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Part of a series of articles on Nanomaterials Fullerenes Carbon nanotubes Buckminsterfullerene Fullerene chemistry Applications In popular culture Timeline Carbon allotropes Nanoparticles Quantum dots Nanostructures Colloidal gold Silver nanoparticles Iron nanoparticles Platinum nanoparticles See also Nanotechnology  v • d • e  Fullerene chemistry is a field of organic chemistry devoted to the chemical properties of fullerenes.[1][2][3] Research in this field is driven by the need to functionalize fullerenes and tune their properties. For example fullerene is notoriously insoluble and adding a suitable group can enhance solubility.[1] By adding a polymerizable group, a fullerene polymer can be obtained. Functionalized fullerenes are divided into two classes: exohedral with substituents outside the cage and endohedral fullerenes with trapped molecules inside the cage. Contents 1 Chemical properties of fullerenes 2 Fullerene reactions 2.1 Nucleophilic addition 2.2 Pericyclic reactions 2.3 Hydrogenation 2.4 Oxidation 2.5 Hydroxylation 2.6 Electrophilic addition 2.7 Retro additions 3 Fullerenes as ligands 4 Multistep fullerene synthesis 5 Open-cage fullerenes 6 Fullerene dimers 7 Nanotube chemistry 8 Fullerene purification 8.1 Experimental purification strategies 9 References // Chemical properties of fullerenes See also: Endohedral fullerenes Fullerene or C60 is soccer-ball-shaped or Ih with 12 pentagons and 20 hexagons. According to Euler's theorem these 12 pentagons are required for closure of the carbon network consisting of n hexagons and C60 is the first stable fullerene because it is the smallest possible to obey this rule. In this structure none of the pentagons make contact with each other. Both C60 and its relative C70 obey this so-called isolated pentagon rule (IPR). The next homologue C84 has 24 IPR isomers of which several are isolated and another 51,568 non-IPR isomers. Non-IPR fullerenes have thus far only been isolated as endohedral fullerenes such as Tb3N@C84 with two fused pentagons at the apex of an egg-shaped cage.[4] or as fullerenes with exohedral stabilization such as C50Cl10 [5] and reportedly C60H8 [6]. Because of the molecule's spherical shape the carbon atoms are highly pyramidalized, which has far-reaching consequences for reactivity. It is estimated that strain energy constitutes 80% of the heat of formation. The conjugated carbon atoms respond to deviation from planarity by orbital rehybridization of the sp² orbitals and pi orbitals to a sp2.27 orbital with a gain in p-character. The p lobes extend further outside the surface than they do into the interior of the sphere and this is one of the reasons a fullerene is electronegative. The other reason is that the empty low-lying pi* orbitals also have high s character. The double bonds in fullerene are not all the same. Two groups can be identified: 30 so-called [6,6] double bonds connect two hexagons and 60 [5,6] bonds connect a hexagon and a pentagon. Of the two the [6,6] bonds are shorter with more double-bond character and therefore a hexagon is often represented as a cyclohexatriene and a pentagon as a pentalene or [5]radialene. In other words, although the carbon atoms in fullerene are all conjugated the superstructure is not a super aromatic compound. The X-ray diffraction bond length values are 135.5 pm for the [6,6] bond and 146.7 pm for the [5,6] bond. C60 fullerene has 60 pi electrons but a closed shell configuration requires 72 electrons. The fullerene is able to acquire the missing electrons by reaction with potassium to form first the K6C6−60 salt and then the K12C12−60 In this compound the bond length alternation observed in the parent molecule has vanished. Fullerene reactions See also: Bingel reaction and Prato reaction Fullerenes tend to react as electrophiles. An additional driving force is relief of strain when double bonds become saturated. Key in this type of reaction is the level of functionalization i.e. monoaddition or multiple additions and in case of multiple additions their topological relationships (new substituents huddled together or evenly spaced). Nucleophilic addition Fullerenes react as electrophiles with a host of nucleophiles in nucleophilic additions. The intermediary formed carbanion is captured by another electrophile. Examples of nucleophiles are Grignard reagents and organolithium reagents. For example the reaction of C60 with methylmagnesium chloride stops quantitatively at the penta-adduct with the methyl groups centered around a cyclopentadienyl anion which is subsequently protonated [7]. Another nucleophilic reaction is the Bingel reaction. Fullerene reacts with chlorobenzene and aluminium chloride in a Friedel-Crafts alkylation type reaction. In this hydroarylation the reaction product is the 1,2-addition adduct (Ar-CC-H) [8]. Pericyclic reactions The [6,6] bonds of fullerenes react as dienes or dienophiles in cycloadditions for instance Diels-Alder reactions. 4-membered rings can be obtained by [2+2]cycloadditions for instance with benzyne. An example of a 1,3-dipolar cycloaddition to a 5-membered ring is the Prato reaction. Fullerenes react with carbenes to methanofullerenes. Hydrogenation Fullerenes are easily hydrogenated by several methods. Examples of hydrofullerenes are C60H18 and C60H36. However, completely hydrogenated C60H60 is only hypothetical because of large strain. Highly hydrogenated fullerenes are not stable, prolonged hydrogenation of fullerenes by direct reaction with hydrogen gas at high temperature conditions results in collapse of cage structure with formation of polycyclic aromatic hydrocarbons. Oxidation Although more difficult than reduction, oxidation of fullerene is possible for instance with oxygen and osmium tetraoxide. Hydroxylation Fullerenes can be hydroxylated to fullerenols or fullerols. Water solubility depends on the total number of hydroxyl groups that can be attached. One method is fullerene reaction in diluted sulfuric acid and potassium nitrate to C60(OH)15 [9] [10] . Another method is reaction in diluted sodium hydroxide catalysed by TBAH adding 24 to 26 hydroxyl groups [11]. Hydroxylation has also been reported using solvent-free NaOH / hydrogen peroxide [12]. C60(OH)8 was prepared using a multistep procedure starting from a mixed peroxide fullerene [13]. The maximum number of hydroxyl groups that can be attached (hydrogen peroxide method) stands at 36-40 [14]. Electrophilic addition Fullerenes react in electrophilic additions as well. The reaction with bromine can add up to 24 bromine atoms to the sphere. The record holder for fluorine addition is C60F48. According to in silico predictions the as yet elusive C60F60 may have some of the fluorine atoms in endo positions (pointing inwards) and may resemble a tube more than it does a sphere.[15] Retro additions Protocols have been investigated for removing substituents via retroadditions after they have served their purpose. Examples are the retro-Bingel reaction and the retro-Prato reaction. Fullerenes as ligands Fullerene is a ligand in organometallic chemistry. The [6,6] double bond is electron-deficient and usually forms metallic bonds with η = 2 hapticity. Bonding modes such as η = 5 or η = 6 can be induced by modification of the coordination sphere. C60 fullerene reacts with tungsten hexacarbonyl W(CO)6 to the (η²-C60)W(CO)5 complex in a hexane solution in direct sunlight.[16] Multistep fullerene synthesis Although the procedure for the synthesis of the C60 fullerene is well established (generation of a large current between two nearby graphite electrodes in an inert atmosphere) a 2002 study described an organic synthesis of the compound starting from simple organic compounds.[17][18] In the final step a large polycyclic aromatic hydrocarbon consisting of 13 hexagons and three pentagons is submitted to flash vacuum pyrolysis at 1100°C and 0.01 Torr. The three carbon chlorine bonds serve as free radical incubators and the ball is stitched up in a no-doubt complex series of radical reactions. The chemical yield is low: 0.1 to 1%. A small percentage of fullerenes is formed in any process which involves burning of hydrocarbons, e.g. in candle burning. The yield through a combustion method is often above 1%. The method proposed above does not provide any advantage for synthesis of fullerenes compared to the usual combustion method, and therefore, the organic synthesis of fullerenes remains a challenge for chemistry. A similar exercise aimed at construction of a C78 cage in 2008 (but leaving out the precursor's halogens) did not result in a sufficient yield but at least the introduction of Stone Wales defects could be ruled out.[19] Open-cage fullerenes A part of fullerene research is devoted to so-called open-cage fullerenes [20] whereby one or more bonds are removed chemically exposing an orifice [21]. In this way it is possible to insert into it small molecules such as hydrogen, helium or lithium. The first such open-cage fullerene was reported in 1995 [22]. In endohedral hydrogen fullerenes the opening, hydrogen insertion and closing back up has already been demonstrated. Fullerene dimers The C60 fullerene dimerizes in a formal [2+2] cycloaddition to a C120 bucky dumbbell in the solid state by mechanochemistry (high-speed vibration milling) with potassium cyanide as a catalyst [23]. The trimer has also been reported using 4-aminopyridine as catalyst (4% yield) [24] and observed with Scanning Tunneling Microscopy as a monolayer [25] Nanotube chemistry Main article: Selective chemistry of single-walled nanotubes Carbon nanotubes, also part of the fullerene family, can be described as graphene sheets rolled into a cylindrical tube. Unlike the spherical fullerenes made up of hexagons and pentagons, nanotubes only have hexagons present but in terms of reactivity both systems have much in common. Due to electrostatic forces nanotubes have a nasty tendency to cluster together into bundles and many potential applications require an exfoliation process. One way to do this is by chemical surface modification. A useful tool for the analysis of derivatised nanotubes is Raman spectroscopy which shows a G-band (G for graphite) for the native nanotubes at 1580 cm-1 and a D-band (D for defect) at 1280 cm-1 when the graphite lattice is disrupted with conversion of sp² to sp³ hybridized carbon. The ratio of both peaks ID/IG is taken as a measure of functionalization. Other tools are UV spectroscopy where pristine nanotubes show distinct Van Hove singularities where functionalized tubes do not, and simple TGA analysis. In one type of chemical modification, aniline is oxidized to a diazonium intermediate. After expulsion of nitrogen, it forms a covalent bond as an aryl radical:[26][27] Also known are protocols for Diels-Alder reactions, one assisted by chromium hexacarbonyl and high pressure [28]. The ID/IG ratio for reaction with Danishefsky’s diene is 2.6. Nanotubes can also be alkylated with alkyl halides using lithium or sodium metal and liquid ammonia (Birch reduction conditions) [29] [30]. The initial nanotube salt can function as an polymerization initiator [31] and can react with peroxides to form alkoxy functionalized nanotubes [32] Fullerene purification Fullerene purification is the process of obtaining a fullerene compound free of contamination. In fullerene production mixtures of C60, C70 and higher homologues are always formed. Fullerene purification is key to fullerene science and determines fullerene prices and the success of practical applications of fullerenes. The first available purification method for C60 fullerene was by HPLC from which small amounts could be generated at large expense. A practical laboratory-scale method for purification of soot enriched in C60 and C70 starts with extraction in toluene followed by filtration with a paper filter. The solvent is evaporated and the residue (the toluene-soluble soot fraction) redissolved in toluene and subjected to column chromatography. C60 elutes first with a purple color and C70 is next displaying a reddish-brown color.[33] In nanotube processing the established purification method for removing amorphous carbon and metals is by competitive oxidation (often a sulfuric acid / nitric acid mixture). It is assumed that this oxidation creates oxygen containing groups (hydroxyl, carbonyl, carboxyl) on the nanotube surface which electrostatically stabilize them in water and which can later be utilized in chemical functionalization. One report [34] reveals that the oxygen containing groups in actuality combine with carbon contaminations absorbed to the nanotube wall that can be removed by a simple base wash. Cleaned nanotubes are reported to have reduced D/G ratio indicative of less functionalization, and the absence of oxygen is also apparent from IR spectroscopy and X-ray photoelectron spectroscopy. Experimental purification strategies A recent kilogram scale fullerene purification strategy was demonstrated by Nagata et al.[35] In this method C60 was separated from a mixture of C60, C70 and higher fullerene compounds by first adding the amidine compound DBU to a solution of the mixture in 1,2,3-trimethylbenzene. DBU as it turns out only reacts to C70 fullerenes and higher which reaction products separate out and can be removed by filtration. C60 fullerenes do not have any affinity for DBU and are subsequently isolated. Other diamine compounds like DABCO do not share this selectivity. C60 but not C70 forms a 1:2 inclusion compound with cyclodextrin (CD). A separation method for both fullerenes based on this principle is made possible by anchoring cyclodextrin to colloidal gold particles through a sulfur - sulfur bridge [36]. The Au/CD compound is very stable and soluble in water and selectively extracts C60 from the insoluble mixture after refluxing for several days. The C70 fullerene component is then removed by simple filtration. C60 is driven out from the Au/CD compound by adding adamantol which has a higher affinity for the cyclodextrin cavity. Au/CD is completely recycled when adamantol in turn is driven out by adding ethanol and ethanol removed by evaporation. 50 mg of Au/CD captures 5 mg of C60 fullerene. References ^ a b Vol. ed.: A. Hirsch. With contributions by C. Bellavia-Lund ... (1993). Fullerenes and Related Structures (Topics in Current Chemistry). Berlin: Springer. ISBN 3-540-64939-5.  ^ François Diederich (1997). "Covalent fullerene chemistry". Pure & Appl. Chem. 69 (3): 395–400. doi:10.1351/pac199769030395.  ^ Prato, Maurizio (1997). "[60]Fullerene chemistry for materials science applications". Journal of Materials Chemistry 7: 1097. doi:10.1039/a700080d.  ^ Beavers, Cm; Zuo, T; Duchamp, Jc; Harich, K; Dorn, Hc; Olmstead, Mm; Balch, Al (Sep 2006). "Tb3N@C84: an improbable, egg-shaped endohedral fullerene that violates the isolated pentagon rule.". Journal of the American Chemical Society 128 (35): 11352–3. doi:10.1021/ja063636k. ISSN 0002-7863. PMID 16939248.  ^ Capturing the labile fullerene[50] as C50Cl10. Xie SY, Gao F, Lu X, Huang RB, Wang CR, Zhang X, Liu ML, Deng SL, Zheng LS. Science. 2004 Apr 30;304(5671):699. doi:10.1126/science.1095567 ^ Simple Combustion Production and Characterization of Octahydro[60]fullerene with a Non-IPR C60 Cage Qun-Hong Weng, Qiao He, Ting Liu, Hui-Ying Huang, Jian-Hua Chen, Zhi-Yong Gao, Su-Yuan Xie, Xin Lu, Rong-Bin Huang, and Lan-Sun Zheng J. Am. Chem. Soc., 2010, 132 (43), pp 15093–15095 doi:10.1021/ja108316e ^ "Synthesis of 6,9,12,15,18-pentamethyl-1,6,9,12,15,18-hexahydro(c60-ih)[5,6fullerene"], Org. Synth. 83: 80, 2006,  ^ Iwashita, A; Matsuo, Y; Nakamura, E (2007). "AlCl(3)-mediated mono-, di-, and trihydroarylation of 60fullerene.". Angewandte Chemie (International ed. in English) 46 (19): 3513–6. doi:10.1002/anie.200700062. ISSN 1433-7851. PMID 17385815.  ^ Chiang, Long Y.; Swirczewski, John W.; Hsu, Chang S.; Chowdhury, S. K.; Cameron, Steve; Creegan, Kathy (1992). "Multi-hydroxy additions onto C60 fullerene molecules". Journal of the Chemical Society, Chemical Communications: 1791. doi:10.1039/C39920001791.  ^ Chiang, Long Y.; Upasani, Ravi B.; Swirczewski, John W.; Soled, Stuart (1993). "Evidence of hemiketals incorporated in the structure of fullerols derived from aqueous acid chemistry". Journal of the American Chemical Society 115: 5453. doi:10.1021/ja00066a014.  ^ Li, Jing; Takeuchi, Atsuo; Ozawa, Masaki; Li, Xinhai; Saigo, Kazuhiko; Kitazawa, Koichi (1993). "C60 fullerol formation catalysed by quaternary ammonium hydroxides". Journal of the Chemical Society, Chemical Communications: 1784. doi:10.1039/C39930001784.  ^ Wang, Sheng; He, Ping; Zhang, Jian‐Min; Jiang, Hu; Zhu, Shi‐Zheng (2005). "Novel and Efficient Synthesis of Water‐Soluble [60]Fullerenol by Solvent‐Free Reaction". Synthetic Communications 35: 1803. doi:10.1081/SCC-200063958.  ^ Zhang, Gang; Liu, Yun; Liang, Dehai; Gan , Liangbing; Li, Yuliang (2010). "Facile Synthesis of Isomerically Pure Fullerenols and Formation of Spherical Aggregates from C60(OH)8". Angewandte Chemie International Edition 49 (31): n/a. doi:10.1002/anie.201001280. PMID 20575126.  ^ Kokubo, Ken; Matsubayashi, Kenji; Tategaki, Hiroshi; Takada, Hiroya; Oshima, Takumi (2008). "Facile Synthesis of Highly Water-Soluble Fullerenes More Than Half-Covered by Hydroxyl Groups". ACS Nano 2 (2): 327. doi:10.1021/nn700151z. PMID 19206634.  ^ Jia, J; Wu, Hs; Xu, Xh; Zhang, Xm; Jiao, H (Mar 2008). "Fused five-membered rings determine the stability of C60F60.". Journal of the American Chemical Society 130 (12): 3985–8. doi:10.1021/ja0781590. ISSN 0002-7863. PMID 18311972.  ^ José E. Cortés-Figueroa (2003). "An Experiment for the Inorganic Chemistry Laboratory The Sunlight-Induced Photosynthesis of (η2-C60)M(CO)5 Complexes (M = Mo, W)". Journal of Chemical Education 80 (7).  ^ Scott, Lt; Boorum, Mm; Mcmahon, Bj; Hagen, S; Mack, J; Blank, J; Wegner, H; De, Meijere, A (Feb 2002). "A rational chemical synthesis of C60.". Science 295 (5559): 1500–3. doi:10.1126/science.1068427. ISSN 0036-8075. PMID 11859187.  ^ The numbers in image correspond to the way the new carbon carbon bonds are formed. ^ Amsharov, Ky; Jansen, M (Apr 2008). "A C78 fullerene precursor: toward the direct synthesis of higher fullerenes.". The Journal of organic chemistry 73 (7): 2931–4. doi:10.1021/jo7027008. ISSN 0022-3263. PMID 18321126.  ^ Vougioukalakis, Gc; Roubelakis, Mm; Orfanopoulos, M (Jan 2010). "Open-cage fullerenes: towards the construction of nanosized molecular containers.". Chemical Society Reviews 39 (2): 817–44. doi:10.1039/b913766a. PMID 20111794.  ^ Roubelakis, Mm; Vougioukalakis, Gc; Orfanopoulos, M (Aug 2007). "Open-cage fullerene derivatives having 11-, 12-, and 13-membered-ring orifices: chemical transformations of the organic addends on the rim of the orifice.". The Journal of organic chemistry 72 (17): 6526–33. doi:10.1021/jo070796l. ISSN 0022-3263. PMID 17655360.  ^ Hummelen, Jan C.; Prato, Maurizio; Wudl, Fred (1995). "There Is a Hole in My Bucky". Journal of the American Chemical Society 117: 7003. doi:10.1021/ja00131a024.  ^ Mechanochemical Synthesis and Characterization of the Fullerene Dimer C120 Koichi Komatsu, Guan-Wu Wang, Yasujiro Murata, Toru Tanaka, Koichi Fujiwara Kazunori , Yamamoto and Martin Saunders J. Org. Chem., 1998, 63 (25), pp 9358–9366 doi:10.1021/jo981319t ^ The Mechanochemical Synthesis and Properties of the Fullerene Trimer C180 Koichi Komatsu, Koichi Fujiwara and Yasujiro Murata Chemistry Letters Vol. 29 (2000) , No. 9 p.1016 doi:10.1246/cl.2000.1016 ^ Structural Analysis of C60 Trimers by Direct Observation with Scanning Tunneling Microscopy Masashi Kunitake, Shinobu Uemura, Osamu Ito, Koichi Fujiwara, Yasujiro Murata, Koichi Komatsu Angewandte Chemie International Edition Volume 41 Issue 6, Pages 969 - 972 2002 doi:10.1002/1521-3773(20020315)41:6<969::AID-ANIE969>3.0.CO;2-I ^ Price, Bk; Tour, Jm (Oct 2006). "Functionalization of single-walled carbon nanotubes "on water".". Journal of the American Chemical Society 128 (39): 12899–904. doi:10.1021/ja063609u. ISSN 0002-7863. PMID 17002385.  ^ The oxidizing agent is isoamyl nitrite and because the optimized reaction takes place as a suspension in water it is a so-called on water reaction. ^ Ménard-Moyon, C; Dumas, F; Doris, E; Mioskowski, C (Nov 2006). "Functionalization of single-wall carbon nanotubes by tandem high-pressure/Cr(CO)6 activation of Diels-Alder cycloaddition.". Journal of the American Chemical Society 128 (46): 14764–5. doi:10.1021/ja065698g. ISSN 0002-7863. PMID 17105260.  ^ Liang, Feng; Sadana, Anil K.; Peera, Asghar; Chattopadhyay, Jayanta; Gu, Zhenning; Hauge, Robert H.; Billups, W. E. (2004). "A Convenient Route to Functionalized Carbon Nanotubes". Nano Letters 4: 1257. doi:10.1021/nl049428c.  ^ Wunderlich, D.; Hauke, F.; Hirsch, A. (2008). "Preferred functionalization of metallic and small-diameter single walled carbon nanotubes via reductive alkylation". Journal of Materials Chemistry 18: 1493. doi:10.1039/b716732f.  ^ Liang, Feng; Beach, Jonathan M.; Kobashi, Kazufumi; Sadana, Anil K.; Vega-Cantu, Yadira I.; Tour, James M.; Billups, W. E. (2006). "In Situ Polymerization Initiated by Single-Walled Carbon Nanotube Salts". Chemistry of Materials 18: 4764. doi:10.1021/cm0607536.  ^ Mukherjee, Arnab; Combs, Rachel; Chattopadhyay, Jayanta; Abmayr, David W.; Engel, Paul S.; Billups, W. E. (2008). "Attachment of Nitrogen and Oxygen Centered Radicals to Single-Walled Carbon Nanotube Salts". Chemistry of Materials 20: 7339. doi:10.1021/cm8014226.  ^ Tracey Spencer, Barney Yoo, and Kent Kirshenbaum (2006). "Purification and Modification of Fullerene C60 in the Undergraduate Laboratory". Journal of Chemical Education 83 (8): 1218.  ^ Verdejo, R; Lamoriniere, S; Cottam, B; Bismarck, A; Shaffer, M (Feb 2007). "Removal of oxidation debris from multi-walled carbon nanotubes.". Chemical communications (Cambridge, England) (5): 513–5. doi:10.1039/b611930a. ISSN 1359-7345. PMID 17252112.  ^ Nagata, Koichi; Dejima, Eiji; Kikuchi, Yasuharu; Hashiguchi, Masahiko (2005). "Kilogram-scale [60]Fullerene Separation from a Fullerene Mixture: Selective Complexation of Fullerenes with 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)". Chemistry Letters 34: 178. doi:10.1246/cl.2005.178.  ^ Liu, Y; Yang, Yw; Chen, Y (Sep 2005). "Thio2-(benzoylamino)ethylamino-beta-CD fragment modified gold nanoparticles as recycling extractors for 60fullerene.". Chemical communications (Cambridge, England) (33): 4208–10. doi:10.1039/b507650a. ISSN 1359-7345. PMID 16100605.