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Current Comments@ EUGENE GARFIELD INSTITUTE FOB SCIENTIFIC !NFORMATION@ I 3501 MARKET ST, PHILADELPHIA, PA I W04 The Birth of : Harold W. Kroto Discusses New Lines of Buckyball Research in a Science Watchm Interview

Number 37 September 13, 1993

A Star Is Born: Discovering the Third Not surprisingly, buckyballs and the new Form of field of fullerene chemistry have attracted Last week in the engineering and phys- much attention in the press, For example, ics/chemi stry editions of Currenr Contents@ Science selected the buckyball as its Mol- (C@), we published a Citufion Classic@ ecule of the Year in 1991,6 and the Econo- commentary by Harold W. Kroto, Univer- misf called it (be Renaissance Molecule in sity of , Brighton, EngIand, on the 1992,7 It was first featured in CC in a 1988 1985 paper describing the discov- essay on the most-cited 1985 chemistry pa- ery of , IZ Working pers.~ with a team of colleagues at Rice Univer- h addition, Kroto was interviewed in sity, Houston, led by Richard E, Smalley, Science WaKh@, ISI@’s newsletter ihat Kroto was interested in learning more about &acks quantitative trends in researches The the interstellar formation of long carbon 1992 interview, reprinted below, focused chains in red giant stars. An unexpected on new directions in fullerene research and result of their effort was the serendipitous its applications in various fields. It is a discovery of a third natural form of car- useful companion piece to Kroto’s Cita- bon—the stable Cm molecule named after tion Classic commentary, ] because both R. for its novel geode- represent “oral histones” or autobiographies sic “soccer ball” structure. of breakthrough research. Interested read- The discovery has turned out to be one ers should also refer to Smalley’s personal of the rare research breakthroughs that fun- account of the discovery in The Sciences. 10 damentally alters conventional scientific In conclusion, it should be noted that wisdom and triggers an explosion of muhi- there is some controversy about who on disciplinary research. It upset centuries-old the research team envisioned the geode- chemical tradition that just two forms of sic spherical structure of buckminster- carbon existed, graphite and diamond. It fullerene. II Kroto and Smalley differ in has since opened up new research areas in their recollections on this point. Such dif- chemistry, physics, materials science, medi- ferences are not unusual in an era of in- cine, and other disciplines. And it shows tensively collaborative research, espe- significant commercial potential for indus- cially when a major scientific break- trial applications as catalysts, lubricants, through is involved. In these instances, bi.gh strength fibers, pharmaceutical magic >ersonal accounts by the authors—such bullets, optical switches, superconductors, is Cifafion Classic commentaries or Sci- etc. Recent laboratory tests also indicate wce Watch interviews—become even that “buckyballs” may inhibit an enzyme nore valuable as a means to tell all sides necessary for the AIDS virus to reproduce.~-~ )f tbe story.

362 RRFERENCIN

1. Kroto H W. Co—the third man. Citation Classicm commentary on Nature 31 t’:162-3, 1985. Current Corrrent&’Rngitreering, Technology & Applied Sciences 24(36) :8-9,6 September 1993 and Current Contems/PhysicaI, Chemical & Earth Science~ 33(36):8-9, 6 September 1993. 2. Kroto H W, Heath J R, O’Brien S C, Curl R F & Smalley R E. Cd buckrninsterfullerene, Nature 318:162-3, 1985. 3. Browne M W. ‘Buckyball’ may block AIDS step. NY Times 3 August 1993, p. C8. 4. Friedman S H, OeCamp D L, Sijbrxma R P, Srdanov G, Wudl F & Kenyon G L. Inhibition of the HIV- I protease by fullerene derivatives mwfel buildlng studies and experimental verification. J. Amer. Chem. Sot. 115(15):6506-9,28 July 1993. 5. Siihesma R, Srdanov G, WudI F, Castoro J A, Wifkins C, Friedman S H, OeCamp D L & Kenyon G L. Synthesis of a fullerene derivative for the inhibition of HIV enzymes. J. Amer. C/rem. SOc. 115(I5):651O-2, 28 July 1993. 6. Crdotta E & Koshland D E. Molecule of the yew. Buckyballs: wide open playing field for . Science 254:1706-9, 1991, 7. The renaissance molecule. Economist 323(7760):91-3,23 May (992. 8. Gafield E. The 1985 chemistry articles most cited in 1985- i987: quantum mechanics, superconductivity, and... Buckrninster Fuller?! Current CiJruerrrs (48):3- 13, 28 November 1988, (Reprinted in: Garffeld E. Essays of an information scientist: science literacy, policy, evaluation, and other essa,w. Philadelphia: JS1 Frcss@, 1990. Vol. 11. p. 383-93. 9. The srarch for carbon in space and the fullerene fallout Science Wamh@ 3( I):3-4, January 1992. 10. Smalley R E. Great bafls of crrrbun-tfre stnry of buckminsterfullerene. The Sc/ence.! 31 (3):22-8, March/APril 1991. 11. Tauftes G. The dkputed bh’th of buckyballs. Science 253:1476-9,27 September 1991.

The Search for Carbon in Space and the Fullerene Fallout

Few stories in the annals of conternporaty science provide a stronger argument for pursuing jimiamental research than the dis- covery of Cm, In the early 1970s, British and microwave spectroscopist hatched a research program at the Univer- sity of Sussex, in Brighton, U.K., to seek long chains of carbon in interstellar space. This effort, with David Walton at Sussex and with and astronomers at the Canadian National Research Council, in Ottawa, eventually led, during 1975-78, to the detection of several diflerent carbon chains, including HC5N, HCYN, and HCJV. Kroto surmised that these chains were the product of carbon-rich, red-giant stars. “But how did the chains form ?,” he won- dered. A few years later, in 1984, Kroto en- countered a unique instrument-a laser va- Harold W. Kroto porization cluster beam apparatus—in the laboratory of at Rice Uni- mediately realized that it could be used to versity, in Houston. .%udley and his group simulate the high-temperature conditions had developed this instrument and were us- under which the carbon chains might form ing it for research on sili- in stars. In Sep:ember 1985, Kroto, together con and clusters, but Kroto im- with Smal[ey ‘.Ygroup and at

363 Rice, tried to create such conditions and and Molecular Sciences. Kroto was named found much more than they had bargained a Fellow of the Royal Society in 1990, and jbr: a stable molecule consisting of exactly last year he was appointed a Royal Society 60 carbon atoms. They suggested that C60 Research Professor. took the form of a closed cage resembling Science Watch recently reached Profi a soccer ball and called the molecule Kroto in the italian A[ps, where he was “buckminsteijidlerene, “ in honor ofthe ar- attending a conference focusing on cluster chitect R, Buckminste r Fuller and /he geo- chemistry. desic structures he had designed which ex- hibit the same fbrm (see Nature, 318:162, SW: It’s an inevitable question, but what 1985; cited 485 times by the end of 1991, do you see as the most promising uses for thus easily qualifying as a citation classic). ? The suggestion of a ne~v and third form of carbon (besides graphite and diamond) Kroto: Well, it’s true. Most people do ask, was both intriguing and controversial, But “What can C@ be used for?” In fact, there it ivas not a subject of ~cidespread in\’esti- was a question in the House of Lords about gation until late 1990 kchen a team of sci- its potential applications, The answer has entists at the University of A ri:ona, in Tuc- to be, at the moment, that it may have many son, and at the Mar- Planck -[nstitut fur uses, and then again it may turn out to Kernphysik in Heidelberg discovered a have none at all. I suspect that the latter is method for making CbOin bu{k quantities highly unlikely, however. It seems to me (see br>.Y),Close on the heels of the Arizond that the CM field will find and develop its Heidelberg group Has Kroto’s team at the own applications. The situation appears to , which chromotograph- be analogous to the discovery of lasers: it ically purijied Cm for the frrst time and was at least a decade before applications of confirmed its structure in the form of a lasers came along. I think that Cm is or single, elegant I-JCNMR line (see box), will be similar. The chemistry itself is quite As soon as the chemistry community novel, and it presents major challenges. For could obtain enough Cm to explore its prop- example, with benzene there are six pos- erties, fulierene fever spread like wildfire. sible positions, but with buckminster- In short order, physicists found high-tem- fullerene there are 60. So, it’s difficult to perature superconductivity in alkali-doped foresee all the potential of the fullerenes, “buckybal[s.” The study of Cbo and other ful[erenes is the hottest area of science to- I guess I shotdd also say that fundamental day: it accounts for nine of the 23 hottest scientists are not necessarily the best people papers of 1991. All this from a fundamen- to ask about applications. People like my- tal question about the chemistry of stars! self have, in a sense, spent a lifetime avoid- Harold W. Kroto earned his B. SC. in ing applications. chemistry, with Jrst class honors, in 1961 and his Ph.D. in 1964, both from the Uni- We’ re puzzled about interesting things for versity of Shefield, U.K. After two years as their own sake, and we follow up on them, a postdoctoral fellow at the NRC, in Ot- However, having said that, I do see some tawa, Kroto spent a year at the (then) Bell possibilities. Telephone Laboratories in Murray Hill, New Jersey, In 1967, he returned to En- SW: Not so long ago, Science Watch spoke gland and joined the faculty of the Univer- to Donald Cram at UCLA about his work sity of Sussex, where he has since remained. on carceplexes and their poterrtiaf application At Sussex he ad~ancedfrom Lzcturer to, in in drugdelivery systems. Many have talked [985, Professor in the School of Chemistry about using fullerenes for the same purpose.

364 Wschmer, et al.,hkture, 347354-8,19W

Hebard,etal, :* 3s0600-1

Taylor,etal, J Chem.SoC-Cliem Gomnr. (20) 1423-5,1990

J-A S-9 N-D $: bl# M-J J-A s-o M-o 40s090 91 91 91 91 BlmonIhly Pertods SOURCE: R. Smalley,Buckminsterlulerene Blblioprsphy,Jan 1,1992: 1S1’sHot Papm Database, 1990-91 IkPaper count still recompletefor Nov.-Dee. 1991.

Kroto: Yes. The work of Cram and others Kroto: Well, C@ is a three-dimensional in producing these cages or carcerands is compound on which one can add many dif- one route. Perhaps C@ and the other fuller- ferent groups, Therefore, we can consider enes represent the ultimate way to encage these as nucleation centers. Linking up C@ an atom. I think it will take some time into polymeric matrices with encapsulated before we have the requisite chemical tech- species is, in principle, a possibility. One nology to incarcerate anything we want. would hope that this might be a way of Whether we can do it etllciently in the near designing computer memories at the mo- future remains to be seen. Certainly we lecular level. know it can be done with certain metal species. Applications involving the superconduct- ing and ferromagnetic properties of certain As for drug delivery, the idea is to encage types of fullerenes represent another area an atom or a molecule, move it to a spe- which people are looking at very carefully. cific site in the body, and then open up the With endohedral complexes, one can cage to release the agent. As I mentioned, choose not only the physical properties but at this stage we don’t yet know exactly also the electrical or magnetic properties how to encage atoms efficiently. We can of the cage. We know the behavior of C@ certainly do it by brute force, vigorous crystals depends on how close atoms are methods. C@ itself is formed in a very crude together, and other aspects, and if one can manner; rational synthesis is a non-trivial put atoms inside them, then it maybe pos- matter. But since we have learned to encage sible to tune the electrical properties to pro- certain metal atoms, one can see a way to duce very high-temperature superconduc- trapping a radioactive species and taking it tivity. somewhere in the body. For a radioactive atom, cage opening is not necessary. As long SW: You mentioned that the fullerenes as the cage surface is non-toxic and stable, present chemists with many challenges. it can be left there or, if not, excreted. Kroto: I think, in fact, fullerenes present SW: What are some other potential appli- massive problems for chemists. Fullerene cations? research is expanding chemists’ horizons.

365 h-s a demanding field analytically and tech- veloping a Sussex Fullerene Program, nically, and it’s taking chemists and others which will include topics in transition- into areas where they’ ve never gone be- metal, organic, and polymer chemistry. fore. Physicists have already put a lot of effort into understanding the properties of One of my own aims at present is to show fullerenes. High-temperature superconduc- that CM is, in fact, in space, but it’s still tivity was one drive, but there will be early days. First, we have to decide how to many others. For example, C60 exhibits detect it in space. As I“ve said before, it’s a strange phases. That’s an area for explo- celestial sphere that fell to earth, and now ration, too. I’m wondering whether it will bounce back into space. I do believe it is there. It was SW: Do you anticipate biologists will get discovered by simulating certain astrophysi- in the game as well? cal conditions, after all. The question is whether it is stable in space. 1 think it is. 1 Kroto: I do. One can think of taking these believe that it would be very surprising if molecules and modifying their overall hy- Cm, in some form, is not responsible for drophobic or hydrophilic properties in or- the diffuse interstellar bands that have der to make a palatable biochemical sys- puzzled astronomers for so long. That’s tem. In particular, if one thinks of the larger my gut reaction, the feeling in my heart. fullerenes, one imagines that it should be But if it’s not there, then there’s some- possible to manipulate their shape, and we thing else out there that may be even more know, of course, that shape is rather im- exciting. portant in biological systems. My other main interest right now con- SW: Has the discovery of the fullerenes cerns how Cm forms. It forms under the pointed to other areas worth pursuing? same sort of conditions that graphite forms. In fact, C@ is really a small round Kroto: There have been many, many ex- form of graphite. On a large scale, such citing and interesting molecules made in as in large slabs, it is flat. But that’s not small quantities over the years. One thinks the most stable form at the microscopic of dodecahedrane, CZOH,O,which is effec- level. The most stable form would be a tively a hydrogenated fuilerene. Its exploi- giant fullerene of some sort. What this tation hasn’t gone very far because it’s so means is that, unbelievably, we have over- difficult to make. That was the case with looked something fundamental from the Cm before we could make it in reasonable very beginnings of organic chemistry. The amounts, or enough so that everyone could discovery of the fullerenes has changed start working on some aspect of it. So, I our picture of how graphite forms and think that there may be many other com- what are the factors controlling its struc- pounds, ones that we already know about, ture. We’re starting to recognize that whose exploitation is inhibited because we graphite doesn’t just happen, and it doesn’t don’t have a good way of making suffi- want to be flat unless it’s in a very large cient material. Probably more effort should piece. And it doesn’t get to be a large be directed at compounds that we already piece unless it was in a smaller form be- have, forehand. We now need to focus on why carbon networks are flat on a large scale SW: What are you and your colleagues at and why they are round on a small scale. Sussex focusing on now? So, my aim is to rewrite the textbook pic- ture of what the most stable form of car- Kroto: We, which is to say myself, Roger bon is and why it takes the different forms Taylor, David Walton, and others, are de- it does. a

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