Fullerenes and Fullerene Derivatives in Properties and Potential Applications

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ullerenes and Fullerene Derivatives in Properties F and Potential Applications §ÿ≥ ¡∫—μ‘·≈–»—°¬¿“æ„π°“√ª√–¬ÿ°μå „™âøŸ≈‡≈Õ√’π·≈–Õπÿæ—π∏å¢ÕßøŸ≈‡≈Õ√’π

. Katsiri Laowachirasuwan . . Full-time Lecturer at General Science Department . . School of Science, University of the Thai Chamber of Commerce . E-mail: [email protected]

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‰«√— HIV-P (Inhibition of HIV-P) “√™’«¿“æμâ“πÕπÿ¡Ÿ≈Õ‘ √– (Biological Antioxidants) “√ μâ“π°“√‡®√‘≠‡μ‘∫‚μ¢Õß·∫§∑’‡√’¬ (Antibacterial Activity) ·≈–„™â‡ªìπμ—«μ—¥¥’‡ÕÁπ‡Õ∑’Ëμ”·Àπàß ®”‡æ“–‚¥¬„™â· ß (DNA Photocleavage) §” ”§—≠: øŸ≈‡≈Õ√’π Õπÿæ—π∏å¢ÕßøŸ≈‡≈Õ√’π §ÿ≥ ¡∫—μ‘ °“√ª√–¬ÿ°μå„™â Abstract After the discovery of Fullerenes, the 60-atom clusters and large carbon-cage molecules, the attention of scientists and materials scientists has been attracted by the syntheses of new materials based on the family of Fullerene molecules. Many properties of Fullerenes are new and unusual. With a better understanding of their chemical and physical properties, the fabrication of new materials for advanced applications has emerged as a challenging possibility. As we know that Fullerenes are easily modified, using organic chemistry and special synthetic techniques, into other molecular structures, this makes them remarkably versatile. The versatility of Fullerenes gives them enormous applications. This paper will review on Fullerenes and Fullerene derivatives properties, what is interesting about these çnewé carbon materials and how their unique properties can be utilized in potential applications. Applications of Fullerenes and Fullerene derivatives in areas such as semiconductors, superconductors, polymer-like materials, catalysts have been reviewed. In the medical field, the potential applications of Fullerenes and Fullerene derivatives include diagnostic or therapeutic agents, inhibition of HIV-P, powerful biological antioxidants, antibacterial activity, and DNA photocleavage. Keywords: Fullerenes, Fullerene Derivatives, Properties, Applications

Introduction far the most common one is C60, also called a çbuckyballé or Buckminsterfullerene. Carbon is one of the common substances Buckminsterfullerene was named after a on earth and widely distributed in nature. noted architect, Richard Buckminster Fuller, Natural carbon can exist in several forms. who popularized the geodesic dome Most people know about graphite and (Applewhite, 1995). Since Buckminsterfullerene diamond, but there is a fourth allotropic form has a similar shape to that of a dome, the of carbon, çFullerenes.é They are new to us. name was thought to be widely credited to Fullerenes are the 60-atom clusters and large R. Buckminster Fuller. carbon-cage molecules (Pierson, 1993). By

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Fullerenes were first discovered in 1985 possible such as C70, C76 and C84. in an apparatus designed by Professor Richard This paper will review Fullerenes and Smalley to produce atomic clusters of the Fullerene derivatives, what is interesting non-volatile element (Kroto, et al., 1985). The about this çnewé carbon material, and how experiments that led to the discovery of their unique properties can be utilized in Fullerenes were aimed at simulating in the potential applications. laboratory the conditions under which carbon nucleates in the atmosphere of a cool Properties of Fullerenes carbon-rich red giant star. The specific goal Fullerenes are fascinating because they of the work was to explore the possibility show unusual properties for carbon material. that long carbon chain molecules such as → cyanopolynes (HCnN, n = 5 11) could form Structure and Bonding when carbon vapor nucleates in the presence of hydrogen and nitrogen. Smalley, Kroto and Fullerenes are a class of closed-cage o Curl had developed a powerful technique in carbon molecules, about 7-15 angstroms ( a) which a laser vaporizes atoms of a refractory in diameter, consisting of a number of material (carbon) into a carrier gas (Helium). five-membered rings (pentagons) and six- Smalley, Kroto and Curlûs experiments showed membered rings (hexagons), with a carbon convincingly that species such as HC N and atom at the corners of each hexagon and a 7 bond along each edge. In order to make a HC9N could be produced in the laboratory simulation of conditions in stars. However, closed cage, all Fullerene molecules should even more significant was the unexpected have the formula C20+m, where m is an integer number. For example, the proposed structure discovery of C60. The discovery of Fullerenes and the insight that led to the interpretation for C60 is a çtruncated icosahedron.é A of the magic number featured in the observed truncated icosahedron is derived from an mass spectra in terms of hollow carbon molecules icosahedron by truncating each of the twelve led to the award of the Noble Prize in Chemistry vertices, each vertex being replaced by to Curl, Kroto, and Smalley in 1996. five-membered rings. The truncating process also converts each of the twenty former The chemistry of Fullerenes is rich and triangular faces into six-membered rings varied, and it allows the properties of basic which resemble a soccer ball with 12 pentagons Fullerenes to be tailored to a given application. and 20 hexagons (Haddon, Brus, and Derivatives of all of the basic Fullerenes are Raghavachari, 1986a). (See Figure 1.)

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Figure 1 a) Icosahedron b) Truncated Icosahedron c) Fullerenes, C60

The truncated icosahedron is not the only Fullerenes include C28, C32, C50, C70, C80, and possible Fullerene-type structure. There are C82. Because the molecular strain tends to many other hollow cage structures that can be be concentrated in the five-membered rings constructed using only pentagons and hexagons. responsible for closure structures that avoid Interestingly, each of these structures contains contiguous (edge-sharing), pentagons are exactly twelve pentagons while the number particularly stable. of hexagons is arbitrary. The pentagons are For C60 bonding, each vertex of the necessary for closure. The number of vertices truncated icosahedron is occupied by a carbon in closed Fullerene-type structure is necessarily atom. Each carbon is bonded to three other even (Kroto, 1987). The smallest possible carbons in an infinite two-dimensional array Fullerenes would be C20, containing twelve by one double bond and two single bonds pentagons and zero hexagons. Other possible (Taylor, 2001). (See Figure 2.)

Figure 2 Dominant Resonance Structure for C60 Carbon atoms with this kind of connectivity the pi-bond. The angle between a p axis and a o are usually referred to as çsp2 carbonsé because C-C bond vector, θ, is 101.6 . The bowl-shape the orbitals used to sigma-bond the three or concavity at each sp2 carbon center introduces adjacent carbons are hybrids of the 2s orbital some strain into the molecule (Haddon, Brus, and the two 2p orbitals (2px and 2py). The and Raghavachari, 1986b). remaining 2p orbital (2px) is responsible for

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Chemically, Fullerenes are stable, but not Synthesis of Fullerenes totally unreactive; breaking the balls requires Fullerenes can be synthesized by temperatures of over 1,000 degrees Celsius evaporating graphite electrodes (rods) via (the exact number depends on which particular resistive heating in an atmosphere of inert Fullerenes). Fullerenes are sparingly soluble gas, about 100 torr of helium, He (1 atm = 760 in many solvents at room temperature. torr) being the best (Kratschmer, et al., 1990). Common solvents for the Fullerenes include This produces a light condensate called toluene and carbon disulfide. At room Fullerenes soot, which contains only a few temperature, the solubility of Fullerenes is percent by weight of C and a variety of about 2.8 mg/mL in toluene. As the size 60 different Fullerenes. C could be extracted increases, the solubility of Fullerenes 60 using benzene as solvent. The red-brown decreases. Solutions of pure C have a deep 60 benzene solution could be decanted from the purple color. Solutions of C are a reddish 70 black insoluble soot and then dried using brown. The higher Fullerenes C -C have a 76 84 gentle heat, leaving a residue of dark brown variety of colors (Taylor, 2001). to black crystalline material yielding Fullerenes. The HOMO-LUMO gap of Fullerenes is 1.68 eV. (Andreoni, Gygi, and Parrinello, 1992). Species of Fullerenes Due to the low-lying LUMO, Fullerenes are (Fullerenes Derivatives) reduced easily, and this is the reason which Can we put something in the cage? The makes Fullerenes a good oxidizing agent. answer is yes. The usual way to combine Fullerenes are unstable at higher temperatures. Fullerenes with other atoms is to put the other The process of decomposition is faster in atoms inside the balls. Fullerenes with the presence of oxygen. The measurable enclosed atoms are called çEndohedral decomposition can be observed about 830 K Fullerenes.é Thus, Endohedral Fullerenes are (Chen, et al., 1992). Fullerenes that have additional atoms, ions or clusters enclosed within their inner spheres. (See Figures 3a, 3b.)

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Figure 3a Empty Fullerenes Figure 3b Fullerenes Containing an Encapsulated Metal Atom The first lanthanum Fullerenes complex endohedral non-metal doped fullerene was synthesized in 1985 called La@C60. The @ complexes with helium, neon, argon, krypton sign in the name reflects the notion of a small and xenon as well as numerous adducts of molecule trapped inside a cage (the first the He@C60 compound could be proven with material is inside the second). Two types operating pressure of 3,000 bars and of Endohedral Fullerenes complexes exist. incorporation of up to 0.1% of the noble gases

Firstly, when the atoms trapped inside happen (Saunders, et al., 1994). Even though C60 is the to be metallic, they are called Endohedral most common Fullerene, few endohedral

Metallofullerenes. Secondly, when the atoms materials have a C60 cage because their trapped inside are non-metal, they are called structures are small inside. Most of these non-metal doped Fullerenes (Saunders, et al., materials are made out of C80, C82, C84 or even

1993). For Endohedral Metallofullerenes, the higher Fullerenes, such as Sc3C2@C80, metals can be transition metals like scandium, Ce2@C80, L@C82, Gd@C82, etc. yttrium as well as lanthanides, alkaline earth Another significant Fullerene species is metals like barium and strontium, alkali metals Exohedral Fullerenes or Fullerene derivatives like potassium and tetravalent metals like which are molecules formed by bonding uranium, zirconium and hafnium. As it is very between fullerenes and other chemical difficult to open up carbon cage molecules to groups, known as functionalized fullerenes. Two enclose a foreign atom inside, metals must be main types of primary chemical transformations synthesized during the formation of the cage are possible on the fullerene surface: addition itself (Lee, et al., 2002). In 1993, Saunders reactions and redox reactions, which lead could prove the existence of the endohedral to covalent exohedral adducts and salts non-metal doped fullerene complexes He@C60 respectively (Schick, et al., 1996). For example, and Ne@C60 which form when C60 is exposed cycloaddition of azomethine yields to to a pressure of 3 bar of the noble gases Fulleropyrrolidne. (See Figure 4.) (Saunders, et al., 1993). The formation of

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Figure 4 Synthesis of Fulleropyrrolidines The azomethine ylides are synthesized and Prato, 1993). This reaction is very useful by condensation of α-amino acids and because it is possible to introduce different aldehydes or ketones. Fulleropyrrolidines are substituents on nitrogen and on carbons 2 obtained with the 5-membered ring fused to a and 5. (See Figure 5.) 6,6 bond on the fullerene (Maggini, Scorrano,

▲

Figure 5 Substituents on Nitrogen and on Carbons 2 and 5 These exohedral Fullerenes retain the attracted by the synthesis of new materials main properties of the parent molecule based on the family of Fullerene molecules.

(Fullerenes, C60) and can be made to be Many properties of Fullerenes are new more highly lipophilic than basic Fullerenes as and unusual, and with a better understanding well as water soluble and amphiphilic. They of their chemical and physical properties, the include copolymers and derivatives with fabrication of new materials for advanced altered electronic and optical properties applications has emerged as a challenging (NanoC, 2007). possibility. As we know that Fullerenes are easily modified, using organic chemistry and Potential Applications of Fullerenes special synthesis techniques, into other and Fullerene Derivatives molecular structures, this makes them After the discovery of Fullerenes, the remarkably versatile. The versatility of Fullerenes attention of materials scientist has been gives them enormous applications.

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Researchers have shown that solids K3C60, when it is cool, its resistivity begins based on Fullerenes can be insulators, to drop sharply at about 18 K, indicating conductors, semiconductors or even the onset of superconductivity (Hebard et al., superconductors when they are inserted with 1991). As larger alkali-metal cations are other atoms or molecules. Pure Fullerene incorporated into the lattice and the fcc lattice solids form crystal structures, like graphite or parameter (a0) increases, the superconducting diamond that are insulators or semiconductors. transition temperature, TC, also increases.

Adding 3 alkali atoms per C60 resulted in Therefore, the TC for Rb3C60 rises to 28 K.

A3C60 compounds (A is one of the alkali This rise in TC may be related to an increase metals such as K, Rb, Cs, Na; and these in the density of states at the Fermi level with solids can become electricity conducting increasing lattice constant (Fleming, et al., metals), which turn out to be superconductors 1991). The correlation between TC and lattice at quite a high temperature (19-40 K). They constant (a0) suggests that even higher TCûs conduct electric current without any resistance could be obtained by incorporating larger at temperature below 19-40 K. For example, and larger cations, A. (See Figure 6.)

Figure 6 Plot of Superconducting Transition Temperature TC (K) vs. o Lattice Parameter a (angstroms) for Various Compositions of A3C60 Fullerenes have been known to have the use of ultra-vacuum equipment which is excellent n-type organic thin film semiconductor expensive and hardly controllable. For this properties (electron acceptor). The high quality reason, to reduce the production costs and to thin film of Fullerenes prepared under ultra-high be applicable to the preparation of large-area vacuum has been known to show the highest devices, a new Fullerene derivative, C60-fused electron mobility. However, the preparation pyrrolidine-meta-C12 phenyl (C60MC12), of crystalline thin film of Fullerenes needs organic semiconductor materials, has been

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Fullerenes (C60). C60MC12 is soluble in organic structures (Chikamatsu, et al., 2005). (See solvent, and found to be a good quality Figure 7.) crystalline thin film by simple coating where

Figure 7 Structure of C60MC12

C60MC12 is used as an n-type organic thin compounds, found in residential environments film transistor. The electron mobility of C60MC12 due to emission from construction materials, is as high as 0.067cm2/Vs, which is the highest paints and glues, at ambient temperature value for an n-type organic semiconductor without additional energy sources. A volatile prepared through a coating process (Chikamatsu, organic compound such as toluene, containing et al., 2005). a benzene ring, is hard to remove from the As mentioned before, the LUMO of living environment. Fullerenes polymer-like Fullerenes is relatively low in energy, and it is materials, C60Pdn, showed good adsorptivity readily reduced. The interesting electronic toward toluene. Even at a low concentration properties of Fullerenes have led to the of 1000 ppb, which is close to the actual possibility of using units of Fullerenes in the toluene concentration in the environment, the formation of polymers. The Fullerenes polymer- adsorptivity is retained (Hayashi, et al., 2004). like materials, C Pd or C Pt are formed This result should open the route to using 60 n 60 n Fullerenes polymer-like materials to remove from C60 and Pd2(dba)3.CHCl3 or Pt(dba)2, (dba = dibenzylideneacetone) respectively. harmful gases from the living environment. These redox-active Fullerene-based polymeric Fullerene materials have also been used materials can be formed by electrochemical as excellent catalysts for H-transfer reaction reduction of Fullerenes under specific such as coupling and transalkylation reaction of conditions (Balch, Costa, and Winkler, 1998). mesitylene, engaged in transfer hydrogenation These Fullerene polymers have possible with dihydroaromatics, and hydrodealkylations. applications to adsorb volatile organic For example, when mesitylene was heated

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Figure 8 Fullerenes Catalyst Coupling and Transalkylation Reactions The key structural feature that endows applications, may prove to have value as Fullerenes with many of their characteristics diagnostic or therapeutic agents in medicine. is the presence of a pentagon surrounded For diagnostic application, Endohedral by hexagons, which endows them with metallofullerenes, such as M@C82 (OH)30, electrophilicity and an ability to stabilize are being used as Magnetic Resonance radicals. Fullerenes are also highly effective in Imaging contrast agents (M = Gd3+) (Wharton, promoting the conversion of methane into et al., 1999), X-ray contrast agents (M = Ho3+) higher hydrocarbons (higher-value fuels and and radio pharmaceuticals (M= 166Ho3+ and other chemicals) (Malhotra, et al., 1997). Methane 170Tm2+) (Ehrhardt, et al., 2000). The radioactive is now burned off rather than transported metal is trapped inside the carbon shell, which from distant oil fields. Adding seven carbon is non toxic, very stable, and resistant to atoms to methane (one carbon atom) would metabolism by the body. They can stay in the convert it to valuable liquid octane (eight body for approximately one hour, allowing carbon atoms). Adding even one carbon atom imaging of circulatory system. For therapeutic would convert methane to ethane, which is application, the potential applications of still a gas but is useful in organic synthesis, Fullerenes and Fullerene derivatives include as a fuel, and in refrigeration (Trulove, 2007). inhibitors of the protease enzyme specific Fullerenes and Fullerene derivatives, to the human immunodeficiency virus 1 because their exceptional stability, large (HIV-P). The bis (monosuccinimide) derivative size, hydrophobic character and outer surface of p,pû-bis(2-aminoethyl)-diphenyl-C60 shown can be easily manipulated for different in Figure 9 is an HIV-protease inhibitor (Friedman, et al., 1993).

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Figure 9 Fullerene Molecule that Inhibits HIV Protease

This molecule has approximately the molecule could fit very well inside the HIV-P same radius as the active site of HIV-P and is cavity. (See Figure 10.) This result might primarily hydrophobic. An opportunity exists prevent the interaction between the catalytic for a strong hydrophobic Van der Waals portions of HIV-P and the virus substrates interaction between the nonpolar active site (Marcorin, et al., 2000). surface and the C60 surface. Therefore, this

Figure 10 Computer Designed Showing the Accommodation of Synthesized Fullerene Compound Inside the HIV-P Cavity Recent results indicate that Fullerenes species, Fullerenes are known to behave like may have potential as powerful biological a çfree radical spongeé and facile addition antioxidants, reacting readily and at a high of up to thirty four methyl radical to C60 has rate with free radicals, which are often the been reported (Wilson, 1999). They can cause of cell damage or death. Because of sponge-up and neutralize twenty or more the large number of conjugated double free radicals per Fullerene molecule (100 times bonds that are readily attacked by radical more effective than current leading antioxidants

174 «“√ “√«‘™“°“√ ¡À“«‘∑¬“≈—¬ÀÕ°“√§â“‰∑¬ ªï∑’Ë 28 ©∫—∫∑’Ë 2 ‡¥◊Õπ‡¡…“¬π - ¡‘∂ÿπ“¬π 2551 Katsiri Laowachirasuwan such as Vitamin E) (NanoC, 2007). Fullerenes could lead to the discharge of metabolites and Fullerene derivatives are probably the and cell death (Da Ros, Spalluto, and Prato, worldûs most efficient radical scavengers. 2001). Scientists employed different alhehydes Another potential biological application (paraformaldehyde or 3,6,9-trioxadecane of Fullerene derivatives is antibacterial activity. aldehyde) to synthesize N-mTEG substituted Fullerene derivatives could produce membrane fulleropyrrolidines (mTEG = monomethoxy disruptions by insertion into phospholipidic triethylene glycol) (Bosi, et al., 2000) as shown bilayers. The consequent menbrane disorder in Figure 11.

Figure 11 Synthesis of mTEG Mycobacterium avium is completely In medicinal chemistry, the potential inhibited by this synthesized molecule at a applications of Fullerenes and Fullerene dose of 260 mg/mL. The possible explanation derivatives include DNA photocleavage. could be that presence of the carbon cage Fullerenes were found to be cytotoxic when destabilizes the tubercular cell wall by exposed to visible light. As shown in Figure 12, intercalation in the hydrophobic part. (Bosi, they have the following mechanism (Ikeda, et al., 2000) et al., 2005).

Figure 12 Mechanism of Fullerenes When Exposed to Visible Light

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Fullerenes (C60) from ground state were unique properties and characteristics showing excited by photoirradiation to an excited state several potential applications in material 1 and converted to short-lived species, C60. science while funtionalization chemistry of 1 This C60 was converted to the long-lived Fullerenes and Fullerene derivatives have 3 species, C60 by intersystem crossing (ISC). emerged as a key tool to design the material 3 In the presence of oxygen (O2), C60 can properties as functions of the applications. transfer its energy to O2 and return to ground 1 References state, generating singlet oxygen, O2 which is known as a highly cytotoxic species or An, Y.Z., et al. 1996. çUse of Fullerene Derivatives reactive species toward DNA. By electron as DNA Compaction Agent.é Tetrahedron 3 transfer C60 can be reduced to Fullerene radical 52: 5179-5189. anion, C60ë- and C60ë- can transfer one Andreoni, W., Gygi, F., and Parrinello, M. 1992. electron to produce superoxide radical anion, çStructure and Electronic Properties of O2ë- which is known as reactive species C70-group of 2.é Chemical and Physical toward DNA. Letters 189: 241-244. 1 3 Applewhite, E.J. 1995. çThe Naming of The excited Fullerenes, C60 and C60 can be reduced in the presence of the guanosine Buckminsterfullerene.é The Chemical residue present to DNA (An, et al., 1996). Intelligencer 1: 3. Cytotoxicity of Fullerenes was mediated by Balch, A.L., Costa, D.A., and Winkler, K. 1998. its ability to cleave DNA. DNA cleavage was çFormation of Redox-Active, Two- found to occur at guanine residue without Component Films by Electrochemical any significant sequence selectivity (Tokuyama, Reduction of C60 and Transition Metal et al., 1993). Therefore, Fullerenes are being Complexes.é Journal of American developed for the treatment of cancer. Chemical Society 120: 9614-9620. Bosi, S., et al. 2000. çAntimycobacterial Activity Conclusion of Ionic Fullerene Derivatives.é Bioorganic The research of Fullerenes has opened Medicinal Chemistry Letters 10: 1043- a new chapter on the chemistry of carbon. 1045. The most important and useful thing that Chen, H.S., et al. 1992. çThermodynamic of C in Pure O , N and Ar.é Journal of came out of this sort of research is new ideas 60 2 2 and paths of investigation. Fullerenes and Physical Chemistry 96: 1016-1018. Fullerene derivatives have been introduced Chikamatsu, M. 2005. çn-type Organic Thin and expected to be very useful with their Film Transistor Prepared by Solution

Process.é AIST Today 5, 12: 21. of Toyota CRDL 40, 1: 15-20. Chikamatsu, M., et al. 2005. çSolution-Processed Hebard, A.F., et al. 1991. çSuperconductivity

n-Type Organic Thin-Film Transistors at 18K in Potassium-Doped C60.é Nature with High Field-Effect Mobility.é Applied 350: 600. Physical Letters 87: 2035.† Ikeda, A., et al. 2005. çEfficient Photocleavage Da Ros, T., Spalluto, G. and Prato, M. 2001. of DNA Utilising Water-Soluble Lipid çBiological Applications of Fullerene Membrane-Incorporated [60] Fullerenes Derivatives: A Brief Overview.é Croatica Prepared Using a [60] Fullerene Chemica ACTA 74, 4: 743-755. Exchange Method.é Organic and Ehrhardt, G.J., et al. 2000. Nuclear and Biomolecular Chemistry 3: 2907-2909.

Radiation Chemical Approaches to Kratschmer, W., et al. 1990. çSolid C60 : A new Fullerene Science. Dordrecht: Kluwer Form of Carbon.é Nature 347: 354. Academic. Kroto, H.W. 1987. çThe Stability of the Fullerenes

Fleming, R.M., et al. 1991. çRelation of Structure Cn with n = 24, 28, 32, 36, 50, 60 and and Superconducting Transition 70.é Nature 329: 529.

Temperatures in A3C60.é Nature 352: Kroto, H.W., et al. 1985. çC60 Buckminsterfullerene.é 787. Nature 318: 162-163. Friedman, S.H., et al. 1993. çInhibition of the Lee, H.M., et al. 2002. çCrystallographic

HIV-1 Protease by Fullerene Derivatives : Characterization of Kr@C60 in (0.09Kr@C60/ . II . Model Building Studies and Experimental 0.91C60) {Ni (OEP)} 2C6H6.é Chemical Verification.é Journal of American Communications: 1352.† Chemical Society 115: 6506-6509. Maggini, M., Scorrano, G., and Prato, M. 1993.

Haddon, R.C., Brus, L.E., and Raghavachari, K. çAddition of Azomethine Ylides to C60: 1986a. çElectronic Structure and bonding Synthesis, Characterization, and

in Icosahedral C60.é Chemical and Functionalization of Fullerene Pyrrolidines.é Physical Letters 125: 459. Journal of American Chemical Society Haddon, R.C., Brus, L.E., and Raghavachari, 115: 9798-9799. K. 1986b. çRehybridization and p-Orbital Malhotra, R., et al. 1997. çCatalytic Properties Alignment: The key to the Existence of of Fullerene Materials.é In Recent Spheroidal Carbon Clusters.é Chemical Advances in Catalytic Materials : and Physical Letters 131: 165. Symposium Held December 2-4, 1997, Hayashi, A., et al. 2004. çThe First Application Boston, Massachusetts, U.S.A., of Fullerene Polymer-Like Materials, pp. 135-136. Warrendale, PA: Materials

C60Pdn, as Gas Adsorbents.é R&D Review Research Society.

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Marcorin, G., et al. 2000. çDesign and Synthesis Addition Pattern and the Addend G.é of Novel [60] Fullerene Derivatives as Chemistry the European Journal 2: Potential HIV Aspartic Protease 935-943. Inhibitors.é Organic Letters 2: 3955- Taylor, R. 2001. Fullerene Chemistry : A 3958. Handbook for Chemists. London: Imperial NanoC. April 15, 2007. Leading the Development College Press. of Nanostructured Carbon Products, Tokuyama, H., et al. 1993. çPhoto-induced Antioxidant & Biopharmaceuticals Biological Activity of Fullerene.é Journal [On-Line]. Available: http://www.nano-c. of American Chemical Society 115: com/fullerenes/applications.htm 7918-7919. Pierson, H.O. 1993. Handbook of Carbon, Trulove, S. July 15, 2007. çFilled Buckyballs Graphite, Diamond and Fullerenes: Diamonds from Soot.é Research Properties, Processing, and Magazine Virginia Tech [On-line serial]. Applications. Park Ridge, NJ: Noyes. Available : http://www.research.vt.edu/ Saunders, M., et al. 1993. çStable Compounds resmag/2002winter/buckyballs.html

of Helium and Neon: He@C60 and Wharton, T., et al. 1999. Recent Advances in

Ne@C60.é Science 259, 5100: 1428-1430. Chemistry and Physics of Fullerenes Saunders, M., et al. 1994. çIncorporation of and Related Materials. Volume 7 : Helium, Neon, Argon, Krypton, and Xenon Proceedings of the Twelfth International into Fullerenes Using High Pressure.é Symposium. Pennington, NJ: Journal of American Chemical Society Electrochemical Society. 116, 5: 2193-2194. Wilson, L.J. 1999. çMedical Application of Schick, G., et al. 1996. çOpening and Closure Fullerenes and Metallofullerenes.é The of the Fullerene Cage in cis-1-Bisimino Electrochemical Society Interface

Adducts of C60: The Influence of the Winter: 24-28.

Mrs. Katsiri Laowachirasuwan received her Master of Science in Chemistry (Inorganic Chemistry) from Texas A&M University, Kingsville, USA. She is currently working at the School of Science, the University of the Thai Chamber of Commerce. Her main interest is in material science, inorganic chemistry and analytical chemistry. Her current research includes the characterization of activated carbons.