Buckminsterfullerene#Endohedral fullerenes

Buckminsterfullerene is the most common naturally occurring fullerene. Small quantities of it can be found in soot.{{cite journal|doi=10.1038/352139a0|title=Fullerenes C₆₀ and C₇₀ in flames |year=1991|last1=Howard|first1=Jack B.|last2=McKinnon|first2=J. Thomas|last3=Makarovsky|first3=Yakov |last4=Lafleur|first4=Arthur L.|last5=Johnson|first5=M. Elaine|journal=Nature|volume=352|issue=6331 |pages=139–141|pmid=2067575 |bibcode=1991Natur.352..139H |s2cid=37159968}}{{cite journal |doi=10.1016/0008-6223(92)90061-Z|title=Fullerenes synthesis in combustion|year=1992|last1=Howard|first1=J |last2=Lafleur|first2=A|last3=Makarovsky|first3=Y |last4=Mitra|first4=S|last5=Pope|first5=C|last6=Yadav |first6=T|journal=Carbon|volume=30|issue=8|pages=1183–1201|bibcode=1992Carbo..30.1183H }}

It also exists in space. Neutral C₆₀ has been observed in planetary nebulae{{cite journal|bibcode=2010Sci...329.1180C|doi=10.1126/science.1192035|title=Detection of C60 and C70 in a Young Planetary Nebula|year=2010|last1=Cami|first1=J.|last2=Bernard-Salas|first2=J. |last3=Peeters |first3=E.|last4=Malek|first4=S. E.|journal=Science|volume=329|issue=5996|pages=1180–1182|pmid=20651118 |s2cid=33588270}} and several types of star.{{cite journal|bibcode=2012MNRAS.421.3277R |doi=10.1111/j.1365-2966.2012.20552.x |title=Detection of C60 in embedded young stellar objects, a Herbig Ae/Be star and an unusual post-asymptotic giant branch star |year=2012 |last1=Roberts |first1=Kyle R. G. |last2=Smith |first2=Keith T. |last3=Sarre |first3=Peter J. |journal=Monthly Notices of the Royal Astronomical Society |volume=421 |issue=4 |pages=3277–3285 |doi-access=free |arxiv=1201.3542 |s2cid=118739732 }} The ionised form, C₆₀⁺, has been identified in the interstellar medium,{{cite journal|bibcode=2013A&A...550L...4B|doi=10.1051/0004-6361/201220730 |title=Interstellar C60+ |year=2013 |last1=Berné |first1=O. |last2=Mulas |first2=G. |last3=Joblin |first3=C.|author3-link=Christine Joblin |journal=Astronomy & Astrophysics |volume=550 |pages=L4 |arxiv=1211.7252 |s2cid=118684608 }} where it is the cause of several absorption features known as diffuse interstellar bands in the near-infrared.{{cite journal|last1=Maier|first1=J. P.|last2=Gerlich|first2=D.|last3=Holz|first3=M.|last4=Campbell |first4=E. K.|date=July 2015|title=Laboratory confirmation of C₆₀⁺ as the carrier of two diffuse interstellar bands|journal=Nature|volume=523|issue=7560|pages=322–323|doi=10.1038/nature14566 |issn=1476-4687|pmid=26178962|bibcode=2015Natur.523..322C|s2cid=205244293}}

{{Further|Fullerene}}

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Image:Football Pallo valmiina-cropped.jpgs have the same arrangement of polygons as buckminsterfullerene, C₆₀.]]

Theoretical predictions of buckminsterfullerene molecules appeared in the late 1960s and early 1970s.Katz, 363Osawa, E. (1970). Kagaku (Kyoto) (in Japanese). 25: 854{{cite journal

|journal = New Scientist

|issue = 32

|year = 1966

|pages = 245

|title = Hollow molecules

|last = Jones

|first = David E. H.

}}{{Cite journal |last=Smalley |first=Richard E. |date=1997-07-01 |title=Discovering the fullerenes |journal=Reviews of Modern Physics |volume=69 |issue=3 |pages=723–730 |doi=10.1103/RevModPhys.69.723|bibcode=1997RvMP...69..723S |citeseerx=10.1.1.31.7103 }} It was first generated in 1984 by Eric Rohlfing, Donald Cox, and Andrew Kaldor,{{cite journal|doi=10.1063/1.447994|bibcode=1984JChPh..81.3322R|title=Production and characterization of supersonic carbon cluster beams|journal=Journal of Chemical Physics|volume=81|issue=7|pages=3322|last1=Rohlfing|first1=Eric A|last2=Cox|first2=D. M|last3=Kaldor|first3=A|year=1984}} using a laser to vaporize carbon in a supersonic helium beam, although the group did not realize that buckminsterfullerene had been produced. In 1985 their work was repeated by Harold Kroto, James R. Heath, Sean C. O'Brien, Robert Curl, and Richard Smalley at Rice University, who recognized the structure of C₆₀ as buckminsterfullerene.

Concurrent but unconnected to the Kroto-Smalley work, astrophysicists were working with spectroscopists to study infrared emissions from giant red carbon stars.{{cite book |last1=Dresselhaus |first1=M. S. |author-link1=Mildred Dresselhaus|last2=Dresselhaus |first2=G. |last3=Eklund |first3=P. C. |title=Science of Fullerenes and Carbon Nanotubes |date=1996 |publisher=Academic Press |location=San Diego, CA |isbn=978-012-221820-0}}{{cite journal |last=Herbig |first=E. |journal=Astrophys. J. |year=1975 |volume=196 |page=129|bibcode = 1975ApJ...196..129H |doi = 10.1086/153400 |title=The diffuse interstellar bands. IV – the region 4400-6850 A}}{{cite journal |last1=Leger |first1=A. |title=Remarkable candidates for the carrier of the diffuse interstellar bands: C₆₀⁺ and other polyhedral carbon ions |last2=d'Hendecourt |first2=L. |last3=Verstraete |first3=L. |last4=Schmidt |first4=W. |journal=Astron. Astrophys. |year=1988 |volume=203 |issue=1 |page=145|bibcode = 1988A&A...203..145L}} Smalley and team were able to use a laser vaporization technique to create carbon clusters which could potentially emit infrared at the same wavelength as had been emitted by the red carbon star.{{cite journal |last1=Dietz |first1=T. G. |last2=Duncan |first2=M. A. |last3=Powers |first3=D. E. |last4=Smalley |first4=R. E. |journal=J. Chem. Phys. |year=1981 |volume=74 |issue=11 |page=6511 |doi=10.1063/1.440991 |bibcode = 1981JChPh..74.6511D |title=Laser production of supersonic metal cluster beams}} Hence, the inspiration came to Smalley and team to use the laser technique on graphite to generate fullerenes.

Using laser evaporation of graphite the Smalley team found C_n clusters (where {{nowrap|n > 20}} and even) of which the most common were C₆₀ and C₇₀. A solid rotating graphite disk was used as the surface from which carbon was vaporized using a laser beam creating hot plasma that was then passed through a stream of high-density helium gas.{{cite journal |last1=Kroto |first1=H. W. |last2=Health |first2=J. R. |last3=O'Brien |first3=S. C. |last4=Curl |first4=R. F. |last5=Smalley |first5=R. E. |title=C₆₀: Buckminsterfullerene |journal=Nature |year=1985 |volume=318 |pages=162–163 |doi=10.1038/318162a0 |bibcode=1985Natur.318..162K |issue=6042|s2cid=4314237 }} The carbon species were subsequently cooled and ionized resulting in the formation of clusters. Clusters ranged in molecular masses, but Kroto and Smalley found predominance in a C₆₀ cluster that could be enhanced further by allowing the plasma to react longer. They also discovered that C₆₀ is a cage-like molecule, a regular truncated icosahedron.

The experimental evidence, a strong peak at 720 atomic mass units, indicated that a carbon molecule with 60 carbon atoms was forming, but provided no structural information. The research group concluded after reactivity experiments, that the most likely structure was a spheroidal molecule. The idea was quickly rationalized as the basis of an icosahedral symmetry closed cage structure.

Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of buckminsterfullerene and the related class of molecules, the fullerenes.

In 1989 physicists Wolfgang Krätschmer, Konstantinos Fostiropoulos, and Donald R. Huffman observed unusual optical absorptions in thin films of carbon dust (soot). The soot had been generated by an arc-process between two graphite electrodes in a helium atmosphere where the electrode material evaporates and condenses forming soot in the quenching atmosphere. Among other features, the IR spectra of the soot showed four discrete bands in close agreement to those proposed for C₆₀.Conference proceedings of "Dusty Objects in the Universe", pp.b 89–93, [https://www.springer.com/us/book/9780792308638# "Search for the UV and IR spectra of C₆₀ in laboratory-produced carbon dust"] {{Webarchive|url=https://web.archive.org/web/20170905142659/https://www.springer.com/us/book/9780792308638 |date=2017-09-05 }}{{cite journal | doi=10.1016/0009-2614(90)87109-5 | volume=170 | issue=2–3 | title=The infrared and ultraviolet absorption spectra of laboratory-produced carbon dust: evidence for the presence of the C₆₀ molecule | year=1990 | journal=Chemical Physics Letters | pages=167–170 | last1 = Krätschmer | first1 = W.| bibcode=1990CPL...170..167K | doi-access=free}}

Another paper on the characterization and verification of the molecular structure followed on in the same year (1990) from their thin film experiments, and detailed also the extraction of an evaporable as well as benzene-soluble material from the arc-generated soot. This extract had TEM and X-ray crystal analysis consistent with arrays of spherical C₆₀ molecules, approximately 1.0 nm in van der Waals diameter as well as the expected molecular mass of 720 Da for C₆₀ (and 840 Da for C₇₀) in their mass spectra.{{Cite journal |doi = 10.1038/347354a0|title = Solid C₆₀: A new form of carbon|journal = Nature|volume = 347|issue = 6291|pages = 354–358|year = 1990|last1 = Krätschmer|first1 = W.|last2 = Lamb|first2 = Lowell D.|last3 = Fostiropoulos|first3 = K.|last4 = Huffman|first4 = Donald R.|bibcode = 1990Natur.347..354K|s2cid = 4359360}} The method was simple and efficient to prepare the material in gram amounts per day (1990) which has boosted the fullerene research and is even today applied for the commercial production of fullerenes.

The discovery of practical routes to C₆₀ led to the exploration of a new field of chemistry involving the study of fullerenes.

The discoverers of the allotrope named the newfound molecule after American architect R. Buckminster Fuller, who designed many geodesic dome structures that look similar to C₆₀ and who had died in 1983, the year before discovery. Another common name for buckminsterfullerene is "buckyballs".{{cite web |title=What is a geodesic dome? |url=https://exhibits.stanford.edu/bucky/feature/what-is-a-geodesic-dome |website=R. Buckminster Fuller Collection: Architect, Systems Theorist, Designer, and Inventor |date=6 April 2017 |publisher=Stanford University |access-date=10 June 2019 |archive-date=12 January 2020 |archive-url=https://web.archive.org/web/20200112232718/https://exhibits.stanford.edu/bucky/feature/what-is-a-geodesic-dome |url-status=live }}The AZo Journal of Materials Online. AZoM.com. "Buckminsterfullerene." 2006.

Soot is produced by laser ablation of graphite or pyrolysis of aromatic hydrocarbons. Fullerenes are extracted from the soot with organic solvents using a Soxhlet extractor.{{cite book|last1=Girolami |first1=G. S.|last2= Rauchfuss|first2= T. B. |last3=Angelici|first3= R. J.|author3-link=Robert Angelici|title= Synthesis and Teknique in Inorganic Chemistry|publisher= University Science Books|location= Mill Valley, CA|date= 1999|isbn=978-0935702484}} This step yields a solution containing up to 75% of C₆₀, as well as other fullerenes. These fractions are separated using chromatography.Katz, 369–370 Generally, the fullerenes are dissolved in a hydrocarbon or halogenated hydrocarbon and separated using alumina columns.{{cite book |last1=Shriver |last2=Atkins |title=Inorganic Chemistry |edition=Fifth |publisher=W. H. Freeman |location=New York |year=2010 |page=356 |isbn=978-0-19-923617-6 }}

Buckminsterfullerene is a truncated icosahedron with 60 vertices, 32 faces (20 hexagons and 12 pentagons where no pentagons share a vertex), and 90 edges (60 edges between 5-membered & 6-membered rings and 30 edges are shared between 6-membered & 6-membered rings), with a carbon atom at the vertices of each polygon and a bond along each polygon edge. The van der Waals diameter of a {{chem|C|60}} molecule is about 1.01 nanometers (nm). The nucleus to nucleus diameter of a {{chem|C|60}} molecule is about 0.71 nm. The {{chem|C|60}} molecule has two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered "double bonds" and are shorter than the 6:5 bonds (between a hexagon and a pentagon). Its average bond length is 0.14 nm. Each carbon atom in the structure is bonded covalently with 3 others.Katz, 364 A carbon atom in the {{chem|C|60}} can be substituted by a nitrogen or boron atom yielding a {{chem|C|59|N}} or C₅₉B respectively.Katz, 374

File:Buckball-electronic-str en.svg

For a time buckminsterfullerene was the largest{{quantify|largest in which way? C60 fullerene is still heavier than the pthalo dye and occupies more space in 3 dimensions so a metric is needed|date=April 2025}} known molecule observed to exhibit wave–particle duality.

{{cite journal |year = 1999 |title = Wave–particle duality of C₆₀ |journal = Nature |volume = 401 |issue = 6754 |pages = 680–682 |doi = 10.1038/44348 |pmid = 18494170| bibcode = 1999Natur.401..680A |last1 = Arndt |first1 = Markus |last2 = Nairz |first2 = Olaf |last3 = Vos-Andreae |first3 = Julian |last4 = Keller |first4 = Claudia |last5 = Van Der Zouw |first5 = Gerbrand |last6 = Zeilinger |first6 = Anton|s2cid = 4424892}} In 2020 the dye molecule phthalocyanine exhibited the duality that is more famously attributed to light, electrons and other small particles and molecules.{{Cite news | title = Wave-particle duality in action—big molecules surf on their own waves | last = Lee | first = Chris | url = https://arstechnica.com/science/2020/07/wave-particle-duality-in-action-big-molecules-surf-on-their-own-waves/ | work = Ars Technica | date = 2020-07-21 |access-date= 26 September 2021 | archive-date = 2021-09-26 | archive-url = https://web.archive.org/web/20210926144828/https://arstechnica.com/science/2020/07/wave-particle-duality-in-action-big-molecules-surf-on-their-own-waves/ | url-status = live}}

File:C60 Fullerene solution.jpg

File:UV-Vis C60.jpg

Fullerenes are sparingly soluble in aromatic solvents and carbon disulfide, but insoluble in water. Solutions of pure C₆₀ have a deep purple color which leaves a brown residue upon evaporation. The reason for this color change is the relatively narrow energy width of the band of molecular levels responsible for green light absorption by individual C₆₀ molecules. Thus individual molecules transmit some blue and red light resulting in a purple color. Upon drying, intermolecular interaction results in the overlap and broadening of the energy bands, thereby eliminating the blue light transmittance and causing the purple to brown color change.

{{chem|C|60}} crystallises with some solvents in the lattice ("solvates"). For example, crystallization of C₆₀ from benzene solution yields triclinic crystals with the formula C₆₀·4C₆H₆. Like other solvates, this one readily releases benzene to give the usual face-centred cubic C₆₀. Millimeter-sized crystals of C₆₀ and {{chem|C|70}} can be grown from solution both for solvates and for pure fullerenes.

{{cite journal |last = Talyzin|first = A. V. |year = 1997 |title = Phase Transition C₆₀−C₆₀*4C₆H₆ in Liquid Benzene |journal = Journal of Physical Chemistry B |volume = 101|pages = 9679–9681 |doi = 10.1021/jp9720303 |issue = 47

}}{{cite journal |last1 = Talyzin|first1 = A. V. |last2 = Engström|first2 = I. |year = 1998 |title = C70 in Benzene, Hexane, and Toluene Solutions |journal = Journal of Physical Chemistry B |volume = 102|pages = 6477–6481 |doi = 10.1021/jp9815255 |issue = 34}}

Image:C60-Fulleren-kristallin.JPG

File:Fullerite structure.jpg

In solid buckminsterfullerene, the C₆₀ molecules adopt the fcc (face-centered cubic) motif. They start rotating at about −20 °C. This change is associated with a first-order phase transition to an fcc structure and a small, yet abrupt increase in the lattice constant from 1.411 to 1.4154 nm.Katz, 372

{{chem|C|60}} solid is as soft as graphite, but when compressed to less than 70% of its volume it transforms into a superhard form of diamond (see aggregated diamond nanorod). {{chem|C|60}} films and solution have strong non-linear optical properties; in particular, their optical absorption increases with light intensity (saturable absorption).

{{chem|C|60}} forms a brownish solid with an optical absorption threshold at ≈1.6 eV.Katz, 361 It is an n-type semiconductor with a low activation energy of 0.1–0.3 eV; this conductivity is attributed to intrinsic or oxygen-related defects.Katz, 379 Fcc C₆₀ contains voids at its octahedral and tetrahedral sites which are sufficiently large (0.6 and 0.2 nm respectively) to accommodate impurity atoms. When alkali metals are doped into these voids, C₆₀ converts from a semiconductor into a conductor or even superconductor.Katz, 381

{{chem|C|60}} undergoes six reversible, one-electron reductions, ultimately generating {{chem|C|60|6-}}. Its oxidation is irreversible. The first reduction occurs at ≈−1.0 V (Fc/{{chem|Fc|+}}), showing that C₆₀ is a reluctant electron acceptor. {{chem|C|60}} tends to avoid having double bonds in the pentagonal rings, which makes electron delocalization poor, and results in {{chem|C|60}} not being "superaromatic". C₆₀ behaves like an electron deficient alkene. For example, it reacts with some nucleophiles.

C₆₀ exhibits a small degree of aromatic character, but it still reflects localized double and single C–C bond characters. Therefore, C₆₀ can undergo addition with hydrogen to give polyhydrofullerenes. C₆₀ also undergoes Birch reduction. For example, C₆₀ reacts with lithium in liquid ammonia, followed by tert-butanol to give a mixture of polyhydrofullerenes such as C₆₀H₁₈, C₆₀H₃₂, C₆₀H₃₆, with C₆₀H₃₂ being the dominating product. This mixture of polyhydrofullerenes can be re-oxidized by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to give C₆₀ again.

A selective hydrogenation method exists. Reaction of C₆₀ with 9,9′,10,10′-dihydroanthracene under the same conditions, depending on the time of reaction, gives C₆₀H₃₂ and C₆₀H₁₈ respectively and selectively.{{cite book| title = Inorganic Chemistry| edition = 3rd| chapter = Chapter 14: The group 14 elements| author1 = Catherine E. Housecroft| author2 = Alan G. Sharpe| publisher = Pearson| year = 2008| isbn = 978-0-13-175553-6}}

Addition of fluorine, chlorine, and bromine occurs for C₆₀. Fluorine atoms are small enough for a 1,2-addition, while Cl₂ and Br₂ add to remote C atoms due to steric factors. For example, in C₆₀Br₈ and C₆₀Br₂₄, the Br atoms are in 1,3- or 1,4-positions with respect to each other. Under various conditions a vast number of halogenated derivatives of C₆₀ can be produced, some with an extraordinary selectivity on one or two isomers over the other possible ones. Addition of fluorine and chlorine usually results in a flattening of the C₆₀ framework into a drum-shaped molecule.

Solutions of C₆₀ can be oxygenated to the epoxide C₆₀O. Ozonation of C₆₀ in 1,2-xylene at 257K gives an intermediate ozonide C₆₀O₃, which can be decomposed into 2 forms of C₆₀O. Decomposition of C₆₀O₃ at 296 K gives the epoxide, but photolysis gives a product in which the O atom bridges a 5,6-edge.

File:Addition of O atom into C60 Scheme.png

The Diels–Alder reaction is commonly employed to functionalize C₆₀. Reaction of C₆₀ with appropriate substituted diene gives the corresponding adduct.

The Diels–Alder reaction between C₆₀ and 3,6-diaryl-1,2,4,5-tetrazines affords C₆₂. The C₆₂ has the structure in which a four-membered ring is surrounded by four six-membered rings.

File:3D structure of C62 derivative from C60 update.jpg

The C₆₀ molecules can also be coupled through a [2+2] cycloaddition, giving the dumbbell-shaped compound C₁₂₀. The coupling is achieved by high-speed vibrating milling of C₆₀ with a catalytic amount of KCN. The reaction is reversible as C₁₂₀ dissociates back to two C₆₀ molecules when heated at {{convert|450|K}}. Under high pressure and temperature, repeated [2+2] cycloaddition between C₆₀ results in polymerized fullerene chains and networks. These polymers remain stable at ambient pressure and temperature once formed, and have remarkably interesting electronic and magnetic properties, such as being ferromagnetic above room temperature.

Reactions of C₆₀ with free radicals readily occur. When C₆₀ is mixed with a disulfide RSSR, the radical C₆₀SR• forms spontaneously upon irradiation of the mixture.

Stability of the radical species C₆₀Y^• depends largely on steric factors of Y. When tert-butyl halide is photolyzed and allowed to react with C₆₀, a reversible inter-cage C–C bond is formed:

File:Free radical reaction of fullerene with tert-butyl radical.png

Cyclopropanation (the Bingel reaction) is another common method for functionalizing C₆₀. Cyclopropanation of C₆₀ mostly occurs at the junction of 2 hexagons due to steric factors.

The first cyclopropanation was carried out by treating the β-bromomalonate with C₆₀ in the presence of a base. Cyclopropanation also occur readily with diazomethanes. For example, diphenyldiazomethane reacts readily with C₆₀ to give the compound C₆₁Ph₂. Phenyl-C₆₁-butyric acid methyl ester derivative prepared through cyclopropanation has been studied for use in organic solar cells.

{{See also|Fullerides}}

The LUMO in C₆₀ is triply degenerate, with the HOMO–LUMO separation relatively small. This small gap suggests that reduction of C₆₀ should occur at mild potentials leading to fulleride anions, [C₆₀]ⁿ⁻ (n = 1–6). The midpoint potentials of 1-electron reduction of buckminsterfullerene and its anions is given in the table below:

C₆₀ forms a variety of charge-transfer complexes, for example with tetrakis(dimethylamino)ethylene:

:C₆₀ + C₂(NMe₂)₄ → [C₂(NMe₂)₄]⁺[C₆₀]⁻

This salt exhibits ferromagnetism at 16 K.

C₆₀ oxidizes with difficulty. Three reversible oxidation processes have been observed by using cyclic voltammetry with ultra-dry methylene chloride and a supporting electrolyte with extremely high oxidation resistance and low nucleophilicity, such as [ⁿBu₄N] [AsF₆].{{cite journal |doi=10.1021/cr980017o|title=Discrete Fulleride Anions and Fullerenium Cations|year=2000|last1=Reed|first1=Christopher A.|last2=Bolskar|first2=Robert D.|journal=Chemical Reviews|volume=100|issue=3|pages=1075–1120|pmid=11749258 |s2cid=40552372 |url=https://escholarship.org/uc/item/60b5m71z}}

{{main|Fullerene ligand}}

C₆₀ forms complexes akin to the more common alkenes. Complexes have been reported molybdenum, tungsten, platinum, palladium, iridium, and titanium. The pentacarbonyl species are produced by photochemical reactions.

: M(CO)₆ + C₆₀ → M(η²-C₆₀)(CO)₅ + CO (M = Mo, W)

In the case of platinum complex, the labile ethylene ligand is the leaving group in a thermal reaction:

: Pt(η²-C₂H₄)(PPh₃)₂ + C₆₀ → Pt(η²-C₆₀)(PPh₃)₂ + C₂H₄

Titanocene complexes have also been reported:

: (η⁵-Cp)₂Ti(η²-(CH₃)₃SiC≡CSi(CH₃)₃) + C₆₀ → (η⁵-Cp)₂Ti(η²-C₆₀) + (CH₃)₃SiC≡CSi(CH₃)₃

Coordinatively unsaturated precursors, such as Vaska's complex, for adducts with C₆₀:

: trans-Ir(CO)Cl(PPh₃)₂ + C₆₀ → Ir(CO)Cl(η²-C₆₀)(PPh₃)₂

One such iridium complex, [Ir(η²-C₆₀)(CO)Cl(Ph₂CH₂C₆H₄OCH₂Ph)₂] has been prepared where the metal center projects two electron-rich 'arms' that embrace the C₆₀ guest.{{cite book| title = Supramolecular Chemistry| edition = 2nd|author1=Jonathan W. Steed |author2=Jerry L. Atwood |name-list-style=amp | publisher = Wiley| year = 2009| isbn = 978-0-470-51233-3}}

{{main|Endohedral fullerene|Endohedral hydrogen fullerene}}

Metal atoms or certain small molecules such as H₂ and noble gas can be encapsulated inside the C₆₀ cage. These endohedral fullerenes are usually synthesized by doping in the metal atoms in an arc reactor or by laser evaporation. These methods gives low yields of endohedral fullerenes, and a better method involves the opening of the cage, packing in the atoms or molecules, and closing the opening using certain organic reactions. This method, however, is still immature and only a few species have been synthesized this way.{{cite journal | last1 = Rodríguez-Fortea | first1 = Antonio | last2 = Balch | first2 = Alan L. | last3 = Poblet | first3 = Josep M. | year = 2011 | title = Endohedral metallofullerenes: a unique host–guest association | journal = Chem. Soc. Rev. | volume = 40 | issue = 7| pages = 3551–3563 | doi = 10.1039/C0CS00225A | pmid = 21505658}}

Endohedral fullerenes show distinct and intriguing chemical properties that can be completely different from the encapsulated atom or molecule, as well as the fullerene itself. The encapsulated atoms have been shown to perform circular motions inside the C₆₀ cage, and their motion has been followed using NMR spectroscopy.

The optical absorption properties of C₆₀ match the solar spectrum in a way that suggests that C₆₀-based films could be useful for photovoltaic applications. Because of its high electronic affinity{{cite journal|last1=Ryuichi|first1=Mitsumoto|title=Electronic Structures and Chemical Bonding of Fluorinated Fullerenes Studied|journal=J. Phys. Chem. A|date=1998 |volume=102|issue=3|pages=552–560 |doi=10.1021/jp972863t|bibcode=1998JPCA..102..552M}} it is one of the most common electron acceptors used in donor/acceptor based solar cells. Conversion efficiencies up to 5.7% have been reported in C₆₀–polymer cells.{{Cite journal |last1=Shang|first1=Yuchen|last2=Liu|first2=Zhaodong|last3=Dong|first3=Jiajun|last4=Yao|first4=Mingguang |last5=Yang|first5=Zhenxing|last6=Li|first6=Quanjun |last7=Zhai|first7=Chunguang|last8=Shen|first8=Fangren |last9=Hou|first9=Xuyuan|last10=Wang|first10=Lin|last11=Zhang|first11=Nianqiang|date=November 2021 |title=Ultrahard bulk amorphous carbon from collapsed fullerene |url=https://www.nature.com/articles/s41586-021-03882-9|journal=Nature|volume=599 |issue=7886|pages=599–604|doi=10.1038/s41586-021-03882-9|pmid=34819685 |bibcode=2021Natur.599..599S |s2cid=244643471 |issn=1476-4687|access-date=2021-11-26|url-status=live|archive-date=2021-11-26|archive-url=https://web.archive.org/web/20211126104002/https://www.nature.com/articles/s41586-021-03882-9}}

{{Further|topic=the basic polymer of the C₆₀ monomer group|Polyfullerene}}

{{Main|Health and safety hazards of nanomaterials|Toxicology of carbon nanomaterials}}

C₆₀ is sensitive to light, so leaving C₆₀ under light exposure causes it to degrade, becoming dangerous. The ingestion of C₆₀ solutions that have been exposed to light could lead to developing cancer (tumors).{{Cite web|last=Grohn, Kristopher J.|title=Comp grad leads research|url=http://weyburnreview.com/news/local-news/comp-grad-leads-research-1.2261882|url-status=live|website=WeyburnReview |access-date=2021-04-17|archive-date=2021-04-17|archive-url=https://web.archive.org/web/20210417041410/https://www.weyburnreview.com/news/local-news/comp-grad-leads-research-1.2261882}} So the management of C₆₀ products for human ingestion requires cautionary measures such as: elaboration in very dark environments, encasing into bottles of great opacity, and storing in dark places, and others like consumption under low light conditions and using labels to warn about the problems with light.

Solutions of C₆₀ dissolved in olive oil or water, as long as they are preserved from light, have been found nontoxic to rodents.{{cite journal|last1=Baati|first1=Tarek|last2=Moussa|first2=Fathi|date=June 2012|title=The prolongation of the lifespan of rats by repeated oral administration of [60]fullerene|journal=Biomaterials|volume=33|issue=19|pages=4936–4946|doi=10.1016/j.biomaterials.2012.03.036|pmid=22498298}}

Otherwise, a study found that C₆₀ remains in the body for a longer time than usual, especially in the liver, where it tends to be accumulated, and therefore has the potential to induce detrimental health effects.{{cite journal | pmc=7005847 | year=2019 | last1=Shipkowski | first1=K. A. | last2=Sanders | first2=J. M. | last3=McDonald | first3=J. D. | last4=Walker | first4=N. J. | last5=Waidyanatha | first5=S. | title=Disposition of fullerene C60 in rats following intratracheal or intravenous administration | journal=Xenobiotica; the Fate of Foreign Compounds in Biological Systems | volume=49 | issue=9 | pages=1078–1085 | doi=10.1080/00498254.2018.1528646 | pmid=30257131}}

An experiment in 2011–2012 administered a solution of C₆₀ in olive oil to rats, achieving a 90% prolongation of their lifespan. C₆₀ in olive oil administered to mice resulted in no extension in lifespan.{{cite journal | vauthors=Grohn KJ, Moyer BS, Moody KJ | title=C60 in olive oil causes light-dependent toxicity and does not extend lifespan in mice | journal=GeroScience | volume=49 | issue=2 | pages=579-591 | year=2021 | doi = 10.1007/s11357-020-00292-z | pmc=8110650 | pmid=33123847 | doi-access=free }} C₆₀ in olive oil administered to beagle dogs resulted in a large reduction of C-reactive protein, which is commonly elevated in cardiovascular disease and cerebrovascular disease.{{cite journal | vauthors=Hui M, Jia X, Shi M | title=Anti-Inflammatory and Antioxidant Effects of Liposoluble C60 at the Cellular, Molecular, and Whole-Animal Levels| journal=Journal of Inflammation Research | volume=16 | pages=83-89 | year=2023 | doi = 10.2147/JIR.S386381 | pmc=8110650 | pmid=36643955 | doi-access=free }}

Many oils with C₆₀ have been sold as antioxidant products, but it does not avoid the problem of their sensitivity to light, that can turn them toxic. A later research confirmed that exposure to light degrades solutions of C₆₀ in oil, making it toxic and leading to a "massive" increase of the risk of developing cancer (tumors) after its consumption.{{Cite web|last=Grohn |first=Kristopher J. |display-authors=etal |title=C60 in olive oil causes light-dependent toxicity|url-status=live |url=https://gwern.net/docs/longevity/2020-grohn.pdf|access-date=2021-04-15|archive-date=2021-04-15|archive-url=https://web.archive.org/web/20210415212442/https://www.gwern.net/docs/longevity/2020-grohn.pdf}}

To avoid the degradation by effect of light, C₆₀ oils must be made in very dark environments, encased into bottles of great opacity, and kept in darkness, consumed under low light conditions and accompanied by labels to warn about the dangers of light for C₆₀.{{Cite magazine|magazine=Nature|title=Degradation of C60 by light|date=23 May 1991|volume=351 |url=https://nature.com/articles/351277a0.pdf|author-first1=Roger|author-first2=Jonathan P. |author-first3=Anthony G. |author-first4=Steven P. |author-first5=T. John|author-first6=Jonathan P. |author-first7=Harold W. |author-first8=David R. M. |author-last1=Taylor|author-last2=Parsons|author-last3=Avent|author-last4=Rannard|author-last5=Dennis|author-last6=Hare|author-last7=Kroto|author-last8=Walton}}

Some producers have been able to dissolve C₆₀ in water to avoid possible problems with oils, but that would not protect C₆₀ from light, so the same cautions are needed.

{{Reflist|refs=

[http://www.chm.bris.ac.uk/motm/buckyball/c60a.htm Buckminsterfullerene, C₆₀] {{Webarchive|url=https://web.archive.org/web/20210227040433/http://www.chm.bris.ac.uk/motm/buckyball/c60a.htm |date=2021-02-27}}. University of Bristol. Chm.bris.ac.uk (1996-10-13). Retrieved on 2011-12-25.

}}

• {{cite book|title=Nanostructured materials for solar energy conversion|editor=Sōga, Tetsuo |chapter=Fullerene Thin Films as Photovoltaic Material|author=Katz, E. A.|year=2006 |isbn=978-0-444-52844-5|publisher=Elsevier|pages= 361–443|chapter-url=https://books.google.com/books?id=GmQR1tuk5IgC&pg=PA361|ref=Katz}}

• {{cite journal|last=Kroto|first=H. W.|author2=Heath, J. R. |author3=O'Brien, S. C. |author4=Curl, R. F. |author5= Smalley, R. E. |title=C₆₀: Buckminsterfullerene|journal=Nature|date=November 1985|volume=318|issue=14|doi=10.1038/318162a0|pages=162–163|bibcode = 1985Natur.318..162K |s2cid=4314237}} – describing the original discovery of C₆₀
• {{cite journal|last=Hebgen|first=Peter|author2=Goel, Anish |author3=Howard, Jack B. |author4=Rainey, Lenore C. |author5= Vander Sande, John B. |title=Fullerenes and Nanostructures in Diffusion Flames|journal=Proceedings of the Combustion Institute|year=2000|volume=28|pages=1397–1404|url=http://web.mit.edu/anish/www/Peter-JBH.pdf|doi=10.1016/S0082-0784(00)80355-0|citeseerx=10.1.1.574.8368}} – report describing the synthesis of C₆₀ with combustion research published in 2000 at the 28th International Symposium on Combustion

{{Sister project links|wikt=buckminsterfullerene|commons=Category:Fullerenes|n=no|q=no|s=no}}

• [http://www.chm.bris.ac.uk/motm/buckyball/c60a.htm History of C₆₀'s discovery carried out by the Chemistry Department at Bristol University]
• [https://web.archive.org/web/20151023071900/http://scifun.chem.wisc.edu/chemweek/buckball/buckball.html A brief overview of buckminsterfullerene described by the University of Wisconsin-Madison]
• [https://archive.today/20121218095142/http://cccmkc.edu.hk/~sbj-chemistry/98-99%20S.6%20Project/Buckminsterfullerene/Properties%20of%20Buckminsterfullerene.htm A report by Ming Kai College detailing the properties of buckminsterfullerene]
• [http://www.nature.com/physics/looking-back/kraetschmer/index.html Donald R. Huffman and Wolfgang Krätschmer's paper pertaining to the synthesis of C₆₀ in Nature published in 1990]
• [https://web.archive.org/web/20130702064627/http://www.ornl.gov/info/ornlreview/rev26-2/text/rndmain1.html A thorough description of C₆₀ by the Oak Ridge National Laboratory]
• [http://cnx.org/content/m14355/latest/ An article about buckminsterfullerene on Connexions Science Encyclopaedia]
• [http://www.creative-science.org.uk/propc60.html Extensive statistical data compiled by the University of Sussex on the numerical quantitative properties of buckminsterfullerene]
• [http://www.eskimo.force9.co.uk/fullerene/ A web portal dedicated to buckminsterfullerene, authored and supported by the University of Bristol]
• [http://www.chm.bris.ac.uk/webprojects2002/knowles/ Another web portal dedicated to buckminsterfullerene, authored and supported by the Chemistry Department at the University of Bristol]
• [http://www.azonano.com/article.aspx?ArticleID=1641 A brief article entirely devoted to C₆₀ and its discovery, structure, production, properties, and applications]
• [https://web.archive.org/web/20121029023510/http://portal.acs.org/portal/acs/corg/content?_nfpb=true American Chemical Society's complete article on buckminsterfullerene]
• [http://www.periodicvideos.com/videos/mv_buckyball.htm Buckminsterfullerene] at The Periodic Table of Videos (University of Nottingham)

{{Allotropes of carbon}}

{{Molecules detected in outer space}}

{{Buckminster Fuller}}

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Category:Fullerenes