Buckminsterfullerene is a type of
fullerene
A fullerene is an allotrope of carbon whose molecule consists of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh, with fused rings of five to seven atoms. The molecule may be a hollow sphere, ...
with the formula C
60. It has a cage-like fused-ring structure (
truncated icosahedron
In geometry, the truncated icosahedron is an Archimedean solid, one of 13 convex isogonal nonprismatic solids whose 32 faces are two or more types of regular polygons. It is the only one of these shapes that does not contain triangles or squares ...
) made of twenty
hexagon
In geometry, a hexagon (from Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple (non-self-intersecting) hexagon is 720°.
Regular hexagon
A '' regular hexagon'' has ...
s and twelve
pentagon
In geometry, a pentagon (from the Greek πέντε ''pente'' meaning ''five'' and γωνία ''gonia'' meaning ''angle'') is any five-sided polygon or 5-gon. The sum of the internal angles in a simple pentagon is 540°.
A pentagon may be sim ...
s, and resembles a
soccer ball
A football (also known as football ball, soccer ball, or association football ball specifically in the United Kingdom) is the ball used in the sport of association football. The name of the ball varies according to whether the sport is called " ...
. Each of its 60
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...
atoms is
bonded to its three neighbors.
Buckminsterfullerene is a black solid that dissolves in
hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...
solvents
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
to produce a violet solution. The compound was discovered in 1985 and has received intense study, although few real world applications have been found.
Occurrence
Buckminsterfullerene is the most common naturally occurring fullerene. Small quantities of it can be found in
soot
Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed ...
.
It also
exists in space. Neutral C
60 has been observed in
planetary nebulae
A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.
The term "planetary nebula" is a misnomer because they are unrelated t ...
and several types of
star
A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
. The ionised form, C
60+, has been identified in the
interstellar medium
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
, where it is the cause of several absorption features known as
diffuse interstellar band
Diffuse interstellar bands (DIBs) are absorption features seen in the spectra of astronomical objects in the Milky Way and other galaxies. They are caused by the absorption of light by the interstellar medium. Circa 500 bands have now been seen, ...
s in the near-infrared.
History
Theoretical predictions of buckyball molecules appeared in the late 1960s and early 1970s.
[ Katz, 363][Osawa, E. (1970). Kagaku (Kyoto) (in Japanese). 25: 854] Buckminsterfullerene was first generated in 1984 by Eric Rohlfing, Donald Cox, and Andrew Kaldor
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
Sir Harold Walter Kroto (born Harold Walter Krotoschiner; 7 October 1939 – 30 April 2016), known as Harry Kroto, was an English chemist. He shared the 1996 Nobel Prize in Chemistry with Robert Curl and Richard Smalley for their discovery o ...
,
James R. Heath
James R. Heath (born 1962) is an American chemist and the president and professor of Institute of Systems Biology. Previous to this, he was the Elizabeth W. Gilloon Professor of Chemistry at the California Institute of Technology, after having move ...
,
Sean C. O'Brien
Sean, also spelled Seán or Séan in Irish English, is a male given name of Irish language, Irish origin. It comes from the Irish versions of the Biblical Hebrew name ''Yohanan'' (), Seán (Anglicisation of names, anglicized as ''Shaun/Shawn (giv ...
,
Robert Curl
Robert Floyd Curl Jr. (August 23, 1933 – July 3, 2022) was an American chemist who was Pitzer–Schlumberger Professor of Natural Sciences and Professor of Chemistry at Rice University. He was awarded the Nobel Prize in Chemistry in 1996 for ...
, and
Richard Smalley at
Rice University
William Marsh Rice University (Rice University) is a Private university, private research university in Houston, Houston, Texas. It is on a 300-acre campus near the Houston Museum District and adjacent to the Texas Medical Center. Rice is ranke ...
, who recognized the structure of C
60 as buckminsterfullerene.
Concurrent but unconnected to the Kroto-Smalley work, astrophysicists were working with spectroscopists to study infrared emissions from giant red carbon stars.
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.
Hence, the inspiration came to Smalley and team to use the laser technique on graphite to generate fullerenes.
Using laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...
evaporation
Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when h ...
of graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...
the Smalley team found C''n'' clusters (where 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. The carbon species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...
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
In geometry, the truncated icosahedron is an Archimedean solid, one of 13 convex isogonal nonprismatic solids whose 32 faces are two or more types of regular polygons. It is the only one of these shapes that does not contain triangles or squares ...
.
Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry
)
, image = Nobel Prize.png
, alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "M ...
for their roles in the discovery of buckminsterfullerene and the related class of molecules, the fullerene
A fullerene is an allotrope of carbon whose molecule consists of carbon atoms connected by single and double bonds so as to form a closed or partially closed mesh, with fused rings of five to seven atoms. The molecule may be a hollow sphere, ...
s.[
The experimental evidence, a strong peak at 720 ]atomic mass unit
The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at ...
s, 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
Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definiti ...
closed cage structure. Kroto mentioned geodesic dome structures of the noted futurist and inventor Buckminster Fuller
Richard Buckminster Fuller (; July 12, 1895 – July 1, 1983) was an American architect, systems theorist, writer, designer, inventor, philosopher, and futurist. He styled his name as R. Buckminster Fuller in his writings, publishing ...
as influences in the naming of this particular substance as buckminsterfullerene.[
In 1989 physicists ]Wolfgang Krätschmer
Wolfgang Krätschmer (born 16 November 1942 in Berlin) is a German physicist.
Krätschmer studied physics in Berlin. After his Diplom he went to the Max Planck Institute for Nuclear Physics in Heidelberg and earned his PhD there in 1971 with ...
, Konstantinos Fostiropoulos
Konstantinos Fostiropoulos is a Greek physicist who has been working in Germany in the areas nano-materials, solid-state physics, molecular physics, astrophysics, and thermodynamics. From 2003 to 2016 he has been founder and head of the ''Organic ...
, 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
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials dep ...
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.
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
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
-soluble material from the arc-generated soot. This extract had TEM and X-ray
An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...
crystal analysis consistent with arrays of spherical C60 molecules, approximately 1.0 nm in van der Waals diameter
The van der Waals radius, ''r'', of an atom is the radius of an imaginary hard sphere representing the distance of closest approach for another atom.
It is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics, ...
as well as the expected molecular mass of 720 Da for C60 (and 840 Da for C70) in their mass spectra
A mass spectrum is a histogram plot of intensity vs. ''mass-to-charge ratio'' (''m/z'') in a chemical sample, usually acquired using an instrument called a ''mass spectrometer''. Not all mass spectra of a given substance are the same; for example ...
. 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.
Etymology
The discoverers of the allotrope named the newfound molecule after Buckminster Fuller
Richard Buckminster Fuller (; July 12, 1895 – July 1, 1983) was an American architect, systems theorist, writer, designer, inventor, philosopher, and futurist. He styled his name as R. Buckminster Fuller in his writings, publishing ...
, who designed many geodesic dome
A geodesic dome is a hemispherical thin-shell structure (lattice-shell) based on a geodesic polyhedron. The triangular elements of the dome are structurally rigid and distribute the structural stress throughout the structure, making geodesic do ...
structures that look similar to C60 and who had died in 1983, the year before discovery. This is slightly misleading, however, as Fuller's geodesic domes are constructed only by further dividing hexagons or pentagons into triangles, which are then deformed by moving vertices radially outward to fit the surface of a sphere. Geometrically speaking, buckminsterfullerene is a naturally-occurring example of a Goldberg polyhedron
In mathematics, and more specifically in polyhedral combinatorics, a Goldberg polyhedron is a convex polyhedron made from hexagons and pentagons. They were first described in 1937 by Michael Goldberg (1902–1990). They are defined by three pro ...
. A common, shortened name for buckminsterfullerene is buckyballs.
Synthesis
Soot is produced by laser ablation of graphite or pyrolysis
The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements '' ...
of aromatic hydrocarbon
Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past groupin ...
s. Fullerenes are extracted from the soot with organic solvents using a Soxhlet extractor
A Soxhlet extractor is a piece of laboratory apparatus invented in 1879 by Franz von Soxhlet. It was originally designed for the extraction of a lipid from a solid material. Typically, Soxhlet extraction is used when the desired compound has a ' ...
. This step yields a solution containing up to 75% of C60, as well as other fullerenes. These fractions are separated using chromatography
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system ( ...
. Generally, the fullerenes are dissolved in a hydrocarbon or halogenated hydrocarbon and separated using alumina columns.
Structure
Buckminsterfullerene is a truncated icosahedron
In geometry, the truncated icosahedron is an Archimedean solid, one of 13 convex isogonal nonprismatic solids whose 32 faces are two or more types of regular polygons. It is the only one of these shapes that does not contain triangles or squares ...
with 60 vertices, 32 faces (20 hexagons and 12 pentagons where no pentagons share a vertex), and 90 edges (30 edges between 5-membered & 6-membered rings and 60 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
The van der Waals radius, ''r'', of an atom is the radius of an imaginary hard sphere representing the distance of closest approach for another atom.
It is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics, ...
of a molecule is about 1.01 nanometers
330px, Different lengths as in respect to the molecular scale.
The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm) or nanometer (American and British English spelling differences#-re ...
(nm). The nucleus to nucleus diameter of a molecule is about 0.71 nm. The molecule has two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered "double bond
In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...
s" 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 can be substituted by a nitrogen or boron atom yielding a or C59B respectively.[ Katz, 374]
Properties
For a time buckminsterfullerene was the largest known molecule observed to exhibit wave–particle duality
Wave–particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave. It expresses the inability of the classical physics, classical concepts "particle" or "wave" to fu ...
; theoretically every object exhibits this behavior. In 2020 the dye molecule phthalocyanine
Phthalocyanine () is a large, aromatic, macrocyclic, organic compound with the formula and is of theoretical or specialized interest in chemical dyes and photoelectricity.
It is composed of four isoindole units linked by a ring of nitrogen ato ...
exhibited the duality that is more famously attributed to light, electrons and other small particles and molecules.
Solution
Fullerenes are sparingly soluble in aromatic solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
s and carbon disulfide
Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical n ...
, 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.
crystallises with some solvents in the lattice ("solvates"). For example, crystallization of C60 from benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
solution yields triclinic crystals with the formula C60·4C6H6. Like other solvates, this one readily releases benzene to give the usual fcc C60. Millimeter-sized crystals of C60 and can be grown from solution both for solvates and for pure fullerenes.
Solid
In solid buckminsterfullerene, the C60 molecules adopt the fcc (face-centered cubic
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
There are three main varieties of ...
) 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]
solid is as soft as graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...
, but when compressed to less than 70% of its volume it transforms into a superhard form of diamond
Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, b ...
(see aggregated diamond nanorod). films and solution have strong non-linear optical properties; in particular, their optical absorption increases with light intensity (saturable absorption).
forms a brownish solid with an optical absorption threshold at ≈1.6 eV. It is an n-type semiconductor
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...
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]
Chemical reactions and properties
Redox (electron-transfer reactions)
undergoes six reversible, one-electron reductions, ultimately generating . It's oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...
is irreversible. The first reduction occurs at ≈-1.0 V ( Fc/), showing that C60 is a reluctant electron acceptor. tends to avoid having double bonds in the pentagonal rings, which makes electron delocalization
In chemistry, delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond.IUPAC Gold Boo''delocalization''/ref>
The term delocalization is general and can have slightly dif ...
poor, and results in not being "superaromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
". C60 behaves like an electron deficient alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic ...
. For example, it reacts with some nucleophiles.[
]
Hydrogenation
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
The Birch reduction is an organic reaction that is used to convert arenes to cyclohexadienes. The reaction is named after the Australian chemist Arthur Birch and involves the organic reduction of aromatic rings in an amine solvent (traditionally ...
. 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
2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (or DDQ) is the chemical reagent with formula C6Cl2(CN)2O2. This oxidant is useful for the dehydrogenation of alcohols, phenols, and steroid ketones. DDQ decomposes in water, but is stable in aqueous mine ...
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.
C60 can be hydrogenated, suggesting that a modified buckminsterfullerene called organometallic buckyballs (OBBs) could become a vehicle for "high density, room temperature, ambient pressure storage of hydrogen". These OBBs are created by binding atoms of a transition metal
In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...
(TM) to C60 or C48B12 and then binding many hydrogen atoms to this TM atom, dispersing them evenly throughout the inside of the organometallic buckyball. The study found that the theoretical amount of H2 that can be retrieved from the OBB at ambient pressure
Ambient or Ambiance or Ambience may refer to:
Music and sound
* Ambience (sound recording), also known as atmospheres or backgrounds
* Ambient music, a genre of music that puts an emphasis on tone and atmosphere
* ''Ambient'' (album), by Moby
* ...
approaches 9 wt %, a mass fraction that has been designated as optimal for hydrogen fuel by the U.S. Department of Energy.
Halogenation
Addition of fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactiv ...
, chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
, and bromine
Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...
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 factor
The steric factor, usually denoted ''ρ'', is a quantity used in collision theory.
Also called the ''probability factor'', the steric factor is defined as the ratio between the experimental value of the rate constant and the one predicted by co ...
s. 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.
Addition of oxygen atoms
Solutions of C60 can be oxygenated to the epoxide
In organic chemistry, an epoxide is a cyclic ether () with a three-atom ring. This ring approximates an equilateral triangle, which makes it strained, and hence highly reactive, more so than other ethers. They are produced on a large scale ...
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.
Cycloadditions
The Diels–Alder reaction
In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical example of a peric ...
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.
The C60 molecules can also be coupled through a +2cycloaddition
In organic chemistry, a cycloaddition is a chemical reaction in which "two or more unsaturated molecules (or parts of the same molecule) combine with the formation of a cyclic adduct in which there is a net reduction of the bond multiplicity" ...
, 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 . Under high pressure and temperature, repeated +2cycloaddition 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
Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials ...
above room temperature.
Free radical reactions
Reactions of C60 with free radicals
In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron.
With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spon ...
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 factor
The steric factor, usually denoted ''ρ'', is a quantity used in collision theory.
Also called the ''probability factor'', the steric factor is defined as the ratio between the experimental value of the rate constant and the one predicted by co ...
s of Y. When ''tert''-butyl halide is photolyzed and allowed to react with C60, a reversible inter-cage C–C bond is formed:
Cyclopropanation (Bingel reaction)
Cyclopropanation (the Bingel reaction The Bingel reaction in fullerene chemistry is a fullerene cyclopropanation reaction to a methanofullerene first discovered by C. Bingel in 1993 with the bromo derivative of diethyl malonate in the presence of a base such as sodium hydride or D ...
) 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 diazomethane
Diazomethane is the chemical compound CH2N2, discovered by German chemist Hans von Pechmann in 1894. It is the simplest diazo compound. In the pure form at room temperature, it is an extremely sensitive explosive yellow gas; thus, it is almost ...
s. 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
An organic solar cell (OSC) or plastic solar cell is a type of photovoltaic that uses organic electronics, a branch of electronics that deals with conductive organic polymers or small organic molecules, for light absorption and charge transport t ...
.
Redox reactions – C60 anions and cations
C60 anions
The LUMO
In chemistry, HOMO and LUMO are types of molecular orbitals. The acronyms stand for ''highest occupied molecular orbital'' and ''lowest unoccupied molecular orbital'', respectively. HOMO and LUMO are sometimes collectively called the ''frontie ...
in C60 is triply degenerate, with the HOMO
''Homo'' () is the genus that emerged in the (otherwise extinct) genus ''Australopithecus'' that encompasses the extant species ''Homo sapiens'' ( modern humans), plus several extinct species classified as either ancestral to or closely relate ...
–LUMO
In chemistry, HOMO and LUMO are types of molecular orbitals. The acronyms stand for ''highest occupied molecular orbital'' and ''lowest unoccupied molecular orbital'', respectively. HOMO and LUMO are sometimes collectively called the ''frontie ...
separation relatively small. This small gap suggests that reduction of C60 should occur at mild potentials leading to fulleride anions, 60">60sup>''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
In chemistry, a charge-transfer (CT) complex or electron-donor-acceptor complex describes a type of supramolecular assembly of two or more molecules or ions. The assembly consists of two molecules that self-attract through electrostatic forces, ...
, for example with tetrakis(dimethylamino)ethylene
Tetrakis(dimethylamino)ethylene (TDAE) is an organic compound with the formula (NMe2)2sub>2 (where Me = CH3). A colorless liquid, this compound is classified as an enamine. Primary and secondary enamines tend to isomerize, but tertiary enamines a ...
:
:C60 + C2(NMe2)4 → 2(NMe2)4">2(NMe2)4sup>+ 60">60sup>−
This salt exhibits ferromagnetism
Ferromagnetism is a property of certain materials (such as iron) which results in a large observed magnetic permeability, and in many cases a large magnetic coercivity allowing the material to form a permanent magnet. Ferromagnetic materials ...
at 16 K.
C60 cations
C60 oxidizes with difficulty. Three reversible oxidation processes have been observed by using cyclic voltammetry
Cyclic voltammetry (CV) is a type of potentiodynamic electrochemical measurement. In a cyclic voltammetry experiment, the working electrode potential is ramped linearly versus time. Unlike in linear sweep voltammetry, after the set potential is r ...
with ultra-dry methylene chloride
Dichloromethane (DCM or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour is widely used as a solvent. Although it is not miscible with ...
and a supporting electrolyte with extremely high oxidation resistance and low nucleophilicity, such as nBu4N">sup>nBu4N 6">sF6
Metal complexes
C60 forms complexes akin to the more common alkenes. Complexes have been reported molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lea ...
, tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isolat ...
, platinum
Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Platinu ...
, palladium
Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...
, iridium
Iridium is a chemical element with the symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal (after osmium) with a density of ...
, and titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
. The pentacarbonyl species are produced by photochemical reaction Organic photochemistry encompasses organic reactions that are induced by the action of light. The absorption of ultraviolet light by organic molecules often leads to reactions. In the earliest days, sunlight was employed, while in more modern times ...
s.
: M(CO)6 + C60 → M(''η''2-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(''η''2-C2H4)(PPh3)2 + C60 → Pt(''η''2-C60)(PPh3)2 + C2H4
Titanocene
Titanocene dichloride is the organotitanium compound with the formula ( ''η''5-C5H5)2TiCl2, commonly abbreviated as Cp2TiCl2. This metallocene is a common reagent in organometallic and organic synthesis. It exists as a bright red solid that slow ...
complexes have also been reported:
: (''η''5- Cp)2Ti(''η''2-(CH3)3SiC≡CSi(CH3)3) + C60 → (''η''5-Cp)2Ti(''η''2-C60) + (CH3)3SiC≡CSi(CH3)3
Coordinatively unsaturated precursors, such as Vaska's complex
Vaska's complex is the trivial name for the chemical compound ''trans''-carbonylchlorobis(triphenylphosphine)iridium(I), which has the formula IrCl(CO) (C6H5)3sub>2. This square planar diamagnetic organometallic complex consists of a central iridi ...
, for adduct
An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...
s with C60:
: ''trans''-Ir(CO)Cl(PPh3)2 + C60 → Ir(CO)Cl(''η''2-C60)(PPh3)2
One such iridium complex, 2-C60)(CO)Cl(Ph2CH2C6H4OCH2Ph)2">r(''η''2-C60)(CO)Cl(Ph2CH2C6H4OCH2Ph)2has been prepared where the metal center projects two electron-rich 'arms' that embrace the C60 guest.
Endohedral fullerenes
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
Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical r ...
. This method, however, is still immature and only a few species have been synthesized this way.
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
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic fiel ...
.
Potential applications in technology
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 it is one of the most common electron acceptor
An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process. Electron acceptors are sometimes mista ...
s used in donor/acceptor based solar cells. Conversion efficiencies up to 5.7% have been reported in C60–polymer cells.
Potential applications in health
Ingestion and risks
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). So the management of C60 products for human ingestion requires caution 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.
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.
Oils with C60 and risks
An experiment in 2011–2012 administered a solution of C60 in olive oil to rats, achieving a major prolongation of their lifespan. Since then, 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 exposition 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.
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.
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.
References
Bibliography
*
Further reading
* – describing the original discovery of C60
* – report describing the synthesis of C60 with combustion research published in 2000 at the 28th International Symposium on Combustion
External links
History of C60's discovery carried out by the Chemistry Department at Bristol University
*[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]
Donald R. Huffman and Wolfgang Krätschmer's paper pertaining to the synthesis of C60 in ''Nature'' published in 1990
* ttp://cnx.org/content/m14355/latest/ An article about buckminsterfullerene on Connexions Science Encyclopaediabr>Extensive statistical data compiled by the University of Sussex on the numerical quantitative properties of buckminsterfullerene
A web portal dedicated to buckminsterfullerene, authored and supported by the University of Bristol
Another web portal dedicated to buckminsterfullerene, authored and supported by the Chemistry Department at the University of Bristol
A brief article entirely devoted to C60 and its discovery, structure, production, properties, and applications
American Chemical Society's complete article on buckminsterfullerene
at ''The Periodic Table of Videos
''Periodic Videos'' (also known as ''The Periodic Table of Videos'') is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics i ...
'' (University of Nottingham)
{{Authority control
Fullerenes