JP5539686B2 - Separation and purification method of endohedral fullerene salts using mobile phase with electrolyte - Google Patents

Description

  In the present invention, a high-performance liquid chromatography apparatus (High Performance Liquid Chromatography: hereinafter abbreviated as “HPLC”) using an eluent to which an electrolyte is added as a mobile phase is efficiently used from a raw material containing an atom-containing fullerene salt. The present invention relates to a method for separating and purifying an atomic inclusion fullerene salt to be separated and purified.

Fullerene is a new molecular structure of carbon with a unique three-dimensional structure (cage structure) that has a highly symmetrical shape like soccer balls and rugby balls with a diameter of about 0.7 to 1.0 nm. It is a generic name for a group of carbon molecules represented by the general formula C _2n (2n ≧ 60), which is composed of a carbon five-membered ring and two or more carbon six-membered rings and is closed in a spherical shell with a size of C ₆₀ or more. . Specific examples include C ₆₀ , C ₇₀ , C ₇₆ , C ₈₂ , C ₉₀ , and C ₉₆ .
This fullerene has a free space in which several atoms can be placed inside the cage, and can serve as a capsule that stably holds even unstable atoms.

A material in which atoms (hereinafter referred to as M) are encapsulated in the inner cavity of this fullerene is called an atomic inclusion fullerene, and is a general term for molecules represented by the general formula M @ C _2n (2n ≧ 60). Here, M is a single atom or a plurality of atoms or an atomic group containing them, and is not necessarily a single atom.
Among the above-mentioned atomic inclusion fullerenes, those in which the inclusion atoms are metal atoms are metal inclusion fullerenes.
Research in this area has made significant progress in recent years because it is expected to develop new electrical properties as electrons move from internal atoms or metals to the carbon cage.

Japanese Patent No. 3926331 WO2007 / 123208 Publication Japanese Patent Application No. 2008-217289 JP 2006-036569 A JP 2005-272159 A

R. Tellgmann, E.E.B.Campbell et al., Nature, 382 (1996) 407-408 "Fullerene Physics and Chemistry" Shinohara and Saito Nagoya University Press 1997

Conventionally, the inclusion metal atoms mainly include Group 3 elements (Sc, Y, La), lanthanide elements, and actinoid elements in the periodic table, and C _2n (2n ≧ 82) as fullerenes. It has been studied (Non-Patent Document 2).

In contrast, more encapsulation of metal atoms of the cage space to a smaller C ₆₀ have been studied. C ₆₀ with the soccer ball-shaped structure is the most symmetric good fullerene is a convenient material in predicting analysis and physical properties after encasing an atom.

In addition, since alkali metals belonging to Group 1 of the periodic table tend to be monovalent cations, in the case of alkali metal inclusion fullerenes, electrons are given to the fullerene cage, and the fullerenes that have obtained the electrons have a negative charge, and the inclusion metal atoms are positive. It is expected to create new physical properties.
Among them, the lithium atom inclusion C ₆₀ (chemical symbol Li @ C ₆₀ ), which is very reactive and has an inclusion of lithium atoms whose oxidation number is always +1, has attracted attention, and its significant and specific properties (Since lithium atoms are said to be derived from the smallest diameter among group 1 elements having low ionization energy, that is, alkali metals), synthesis / separation techniques for application development are being studied.
In particular, it has attracted attention as a material that contributes to improving the photoelectric conversion efficiency of organic thin-film solar cells that use clean solar energy.

By the way, the endohedral fullerene is synthesized by a laser vapor deposition method, an arc discharge method, an ion implantation method, a plasma irradiation method, or the like. In the products synthesized by the respective methods, impurities such as empty fullerenes and non-encapsulated metal atoms are contained in addition to the endohedral fullerenes of the metal atoms.
For this reason, in order to produce a highly pure endohedral fullerene, it is necessary to separate the endohedral fullerene and other impurities from the synthesized product before purification.

Conventionally, various techniques have been disclosed in Non-Patent Documents 1 and 2 and Patent Documents 1 to 5 regarding the method for separating and purifying endohedral fullerenes or the separated endohedral fullerenes. Each document will be described below.
In the following, the chemical formula M @ Cn is a general formula representing an endohedral fullerene, and indicates that an atom or molecule M is encapsulated in a fullerene cage composed of n carbon atoms.

(Non-Patent Document 1)
Non-Patent Document 1 is a report by researchers of the Campbell group.
Non-Patent Document 1 reports the generation of lithium inclusion C60 by ion implantation.
In the above report, in the mass spectrum of a laser desorption ionization time-of-flight mass spectrometer (hereinafter referred to as “LDI-TOF-MS”), in addition to the peak at mass number 727 indicating the production of Li @ C60, the mass number A peak of 720 empty fullerene C60 is also seen. And when looking at the peak intensity ratio, C60 / Li @ C60 is about 1/4 and still contains a lot of C60, and it is separated into a single peak or a single isolated state having a peak overwhelming others. It is difficult to say that it is in an isolated state.

(Non-Patent Document 2)
Non-Patent Document 2 states that separation of metal-encapsulated fullerene is extremely difficult, and in FIG. 8.9 (c), the La @ C82 single peak of La @ C82 in LDI-TOF-MS The fact that the isolation was successful is described.
In the technique described here, metal-encapsulated fullerene is separated and purified by two-stage HPLC using two stationary phases (columns) having different adsorption mechanisms. The principle is described as follows. “Metal-encapsulated fullerenes often appear on chromatograms at the same retention time as empty fullerenes. In such a case, the target metal inclusion fullerene can be completely separated from the empty fullerene by using a plurality of stationary phases having different adsorption functions. (Page 206).

Regarding M @ C60, “Ca @ C60 and Ca @ C70 are reported to be extracted by pyridine at room temperature under oxygen removal. (Page 221).
And even if it is not under oxygen removal, "Ca @ C60 is extracted comparatively efficiently by ultrasonic extraction around 5 ° C. (Page 232, note 101)).

  However, the LDI-TOF-MS diagram of the pyridine extract at room temperature (Fig. 8.17) shows that Ca @ C60 and Ca @ C70 are not completely isolated, and Ca @ C60, Ca @ C70, This indicates that C60, C70, and C74 are mixed. That is, Ca @ C60 or Ca @ C70 is accompanied by other endohedral fullerenes or empty fullerenes, and gives a single peak, or a state of being separated almost alone having a peak overwhelming others. It cannot be said that it is (isolated).

In the first place, as described in Non-Patent Document 2, as a separation / purification method widely applied to various fullerenes including C60 fullerene, a sublimation method, an HPLC method, a solubility difference method, and the like are known.
The sublimation method is a separation / purification method using a difference in sublimation temperature depending on substances, and is used for separation / purification of various fullerenes.
The solubility difference method is a separation / purification method using a difference in solubility due to a substance in a solvent, and is generally used widely including extraction and washing (illustrated in Patent Documents 1 to 3 described later).
The HPLC method, which is a type of column chromatography, determines the difference in the interaction (adsorbability, partition coefficient, etc.) between the target substance and the stationary phase (solid) and mobile phase (developing solution, organic solvent, water, etc.). This is a separation / purification method used (illustrated in Patent Documents 4 and 5 described later).

(Patent Document 1)
Patent Document 1 discloses a method of separating a first fullerene group and a second fullerene group in a fullerene mixture as follows.
That is,
(Step 1) A fullerene mixture containing the first and second fullerene groups is prepared.
(Step 2) A stable fullerene cation is formed in a solvent for either one of the first or second fullerene group, and the fullerene cation is separated from the other fullerene group. Here, the selective formation of cations is carried out by chemical oxidation, electrochemical oxidation, or chemical addition of a cationic electrophilic group.
(Step 3) Cationized fullerene and neutral fullerene are separated by a recrystallization or precipitation technique.

Then, desirable fullerenes are chemically modified to impart different chemical properties to target fullerenes and non-target fullerenes, thereby enabling separation and purification of these fullerenes.
Here, as an example of separation of the first fullerene group and the second fullerene group, separation of metal-encapsulated fullerene and empty fullerene is also exemplified.

Further, in claim 28 and the present specification, a sublimated fullerene material containing M @ C2n which is easily oxidized (oxidation potential is 0.8 V or less) is contacted with an oxidizing agent (AgSbF6) in a first solvent. This shows that M @ C2n has been purified using the technique of forming a first solution containing M @ C2n cations.
As described above, in Patent Document 1, the endohedral fullerene is separated and purified by forming a cation of the endohedral fullerene. In the cation formation process, an oxidizing agent and a proton agent are used.
Specifically, Patent Literature 1 presents three methods. Each method will be described below.

[Method 1 (page 25 (Table 3))]
Hereinafter, the processing outline of method 1 is shown in order.
(1) Synthesize empty fullerene and encapsulated fullerene with carbon arc method.
(2) Soot is sublimated at 750 ° C. to sublimate fullerene having a low sublimation temperature and a small number of carbon atoms, thereby removing the remaining giant fullerenes without sublimation. Then, the fullerene sublimate is collected under anaerobic conditions.
(3) The sublimate is extracted with ODCB (o-dichlorobenzene) and then filtered to remove insoluble substances (C74, M @ C60, M @ C70, other M @ C2n), and soluble filtrate ( M @ C82, empty C2n) is extracted into ODCB.
(4) The soluble filtrate (M @ C82, empty C2n) is oxidized with [Ag +] [SbF6-] in ODCB, and then filtered. This removes the precipitated Ag metal precipitate and leaves [M @ C82 +] [SbF6-] and neutral C2n which are soluble mixtures in the ODCB.
(5) The soluble mixture is precipitated in hexane and filtered, and a solid containing C60 and C70 which are soluble filtrates and insoluble [M @ C82 +] [SbF6-] and neutral C2n is separated.
(6) Thereafter, M @ C82 final product is obtained after various steps.
In Method 1, M @ C82 is processed as a final product, and M @ 60 and M @ 70 are removed by ODCB extraction and filtration during the process. It is not. Furthermore, Method 1 is separation / purification using a solubility difference method, and is not separation / purification by the HPLC method.

[Method 2 (page 30 (Table 4))]
Hereinafter, the processing outline of method 2 is shown in order.
(1) Synthesize empty fullerene and encapsulated fullerene with carbon arc method.
(2) Soot is sublimated at 750 ° C. to sublimate fullerene having a low sublimation temperature and a small number of carbon atoms, thereby removing the remaining giant fullerenes without sublimation. Then, the fullerene sublimate is collected under anaerobic conditions.
(3) The sublimate is extracted with an oxidizing agent in which [Ag +] [SbF6-] is mixed in ODCB, and then filtered. In this way, the precipitated insoluble substances (M @ C60, M @ C70, C74) are removed, and Ag metal precipitates are removed, and [Mm @ C2n +] [SbF6-] and medium that are soluble filtrates in ODCB. Leave sex C2n.
(4) Precipitated filtrate in ODCB was deposited in hexane and filtered, and C60 and C70 which are soluble in hexane, [Mm @ C2n +] [SbF6-] and polarity that were insoluble in hexane were reduced. A solid containing neutral C2n is isolated.
(5) Thereafter, the final product of Mm @ C2n is obtained after the processing in various steps.

In Method 2, the final product is Mm @ C2n, but n is 36 or more (Patent Document, page 29, paragraph number [0019]). That is, M @ C60 is not isolated or purified.
In the ODCB [Ag +] [SbF6-] extraction step, M @ C60 and M @ C70 have become insoluble substances without being oxidized. In addition, Gd @ C72 and Gd @ C82 coexist in the final product (see FIG. 6 of Patent Document 1). After all, in method 2, even if 2n> 60 in M @ C2n, it is not isolated and even if 2n = 60, it is not isolated. This method 2 is also separation / purification using the solubility difference method, and not the HPLC method.

[Method 3 (page 33 (Table 5))
In Patent Document 1, “M @ C2n including some lanthanoid metals (M = Sm, Eu, Tm, Yb and possibly Er)” is “of oxidation-resistant and insoluble M @ C60 class. Includes deviations from properties .... can be oxidized using an oxidizing agent of moderate oxidizing power, resulting in a new soluble cation M @ C60 +. (Patent Document 1, page 32, line 11 to line 18).

(Patent Document 2, Patent Document 3)
Patent Document 2 and Patent Document 3 are already filed by the inventors of the present application.

  First, a method for producing a compound of endohedral fullerenes by a plasma irradiation method employed by the inventors and the resulting fullerene base material will be described with reference to FIGS.

  In the plasma irradiation method, a plasma flow containing ions composed of atoms to be included is generated in a vacuum vessel, and the ions in the generated plasma flow are reacted with fullerene vapor generated by a fullerene oven to be contained on a deposition substrate. A film containing fullerene is formed.

  FIG. 6 is a schematic explanatory view for explaining the structure of a film forming apparatus for producing an endohedral fullerene by a plasma irradiation method. In FIG. 6, 301 is a vacuum chamber, 302 is a vacuum pump, 303 is an electromagnetic coil, 304 and 308 are ovens, 305 and 309 are nozzles, 306 is a heating substrate, 307 is a plasma flow, 310 is a deposition substrate, and 311 is a composite. , 312 indicates a bias voltage applying device, and 313 indicates a heating filament.

The vacuum chamber 301 is made of a corrosion-resistant metal such as stainless steel, has a cylindrical shape that is long in the lateral direction and has a circular or rectangular cross section as shown in FIG. 6, and is provided with a lid at both openings of the cylinder. In addition, the structure is provided with an openable / closable lid that is not shown for replacement and maintenance of components in the vacuum chamber 301. In addition, since the inside of the inside is reduced in pressure by a vacuum pump 302 described later, a structure that can withstand pressure due to atmospheric pressure is adopted.
The heating filament 313 is made of a thin wire wound in a coil shape of a refractory metal such as tungsten, and heats the heating substrate 306 described later from the left side shown in FIG. 6 to, for example, about 2700 ° C. in a vacuum. Power is supplied from a power source (not shown) from a lid 301 via a current introduction terminal (not shown).

The heating substrate 306 is a plate having heat resistance and corrosion resistance due to a refractory metal such as tungsten or rhenium. As shown in FIG. 6, the central axis of the vacuum chamber 301 is inside the vacuum chamber 301 with respect to the heating filament 313. The plate surface is disposed so as to be substantially orthogonal to the plate.
The deposition substrate 310 is a plate having a smooth surface made of stainless steel or the like, and is disposed with the smooth surface facing the heating substrate 306 as shown in FIG. A desired film is formed on the smooth surface of the deposition substrate 310.

  The bias voltage applying device 312 applies a negative voltage to the deposition substrate 310 so as to give acceleration energy to ions of inclusion target atoms guided to the vicinity of the deposition substrate 310 by a plasma flow 307 to be described later. One end is connected to the deposition substrate 310 and the other end is grounded via a current introduction terminal (not shown) from the right lid shown in FIG.

  The vacuum pump 302 reduces the internal pressure of the vacuum chamber 301 to about 10 −4 Pa to facilitate the generation of plasma, increases the mean free path of desired molecules in the gas state, and allows molecules that reach the deposition substrate 310 to increase. Many are secured. In order to make the ultimate pressure smaller than 10 −4 Pa, for example, a combination of a rotary pump as a roughing pump, a diffusion pump, a turbo molecular pump, etc. as an auxiliary pump is used.

  The electromagnetic coil 303 is a large coil in which the outer periphery of the vacuum chamber 301 is wound with a metal wire such as copper having a relatively large current capacity and good electrical conductivity. By supplying power to the electromagnetic coil 303 from a current source (not shown), a magnetic field B in the direction of the arrow shown in FIG.

In addition, the ovens 304 and 308 are in close contact with the nozzles 305 and 309 provided with heaters (not shown) that cover the opening and have a bent tube as shown in FIG. 6 on the opening side of the vaporizer that stores the material to be vaporized. It is fixed. The nozzles 305 and 309 of the ovens 304 and 308 are exposed to the inside of the vacuum chamber 301, and the center axis of the nozzle tip is provided toward the approximate center of the heating substrate 306 and the deposition substrate 310.
Although not shown, the film forming apparatus 300 is provided with an air supply pipe provided with an opening / closing valve such as nitrogen gas for returning the vacuum chamber 301 to the atmospheric pressure.

In the film forming apparatus configured in this way, for example, lithium as an inclusion target atom (hereinafter referred to as “Li”) is supplied to the oven 304 in advance and, for example, C60 powder or the like is supplied to the oven 308. .
First, the inside of the vacuum chamber 301 is depressurized to, for example, 10 −4 Pa by the vacuum pump 302, and then the heating substrate 306 is heated to about 2700 ° C. by supplying power to the heating filament 313 from a power source (not shown).

  On the other hand, the heaters (not shown) of the oven 304 and the oven 308 are energized and heated to such an extent that lithium and C60 do not vaporize. At this time, since the internal pressure increases due to the gas release from the heating substrate 306 and the inner surfaces of the ovens 304 and 308, the vacuum evacuation is continued until the vacuum chamber 301 reaches a predetermined pressure. At this time, the nozzles 305 and 309 are also heated by a heater (not shown).

  Next, when the vacuum chamber 301 is stabilized at a predetermined pressure, a bias voltage is applied to the deposition substrate 310 by the application device 312. Then, the electromagnetic coil 303 is fed from a current source (not shown) to generate a magnetic field (2 to 7 kG) substantially parallel to the axis L in the vacuum chamber 301.

  Next, the oven 304 to which lithium is supplied is reset to 500 to 550 ° C., which is higher than the boiling point under reduced pressure, and heated to vaporize lithium, and the oven 308 to which C60 is supplied is changed to a sublimation temperature. Re-set to higher 400-650 ° C. and heat to vaporize C60.

  At this time, since the atmospheres of the ovens 304 and 308 and the vacuum chamber 301 are connected via the nozzles 305 and 309, the molecules in the gas phase state in these have a sufficiently large mean free path.

  Here, the behavior of vaporized lithium and C60 in the vacuum chamber 301 will be described.

The vaporized lithium is ejected from the nozzle 305 and collides with the high-temperature heating substrate 306. At this time, the lithium atoms in the vapor phase that collide with the high-temperature heating substrate 306 and are in thermal contact are supplied with larger thermal energy in addition to the kinetic energy accompanying vaporization, and the lithium atoms themselves release electrons and become positive ions. Macroscopically neutral plasma is formed with nearby electrons (thermal contact ionization).
Further, since the magnetic field B is formed in the longitudinal direction in the vacuum chamber 301, it is limited that lithium ions having a positive charge are spread by receiving a force from the magnetic field B.

On the other hand, lithium ions and electrons that have been thermally contact-ionized on the heating substrate 306 move in pairs, but the electrons are overwhelmed by lithium ions having a large mass.
Due to the force that suppresses the spread by the magnetic field B received by the lithium ions, the movement direction of the lithium ion / electron pair after the collision is substantially the longitudinal direction of the vacuum chamber 301, and the plasma flow 307 moves to the right side shown in FIG. Is generated. The flow velocity of this plasma is about the speed of sound and can be said to be extremely low.

The vaporized C60 is ejected from the nozzle 309 toward the deposition substrate 310 in the vacuum chamber 301. The ejected molecules form a high concentration C60 atmosphere in the vicinity of the deposition substrate 310. Since the deposition substrate 310 is applied so as to have a small negative potential, an extremely thin ion sheath is formed in the vicinity of the deposition substrate 310. Then, lithium ions are accelerated only in the vicinity of the deposition substrate 310 where C60 is densely present, and lithium atoms are included without destroying C60.
As a result, a reaction product film containing the endohedral fullerene is sequentially generated on the deposition substrate 310.

  In this method, since the plasma flow 307 is formed by a relatively small magnetic field, and the lithium ions themselves are weakly accelerated by the electric field in the vicinity of the deposition substrate 310, the interaction of the lithium ions with the C60 molecule is not a physical reaction but a chemical reaction. Is the main thing. As a result, the rate at which C60 itself is destroyed by impact is reduced, and the endohedral fullerene synthesis with higher yield can be performed.

  FIG. 7 shows the mass analysis result by LDI-TOF-MS (laser desorption ionization time-of-flight mass spectrum) of the film thus formed on the deposition substrate 310, and the mass number indicating the presence of empty C60. In addition to the peak at 720, a peak with a mass number of 727 indicating the presence of Li @ C60 can be confirmed, indicating that Li @ C60, which is a fullerene in which lithium is included in the deposited film 310, was generated.

  In this way, the synthetic film generated on the deposition substrate 310 is not only Li @ C60 in which lithium atoms are included in the cage of C60 and C60 but also a mixed film in which lithium atoms and the like not included are mixed (hereinafter, referred to as “a mixed film”). The mixed film at this stage is referred to as “unpurified endohedral fullerene”).

  In Patent Document 2, the inventors of the present invention encapsulate fullerenes such as atoms to be encapsulated by the above-described plasma irradiation method, a method for producing a compound containing fullerene encapsulating target atoms, and this compound as a solvent. It shows that the fullerene base material (also referred to as “TCE”), which is a precipitate obtained by extraction / purification by the above method, has a cluster structure in which a plurality of empty fullerenes are surrounded and bonded around one endohedral fullerene It was.

  The method for producing a fullerene base material disclosed in Patent Document 2 includes a first treatment for removing at least an inclusion target atom and a compound of an inclusion target atom that have not been included in an aqueous solvent from a synthetic product containing an inclusion fullerene, and an inclusion fullerene. The molecular cluster containing the endohedral fullerene is separated and purified by performing a second treatment for extracting the fullerene into the solvent and a third treatment for removing empty fullerene by the reprecipitation method.

  In this way, the separation and purification of the endohedral fullerene is performed by a combined process consisting of at least an unreacted inclusion target atom removal process, an endohedral fullerene solvent extraction process, and an empty fullerene removal process by reprecipitation. Thus, separation and purification of the endohedral fullerene, which has been insufficient only by solvent extraction, is performed with high purity, and the yield of the endohedral fullerene that can be purified and recovered from the synthesized product is improved.

  Patent Document 2 shows a product obtained by measuring the particle size distribution of the product in the solution by a dynamic light scattering method. From the particle size distribution in the solution of C60, the diameter size of C60 is 0.7 nm. The particle size distribution in the chloronaphthalene solution indicates that the particle size in this solution has a peak at 4 to 6 nm.

(Patent Document 3) IS503 Isolated Encapsulated Fullerene Patent Therefore, in Patent Document 3, instead of the treatment described in Patent Document 2, a fullerene base material that forms a cluster structure by cutting the binding force between empty fullerene and encapsulated fullerene is used. Further separation and purification were performed.

Patent Document 3 discloses a technique for producing an isolated endohedral fullerene, and the endohedral fullerene generally has the following steps.
That is,
(A) a step of introducing a material having a cluster structure composed of an endohedral fullerene and a plurality of empty fullerenes surrounding the inner fullerene into a solvent;
(B) a step of decomposing the cluster structure of the material in this solvent and forming an endohedral fullerene cation;
(C) a step of precipitating a salt of an endohedral fullerene cation,
(D) a step of separating the solvent and the salt of the encapsulated fullerene cation

As a result, it was found that a material having a cluster structure can be decomposed, and it was disclosed that an isolated endohedral fullerene represented by M @ C2n was obtained.
The present inventors succeeded in loosening the cluster structure by deelectron oxidation reaction and obtaining lithium-encapsulated C ₆₀ fullerene as a cation salt. The lithium-encapsulated C ₆₀ fullerene cation (Li @ C ₆₀ ⁺ ) salt shown as an example is a kind of atomic-encapsulated fullerene salt.
Here, a salt is generally a compound in which a cation (cation) and an anion (anion) are ion-bonded. A familiar representative example is sodium chloride (chemical symbol NaCl, also referred to as Na ⁺ Cl ⁻ to emphasize that it is an ion-bonded compound or salt). Therefore, the atomic inclusion fullerene salt refers to a salt containing a cation (cation) or an anion (anion) of the atomic inclusion fullerene.

  That is, the isolated endohedral fullerene represented by M @ C2n was obtained, and the peak intensity of the other endohedral fullerene with respect to the peak intensity of this endohedral fullerene in LDI-TOF-MS was obtained. The ratio was 0.5% or less in the positive mode and 50% or less in the negative mode. “Isolated” was used in the meaning of a state giving a single peak when viewed in a mass spectrum, or a state of being separated almost alone having a peak overwhelming others.

(Patent Document 4, Patent Document 5) HPLC
Patent Documents 4 and 5 disclose a technique for separating or purifying a desired endohedral fullerene from a material containing the endohedral fullerene using HPLC (High Performance Liquid Chromatography).
Here, when HPLC is abbreviated, this HPLC is a kind of column chromatography and uses a liquid pressurized to a high pressure as a mobile phase.
Column chromatography is one of the methods for purifying compounds and utilizes the distribution of substances between two different phases (solid phase and liquid phase). A cylindrical container (column) is filled with a packing material (stationary phase) such as silica gel, and a reaction mixture (eluent) dissolved in a solvent is poured into it, and the compound has an affinity for the packing material and molecular size. Separation of the mixture is performed by utilizing the difference in length.

The separation here depends on the degree of partitioning between both phases of each molecule (or ion) in the sample. And the smaller the particle size of the stationary phase that is the filler in the container, the higher the number of theoretical plates, but the greater the flow resistance.
The number of theoretical plates is an index that represents the performance of an apparatus that separates substances using the difference in the distribution ratio of substances between two phases, and is also used as an index that represents the performance of a column. If this value is high, it is said to be a high-performance column, that is, a column with good separation performance.
In HPLC, a method of flowing the eluent at high speed using a high-pressure pump and a method of recording a chart on recording paper using a detector greatly increase the time required for analysis and sorting. Can be shortened.

Patent Document 4 discloses an efficient and selective extraction method for metal-encapsulated fullerenes, which has improved the disadvantages of conventional methods for extracting metal-encapsulated fullerenes. In the extraction method of metal fullerene disclosed in Patent Document 4, for example, a soot-like mixture containing metal-encapsulated fullerene and empty fullerene, a solvent (A) having a donor number of 25 or more and a donor number of less than 25, And it extracts with a mixed solvent with the solvent (B) whose dielectric constant is larger than 10.
In the technique disclosed in Patent Document 4, the content of metal-encapsulated fullerene in the mixture can be increased by selectively extracting the metal-encapsulated fullerene from the mixture containing the metal-encapsulated fullerene and the empty fullerene. For this reason, by using extraction with a mixed solvent as a pretreatment for separation work using HPLC, the time required for HPLC treatment and the elution solvent are reduced, and efficient and selective extraction of metal-encapsulated fullerenes is achieved. It is supposed to contribute to.

Among the mixed solvents for extraction which are eluents here, the solvent (A) is selected from amine solvents such as tritylamine and ethylamine, dimethyl sulfoxide and the like, and the solvent (B) is a ketone such as acetone and cyclohexane. System solvents, nitrile solvents such as acetonitrile, ether solvents such as tetrahydrofuran and 1,2-dimethoxyethane, and others are used.
In the pretreated liquid by this mixed solvent extraction, empty fullerenes and the like are hardly detected, and therefore it is said that only metal-encapsulated fullerenes can be purified more efficiently by applying HPLC. In this HPLC, it is considered that the above mixed solvent was used as the eluent.

Patent Document 5 discloses a technique relating to a method for producing an endohedral fullerene in which a guest element such as copper is encapsulated inside a fullerene molecule such as C60.
The method for producing an endohedral fullerene disclosed in Patent Document 5 includes a step of causing a guest element supply source and a fullerene molecule supply source to exist in a plasma generation chamber, and a guest element from the supply source in the plasma generation chamber. And a step of causing the fullerene molecules to collide with each other under plasma excitation to introduce guest elements into the fullerene molecules, and purify the endohedral fullerenes obtained.
The purification process of the endohedral fullerene includes a process of extracting a soluble part of the deposit with a solvent, a process of filtering unnecessary precipitates, and a process of separating the target product by HPLC.

Since it did in this way, a guest element can be included easily and effectively in a fullerene molecule, and since it is a manufacturing method by low temperature (for example, 25 degreeC) and low pressure (for example, 25 Pa), all the periodic tables It can be applied to any element.
Although separation by HPLC in the purification step is not clearly described here, it is considered that carbon disulfide is used for the liquid phase and a general stationary phase column is used.

As described in Non-Patent Document 1, the presence / generation of Li @ C ₆₀ has been confirmed by electromagnetic spectrum observation and mass spectrometry. However, as shown in Patent Document 2, the endohedral fullerene in the composite is a so-called clustered state in which empty C ₆₀ fullerene is wrapped around, and it is not a cluster structure but an isolated pure one. Li @ C ₆₀ could not be obtained stably in the amount (milligram order by weight), and the properties were not measured and evaluated in detail.

Moreover, when the mass spectrum MS of the material supposed to be separated, which is actually shown in FIG. 13 of Patent Document 1, is observed, both are empty fullerene (C60) and / or plural fullerene inclusions (Tm @ C60, Tm @ C70 etc.) are mixed, and it is difficult to say that they are isolated (separated separately).
In particular, the technique described in Patent Document 1 indicates that cation formation by oxidation is difficult for _{M @ C60} , except when M is Tm. That is, (Table 4) of Patent Document 1 (processing step described in the frame in method 2 flow) “ODCB [Ag +] [SbF6-] extraction and subsequent filtration” removes M @ C60 as an insoluble matter without being oxidized. Has been. It is thought that it implicitly suggests that it is not applicable to the separation between M @ C60 and C60 which are hardly oxidized fullerenes.

As described above, in Patent Document 1, there is no description suggesting a route for isolation / purification of M @ C60 or M @ C70 after oxidation treatment.
Furthermore, Patent Document 1 is a purification method based on a solubility difference method using a clear difference in chemical characteristics between empty fullerenes and encapsulated fullerenes, both of which are in solution or insoluble, respectively. This is effective when there is no interaction in the object. This is not a bond decomposition method in the case where different fullerenes form a bonded state (cluster state) as in the processing object in the present application described later.

  On the other hand, in the technique described in Patent Document 2, purification of Li @ C60 by HPLC was tried a plurality of times, but the purified amount of the endohedral fullerene could not be 7 to 8% or more of the weight of the sample. That is, in the technique described in Patent Document 2, there is a limit to the removal of empty fullerene, so that the yield cannot be improved beyond a certain level by purification, and still has a classifier structure.

Under this circumstance, as disclosed in Patent Document 3, the present inventors have succeeded in loosening the cluster structure by deelectron oxidation and obtaining lithium-encapsulated C ₆₀ fullerene as a cation salt. This lithium-encapsulated C ₆₀ fullerene cation (Li @ C ₆₀ ⁺ ) salt is a kind of atomic-encapsulated fullerene salt.
As mentioned above, an atomic inclusion fullerene salt is a salt containing a cation (cation) or anion (anion) of an atomic inclusion fullerene, and Li @ C ₆₀ PF ₆ (Li @ C ₆₀ ⁺ PF ₆ ^- and also referred), such as Li @ C ₆₀ SbCl ₆ is a specific representative examples.

In order to further separate and purify Li @ C ₆₀ SbCl ₆ , which is a typical example of the atom-encapsulated fullerene salt obtained by deelectronization described in Patent Document 3, the present inventors tried a sublimation method or an HPLC method. . However, it did not get enough results.
In other words, Li @ C ₆₀ SbCl ₆ was easily decomposed, and it was found that purification by heating sublimation was inappropriate. Moreover, when the HPLC method conventionally used for the production of endohedral fullerene was applied as it was, the Li @ C ₆₀ salt and the same cation were not discharged from the column. This is presumed to be because the Li @ C ₆₀ salt and the same cation were held strongly adsorbed on the stationary phase in the HPLC column and were not easily desorbed.

In addition, as shown in Patent Document 3, although the Li @ C ₆₀ salt was successfully separated and purified by the solubility difference method, the obtained atomic-encapsulated fullerene salt has a low purity and a low recovery rate. There was an inconvenience.
That is, the above-described method has not yet been sufficiently separated and purified, and the impurities have not been sufficiently removed and the purity has been low. In addition, because the difference in solubility was not sufficiently secured, problems such as low recovery due to leakage of the target product into the liquid on the impurity side or loss due to adhesion to containers and jigs remained. .

In view of this point, the present invention is an inexpensive and simple method that can solve the above-mentioned disadvantages of the solubility difference method and achieve high purity and high recovery rate as a method for separating and purifying atomic inclusion fullerene salts. Is to establish.
That is, among the various separation / purification methods known or studied by the inventors, the HPLC method is one of well-known methods for separation / purification of various organic substances including fullerenes, and is simple and highly efficient. (High separation rate, high purification rate, low process loss), so it is widely used.
Therefore, the present invention overcomes the problem that the endohedral fullerene salt or ion (cation or anion), which is a disadvantage of the conventional HPLC method, is not adsorbed by the HPLC column packing material and discharged from the column. Proposes a novel HPLC method in which is separated from other components and easily discharged from the column.

The outline of HPLC will be described below.
Chromatography is one of the techniques (techniques) used to separate gases, liquids, and solutes. Among these, in liquid chromatography, initially, a straight glass tube packed with an adsorbate such as alumina or diatomaceous earth was used as a column. A sample is poured from the top of the column to be adsorbed, and then a new solvent is continuously dropped from above (“development” operation). Among the samples adsorbed on the top by the development, those that are easily dissolved in the solvent move to the liquid side and descend in the column.
When the column is washed by adding new solvent (“elution” operation), each component is separated from the sample in the order of the distribution ratio of the adsorbent and the solvent, so that it elutes from the lower end of the column. Each component can be separated by separating each fraction.

In contrast, HPLC (High Pressure Liquid
Chromatography (High-Performance Liquid Chromatography) uses a high-speed pump to flow the eluent, which is a solvent for elution, to greatly reduce the time required for analysis. . Moreover, what was observed visually in the glass tube column at the time of discovery of the principle has been improved to a method of recording as a chart on recording paper using a detector.

Chromatography refers to the use of substance distribution between two different phases (stationary phase and mobile phase). Separation by this distribution is the separation of each molecule (or ion) in a sample. Depends on the degree of distribution between the two phases. Column chromatography in the previous chlorophyll is typical of what is called “adsorption” chromatography, in which the sample is adsorbed onto an adsorption medium such as alumina.
In “partition chromatography”, a liquid (for example, water) is included in the stationary phase, and another liquid that does not mix with the liquid is used as the mobile phase. In this case, it is the distribution of the solute between the two liquid phases that influences the separation.
In “ion exchange chromatography”, separation is performed by using the competition between the ionic functional groups of the stationary phase (ion exchange resin, etc.) and the respective ions and complex formation.
In “gel filtration chromatography”, the molecular size of the sample affects the separation. (From John Dintis, Bluebucks “New Encyclopedia of Chemical Terms”, November 1993)

Although briefly described above, the HPLC will be described below with reference to the drawings.
The HPLC system includes units such as an eluent bottle, a degassing device, a pump, an injector, a column and a column thermostat, a detector, and a recording device.
Hereinafter, each unit will be described.

a) Deaeration device This is used to remove oxygen and other gases mixed in the eluent, which become noise during detection by the detector and cause baseline instability.
b) Pump The pump is installed in the uppermost stream of the HPLC system and sends the eluent in the eluent bottle to the system.
Various devices have been devised to reduce periodic pressure fluctuations (called pulsations) as much as possible and to flow the eluent at a constant flow rate under any conditions without affecting the measurement. As a result, a very small amount of sample can be analyzed with high sensitivity.

c) Injector The injector is installed next to the pump, and a sample to be analyzed is injected into the eluent through a syringe called a syringe. Note that when a large number of samples are continuously injected at regular intervals, an autoinjector (autosampler) is often used.
d) Column Although the principle is the same as that of the glass tube used at the beginning as described above, the stainless steel tube is used instead of the glass tube. And what is stuffed inside is silica gel or polymer gel. It is the most important part of the HPLC system because sample separation takes place in the column.

e) Column thermostat Since the separation in HPLC analysis may vary considerably depending on the temperature, the column is placed in the column thermostat depending on the object to be analyzed.
f) Detector Although the sample is separated in the column, the detector converts the separated result into a visible form. While the composition of the eluent that does not contain the sample is constant, the composition changes when the components in the sample are contained in the eluent, and this change is taken out as an electrical signal.
g) Recorder To make the detected result output as an electrical signal from the detector visible, from a conventional pen recorder to a data processor (also called an integrator) using a computer, It is simpler and more functional.

  The HPLC thus configured purifies the compound using the partition of the material between two different phases (solid phase and liquid phase) as described above. Fill a stainless steel column with a packing material (stationary phase) such as silica gel, and flow a reaction mixture (eluent) dissolved in a solvent into it. The affinity with the packing material and the molecular size differ depending on the compound. To separate the mixture.

The separation here depends on the degree of partitioning between both phases of each molecule (or ion) in the sample. And the smaller the particle size of the stationary phase that is the filler in the container, the higher the number of theoretical plates, but the greater the flow resistance.
The number of theoretical plates is an index that represents the performance of an apparatus that separates substances using the difference in the distribution ratio of substances between two phases, and is also used as an index that represents the performance of a column. If this value is high, it is said to be a high-performance column, that is, a column with good separation performance.

  In addition, liquid chromatography including HPLC is classified as adsorption chromatography, distribution chromatography, ion exchange chromatography, gel filtration chromatography, etc., based on the difference in the degree of partitioning between phases as described above. Then, it is not limited to the HPLC of a specific aspect.

Separation and purification method of the present invention atom endohedral salts are the well Ru used a solution prepared by adding an electrolyte containing PF6 anion as the mobile phase.

According to the method for separating and purifying an atomic inclusion fullerene salt of the present invention, since the HPLC method using a solution with an electrolyte added as a mobile phase is adopted, the atomic inclusion fullerene salt or the same ion is easily discharged from the column that is a stationary phase. Separation / purification becomes possible.
That is, as a result of the inventors' trials, an organic solvent solution obtained by adding a soluble electrolyte to a mobile phase and dissolving it in an organic solvent that is usually used as a mobile phase is used as a mobile phase in HPLC. By injecting a solution containing an endohedral fullerene salt from an injector that is a solution injection port for sampling and analysis, the endohedral fullerene salt or ions can be easily discharged from the stationary phase column, allowing separation and purification. I found out.

This is considered to be expressed for the following reasons. When a normal mobile phase to which no electrolyte is added is used, the atom-containing fullerene cations injected into the active adsorption sites on the surface of the stationary phase of the column filler are strongly adsorbed and are not easily discharged.
On the other hand, when the mobile phase to which the electrolyte of the present invention is added is used, the electrolyte ions are adsorbed on the active adsorption sites on the surface of the stationary phase of the filler before the atomic fullerene ions, and the atomic fullerene ions are adsorbed. It is considered that the endohedral fullerene ions are discharged from the stationary phase.
In addition, the mechanism by which the endohedral fullerene ions and other components (impurities) are separated is based on the difference between the interaction between the binder phase and the endohedral fullerene ions and the interaction between the binding phase and other components (impurities). It is based on the separation mechanism of a normal HPLC method.

  Hereinafter, terms will be described. The above items were reprinted as necessary.

(Fullerene, atomic inclusion fullerene)
Fullerene is a group of carbons represented by the general formula C _2n (2n ≧ 60), which consists of 12 five-membered rings and two or more six-membered rings, and is actually closed into a spherical shell with a size of C ₆₀ or more. A general term for molecules. Specific examples include, but are not limited to, C ₆₀ , C ₇₀ , C ₇₆ , C ₈₂ , C ₉₀ , C _{96 and the} like.
Fullerenes are three-dimensional closed spherical molecules consisting of five- and six-membered rings of carbon atoms.
Atomic endohedral fullerene is a generic name for molecules represented by the general formula M @ C _2n (2n ≧ 60) having a structure in which atoms (hereinafter referred to as M) are confined in the spherical shell of fullerene. Here, M is a single atom or a plurality of atoms or an atomic group containing them, and is not necessarily a single atom.

(Atomic inclusion fullerene salt)
In general, a salt is a compound in which a cation (cation) and an anion (anion) are ion-bonded. A familiar representative example is sodium chloride (chemical symbol NaCl, also referred to as Na ⁺ Cl ⁻ to emphasize that it is an ion-bonded compound or salt).
The atomic inclusion fullerene salt is a salt containing a cation (cation) or an anion (anion) of the atomic inclusion fullerene. The valence of the ion is 1 or 1 or more. Li @ C ₆₀ PF ₆ (emphatically Li @ C ₆₀ ⁺ PF ₆ that the salt ^- also referred to as a), Li @ the like C ₆₀ SbCl ₆ is a specific representative example, limited to is not.

(Substances for separation / purification)
In the present invention, the target substance is an atom-encapsulated fullerene salt. However, as long as it is a general salt, the present invention, that is, a separation / purification method using an HPLC method using an electrolyte-added mobile phase is applicable without limitation to the atom-encapsulated fullerene salt. It is.
(Electrolytes)
An electrolyte is a substance that ionizes into a cation (cation) and an anion (anion) when dissolved in a solvent. Generally, it is a substance such as an acid, a base or a salt.
The material used in the present application may be any substance (electrolyte) that is soluble in the solvent of the mobile phase and dissolves and ionizes into a cation and an anion. Typical examples of the electrolyte are combinations of cations and anions listed below. Although it is a thing, it is not particular.

(Type of electrolyte)
The electrolyte is not particularly limited as long as it is soluble in the mobile phase solvent. Hereinafter, examples of cations (cations) and anions (anions) constituting the electrolyte are specifically listed, but are not limited thereto.

Examples of cations (cations) include protons (H ⁺ ), alkali metal cations (Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , Cs ⁺ ), other metal cations (Ag ⁺ , Tl ⁺ ), ammonium cations (NH ₄ ⁺ ), organic ammonium cation (primary to quaternary) (CH ₃ NH ₃ ⁺ , (C ₂ H ₅ ) ₃ NH ⁺ , (C ₄ H ₉ ) ₄ N ⁺ = TBA (Tetrabutlyammonium) ⁺ ), Onium cations other than ammonium ((CH ₃ ) ₃ S ⁺ , (C ₄ H ₉ ) ₄ P ⁺ , (C ₆ H ₅ ) ₄ P ⁺ , (C ₆ H ₅ ) ₄ As ⁺ , (C ₆ H ₅ ) ₄ Sb ⁺ )

Examples of examples of the anion (negative ion), halogen anions ^{(Cl -, Br -, I} -), and other inorganic anions _{^{(SCN -, NO 3 -,}} ClO 4 -), boron-containing anions (B (C ₄ H ^{_{9) 4 -, B (C}} 6 H 5) 4 -), alkyl sulfonic acid (CH ₃ SO ₃ ^-), allyl sulfonic acid _{(p-CH 3 C 6 H} 4 SO 3 -), the fluorine-containing anion (BF _{4 ^{-, PF 6 -, AsF 6}} -, SbF 6 -, CF 3 SO 3 -, C 4 H 9 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 3 SO 2) 3 -), containing chloride anions _{^{(SbCl 6 -, PCl 6 -}} ), other organic anions ^{_{(CH 3 CO 2 -, CH}} 3 CO 3 -, C 2 H 5 CO 3 -, C 2 H 5 O -)

(Electrolyte concentration)
The concentration of the electrolyte added to the mobile phase solvent is desirably 1 mmol (1 mmol / l) or more with respect to 1 L (liter) of the solvent. When insufficient (low concentration), the endohedral fullerene salt is difficult to be discharged from the HPLC. Further, as an upper limit of the concentration, a saturation solubility (saturation concentration) by a combination of an electrolyte and a solvent is a standard.
(Mobile phase solvent)
The solvent of the mobile phase may be any solvent that can be dissolved without altering the target substance to be separated and purified and can be used as a mobile phase for HPLC. Preferably, a solvent having a relative dielectric constant of 10 or more is selected. This is because the target substance for separation / purification is an atomic inclusion fullerene salt, which is easily dissolved in a highly polar solvent, that is, a solvent having a large relative dielectric constant. Several examples of solvents having a relative dielectric constant of 10 or more are listed below (numerical values are relative dielectric constants), but are not limited thereto.
For example, N-methylacetamide C ₃ H ₇ NO 179.0, formamide CH ₃ NO
111.0, dimethyl sulfoxide C ₂ H ₆ OS 47.24, acetonitrile (abbreviated as AN) C ₂ H ₃ N 36.64, methanol
33.0, ethanol 25.3, acetone 21.01, o-dichlorobenzene C ₆ H ₄ Cl ₂ (abbreviated as ODCB) 10.12.
As the mobile phase solvent, a mixed solvent composed of two or more kinds of solvents may be used. Also in this case, a mixed solvent having a relative dielectric constant of substantially 10 or more is preferable.

It is an explanation flow of the separation and purification method of the endohedral fullerene of the present invention. It is a positive MS figure of Li @ C ₆₀ salt obtained in the example. It is a negative MS figure of Li @ C ₆₀ salt obtained in the example. It is a schematic explanatory drawing which shows the structure of the film-forming apparatus for producing | generating an endohedral fullerene composite. It is explanatory drawing of a fullerene cluster, (a) shows the endohedral fullerene and fullerene of an isolation state, (b) is a cluster which has empty fullerene in single layer form, (c) is a cluster which has empty fullerene in two layers form . It is a schematic diagram of a typical molecular structure of the Li @ C60 salt obtained in the present invention. (A) is an SbCl ₆ salt and (b) is a PF ₆ salt. It is a graph which shows the electrolyte addition effect in the HPLC chromatogram of Li @ C60 salt.

DETAILED DESCRIPTION separation and purification method of atomic endohedral salts of the present example, lithium as contained target atoms (hereinafter, referred to as "Li".), Described in example using C ₆₀ as the endohedral fullerenes.
As described above, C60 containing Li is described as Li @ C60.

Li @ C ₆₀ cation was synthesized, separated and purified according to the process shown in FIG.

S1: Synthesis (S11: (Cluster material) synthesis)
For the production of the endohedral fullerene containing Li, a production apparatus having a structure shown in FIG. 6 having a structure in which an electromagnetic coil is arranged around a cylindrical stainless steel container was used.
Li used as raw material used was unpurified Li for isotopes manufactured by Aldrich, and C ₆₀ used as raw material used was C ₆₀ manufactured by Frontier Carbon.
(I) The vacuum vessel 301 was evacuated to a vacuum degree of 4.2 × 10 ⁻⁴ Pa, and a magnetic field with a magnetic field strength of 0.044 T was generated by the electromagnetic coil 303.
(Ii) Encapsulated atom sublimation oven 304 was filled with solid Li and heated to a temperature of 400 to 600 ° C. to sublimate Li to generate Li gas.
(Iii) The generated Li gas was introduced through a gas introduction tube heated to 500 ° C. and sprayed onto the thermoionization plate 306 heated to 2500 ° C.
(Iv) Li vapor was ionized on the surface of the thermoionization plate 306, and a plasma flow composed of Li positive ions and electrons was generated.
(V) Further, C ₆₀ vapor heated and sublimated to 610 ° C. in a chimney type fullerene oven 308 was introduced into the generated plasma flow.
(Vi) A bias voltage of −30 V was applied to the cup-shaped deposition substrate 310 that was in contact with the plasma flow, and a thin film containing an endohedral fullerene was deposited on the surface of the deposition substrate 301.
The raw material supply ratio (Li ion / C ₆₀ ) was 0.5.
(Vii) Deposition was performed for about 2 hours, and a thin film having a thickness of 0.8 to 1.4 μm was deposited.

(S12: Compound recovery)
Next, the synthesized product was collected and collected by the following procedure.
(I) While replacing the inside of the glove bag provided at the stacking substrate loading / unloading port of the synthesis apparatus with an anaerobic atmosphere (argon gas), the deposition board mounting portion in the apparatus is returned to atmospheric pressure by the anaerobic gas (into the glove bag) In this case, a desiccator whose interior space was opened with a cock or the like was placed in advance, and the anaerobic atmosphere substitution including the inside of the desiccator was performed by introducing argon gas after evacuating the glove bag).
(Ii) The deposition substrate mounting portion in the apparatus was opened from the inside of the glove bag, the inside substrate was taken out, put in a desiccator, covered with a lid, shut off from outside air, and the substrate mounting / extraction port of the apparatus was closed.
(Iii) From the glove bag, the desiccator in which the deposition substrate was accommodated in a state of being shielded from the outside air in an anaerobic gas by argon was taken out.
(Iv) A desiccator containing a deposition substrate was placed in a collection glove box in an anaerobic atmosphere with argon gas, and the composite on the substrate was scraped off with a spatula and collected on an aluminum foil.
(V) Next, the collected material was ground in an agate mortar in a glove box.
(Vi) The collected material was weighed with an electronic balance in the glove box.
The recovered material (soot), which is the composition, is used as a starting material, and 5.66 g, 5.60 g, 5.62 g, and 5.63 g of 4 lots are prepared, and each of the following treatments (S2 to S3) )
Recovery under anaerobic conditions can suppress the influence of oxygen and moisture in the atmosphere on the composition, such as insolubilization in a solvent and reduction of cluster decomposition efficiency during the recovery operation.

S2: Oxidation Since S2 to S3 indicate treatment methods, the case where 5.66 g of recovered material is used will be described as a representative.

(S21: Cluster decomposition (oxidation))
In this step, a recovered material (soot), which is a composition containing Li @ C ₆₀ having a cluster structure and a plurality of empty fullerenes, is added to a solvent (mixed solvent of first and second solvents) together with an oxidizing reagent. In this process, Li @ C ₆₀ , empty fullerene, and other components are released and exist in the solution by a chemical reaction of deelectron oxidation.
(I) In a glove box made an anaerobic atmosphere with argon gas, 42.45 g of the recovered product and an aminium salt as an oxidizing reagent were charged into a 1 L eggplant-shaped flask.
Here, the input amount of the aminium salt is larger than the calculated expected amount of Li @ C60, and lithium atoms that are not circumscribed or encapsulated with the C60 fullerene contained in the composition (free lithium) ) Was also removed.
The glove box used was manufactured by Miwa Seisakusho with an internal volume of 6 m ³ , the water content was 2 ppm (corresponding to a dew point of −75 ° C.), and the oxygen content was 60 ppm.
Hereinafter, the aminium salt that is an oxidizing reagent is described as “aminium A” according to the following chemical formula.
That is, "aminium A" in this example, compound name: hexachloroantimonate tris (4-bromophenyl) aminium, rational _{formula: (4-BrC 6 H 4} ) is 3 NSbCl ₆ That Is.
As this aminium A, a reagent manufactured by Aldrich was used.

(Ii) In the glove box, 283 ml of o-dichlorobenzene (hereinafter referred to as ODCB) which is a non-polar solvent as a first solvent and a polar solvent as a second solvent in the eggplant-shaped flask containing the materials. 142 ml of acetonitrile (hereinafter also referred to as AN) was added.
Dehydrated o-dichlorobenzene (Aldrich) and dehydrated acetonitrile (Wako Pure Chemical Industries, Ltd.) were used as the solvents, respectively.
(Iii) The eggplant-shaped flask was placed in a tank of an ultrasonic cleaner, and ultrasonic energy was applied for 10 minutes to disperse or dissolve the recovered material and aminium A in a solvent.
As a result, the contents of the flask with a volume of 1 L became a dark black suspension with a slight bluish tint.
(Iv) The suspension eggplant-shaped flask was subjected to a decomposition reaction for 23.5 hours while stirring magnetically in a glove box at room temperature (particularly temperature control was not performed, but the internal temperature was 30 ° C.).

(S22: AN evaporation)
The purpose was to facilitate precipitation of Li @ C ₆₀ cations in the next step S31 by distilling off AN from the suspension after the oxidation reaction.
The eggplant-shaped flask containing the suspension was taken out from the glove box and connected to an evaporator. The eggplant-shaped flask was immersed in a high-temperature water tank maintained at 70 ° C., and the pressure was reduced to 75 hPa or less with a diaphragm pump to distill off AN.
The guideline for the completion of the AN distillation was the point at which foaming from the solution surface was no longer observed visually.

S3: Cleaning / extraction process

(S31: Reprecipitation filtration)
By adding hexane and toluene (third solvent), which are poor solvents of all dissolved components in the solution, to the solution containing ODCB as a main component after the AN distillation, all of the Li @ C ₆₀ cations are added. It is a process for precipitating a solute to obtain a solid content.
(I) In order to promote precipitation of hexane and toluene insoluble components in the above suspension solution exhibiting a blackish brown color, 611 ml of hexane and 306 ml of toluene were added to an eggplant type flask to lower the dissolved amount.
(Ii) The Erlenmeyer flask containing “solution, hexane, and toluene” was stoppered, held in your hand, and shaken well.
(Iii) In order to produce a sufficient precipitate, the Erlenmeyer flask containing the suspension was further allowed to stand in a cool dark place for 1 hour.
(Iv) The suspension after standing was filtered with a pressure filter.
A membrane filter (Omnipore membrane filter manufactured by Nippon Millipore, model number JGWP09025, specification pore diameter 0.2 μm, diameter 90 mmφ, thickness 65 μm) was used as the filtration filter.
As a result, a black excess residue as the first composition was obtained on the filter.

(S32: Salt removal (AN cleaning))
This is a step for dissolving and removing unreacted substances and reactants of an aminium salt as an oxidizing agent from a filtration residue (first composition) with a solvent (fourth solvent).
Here, AN, which is a good solvent for the unreacted aminium salt and the reactant, and a poor solvent for Li @ C ₆₀ cations and C ₆₀ fullerene, is used as the fourth solvent.
(I) A filtration residue and a filter were put into an eggplant-shaped flask having a capacity of 500 ml, and 300 ml of AN, which is a fourth solvent, was poured so that they were immersed.
(Ii) This Erlenmeyer flask was placed in an ultrasonic cleaner, and ultrasonic energy was applied for 3 minutes to obtain a suspension in which the filtration residue was dispersed in AN.

(Iii) The suspension was filtered through a pressure filter into a filtrate receiving Erlenmeyer flask. Filter solids remained as a residue on the filter ("Filtration 1" treatment).
As the filtration filter, a membrane filter (Omnipore membrane filter manufactured by Nippon Millipore, model number JGWP09025, specification pore diameter 0.2 μm, diameter 90 mmφ, thickness 65 μm) was used.
(Iv) 300 ml of AN was put into a 500 ml eggplant type flask which was used in the above-mentioned “filtration 1” treatment and the solid content was still slightly fixed, and the residue of filtration 1 was put together with the filter into the eggplant type flask. Dispersion with an ultrasonic cleaner was performed for 3 minutes.
(V) The suspension was filtered with a pressure filter into a filtrate receiving Erlenmeyer flask. Filtration solids remained as a residue on the filter ("filtration 2" treatment).

(Vi) 150 ml of AN was put into a 500 ml eggplant-shaped flask used in the above-mentioned “filtration 2” treatment and the solid content was still slightly fixed, and the residue of filtration 2 was put together with the filter into the eggplant-shaped flask. Dispersion with an ultrasonic cleaner was performed for 3 minutes.
(Vii) The suspension was filtered through a pressure filter into a filtrate receiving Erlenmeyer flask. Filter solids remained as a residue on the filter ("filtration 3" treatment). As described above, unreacted substances and reactants of the aminium salt in the solid content remaining in the eggplant-shaped flask having a volume of 500 ml were eluted.
(Viii) The residue solid content obtained by repeated filtration up to “Filtration 3” is the filtration residue solid content that is the second composition.
Note that the amount of AN used in the salt removal treatment was 300 ml for “Filtration 1”, 300 ml for “Filtration 2”, and 150 ml for “Filtration 3”, for a total of 750 ml.

(S33: Empty fullerene removal (toluene washing))
In this step, empty fullerene (C ₆₀ ) is dissolved and removed from the filtration residue solid content of the second composition using a fifth solvent (toluene). As the fifth solvent, a good solvent for empty fullerene and a solvent that does not substantially dissolve the endohedral fullerene cations are selected.
(I) A filtration residue solid of the second composition and a filter were placed in a 500 ml eggplant-shaped flask, and 300 ml of toluene as the fifth solvent was poured therein so that they were immersed. This Erlenmeyer flask was placed in an ultrasonic cleaner, and ultrasonic energy was applied for 3 minutes to obtain a suspension in which the second composition filtration residue solid was dispersed in toluene.
(Ii) The suspension was filtered through a pressure filter into a filtrate receiving Erlenmeyer flask. Filter solids remained as a residue on the filter ("Filtration 1" treatment).
Toluene was a special grade toluene (manufactured by Wako Pure Chemical Industries, Ltd.), and a membrane filter (Nihon Millipore Omnipore membrane filter, model number JGWP09025, specification pore diameter 0.2 μm, diameter 90 mmφ, thickness 65 μm) was used as a filtration filter.
(Iii) The solid content obtained by the “filtration 1” treatment is the solid content of the filtration residue as the third composition.

(S34: redissolving (Li @ C ₆₀ cation extraction))
In this step, the encapsulated fullerene cation is dissolved and extracted from the solid residue of the filtration residue, which is the third composition, using a sixth solvent (ODCB and AN). As the sixth solvent, a good solvent for the endohedral fullerene cation is selected.
(I) The third composition filtration residue solid and the filter were placed in a eggplant-shaped flask having a capacity of 500 ml, and ODCB 40 ml and AN 40 ml, which were sixth solvents, were poured therein so that they were immersed. This Erlenmeyer flask was placed in an ultrasonic cleaner, and ultrasonic energy was applied for 3 minutes to obtain a suspension in which the third composition filtration residue solids were dispersed in ODCB and AN.
(Ii) The suspension was filtered with a pressure filter into a filtrate receiving eggplant type flask having a volume of 200 ml. ODCB is a special grade ODCB (manufactured by Aldrich), AN is a special grade AN (manufactured by Wako Pure Chemical Industries, Ltd.) Filtration filter is a membrane filter (Nihon Millipore omnipore membrane filter, model number JGWP09025, specification pore size 0.2 μm, A diameter of 90 mmφ and a thickness of 65 μm) was used.

(S35: Solid precipitation)
In this step, the endohedral fullerene cation is precipitated as a solid content from the filtrate. The amount of cation dissolved is reduced by distilling off AN and cooling the filtrate.
(I) A liquid nitrogen cooling trap was attached to the rotary pump, and an eggplant-shaped flask was connected and distilled off under reduced pressure.
The guideline for the completion of the AN distillation was 30 minutes after foaming from the solution surface was no longer observed visually.
(Ii) The eggplant-shaped flask was stoppered, clamped, placed in a refrigerator set at 5 ° C. and allowed to stand for 68 hours. As the refrigerator, model KT-1744 manufactured by Nippon Freezer Co., Ltd. was used.
(Iii) After standing at low temperature, precipitation of a black powdery solid (referred to as OxAm-C) was confirmed in the filtrate of the eggplant type flask.

(S36: Solid recovery)
In this step, the precipitated black powdered solid OxAm-C is washed to remove unnecessary materials and collect the necessary solid.
(I) After standing at low temperature, the supernatant of the filtrate of the eggplant flask was poured into a filter holder of a suction filtration device and filtered (decantation filtration). A slight black powdery solid that flowed out with the supernatant remained on the filter.
(Ii) 2 ml of toluene was poured into an eggplant-shaped flask in which most of the black powdery solid was left on the inner wall and bottom, and the black powdery solid was washed.
(Iii) Subsequently, the supernatant of the eggplant-shaped flask was poured from above the black residue filtration solids on the filter of the filtration device after decantation filtration, and decantation filtered (“toluene decantation” treatment).

(Iv) 3 ml of AN was poured into an eggplant-shaped flask in which most of the black powdery solid remained on the inner wall and the bottom, and the black powdery solid was washed. Subsequently, the supernatant in the eggplant-shaped flask was poured from above the black residue filtration solids on the filter of the filtration device after “toluene decantation”, and decantation filtered (“AN decantation” treatment). This was repeated three times.
(V) Pour 500 μl of ODCB into an eggplant-shaped flask with most of the black powdery solid left on the inner wall and bottom, wash the black powdered solid, and aspirate the contents in the eggplant-shaped flask with a micropipette as much as possible. It poured from the upper part of black residue filtration solid content on the filter of the filtration apparatus after AN decantation, and was suction-filtered. ("ODCB Decantation")

(Vi) After pouring 1 ml of hexane into an eggplant-shaped flask with most of the black powdered solid left on the inner wall and bottom, the black powdered solid was washed, and the contents in the eggplant-shaped flask were sucked as much as possible with a micropipette. Was poured from above the black residue filtration solids on the filter of the filtration apparatus after ODCB decantation, and suction filtered. This was repeated three times. ("Hexane Decantation")
(Vii) The obtained black residue filtration solids were taken out together with a filter onto an aluminum foil, put in a vacuum desiccator and dried with a diaphragm pump.
(Viii) The black powdered solid after drying contains the inclusion endohedral fullerene cation Li @ C60 cations and will be referred to as OxAm-C. The weight of OxAm-C obtained here was 26.9 mg.

(S41: OxAm-C (crude product) solution)
In the following examples, prototype type 2 (OxAm199-202-H26) is used.
26.9 mg of OxAm-C obtained in the above S36 (viii) was placed in an Erlenmeyer flask containing 40.36 ml of the following mixed solvent, and dissolved by applying ultrasonic waves for 3 minutes with an ultrasonic cleaner UT205HS. .
AN (acetonitrile) 20.18 ml for HPLC chromatogram manufactured by Wako Pure Chemical Industries, Ltd.
ODCB (Orthodichlorobenzene) 20.18 ml Aldrich HPLCgrade
AN: ODCB = 1: 1 volume ratio of mixed solvent OxAm-C 1mg mixed solvent 1.5ml
A reddish purple solution was obtained, but a part of the residue (residual solid content) was observed.
The above solution was filtered using a 0.2 μm filter with a diaphragm pump suction filter to obtain 40.36 ml of filtrate. The target product Li @ C ₆₀ cation is dissolved in the filtrate. The solid content of the filtration residue remaining on the filter is an insoluble impurity.
Other 3 lots of OxAm-C 26.4 mg, 19.0 mg, and 16.5 mg were also dissolved by the above treatment method, and 4 lots of solutions were combined to obtain 130.5 ml of filtrate.

(S42: HPLC fractionation)
HPLC fractionation was performed.
The analyzer was an LC-Avp series manufactured by Shimadzu Corporation, and the column used was an NPE column manufactured by Nacalai Tesque-size 10φ × 250 mm.
As the mobile phase, a solution in which 50 mmol / L of electrolyte TBAPF ₆ was added to a mixed solvent of ODCB: AN = 1: 2 by volume as in the case of the above analysis was used.

The HPLC preparative conditions were as follows.
Mobile phase: ODCB / AN 1: 2 50 mmol / l electrolyte TBAPF ₆ added flow rate: 6.0 ml / min
Column: 5NPE column made by Nacalai Tesque-Size 10φ × 20mm + 10φ × 250mm
Oven temperature; 30 ° C
Detection UV wavelength: 380 nm
HPLC fractionation was performed under the above conditions to obtain 429 ml of a fraction from 130.5 ml of the filtrate of S41.

S5: (Preparation liquid) Concentration measurement of solidified preparative liquid The Li @ C60 + concentration in the preparative liquid is measured by HPLC analysis. It is possible to judge the quality of the preparative HPLC fractionation and predict the final amount of Li @ C60 salt.
AN distillation
In order to concentrate Li @ C60 salt by reducing the amount of solvent as part of Li @ C60 salt precipitation solidification, AN (acetonitrile), one component of the mixed solvent, is distilled off (short for distillation removal) To do.
The bp (boiling point) of AN is 82 ° C., which is lower than bp 180 ° C. of one component ODCB of the mixed solvent, and is easily distilled off.

<S5-01:> AN distillation
As part of Li @ C60 salt precipitation solidification, AN (acetonitrile), which is a component of the mixed solvent, was distilled off in order to concentrate the Li @ C60 salt by reducing the amount of solvent. 492 ml of the preparative liquid obtained in the above step S42 was put into a 1 L eggplant type flask and connected to an evaporator. The concentrated eggplant-shaped flask was immersed in a high-temperature water tank maintained at 35 ° C., and the pressure was reduced to 75 hPa or less with a diaphragm pump to distill off AN.
The guideline for the completion of the AN distillation was the point at which foaming from the solution surface was no longer observed visually.
Furthermore, in order to distill off AN at a lower pressure, a liquid nitrogen cooling trap was attached to the rotary pump, and an eggplant type flask was connected to distill off under reduced pressure.
The guideline for the completion of the AN distillation was 30 minutes after foaming from the solution surface was no longer observed visually.

(S51: Hexane reprecipitation)
In this step, hexane, which is a poor solvent, is added to the solution containing the Li @ C ₆₀ cation separated above to precipitate a Li @ C ₆₀ salt.
492 ml of hexane was added to 164 ml of the solution obtained by distilling off AN in the step S5-02. This mixed solution was allowed to stand in the cupboard (room temperature dark) at the bottom of the experimental table for 60 minutes to fully precipitate the solid content.
The amount of hexane to be added is 3 times the amount of liquid obtained for HPLC.

(S52: (OxAm-H) filtration and drying)
The Li @ C ₆₀ salt was purified by removing the coexisting impurities (mainly co-precipitated during the precipitation with the electrolyte added to the HPLC mobile phase) from the Li @ C ₆₀ salt precipitated in the above step S51 by solvent washing, and further In this step, the washing solvent is removed by drying to obtain the final product Li @ C ₆₀ salt having a high purity.
(S52-1: Filtration)
The solution containing the solid content obtained in the 51 step was filtered using a membrane filter having a pore diameter of 0.2 μm with a suction filter equipped with a diaphragm pump. The target product is contained in the filtration residue on the filter.
(S52-2: Cleaning)
In this step, impurities coexisting with the target substance (mainly the electrolyte added to the HPLC mobile phase and coprecipitated during the precipitation in step S51) are removed by washing with a solvent.
82 ml of AN (acetonitrile) was poured into the residue on the filter obtained in the step S52-1 and suction filtered to wash.
Subsequently, the solid residue after the AN cleaning was dissolved in 5 ml of AN placed in a centrifuge tube, and ultrasonic waves were applied for 1 to 2 minutes. Thereafter, it was applied with a centrifugal separator at 2000 rpm × 10 minutes. The supernatant was discarded by decantation.
Again, 5 ml of AN was added to the centrifuge tube where the residue remained, and the mixture was sonicated and centrifuged, and the supernatant was discarded.
Thereafter, 1 ml of AN is added to the centrifuge tube, and ultrasonic waves are applied for 1 minute to suspend the residue. The suspension is filtered using a membrane filter having a pore size of 0.2 μm and collected on the filter. The operation of adding 1 ml of AN, applying ultrasonic waves and filtering was repeated 3 times so that no residue remained in the centrifuge tube. The solid on this filter is the target.
(S52-3: Drying)
This is a step of drying the target substance collected on the filter and evaporating AN.
The solid on the filter obtained in step S52-2 was wrapped in an aluminum foil, placed in a glass desiccator at room temperature, and dried under reduced pressure for 15 hours with a diaphragm pump.
(S52-4: Recovery)
The solid on the filter after drying was removed from the filter using a spatula.

(S61: Weighing)
This is a step of measuring the acquisition weight of the final target Li @ C ₆₀ salt (solid). The yield is calculated from the measurement result.
The acquisition weight was 31.1 mg.
The final obtained weight was 0.14% with respect to the yield, that is, the weight of the recovered material (soot) as the starting material described in S12.
(S62: Characteristic measurement)
The following various measurements were performed on the final product obtained in S52.

(LDI-TOF-MS measurement posi / nega)
When a mass spectrum (LDI-TOF-MS, apparatus name: AXIMA-CFR plus, manufactured by Shimadzu Corporation, laser power 60) was measured, a strong peak at m / z = 727 was observed.
This peak is attributed to the Li @ C ₆₀ ion (hereinafter this peak is referred to as (A) peak). In both the positive mode and the negative mode, the peak (A) was a base peak (maximum intensity peak) in the molecular weight range of 700 to 800, and other impurity peaks were hardly observed. FIG. 2 shows the measurement result in the positive mode, and FIG. 3 shows the measurement result in the negative mode.

(Li content (Li determination) and carbon / hydrogen / nitrogen content (CHN determination))
Li analysis was performed by the ICP-OES method using a RIS-AP type apparatus of JARRELL-ASH, adjusting the analysis sample by a wet ashing method.
For C, H, and N analysis, a CHN analyzer MT-6 manufactured by YANACO was used.
The results of analytical measurement are shown below.

Li content (Li quantitative)
Li [wt.%]; 0.728
CHN content (CHN determination)
C [wt.%]; 81.913
H [wt.%]; 0.244
N [wt.%]; 0.244
The theoretical content of Li @ C ₆₀ PF ₆ is
Li [wt.%]; 0.80
C [wt.%]; 82.59
H [wt.%]; 0.0
N [wt.%]; 0.0
Although some amounts of residual solvent or residual electrolyte or H and N, which are considered to be derived from the residual electrolyte, are observed, the desired product having a purity of 90% or more was obtained.

In the following, instead of HPLC fractionation, a chromatogram obtained when a solution without addition of an electrolyte is treated as a mobile phase and the contents of examination of HPLC application conditions in the present application will be described.
Therefore, it should be noted that the following implementation conditions are different from the conditions described for “S4: HPLC” in FIG. 1 described above.

When HPLC is used to analyze the solution with no electrolyte added as the mobile phase, the peak of the target substance is not observed (that is, it is not separated), but as the electrolyte concentration increases, the peak appears and the peak itself is also separated into multiple peaks. Become so.
When the concentration is such that the peaks are separated, the target product can be concentrated and obtained by HPLC using the retention time as a guide (HPLC preparative).
The TOF-MS diagram for the collected target product has already been described with reference to FIG. 3. However, in the case of using a solution with no electrolyte added, since there is no peak, it cannot be separated and cannot be measured. That is, a TOF-MS diagram cannot be obtained.

Hereinafter, chromatograms (spectral intensity-retention time charts) at different electrolyte concentrations will be described with reference to FIGS.
Fig. 7 (a) Chromatogram concentration in mobile phase using solution without addition of electrolyte, Fig. 7 (b) is 20 mmol / l with 20 mmol electrolyte for 1 l mobile phase, Fig. 7 (c) is 50 mmol concentration. / l, FIG. 7 (d) is a chromatogram at 100 mmol / l.

Since Li @ C60 salt is ionic, an electrolyte must be added to the mobile phase to compensate for the Coulomb force. Tetrabutylammonium hexafluorophosphate (TBAPF6) was selected as a stable electrolyte that has sufficient solubility in organic solvents and is easily ionized.
The HPLC analysis conditions were as follows.
a) Column: NPE column φ4.6 mm x 250 mm
b) Mobile phase: Mixed solution (ODCB: AN = 1: 1),
Additive electrolyte (TBAPF ₆ )
Electrolyte concentration Add 0, 20, 50, 100 mmol to 1 liter of mixed solution c) Flow rate: 1.5 mL / min
d) Column temperature: 30 ° C
e) Detection wavelength: UV 380 nm

As shown in Figures YY (a) to (d), no peak is seen without addition, and as the electrolyte concentration is increased to 20 mmol / l, 50 mmol / l, 100 mmol / l, the original retention time is around 4 minutes. It can be seen that the peak of the target object that should be present appears remarkably.
In addition, although there was a difference in retention time between the concentrations of 50 mmol / l and 100 mmol / l, the peak intensity was almost the same. It was also found that the effect of the electrolyte was almost saturated at 50 mmol / l.

Considering the intensity scale difference on the vertical axis in each figure, it can be understood that as the concentration increases, the peak clearly sharpens and is separated. That is, it can be seen that the peak intensity of the other components is relatively small with respect to the target, which is a more suitable condition for separation of the target.
And it was found that the Li @ C60 cation introduced gave a peak by using a mobile phase to which an electrolyte was added.
Furthermore, as a result of examining separation conditions from C60 and other impurities, it was decided to use a solution in which TBAPF6 was added to a mixed solvent of ODCB: AN = 1: 2 to a concentration of 50 mmol / l as the mobile phase. .

According to the present invention, a high-purity atomic inclusion fullerene salt can be obtained easily and stably in a quantity to be obtained (milligram mg order or more).
・ Elucidation of physical properties of atomic inclusion fullerene salt or atomic inclusion fullerene.
・ With the elucidation of physical properties, the scope of application and application development will expand.
・ Molecular dispersion is possible, and molecular functions can be expressed.
-Derivative synthesis becomes easy, so various functions can be added.
Such effects can be expected.

  As specific industrial application fields that make use of the above effects, organic thin film solar cells and fiber solar cells are most promising. In addition, applications as electronic materials and high-temperature superconducting materials are extensive. Furthermore, blood pressure measuring devices and acoustic devices such as speakers are also promising fields in application as piezoelectric elements utilizing dielectric properties.

301 vacuum chamber,
302 vacuum pump,
303 electromagnetic coil,
304 oven,
305 nozzles,
306 heating substrate,
307 plasma flow,
310 deposition substrate,
308 oven,
309 nozzle,
310 deposition substrate,
311 compound,
312 Bias voltage applying device,
313 Heating filament

Claims (8)

A method for separating and purifying an endohedral fullerene salt using a solution containing an electrolyte containing a PF6 anion as a mobile phase . Claim 1 separation and purification method of atomic endohedral salt, wherein the electrolyte is a TBAPF6. 3. The method for separating and purifying an atom-containing fullerene salt according to claim 1, wherein the solvent of the solution is a highly polar organic solvent having a relative dielectric constant of 10 or more. 2 solvent solution of acetonitrile and o- dichlorobenzene: 1 claim 1-3 separation and purification method of atomic endohedral salts, wherein the mixture is a solvent (volume ratio). Claim 1-4 separation and purification method of atomic endohedral salt wherein the atomic endohedral salt is a metal containing fullerene salt. 6. The method for separating and purifying an atomic inclusion fullerene salt according to claim 5, wherein the atomic inclusion fullerene salt is an alkali metal inclusion fullerene salt. 6. separation and purification method of atomic endohedral salt wherein the alkali metal containing fullerene salt is an alkali metal containing C ₆₀ fullerene salt. The method for separating and purifying an atomic inclusion fullerene salt according to claim 7, wherein the alkali metal inclusion C ₆₀ fullerene salt is a lithium atom inclusion C ₆₀ fullerene salt.

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