Fullerene Nanogears - GPN-2000-001535.jpg
   HOME

TheInfoList



OR:

A fullerene is an
allotrope of carbon Carbon is capable of forming many allotropy, allotropes (structurally different forms of the same element) due to its Valence (chemistry), valency. Well-known forms of carbon include diamond and graphite. In recent decades, many more allotrope ...
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,
ellipsoid An ellipsoid is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation. An ellipsoid is a quadric surface;  that is, a surface that may be defined as the ...
,
tube Tube or tubes may refer to: * ''Tube'' (2003 film), a 2003 Korean film * ''The Tube'' (TV series), a music related TV series by Channel 4 in the United Kingdom * "Tubes" (Peter Dale), performer on the Soccer AM television show * Tube (band), a ...
, or many other shapes and sizes. Graphene (isolated atomic layers of graphite), which is a flat mesh of regular hexagonal rings, can be seen as an extreme member of the family. Fullerenes with a closed mesh topology are informally denoted by their empirical formula C''n'', often written C''n'', where ''n'' is the number of carbon atoms. However, for some values of ''n'' there may be more than one
isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...
. The family is named after buckminsterfullerene (C60), the most famous member, which in turn is named after Buckminster Fuller. The closed fullerenes, especially C60, are also informally called buckyballs for their resemblance to the standard
ball A ball is a round object (usually spherical, but can sometimes be ovoid) with several uses. It is used in ball games, where the play of the game follows the state of the ball as it is hit, kicked or thrown by players. Balls can also be used f ...
of association football ("soccer"). Nested closed fullerenes have been named bucky onions. Cylindrical fullerenes are also called carbon nanotubes or buckytubes. The bulk solid form of pure or mixed fullerenes is called fullerite. Fullerenes had been predicted for some time, but only after their accidental synthesis in 1985 were they detected in nature and outer space.Stars reveal carbon 'spaceballs'
BBC, 22 July 2010.
The discovery of fullerenes greatly expanded the number of known allotropes of carbon, which had previously been limited to graphite, diamond, and
amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal. Etymology The term comes from the Greek ''a'' ("wi ...
carbon such as soot and
charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...
. They have been the subject of intense research, both for their chemistry and for their technological applications, especially in materials science, electronics, and
nanotechnology Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal o ...
.


History


Predictions and limited observations

The icosahedral cage was mentioned in 1965 as a possible topological structure.
Eiji Osawa is a former professor of computational chemistry, noted for his prediction of the C60 molecule in 1970. Osawa received his Master's of Engineering in chemistry from Kyoto University's Department of Industrial Chemistry and then became an enginee ...
predicted the existence of in 1970. He noticed that the structure of a
corannulene Corannulene is a polycyclic aromatic hydrocarbon with chemical formula C20 H10. The molecule consists of a cyclopentane ring fused with 5 benzene rings, so another name for it is irculene. It is of scientific interest because it is a geodesic ...
molecule was a subset of the shape of a football, and hypothesised that a full ball shape could also exist. Japanese scientific journals reported his idea, but neither it nor any translations of it reached Europe or the Americas. Also in 1970,
R. W. Henson R. or r. may refer to: * ''Reign'', the period of time during which an Emperor, king, queen, etc., is ruler. * '' Rex'', abbreviated as R., the Latin word meaning King * ''Regina'', abbreviated as R., the Latin word meaning Queen * or , abbreviat ...
(then of the UK
Atomic Energy Research Establishment The Atomic Energy Research Establishment (AERE) was the main Headquarters, centre for nuclear power, atomic energy research and development in the United Kingdom from 1946 to the 1990s. It was created, owned and funded by the British Governm ...
) proposed the structure and made a model of it. Unfortunately, the evidence for that new form of carbon was very weak at the time, so the proposal was met with skepticism, and was never published. It was acknowledged only in 1999. In 1973, independently from Henson, a group of scientists from the USSR made a quantum-chemical analysis of the stability of and calculated its electronic structure. The paper was published in 1973, but the scientific community did not give much importance to this theoretical prediction. Around 1980, Sumio Iijima identified the molecule of from an electron microscope image of carbon black, where it formed the core of a particle with the structure of a "bucky onion". Also in the 1980's at MIT, Mildred Dresselhaus and Morinobu Endo, collaborating with T. Venkatesan, directed studies blasting graphite with lasers, producing carbon clusters of atoms, which would be later identified as "fullerenes."


Discovery of

In 1985, Harold Kroto of the University of Sussex, working with
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 O'Brien, Robert Curl and
Richard Smalley Richard Errett Smalley (June 6, 1943 – October 28, 2005) was an American chemist who was the Gene and Norman Hackerman Professor of Chemistry, Physics, and Astronomy at Rice University. In 1996, along with Robert Curl, also a professor of ch ...
from Rice University, discovered fullerenes in the sooty residue created by vaporising carbon in a helium atmosphere. In the mass spectrum of the product, discrete peaks appeared corresponding to molecules with the exact mass of sixty or seventy or more carbon atoms, namely and . The team identified their structure as the now familiar "buckyballs". The name "buckminsterfullerene" was eventually chosen for by the discoverers as an homage to
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
architect Buckminster Fuller for the vague similarity of the structure to the geodesic domes which he popularized; which, if they were extended to a full sphere, would also have the icosahedral symmetry group. The "ene" ending was chosen to indicate that the carbons are unsaturated, being connected to only three other atoms instead of the normal four. The shortened name "fullerene" eventually came to be applied to the whole family. Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of this class of molecules.


Further developments

Kroto and the Rice team already discovered other fullerenes besides C60, and the list was much expanded in the following years. Carbon nanotubes were first discovered and synthesized in 1991. After their discovery, minute quantities of fullerenes were found to be produced in sooty flames, and by lightning discharges in the atmosphere. In 1992, fullerenes were found in a family of mineraloids known as
shungite Shungite is a black and lustrous mineraloid that was first described from a deposit near Shunga village, in Karelia, Russia, from where it gets its name. Shungite can be low-carbon (5% C), medium-carbon (5-25% C) and high-carbon (25-80% C) perc ...
s in
Karelia Karelia ( Karelian and fi, Karjala, ; rus, Каре́лия, links=y, r=Karélija, p=kɐˈrʲelʲɪjə, historically ''Korjela''; sv, Karelen), the land of the Karelian people, is an area in Northern Europe of historical significance for ...
, Russia. The production techniques were improved by many scientists, including
Donald Huffman Donald R. Huffman (born 1935) is a Professor Emeritus of Physics at the University of Arizona. With Wolfgang Krätschmer, he developed a technique in 1990 for the simple production of large quantities of C60, or Buckminsterfullerene. Previousl ...
,
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 a t ...
,
Lowell D. Lamb Lowell may refer to: Places United States * Lowell, Arkansas * Lowell, California * Lowell, Florida * Lowell, Idaho * Lowell, Indiana * Lowell, Bartholomew County, Indiana * Lowell, Maine * Lowell, Massachusetts ** Lowell National Historical ...
, and
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 ''Organ ...
. Thanks to their efforts, by 1990 it was relatively easy to produce gram-sized samples of fullerene powder.
Fullerene purification Fullerene chemistry is a field of organic chemistry devoted to the chemical properties of fullerenes. Research in this field is driven by the need to functionalize fullerenes and tune their properties. For example, fullerene is notoriously insolub ...
remains a challenge to chemists and to a large extent determines fullerene prices. In 2010, the spectral signatures of C60 and C70 were observed by NASA's
Spitzer Spitzer is a surname. Notable people with the surname include: * Andre Spitzer (1945–1972), Israeli fencing coach and victim of the Munich massacre * Bernard Spitzer (1924–2014), American real estate developer and philanthropist, father of Eli ...
infrared telescope in a cloud of cosmic dust surrounding a star 6500 light years away. Kroto commented: "This most exciting breakthrough provides convincing evidence that the buckyball has, as I long suspected, existed since time immemorial in the dark recesses of our galaxy." According to astronomer Letizia Stanghellini, "It’s possible that buckyballs from outer space provided seeds for life on Earth." In 2019, ionized C60 molecules were detected with the Hubble Space Telescope in the space between those stars.


Types

There are two major families of fullerenes, with fairly distinct properties and applications: the closed buckyballs and the open-ended cylindrical carbon nanotubes. However, hybrid structures exist between those two classes, such as
carbon nanobuds 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 makes up o ...
— nanotubes capped by
hemispherical A sphere () is a Geometry, geometrical object that is a solid geometry, three-dimensional analogue to a two-dimensional circle. A sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...
meshes or larger "buckybuds".


Buckyballs


Buckminsterfullerene

Buckminsterfullerene is the smallest fullerene molecule containing pentagonal and hexagonal rings in which no two pentagons share an edge (which can be destabilizing, as in pentalene). It is also most common in terms of natural occurrence, as it can often be found in soot. The empirical formula of buckminsterfullerene is and its structure is a truncated icosahedron, which resembles an association football ball of the type made of twenty hexagons and twelve pentagons, 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 buckminsterfullerene molecule is about 1.1
nanometer 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 ...
s (nm). The nucleus to nucleus diameter of a buckminsterfullerene molecule is about 0.71 nm. The buckminsterfullerene 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 1.4 Å.


Other fullerenes

Another fairly common fullerene has empirical formula , but fullerenes with 72, 76, 84 and even up to 100 carbon atoms are commonly obtained. The smallest possible fullerene is the dodecahedral . There are no fullerenes with 22 vertices. The number of different fullerenes C2n grows with increasing ''n'' = 12, 13, 14, ..., roughly in proportion to ''n''9 . For instance, there are 1812 non-isomorphic fullerenes . Note that only one form of , buckminsterfullerene, has no pair of adjacent pentagons (the smallest such fullerene). To further illustrate the growth, there are 214,127,713 non-isomorphic fullerenes , 15,655,672 of which have no adjacent pentagons. Optimized structures of many fullerene isomers are published and listed on the web.
Heterofullerene Heterofullerenes are classes of fullerenes, at least one carbon atom is replaced by another element. Based on spectroscopy, substitutions have been reported with boron (borafullerenes), nitrogen ( azafullerenes), oxygen, arsenic, germanium, phosp ...
s have heteroatoms substituting carbons in cage or tube-shaped structures. They were discovered in 1993 and greatly expand the overall fullerene class of compounds and can have dangling bonds on their surfaces. Notable examples include boron, nitrogen (
azafullerene Azafullerenes are a class of heterofullerenes in which the element substituting for carbon is nitrogen. They can be in the form of a hollow sphere, ellipsoid, tube, and many other shapes. Spherical azafullerenes resemble the balls used in football ( ...
), oxygen, and phosphorus derivatives.


Carbon nanotubes

Carbon nanotubes are cylindrical fullerenes. These tubes of carbon are usually only a few nanometres wide, but they can range from less than a micrometer to several millimeters in length. They often have closed ends, but can be open-ended as well. There are also cases in which the tube reduces in diameter before closing off. Their unique molecular structure results in extraordinary macroscopic properties, including high tensile strength, high
electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allow ...
, high ductility, high heat conductivity, and relative chemical inactivity (as it is cylindrical and "planar" — that is, it has no "exposed" atoms that can be easily displaced). One proposed use of carbon nanotubes is in paper batteries, developed in 2007 by researchers at
Rensselaer Polytechnic Institute Rensselaer Polytechnic Institute () (RPI) is a private research university in Troy, New York, with an additional campus in Hartford, Connecticut. A third campus in Groton, Connecticut closed in 2018. RPI was established in 1824 by Stephen Van ...
. Another highly speculative proposed use in the field of space technologies is to produce high-tensile carbon cables required by a space elevator.


Derivatives

Buckyballs and carbon nanotubes have been used as building blocks for a great variety of derivatives and larger structures, such as *Nested buckyballs ("carbon nano-onions" or "buckyonions") proposed for lubricants; *Nested carbon nanotubes ("carbon megatubes") *Linked "ball-and-chain" dimers (two buckyballs linked by a carbon chain) *Rings of buckyballs linked together.


Heterofullerenes and non-carbon fullerenes

After the discovery of C60, many fullerenes have been synthesized (or studied theoretically by molecular modeling methods) in which some or all the carbon atoms are replaced by other elements.
Non-carbon nanotube A non-carbon nanotube is a cylindrical molecule often composed of metal oxides, or group III-Nitrides and morphologically similar to a carbon nanotube. Non-carbon nanotubes have been observed to occur naturally in some mineral deposits. A few year ...
s, in particular, have attracted much attention.


Boron

A type of buckyball which uses
boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...
atoms, instead of the usual carbon, was predicted and described in 2007. The structure, with each atom forming 5 or 6 bonds, was predicted to be more stable than the buckyball. However, subsequent analysis found that the predicted Ih symmetric structure was vibrationally unstable and the resulting cage would undergo a spontaneous symmetry break, yielding a puckered cage with rare Th symmetry (symmetry of a volleyball). The number of six-member rings in this molecule is 20 and number of five-member rings is 12. There is an additional atom in the center of each six-member ring, bonded to each atom surrounding it. By employing a systematic global search algorithm, it was later found that the previously proposed fullerene is not a global maximum for 80-atom boron clusters and hence can not be found in nature; the most stable configurations have complex. The same paper concluded that boron's energy landscape, unlike others, has many disordered low-energy structures, hence pure boron fullerenes are unlikely to exist in nature. However, an irregular complex dubbed borospherene was prepared in 2014. This complex has two hexagonal faces and four heptagonal faces with in D2d symmetry interleaved with a network of 48 triangles.


Other elements

Inorganic (carbon-free) fullerene-type structures have been built with the
molybdenum(IV) sulfide Molybdenum disulfide (or moly) is an inorganic compound composed of molybdenum and sulfur. Its chemical formula is . The compound is classified as a transition metal dichalcogenide. It is a silvery black solid that occurs as the mineral molybde ...
(MoS2), long used as a graphite-like lubricant, tungsten (WS2), titanium (TiS2) and niobium (NbS2). These materials were found to be stable up to at least 350 tons/cm2 (34.3 GPa). Icosahedral or distorted-icosahedral fullerene-like complexes have also been prepared for
germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors s ...
, tin, and lead; some of these complexes are spacious enough to hold most transition metal atoms.


Main fullerenes

Below is a table of main closed carbon fullerenes synthesized and characterized so far, with their
CAS Cas may refer to: * Caș, a type of cheese made in Romania * ' (1886–) Czech magazine associated with Tomáš Garrigue Masaryk * '' Čas'' (19 April 1945–February 1948), the official, daily newspaper of the Democratic Party of Slovakia * ''CA ...
number when known. Fullerenes with fewer than 60 carbon atoms have been called "lower fullerenes", and those with more than 70 atoms "higher fullerenes". In the table, "Num.Isom." is the number of possible
isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...
s within the "isolated pentagon rule", which states that two pentagons in a fullerene should not share edges. "Mol.Symm." is the symmetry of the molecule, whereas "Cryst.Symm." is that of the crystalline framework in the solid state. Both are specified for the most experimentally abundant form(s). The asterisk * marks symmetries with more than one chiral form. When or crystals are grown from toluene solution they have a monoclinic symmetry. The crystal structure contains toluene molecules packed between the spheres of the fullerene. However, evaporation of the solvent from transforms it into a face-centered cubic form. Both monoclinic and face-centered cubic (fcc) phases are known for better-characterized and fullerenes.


Properties


Topology

Schlegel diagrams are often used to clarify the 3D structure of closed-shell fullerenes, as 2D projections are often not ideal in this sense. In mathematical terms, the combinatorial topology (that is, the carbon atoms and the bonds between them, ignoring their positions and distances) of a closed-shell fullerene with a simple sphere-like mean surface ( orientable, genus zero) can be represented as a convex polyhedron; more precisely, its one-dimensional skeleton, consisting of its vertices and edges. The Schlegel diagram is a projection of that skeleton onto one of the faces of the polyhedron, through a point just outside that face; so that all other vertices project inside that face. Graph of 20-fullerene w-nodes.svg, C20
(dodecahedron) Graph of 26-fullerene 5-base w-nodes.svg, C26 Graph of 60-fullerene w-nodes.svg, C60
(truncated icosahedron) Graph of 70-fullerene w-nodes.svg, C70
The Schlegel diagram of a closed fullerene is a graph that is planar and 3-regular (or "cubic"; meaning that all vertices have
degree Degree may refer to: As a unit of measurement * Degree (angle), a unit of angle measurement ** Degree of geographical latitude ** Degree of geographical longitude * Degree symbol (°), a notation used in science, engineering, and mathematics ...
3). A closed fullerene with sphere-like shell must have at least some cycles that are pentagons or heptagons. More precisely, if all the faces have 5 or 6 sides, it follows from Euler's polyhedron formula, ''V''−''E''+''F''=2 (where ''V'', ''E'', ''F'' are the numbers of vertices, edges, and faces), that ''V'' must be even, and that there must be exactly 12 pentagons and ''V''/2−10 hexagons. Similar constraints exist if the fullerene has heptagonal (seven-atom) cycles. Open fullerenes, like carbon nanotubes and graphene, can consist entirely of hexagonal rings. In theory, a long nanotube with ends joined to form a closed torus-like sheet could also consist entirely of hexagons.


Bonding

Since each carbon atom is connected to only three neighbors, instead of the usual four, it is customary to describe those bonds as being a mixture of
single Single may refer to: Arts, entertainment, and media * Single (music), a song release Songs * "Single" (Natasha Bedingfield song), 2004 * "Single" (New Kids on the Block and Ne-Yo song), 2008 * "Single" (William Wei song), 2016 * "Single", by ...
and
double A double is a look-alike or doppelgänger; one person or being that resembles another. Double, The Double or Dubble may also refer to: Film and television * Double (filmmaking), someone who substitutes for the credited actor of a character * Th ...
covalent bond A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...
s. The hybridization of carbon in C60 has been reported to be sp2.01. The bonding state can be analyzed by
Raman spectroscopy Raman spectroscopy () (named after Indian physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman sp ...
, IR spectroscopy and X-ray photoelectron spectroscopy.


Encapsulation

Additional atoms, ions, clusters, or small molecules can be trapped inside fullerenes to form
inclusion compound In host–guest chemistry, an inclusion compound (also known as an inclusion complex) is a chemical complex in which one chemical compound (the "host") has a cavity into which a "guest" compound can be accommodated. The interaction between the ho ...
s known as
endohedral fullerenes Endohedral fullerenes, also called endofullerenes, are fullerenes that have additional atoms, ions, or clusters enclosed within their inner spheres. The first lanthanum C60 complex called La@C60 was synthesized in 1985. The @ (at sign) in the n ...
. An unusual example is the egg-shaped fullerene Tb3N@, which violates the isolated pentagon rule. Evidence for a meteor impact at the end of the Permian period was found by analyzing noble gases preserved by being trapped in fullerenes.


Research

In the early 2000s, the chemical and physical properties of fullerenes were a hot topic in the field of research and development. ''
Popular Science ''Popular Science'' (also known as ''PopSci'') is an American digital magazine carrying popular science content, which refers to articles for the general reader on science and technology subjects. ''Popular Science'' has won over 58 awards, incl ...
'' discussed possible uses of fullerenes (graphene) in armor. In the field of
nanotechnology Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal o ...
,
heat resistance Thermal resistance is a heat property and a measurement of a temperature difference by which an object or material resists a heat flow. Thermal resistance is the reciprocal of thermal conductance. * (Absolute) thermal resistance ''R'' in kelvin ...
and
superconductivity Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material. Any material exhibiting these properties is a superconductor. Unlike ...
are some of the more heavily studied properties. There are many calculations that have been done using
ab-initio ''Ab initio'' ( ) is a Latin term meaning "from the beginning" and is derived from the Latin ''ab'' ("from") + ''initio'', ablative singular of ''initium'' ("beginning"). Etymology Circa 1600, from Latin, literally "from the beginning", from ab ...
quantum methods applied to fullerenes. By DFT and TD-DFT methods one can obtain IR,
Raman Raman may refer to: People * Raman (name) *C. V. Raman (1888–1970), Indian Nobel Prize-winning physicist Places * Raman, Punjab (India) * Raman, Rawalpindi, Pakistan * Raman District, Yala Province, Thailand ** Raman Railway Station * Ra ...
and UV spectra. Results of such calculations can be compared with experimental results. Fullerene is an unusual reactant in many
organic reaction 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, Mechanistic Organ ...
s such as the Bingel reaction discovered in 1993.


Aromaticity

Researchers have been able to increase the reactivity of fullerenes by attaching active groups to their surfaces. Buckminsterfullerene does not exhibit "
superaromaticity 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 saturat ...
": that is, the electrons in the hexagonal rings do not
delocalize 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 diff ...
over the whole molecule. A spherical fullerene of ''n'' carbon atoms has ''n'' pi-bonding electrons, free to delocalize. These should try to delocalize over the whole molecule. The quantum mechanics of such an arrangement should be like only one shell of the well-known quantum mechanical structure of a single atom, with a stable filled shell for ''n'' = 2, 8, 18, 32, 50, 72, 98, 128, etc. (i.e., twice a perfect square number), but this series does not include 60. This 2(''N'' + 1)2 rule (with ''N'' integer) for
spherical aromaticity In organic chemistry, spherical aromaticity is formally used to describe an unusually stable nature of some spherical compounds such as fullerenes, polyhedral boranes. In 2000, Andreas Hirsch and coworkers in Erlangen, Germany, formulated a rule to ...
is the three-dimensional analogue of Hückel's rule. The 10+
cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
would satisfy this rule, and should be aromatic. This has been shown to be the case using quantum chemical modelling, which showed the existence of strong diamagnetic sphere currents in the cation. As a result, in water tends to pick up two more electrons and become an anion. The ''n'' described below may be the result of trying to form a loose metallic bond.


Reactions


Polymerization

Under high pressure and temperature, buckyballs collapse to form various one-, two-, or three-dimensional carbon frameworks. Single-strand polymers are formed using the Atom Transfer Radical Addition Polymerization (ATRAP) route. "Ultrahard fullerite" is a coined term frequently used to describe material produced by high-pressure high-temperature (HPHT) processing of fullerite. Such treatment converts fullerite into a nanocrystalline form of diamond which has been reported to exhibit remarkable mechanical properties.


Chemistry

Fullerenes are stable, but not totally unreactive. The sp2-hybridized carbon atoms, which are at their energy minimum in planar graphite, must be bent to form the closed sphere or tube, which produces angle strain. The characteristic reaction of fullerenes is electrophilic addition at 6,6-double bonds, which reduces angle strain by changing sp2-hybridized carbons into sp3-hybridized ones. The change in hybridized
orbital Orbital may refer to: Sciences Chemistry and physics * Atomic orbital * Molecular orbital * Hybrid orbital Astronomy and space flight * Orbit ** Earth orbit Medicine and physiology * Orbit (anatomy), also known as the ''orbital bone'' * Orbito ...
s causes the bond angles to decrease from about 120° in the sp2 orbitals to about 109.5° in the sp3 orbitals. This decrease in bond angles allows for the bonds to bend less when closing the sphere or tube, and thus, the molecule becomes more stable.


Solubility

Fullerenes are soluble in many organic solvents, such as toluene, chlorobenzene, and
1,2,3-trichloropropane 1,2,3-Trichloropropane (TCP) is an organic compound with the formula CHCl(CH2Cl)2. It is a colorless liquid that is used as a solvent and in other specialty applications. Production 1,2,3-Trichloropropane is produced the addition of chlorine t ...
. Solubilities are generally rather low, such as 8 g/L for C60 in carbon disulfide. Still, fullerenes are the only known
allotrope Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element: the ...
of carbon that can be dissolved in common solvents at room temperature. Among the best solvents is 1-chloronaphthalene, which will dissolve 51 g/L of C60. Solutions of pure buckminsterfullerene have a deep purple color. Solutions of are a reddish brown. The
higher fullerenes 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, ...
to have a variety of colors. Millimeter-sized crystals of and , both pure and solvated, can be grown from benzene solution. Crystallization of from benzene solution below 30 °C (when solubility is maximum) yields a triclinic solid
solvate Solvation (or dissolution) describes the interaction of a solvent with dissolved molecules. Both ionized and uncharged molecules interact strongly with a solvent, and the strength and nature of this interaction influence many properties of the ...
·4. Above 30 °C one obtains solvate-free fcc .


Quantum mechanics

In 1999, researchers from the University of Vienna demonstrated that wave-particle duality applied to molecules such as fullerene.


Superconductivity

Fullerenes are normally electrical insulators, but when crystallized with alkali metals, the resultant compound can be conducting or even superconducting.


Chirality

Some fullerenes (e.g. , , , and ) are inherently chiral because they are D2-symmetric, and have been successfully resolved. Research efforts are ongoing to develop specific sensors for their enantiomers.


Stability

Two theories have been proposed to describe the molecular mechanisms that make fullerenes. The older, “bottom-up” theory proposes that they are built atom-by-atom. The alternative “top-down” approach claims that fullerenes form when much larger structures break into constituent parts.Support for top-down theory of how 'buckyballs’ form
kurzweilai.net. 24 September 2013
In 2013 researchers discovered that asymmetrical fullerenes formed from larger structures settle into stable fullerenes. The synthesized substance was a particular
metallofullerene In chemistry, a metallofullerene is a molecule composed of a metal atom trapped inside a fullerene cage. Simple metallofullerenes consist of a fullerene cage, typically , with one or two metal atoms trapped inside. Recently, research has produced ...
consisting of 84 carbon atoms with two additional carbon atoms and two yttrium atoms inside the cage. The process produced approximately 100 micrograms. However, they found that the asymmetrical molecule could theoretically collapse to form nearly every known fullerene and metallofullerene. Minor perturbations involving the breaking of a few molecular bonds cause the cage to become highly symmetrical and stable. This insight supports the theory that fullerenes can be formed from graphene when the appropriate molecular bonds are severed.


Systematic naming

According to the IUPAC, to name a fullerene, one must cite the number of member atoms for the rings which comprise the fullerene, its
symmetry point group In abstract algebra, group theory studies the algebraic structures known as groups. The concept of a group is central to abstract algebra: other well-known algebraic structures, such as rings, fields, and vector spaces, can all be seen as g ...
in the Schoenflies notation, and the total number of atoms. For example, buckminsterfullerene C60 is systematically named (-''I''h) ,6ullerene. The name of the point group should be retained in any derivative of said fullerene, even if that symmetry is lost by the derivation. To indicate the position of substituted or attached elements, the fullerene atoms are usually numbered in a spiral path, usually starting with the ring on one of the main axes. If the structure of the fullerene does not allow such numbering, another starting atom was chosen to still achieve a spiral path sequence. The latter is the case for C70, which is (-''D''5h(6)) ,6ullerene in IUPAC notation. The symmetry ''D''5h(6) means that this is the isomer where the ''C''5 axis goes through a pentagon surrounded by hexagons rather than pentagons. Buckminsterfullerene-2D-skeletal numbered.svg, (-''I''h) ,6ullerene
Carbon numbering. C70fullerene-2D-skeletal numbered.svg, (-''D''5h(6)) ,6ullerene
Carbon numbering. C70fullerene-2D-skeletal numbered isobonds.svg, (-''D''5h(6)) ,6ullerene
Non-equivalent bonds shown by different colours. Cyclopropa12 C70fullerene-2D-skeletal renumbered.svg, 3H''-Cyclopropa ,2-''D''5h(6)) ,6ullerene. Cyclopropa212 C70fullerene-2D-skeletal renumbered.svg, 3H''-Cyclopropa
,12 This list contains selected positive numbers in increasing order, including counts of things, dimensionless quantities and probabilities. Each number is given a name in the short scale, which is used in English-speaking countries, as well as a ...
-''D''5h(6)) ,6ullerene. PC71BM.svg, -PCBM, ,2isomer.
IUPAC name is methyl 4-(3’-phenyl-3’H-cyclopropa ,2-''D''5h(6)) ,6ullerene-3’-yl)butyrate.
In IUPAC's nomenclature, fully saturated analogues of fullerenes are called ''fulleranes''. If the mesh has other element(s) substituted for one or more carbons, the compound is named a ''heterofullerene''. If a double bond is replaced by a methylene bridge , the resulting structure is a ''homofullerene''. If an atom is fully deleted and missing valences saturated with hydrogen atoms, it is a ''norfullerene''. When bonds are removed (both sigma and pi), the compound becomes ''secofullerene''; if some new bonds are added in an unconventional order, it is a ''cyclofullerene''.


Production

Fullerene production generally starts by producing fullerene-rich soot. The original (and still current) method was to send a large electric current between two nearby graphite electrodes in an
inert Inert may refer to: * Chemically inert, not chemically reactive ** Inert gas ** Noble gas, historically called inert gas * Inert knowledge, information which one can express but not use * Inert waste, waste which is neither chemically nor biol ...
atmosphere. The resulting electric arc vaporizes the carbon into a
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...
that then cools into sooty residue. Alternatively, soot is produced by
laser ablation Laser ablation or photoablation (also called laser blasting) is the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser ...
of graphite or pyrolysis of aromatic hydrocarbons. Combustion of benzene is the most efficient process, developed at MIT. These processes yield a mixture of various fullerenes and other forms of carbon. The fullerenes are then extracted from the soot using appropriate organic solvents and separated by chromatography. One can obtain milligram quantities of fullerenes with 80 atoms or more. C76, C78 and C84 are available commercially.


Applications

Fullerenes have been extensively used for several biomedical applications including the design of high-performance MRI contrast agents, X-ray imaging contrast agents, photodynamic therapy and drug and gene delivery, summarized in several comprehensive reviews.G. Lalwani and B. Sitharaman, Multifunctional fullerene and metallofullerene based nanobiomaterials, NanoLIFE 08/2013; 3:1342003. DOI: 10.1142/S179398441342003
Full Text PDF
/ref>


Tumor research

While past cancer research has involved radiation therapy, photodynamic therapy is important to study because breakthroughs in treatments for tumor cells will give more options to patients with different conditions. Recent experiments using HeLa cells in cancer research involves the development of new photosensitizers with increased ability to be absorbed by cancer cells and still trigger cell death. It is also important that a new photosensitizer does not stay in the body for a long time to prevent unwanted cell damage. Fullerenes can be made to be absorbed by HeLa cells. The derivatives can be delivered to the cells by using the functional groups L-phenylalanine, folic acid, and L-arginine among others. Functionalizing the fullerenes aims to increase the solubility of the molecule by the cancer cells. Cancer cells take up these molecules at an increased rate because of an upregulation of transporters in the cancer cell, in this case amino acid transporters will bring in the L-arginine and L-phenylalanine functional groups of the fullerenes. Once absorbed by the cells, the derivatives would react to light radiation by turning molecular oxygen into reactive oxygen which triggers
apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...
in the HeLa cells and other cancer cells that can absorb the fullerene molecule. This research shows that a reactive substance can target cancer cells and then be triggered by light radiation, minimizing damage to surrounding tissues while undergoing treatment. When absorbed by cancer cells and exposed to light radiation, the reaction that creates reactive oxygen damages the DNA, proteins, and lipids that make up the cancer cell. This cellular damage forces the cancerous cell to go through apoptosis, which can lead to the reduction in size of a tumor. Once the light radiation treatment is finished the fullerene will reabsorb the free radicals to prevent damage of other tissues. Since this treatment focuses on cancer cells, it is a good option for patients whose cancer cells are within reach of light radiation. As this research continues, the treatment may penetrate deeper into the body and be absorbed by cancer cells more effectively.


Safety and toxicity

In 2013, a comprehensive review on the toxicity of fullerene was published reviewing work beginning in the early 1990s to present and concluded that very little evidence gathered since the discovery of fullerenes indicate that is toxic. The toxicity of these carbon nanoparticles is not only dose- and time-dependent, but also depends on a number of other factors such as: * type (e.g.: , , M@, M@) * functional groups used to water-solubilize these nanoparticles (e.g.: OH, COOH) * method of administration (e.g.: intravenous, intraperitoneal) It was recommended to assess the pharmacology of every new fullerene- or metallofullerene-based complex individually as a different compound.


Popular culture

Examples of fullerenes appear frequently in popular culture. Fullerenes appeared in fiction well before scientists took serious interest in them. In a humorously speculative 1966 column for '' New Scientist'', David Jones suggested the possibility of making giant hollow carbon molecules by distorting a plane hexagonal net with the addition of impurity atoms.


See also

*
Buckypaper Buckypaper is a thin sheet made from an aggregate of carbon nanotubes or carbon nanotube grid paper. The nanotubes are approximately 50,000 times thinner than a human hair. Originally, it was fabricated as a way to handle carbon nanotubes, but i ...
*
Carbocatalysis Carbocatalysis is a form of catalysis that uses heterogeneous carbon materials for the transformation or synthesis of organic or inorganic substrates. The catalysts are characterized by their high surface areas, surface functionality, and large, a ...
* Dodecahedrane *
Fullerene ligand A transition metal fullerene complex is a coordination complex wherein fullerene serves as a ligand. Fullerenes are typically spheroidal carbon compounds, the most prevalent being buckminsterfullerene, C60. One year after it was prepared in millig ...
* Goldberg–Coxeter construction * Lonsdaleite *
Triumphene Triumphene is a fluorinated and phenylated fullerene derivative. It was first synthesized in 1998 by Boltalina, Street, and Taylor by reaction of C60F18 in a benzene-iron(III) chloride, FeCl3 solution for two weeks at room temperature. It is the f ...
*
Truncated rhombic triacontahedron In geometry, the chamfered dodecahedron is a convex polyhedron with 80 vertices, 120 edges, and 42 faces: 30 hexagons and 12 pentagons. It is constructed as a chamfer (edge-truncation) of a regular dodecahedron. The pentagons are reduced in size ...


References


External links


Nanocarbon: From Graphene to Buckyballs
Interactive 3D models of cyclohexane, benzene, graphene, graphite, chiral & non-chiral nanotubes, and C60 Buckyballs - WeCanFigureThisOut.org.
Properties of fullerene

Sir Harry Kroto's webpageSimple model of Fullerene

Bucky Balls, a short video explaining the structure of by the Vega Science TrustGiant Fullerenes, a short video looking at Giant FullerenesGraphene
15 September 2010, BBC Radio program ''Discovery'' {{Authority control Emerging technologies