy soot produced by
resistive heating of graphite. By repeated chromatography
on alumina. Dirderirh et al.[361obtained small quantities of
C,,, C8,. C,,, and C,,, which, like C,, and C,,, are mem-
bers of the same family of hollow-cage all-carbon molecules
called the f ~ l l e r e n e s . [ In
~ ' ~addition. they also showed that
the toluene-insoluble fraction of the soot contains a variety
of larger fullereni:s in the range between Ciao and C,,, that
dissolve in boiling 1.2,4-tri~hlorobenzene.[~~.
381 The structures of the higher fullerenes above C,, have yet to be determined. The UCLA group also isolated C,,O, a stable oxide
of D,,-C,, with the oxygen atom covalently attached to the
convex external surface of the
Apparently, this
oxide forms from trace oxygen impurities in the helium gas
used as the inert atmosphere during the resistive heating
process. A recent study by Smcillej~et al. suggests the existence of heterofullerenes, and it should not take long before
such compounds are actually
Supersonic beams
produced by laser vaporization of a graphite pellet containing boron nitride powder were found to contain heterofullerenes, e.g. C,,B, and C,,B, in which presumably one or
more atoms of thc soccerball are replaced by a boron atom.
The doped carbon balls are Lewis acidic and readily
chemisorb one ammonia molecule per boron atom.
It is obvious from this short account that research on C,,
and the other fullerenes is about to revolutionize chemistry
within a rather short period of time. Since these new materials are readily prepared[3,22,401
as well as commercially
avaiIable.'"l the exploration of their tremendous basic research and technological perspectives is now limited only by
the imagination of the individual investigators.["]
[ I ] W. Kritschmer. L. D. Lamb. K. Fostiropoulos. D . R . Huffman. Nururc,
/London) 347 (1990) 354.
[Z] H. W, Kroto. J. R. Heath. S. C. O'Brien. R. F. Curl. R . E.Smalley. Norrrrc.
(Londonj 31X (1985) 162.
(31 J. F Stoddart. Ang.,n.. C ' h m i . I03 (1991) 71: .4rigrw. Chem. Inr. Ed. EnRI.
30 (1991) 70. For :I more recent account see: J. S. Miller. Adr. M u w r . 3
(1991) 262.
(41 D M . Cox. S. Betal. M. Disko. S. M Gorun. M . Greaney. C. S Hsu.
E. B. Kollin. J. Milhr. J. Rohhins. W Rohhins. R D . Shcrwood. P. Tindall.
J. Am. ('hcwr. So(. 113 (1991) 2940.
[S] J. P. Hare, T, J. Dcnnts. H. W. Kroto, R . Taylor, A. W. Allaf. S. Balm.
D. R. M . Walton. Chcm. .%I(.. Chcwr. Commun. 1991. 412.
[h] D . S. Bethune, 0 . Meijer, W C. Tang. H. J Rosen. W. G. Golden. H Seki.
C A Brown. M S de Vriea. Chrm Phi,.\. Lerr 179 (1991) 181.
171 D. L. Lichtenherger, K. W. Nehesny. C. D Ray. D . R Huffmann. L. D .
. (1991) 203.
Lamb, Chtwi. Phy.5 L ~ r r 176
[XI R . J. Wilson. G . McijCr. D . S. Bethunc. R. D . Johnson. D. D. Chamhliss,
M S. de Vrica. H. E . Hunriker. H . R . Wendt, Nurirrc iLon(fon) 348(1990)
62 1
[9] J. L. Wragg. J. t.Chamberlain. H. W. White. W Kritschmer, D . R . Huffman. Nurun, 1 Lonubri) 34X (1990) 623
1101 Y, Z. Li. J. C. Patriii. M . Chandler. J. H . Weaver. L. P. F. Chihante, R. E.
Smalley. S ~ i c w ciiVu.$hrnyrori D.C.1 252 (1991) 547.
[ I l l C. S. Yannoni. R I). Johnson. G. Meijer. D. S. Bethune. J. R. Salem, J.
phi.^. Chcwr. 95 (1991) 9.
1121 R . Tycko, R . C. H.iddon, G. Dahbagh. S.H . Glarum. D. C. Douglass.
A . M . MUJSce. J P/II.s.Chew 95 (1991) 518.
1131 J. M . Hawkins, T. A . Lewis, S. D. Loren. A. Meyer. J. R. Heath. Y. Shihato. R J. Saykally, J Org. Chwr 5.5 (1990) 6250.
1141 1. M . Hawkins. A. Ideyer. T A. Lewis. S. Loren. F. J. Hollander. Si.r~nct'
/ Wu.\/irngrorr D.C . ) 3 2 (1991) 312.
[ 151 C. S. Yannoni. P. P. Bernier. D. S. Bethune. G. Meijer. J. R. Salem. J. Am.
Chc~ni.S o < . 113 (1991) 3190.
1161 We thank Profcsso- J M . fluakrru, Univ. o f California. Berkeley. for
providing the pictuie of the X-ray cryst;il structure analysis.
1171 R . C. Haddon. L. E Brus. K. Raghavachari.Chrm. Phvs. L P / I ./25(1986)
A n R r u . Chcvri. 103 / 1991 I Nr. 6
R . C. Haddon. L. F. Schneemeyer. J. V. Wasfcrak. S. H . Glarum. R.
Tycko. G. Dahhagh. A. R Kortan. A. J. Muller. A. M. MUJSCC.
M J. Rosseinsky. S. M . Zahurdk. A . V Makhija. F. A. Thiel. K . Ragh;ivach:iri. E.
Cockayne, V. Elser, Nurun, i Lond(~ir)350 (1991 ) 46.
R . D Beck, P. St. John. M . M . Alvarei.. F. Diederich. R . L. Whetten. J.
Phy.r. Chenr.. in press.
V. Elser. R . C. Haddon. Nurure ( L o n d o n ~325 (1987) 792
R . S. Ruoff. D. Beach. J. Cuomo. T. McGuire, R. L. Whetten. F. Diederich. J. P h w Chon. YS (1991) 3457
P. M . Allemand. A. Koch, F. Wudl. Y. Ruhin. F. Diederich. M M . Alvarez. S J. Anr. R. L. Whetten, J Am. Chrm. Soc. 113 (1991) 1050.
J W. Bausch, G. K. Surya Prakash. G. A. Olah. D. S. Tse. D. C. Lorents.
Y. K . Bae. R . Malhotra. J A m . Chcm So(,. 113 (1991) 3205.
Professor E Wud/. cited in: I. Amato: "Buckyballs. Hairyhalls. Dopeyhalls". .'%'fence (Wushin~/ori.
D.C./ 252 (1991) 646.
I. W. Arhogast, A. P. Darmanyan. C. S. Foote. Y. Rubin. F. N Diederich.
M . M . Alvarei.. S. J. An7. R . L. Whetten. J. P h w . Chrnr. 95 (1991) 11
R. E. Haufler. L A . Wang. 1.. P. F Chihante. C Jin. J. Conceicao. Y Chai.
R. E. Smalley. Ch[vri.P h v L ~ r r 179
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M . R . Wasielewski. M . P. O'Neil. K. R . Lykke. M . J Pellin. D M. Grucn.
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12x1 C. Reher. L. Yee. J. McKicrnan. J. I . Zink. R . S. Williamb. W. M Tong.
D A. A. Ohlherg. R . L Whetten. F. Diederich. J. P h n Chiwr. 95 (1991)
[?Y] R. C. Haddon. A. F. Hehard. M . J. Rosseinshy. D. W. Murphy. S. J.
Ducloa, K. B. Lyons. B. Miller. J. M . Rosamili:i. R . M . Fleming. A R.
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(301 A. F. Hehard. M . J . Rnsseinsky. R . C . Haddon. D . W Murphy. S. H .
Glarum. T. T M . Palstra. A. P. Ramirer. A R. Kortan. Nurirrc, 1Londorrl
350 ( 1991 ) 600.
1311 P.-M. Allemand. G. Srdanov. A Koch, K . Khemani. F Wudl. Y Ruhin.
F. Diederich. M . M Alvarez. S J. Anr. R. L. Whetten. J. Ani. Chcvrr. So<..
113 (1991) 2780.
1321 K. H o i c r e r . 0 . K1ein.S.-M Huang. R. B. Kaner. K.-J. Fu. R . L. Whetten.
F. Diederich. Scriwc~1 Wuvhingion. D. C'. 252 ( 1 9 1 ) 1154.
1331 M . J. Rosseinsky. A. P. Ramirez. S. H . Glarum. D. W. Murphy, R C .
Haddon. A . F. Hehard. T. T. M . Palstra, A. R . Kortan. S. M . Zahurak.
A. V. Makhija, PhI,s. Rcv Lrrr. May 27, 1991.
1.341 S. Chakravart). S. Kivelson, phi..^. R r r . Let/. submitted
[XI R. D Johnson. G. Meijer. J. R. Salem. D. S. Bethune. J. Am. Chrnr.SO(..
113 (1991) 3619.
[36] F. Diederich, R . Ettl. Y. Ruhin. R . L. Whetten. R . Beck. M . Albarer. S
Anz. D. Sensharma, F. Wudl. K C. Khemani. A. Koch. . S m v i w i Uh.rhrng!on. D. C . ) 252 (1991) 54X.
H Kroto. Purr Appl. Chrm.62(1990)407. R . E Smallcy.S~icvi~c~\
31 (1991) No. 2. p. 22.
D . Ben-Amotz. personal communication.
T. Gun. C. Jin. R . E. Smalley. J. Phi,\. Chcnr.. in press. see also ref. 12.11.
A simple benchtop reactor for the preparation o f fullerene.; has hecn
developed : A. Koch. K. C K hemani. F. Wudl. J Org Chcwr.. in
Commercial sources of fullerenes: a ) Texas Fullerenes Corporation.
2415 Shakespeare. Suite 5. Houston. T X 77030-1038 (Tel. 713-227-9003.
FAX 713-6x6-5139). Crude Soot: 20 S per gram. 10 5 with University dis500 $ p e r gram. Pure
count Benrene~soluhleextract(mainly C,, and c-,,):
C,,,: 6 5 per milligram b) Materials and Electrochemical Research ( M E R )
Corporation, 7960 S. Kolh Road. Tucson, A Z 85706 (Tel. 602-574-1980.
FAX 602-574-1983). Crude Soot: XO S per gram. C,,,/C,,, mixture. 5 1250
per gram. c ) Research Materials Incorporated. 1667 Cole Blvd.. Building 19. Suite 400. Golden. CO X0401 (Tel. 303-238-9369. FAX 303-2371103). All three companies deliver worldwide.
Editorial note- We have just learnt of snme exciting results of a group at
the Laboratory for Research on the Structure of Matter. Unibersity of
Pennsylvania, Philadelphia. PA 19104. In press are the following articles
Fluorinated Fullerenes ( H . Selig. C. LifshitL. T Peres. J. E. Fischer. A. B.
Smith 111. A. R . McGhie. W. J. Romanow. J. P. McCauley. Jr . J. A m .
Cht~m.Sot.). Orientational Ordering Transition in Solid C,, (P. A Heiney.
1. E. Fischer. A. R . McCihie. W. J. Romanow. A. M . Denenstein. J. P. McCauley. Jr., A. B. Smith 111. D. E.Cox. Phvs. R w . Lrrr.):Compressibility
of Solid C,,, (J. E. Fischer. P. A. Heiney. A. R. McGhie. W. J. Romanow.
A. M . Denenstein. J. P. McCauley, Jr.. A. B. Smith 111. S(.rtwcr i Wu.shinpron. D. C)).Structure and Bonding in Alkali-Metal-Doped O,,, (0.Zhou.
J. E. Fischer. N . Coustel. S. Kycin. Q . Zhu. A. R. McGhie. W. 1. Romanow, J. P. McCauley J r , A . B. Smith 111. D . E. Cox. Narrrrc, /Loii~forr~).
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