JPWO2010023968A1 - Isolated endohedral fullerenes and salts - Google Patents

Abstract

Obtain isolated M @ C2n. An isolated endohedral fullerene represented by M @ C2n. M: In a laser desorption ionization time-of-flight mass spectrum (hereinafter referred to as “LDI (or LD) -TOF-MS”) in a single mode or a plurality of metal atoms or an atomic group containing them 2n = 60 or 70 positive mode. An endohedral fullerene represented by the following formula in which the peak intensity of other fullerene is 0.5% or less with respect to the peak intensity of the endohedral fullerene. M @ C2nM: single or plural metal atoms or atomic groups containing them 2n = 60 or 70

Description

  The present invention relates to isolated endohedral fullerenes and salts.

JP 2002-37615 A Japanese Patent No. 3926331 WO2007 / 123208 Publication Table 2005/066385 R. Tellgmann, E.E.B.Campbellet.al., Nature, 382 (1996) 407-408 "Fullerene Physics and Chemistry" Shinohara and Saito Nagoya University Press 1997 A. Gromov, E.E.B. Campbell etal., J. Phys. Chem. B, 107 [41] (2003) 11290 – 11301 A. Gromov, E.E.B. Campbell et.al., Chem. Comm., 20 (1997), 2003-2004

  Fullerene is a new molecular structure of carbon that takes a unique three-dimensional structure (cage structure) and has a highly symmetrical shape such as a soccer ball or rugby ball having a diameter of about 0.7 to 1.0 nm. 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.

  Encapsulated fullerenes with metal atoms encapsulated in the internal cavity of this fullerene are expected to develop new electronic properties as electrons move from the internal metal atoms to the carbon cage. Significant progress has been made.

  Conventionally, the group 3 elements (Sc, Y, La), lanthanide elements, and actinoid elements of the periodic table as inclusion metal atoms, and C2n (2n ≧ 82) as fullerene have been mainly studied. (See Non-Patent Document 2).

  In contrast, the inclusion of metal atoms in C60, which has a smaller cage space, has been studied. C60 having this soccer ball type structure is the most symmetric fullerene, and is a convenient material for analysis and physical property prediction after enclosing atoms.

In addition, since alkali metals belonging to Group 1 of the periodic table tend to be monovalent cations, the inclusion metal fullerenes in the alkali metal give electrons to the fullerene cage and have a negative charge, and the inclusion metal has a positive charge. It is expected to create physical properties.
That is, as a typical endohedral fullerene, lithium encapsulating C60, which is very reactive and encapsulates lithium whose oxidation number is always +1, has been attracting attention and synthesis / separation has been studied.

  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 high-purity 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 Patent Documents 1 to 3 and Non-Patent Documents 1 to 4 regarding methods for separating and purifying endohedral fullerenes or separated endohedral fullerenes. Each document will be described below.

(Patent Document 1)
Patent Document 1 describes a technique related to anion species and cation species formed by electrolytic reduction or oxidation of metal-encapsulated fullerenes.
This metal-encapsulated fullerene ion has the general formula M @ Cn (where M = Sc, Y, La, lanthanide element, actinoid element, n = 60, 70 and more) in which the electronic structure formed by electrolysis is a closed shell structure. Even number).
Thereby, the cation species and the anion species of the metal-encapsulated fullerene are stable fullerenes each having a closed shell structure, and handling is facilitated.

  In Patent Document 1, the unstable structure of the metal-encapsulated fullerene is based on an open shell structure because radicals (electron spins) are on the carbon gauge, so the unstable characteristics are improved by converting to a closed shell structure. I think I can do it. And, it is considered that the metal-encapsulated fullerene can be made into a closed shell structure by giving electrons to or depriving the metal-encapsulated fullerene (reducing or oxidizing the metal-encapsulated fullerene). In this case, the metal-encapsulated fullerene anion or cation is present in a state where it can be stably handled under atmospheric pressure and in the presence of light.

The electronic structure formed by the electrolytic method is a closed shell structure represented by the general formula M @ Cn (where M = Sc, Y, La, lanthanide element, actinoid element, n = 60, 70 and an even number greater than that). Metal-encapsulated fullerene ions are provided.
However, the endohedral fullerenes actually disclosed in the technology described in Patent Document 1 are only for n = 82 and are not disclosed for n = 60,70. Not only data for M @ C82 is shown, but isolated from other fullerenes (eg, C82) to be a single entity (a single M @ C82 without other fullerenes).

(Patent Document 2)
Patent Document 2 discloses a method for 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) One stable fullerene cation of the first or second fullerene group is formed in the solvent, 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, in the separation of the first fullerene group and the second fullerene group, separation of metal-encapsulated fullerene and empty fullerene is also exemplified.

In addition, 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 (Claim 28)) in a first solvent, whereby M @ C2n M @ C2n has been purified using a technique that forms a first solution containing a number of cations.
In Patent Document 2, 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 2 presents three methods. Each method will be described below.

[Method 1 (Patent Document 2, page 25 (Table 3))]
(1) Synthesize empty fullerene and encapsulated fullerene containing soot by carbon arc method.
(2) Sublimate the soot 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 to separate a solid containing C60 and C70 which are soluble filtrates and insoluble [M @ C82 +] [SbF6-] and neutral C2n.
(6) Thereafter, M @ C82 final product is obtained after various steps.
However, in this method 1, M @ 60 and M @ 70 are removed by ODCB extraction / filtration in the first place, and are not subject to isolation / purification.

[Method 2 (Patent Document, page 30 (Table 4))]
(1) Synthesize empty fullerene and encapsulated fullerene containing soot by carbon arc method.
(2) Sublimate the soot 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 mixed with [Ag +] [SbF6-] 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) Precipitating soluble filtrate in hexane and filtering, solid containing C60 and C70 which are soluble filtrate, insoluble [Mm @ C2n +] [SbF6-] and neutral C2n with reduced polarity Isolate.
(5) Thereafter, Mm @ C2n final product is obtained after various steps.

However, 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 as well (see Patent Document 2 FIG. 6). After all, in method 2, even if 2n> 60 in M @ C2n, it is not isolated. Even if 2n = 60, it is not isolated.

[Method 3 (Patent Document 2, page 33, Table 5)
In Patent Document 2, with respect to method 3, “M @ C2n including some lanthanoid metals (M = Sm, Eu, Tm, Yb and possibly Er)” is “oxidation resistant and insoluble M Including deviations from the properties of @ C60 class .... can be oxidized using an oxidizing agent with moderate oxidizing power, resulting in a new soluble cation M @ C60 +. (Patent Document 2, page 32, line 11 to line 18).

However, when the mass spectrum MS ([FIG. 13]) of the material that is supposed to be separated / isolated actually shown in Patent Document 2 is observed, both empty fullerenes and / or plural kinds of fullerene inclusions are mixed. It is difficult to say that it is isolated (separated separately).
In particular, the technique described in Patent Document 2 shows that cation formation by oxidation is difficult for M @ C60, except when M is Tm. That is, according to Table 4 “ODCB [Ag +] [SbF6-] extraction and subsequent filtration” of Patent Document 2, M @ C60 is not oxidized but removed as an insoluble matter. It is thought that it implicitly suggests that it is not applicable to M @ C60 and C60 that are not easily oxidized.
As described above, in Patent Document 2, there is no description suggesting a route for isolation / purification after oxidation treatment of M @ C60 or M @ C70.

  Further, Patent Document 2 is a purification method that utilizes a clear difference in chemical characteristics between empty fullerenes and encapsulated fullerenes, and different fullerenes form a bonded state (cluster state). It is not a bond decomposition technique.

(Non-patent document 1, Non-patent document 3, Non-patent document 4)
Non-patent documents 1, 3 and 4 are reports by researchers of the same Campbell group. Non-Patent Document 1 reports the generation of lithium inclusion C60 by ion implantation, and Non-Patent Documents 3 and 4 relate to solvent extraction of lithium inclusion C60 (hereinafter referred to as “Li @ C60”). Are listed.

  In Non-Patent Document 4, lithium is ion-implanted at a low energy of about 30 eV with respect to an empty C60 deposited film formed in advance on a substrate to generate Li @ C60 in the film, and then ion-implanted fullerene deposited film Is dissolved in carbon disulfide (CS2), and Li @ C60 and C60 are separated using high performance liquid chromatography (hereinafter referred to as “HPLC”). And mass spectrometry by LDI-TOF-MS (laser desorption ionization time-of-flight mass spectrum) is performed, and the ratio of Li @ C60 contained in the solution is evaluated.

  However, in the above report, in addition to the Li @ C60 peak having a mass number of 727 indicating the production of Li @ C60 in LDI-TOF-MS, a peak of empty fullerene C60 having a mass number of 720 is also seen. Looking at the peak intensity ratio, C60 / Li @ C60 is about 1/4 and still accompanied by C60, and it is difficult to say that it is isolated (separated separately).

(Non-Patent Document 2)
Non-Patent Document 2 describes that separation of La @ C82 was successful in FIG. 8.9 (c), stating that separation of metal-encapsulated fullerene is extremely difficult.
In this technique, metal-encapsulated fullerenes are 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. (Non-Patent Document 2, page 206).

  Regarding M @ C60, Ca @ C60 and Ca @ C70 are reported to be extracted by pyridine at room temperature under oxygen removal (Non-Patent Document 2, page 221). And even if it is not under oxygen removal, "Ca @ C60 is extracted comparatively efficiently by ultrasonic extraction around 5 ° C. (Non-Patent Document 2, page 232, 101)).

  However, in the laser desorption mass spectrum diagram of the extract (Non-patent Document 2, FIG. 8.17), Ca @ C60 and Ca @ C70 are not completely isolated, but Ca @ C60, Ca @ C70. , C60, C70, and C74 are mixed. That is, Ca @ C60 or Ca @ C70 is accompanied by other endohedral fullerene or empty fullerene and cannot be an isolated metal fullerene.

(Patent Document 3, Patent Document 4)
On the other hand, in Patent Document 3, the present inventors have reported on a method for producing a fullerene-based material, in which atoms are encapsulated in fullerenes by a unique plasma irradiation method, and molecular clusters containing the encapsulated fullerene clusters are separated and purified. ing.

  The method for producing a fullerene base material of Patent Document 3 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 synthesis of an inclusion fullerene, and the inclusion fullerene as a solvent. The molecular cluster containing the endohedral fullerene is separated and purified by performing the second treatment to be extracted and the third treatment to remove 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, the endohedral fullerene that has been separated and purified by solvent extraction alone is purified to a high purity, and the yield of the endohedral fullerene that can be purified and recovered from the synthesized product is improved.

Hereinafter, a method for producing a compound of endohedral fullerene by a plasma irradiation method adopted by the inventors and the obtained 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 in FIG. 6, an air supply pipe provided with an opening / closing valve such as nitrogen gas for returning the vacuum chamber 301 to the atmospheric pressure is provided.

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 oven 304 and the oven 308 are also energized to a heater (not shown) and heated to such an extent that lithium and C60 are not vaporized. 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 molecules 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 associated with vaporization, and the lithium itself releases electrons to become positive ions and become nearby ions. Along with electrons, macroscopically neutral plasma is formed (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 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 on 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 of the film thus formed on the deposition substrate 310 by laser desorption ionization time-of-flight mass spectrum (LDI-TOF-MS), 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”).

  Next, this endohedral fullerene unpurified product will be described with reference to FIG. FIG. 8 is a process flow of separation and purification by solvent extraction in the prior art.

  Separation and purification by the process flow shown in FIG. 8 first prepares an unpurified endohedral fullerene (step 201), and then obtains a product obtained by removing unreacted encapsulated atoms from the unpurified endohedral fullerene (step 202). . Then, the product obtained in Step 202 is washed with a solvent, and components dissolved in the solvent are removed to obtain a product containing endohedral fullerenes concentrated in an insoluble residue (Step 203).

  Then, the product obtained in step 203 is dissolved in the solution, and the endohedral fullerene is extracted in the solvent (step 204). The endohedral fullerene extraction solution obtained in step 204 is dropped into a solvent (poor solvent) in which the endohedral fullerene is difficult to dissolve by reprecipitation to precipitate and concentrate the endohedral fullerene, and the endohedral fullerene precipitated in the solvent is finally added. Filter out (concentration step 205).

  A synthetic film formed on the deposition substrate 310 so that lithium is included in the C60 fullerene will be described. In step 201, the film produced on the deposition substrate 310 is peeled off or scraped off to recover the cocoon-like inclusion fullerene unpurified material.

In step 202, this unencapsulated fullerene product is prepared by using an aqueous solvent (pure water, purified water, etc.) or an acidic solution such as dilute hydrochloric acid as a treatment liquid. Stir well while applying vibration energy. And insoluble matter is taken out by filtration using a centrifugal separation and a membrane filter in combination, or only one of them, recovered as a residue, dried and powdered.
At this time, the atoms to be encapsulated chemically react with the aqueous solvent to become a water-soluble substance such as hydroxide. On the other hand, since endohedral fullerenes are difficult to dissolve in water, the endohedral fullerenes and unreacted encapsulated atoms are separated by removing the residue.

In Step 203, the powdery residue obtained in Step 202 is mixed with a toluene solution and sufficiently stirred while applying vibration energy by ultrasonic waves. And insoluble matter is taken out by filtration using a centrifugal separation and a membrane filter in combination, or only one of them, recovered as a residue, dried and powdered.
At this time, empty fullerene is dissolved in the toluene solution, and the endohedral fullerene insoluble in toluene is concentrated in the residue.

In step 204, the powdery residue obtained in step 203 is mixed with the chloronaphthalene solution and sufficiently stirred while applying vibrational energy by ultrasonic waves. And it filters with a membrane filter and collect | recovers both a solution and a residue. Since the residue contains a large amount of endohedral fullerene, it is recovered and re-separated and purified without discarding.
In the concentration step 205, the solution obtained in step 204 is dropped into a toluene solution and kept stationary for a certain period of time, and then filtered through a membrane filter to collect the precipitate and the solution (reprecipitation method).

  Here, a toluene solution is described as an example as a solvent (poor solvent) that is a good solvent for the empty fullerene and is difficult to dissolve the endohedral fullerene. The solution also contains a large amount of endohedral fullerene, so it is recovered and re-separated and purified without discarding.

  As a result, the endohedral fullerene is concentrated in the precipitate obtained in the concentration step 205 (hereinafter, this precipitate is referred to as “fullerene base material”).

The result of evaluating a fullerene base material enriched in C60 containing lithium atoms as the endohedral fullerene will be described.
The inclusion rate of Li @ C60 with respect to the sample (hereinafter simply referred to as Li inclusion rate) is defined as Li inclusion rate = [weight of Li @ C60] / [initial weight of sample]. Here, the sample is a powder obtained by treating the unencapsulated endohedral fullerene obtained in step 202 with an aqueous solvent or acidic solution as a residue from which unreacted lithium atoms have been removed and drying it. It is.

In the endohedral fullerene production process, one Li @ C60 (mass 727) corresponds to one lithium atom (mass 7), and 1 mol of lithium corresponds to 1 mol of Li @ C60. @ C60 weight] / [lithium weight] = 727/7, and the Li @ C60 weight is converted to about 104 times the lithium weight.
Therefore,
Li inclusion rate = ((727/7) × [lithium weight] / [initial weight of sample]) × 100 (%)

  FIG. 4 of Patent Document 3 shows the dependency of the inclusion rate on the raw material supply ratio. Regarding the “inclusion rate during synthesis” in step 201 and the “inclusion rate after extraction” for the precipitate obtained in the concentration step 20. The Li inclusion rate of the lithium is determined with respect to the supply ratio (Li / C60) in terms of weight of lithium (Li) and C60 fullerene.

  Here, the supply amount of lithium ions is calculated from the ion current flowing through the deposition substrate 310, and the supply amount of fullerene is calculated from the decrease amount of fullerene filled in the fullerene oven 308.

Although the inclusion rate at the time of synthesis varies, there is a tendency to saturate when the supply ratio becomes large and rises to the right. The inclusion rate after extraction has a maximum value at a supply ratio of 0.4 to 0.5. That is, even if the supply ratio is set to 0.6 or more, for example, the inclusion rate after extraction is not improved, and the proportion of inclusion fullerenes that cannot be extracted increases. Moreover, the maximum value was at the inclusion rate of 7 to 8%, and the inclusion rate was almost the same even if the extraction method was changed.
That is, the content of endohedral fullerene by solvent extraction is 7 to 8% at most of the weight of the sample.

  In this regard, the inventors repeatedly tried purification of Li @ C60 by HPLC several times, but nevertheless, the amount of endohedral fullerene purified could not be 7-8% or more of the weight of the sample. . In other words, it was found that there is a limit to removing empty fullerene.

The upper right insets in FIGS. 2 and 3 are LDI-TOF-MS of the precipitate obtained in the concentration step 205 (abbreviated as “fullerene base material” or TCE). FIG. 2 shows a positive mode, and FIG. 3 shows a negative mode.
In addition to the Li @ C60 peak with a mass number of 727, a C60 peak with a mass number of 720 has also been observed (especially, 727 is not detected in the inset in the negative mode FIG. 4) and is still far from isolation. I understand.

FIG. 8 of Patent Document 3 shows a product obtained by measuring the particle size distribution of the product in the solution by the dynamic light scattering method, and FIG. 8A of the same document shows C60 existing in the solution. FIG. 8B shows the particle size distribution of the product in the chloronaphthalene solution in the step corresponding to step 206 described above.
In Patent Document 3, from the particle size distribution in the solution of C60 in FIG. 8 (a), the diameter size of C60 has a peak at 0.7 nm, and from the particle size distribution in the chloronaphthalene solution in FIG. 8 (b). It states that the particle size in this solution has a peak at 4-6 nm.

From the above discussion, it is considered that the endohedral fullerene extracted by the solvent does not exist as a single molecule but has a cluster structure in which a plurality of empty fullerenes are gathered and bound around the endohedral fullerene.
This is because the redox potential of the alkali metal itself such as lithium is extremely small, emits electrons and strongly reduces the surroundings, and has a strong tendency to oxidize itself, and in the encapsulated state, the electrons are transferred to the cage side of the alkali metal-encapsulated fullerene. Therefore, the cage itself was considered to be negatively charged (Patent Document 3).

That is, in the initial prediction, as shown in the left side view of FIG. 9A, it was in the form of Li @ C60 fullerene 11 in which one lithium atom was encapsulated in a single C60 fullerene 12, but actually, FIG. As shown in (b) and (c), it was considered that one Li @ C60 fullerene 11 forms a fullerene cluster 13 or 14 surrounded by a plurality of C60 fullerenes 12 (Patent Document 3).
Whatever the cause, M @ C60 described in Patent Document 3 is not a single M @ C60 but has a cluster structure.

After all, M @ C60 or M @ C70 disclosed in the above-mentioned conventional patent document or non-patent document always involves another fullerene (empty fullerene or metal-encapsulated fullerene of another kind of fullerene). M is a metal.
That is, at present, there is no M @ C60 or M @ C70 without other fullerenes. Also, there is no isolated M @ C60 or M @ C70. M @ C60 or M @ C70 coexists in a bound state with C60 or C70, and obtaining M @ C60 or M @ C70 desorbed from this bound state (ie, isolated) Despite being eagerly desired, it has not been realized. In addition, an endohedral fullerene that has been purified to a high purity and does not contain other fullerenes other than M @ C60 or M @ C70 has not been realized even though there is a strong demand.

The present invention solves the above-described conventional problems.
The present invention aims to provide isolated M @ C60 or M @ C70.

The invention according to claim 1 is an isolated endohedral fullerene represented by M @ C2n.
M: single or plural metal atoms or atomic group containing them 2n = 60 or 70
The invention according to claim 2 is the peak intensity of another fullerene with respect to the peak intensity of the endohedral fullerene in the laser desorption ionization time-of-flight mass spectrum (hereinafter referred to as “LDI (or LD) -TOF-MS”) in the positive mode. Is an endohedral fullerene represented by the following formula wherein 0.5% or less.
M @ C2n
M: single or plural metal atoms or atomic group containing them 2n = 60 or 70

The invention according to claim 3 is an endohedral fullerene represented by the following formula in which the peak intensity of another fullerene is 50% or less with respect to the peak intensity of the endohedral fullerene in LDI-TOF-MS in a negative mode.
M @ C2n
M: single or plural metal atoms or atomic group containing them 2n = 60 or 70
The invention according to claim 4 is the endohedral fullerene according to claim 3, wherein the peak intensity is 20% or less.
The invention according to claim 5 is the endohedral fullerene according to any one of claims 1 to 4, wherein M is a metal of group 1 to group 4.
The invention according to claim 6 is the endohedral fullerene according to any one of claims 1 to 5, wherein M is an alkali metal.

The invention according to claim 7 is the endohedral fullerene according to claim 6, wherein M is any one of Li, Na, and K.
The invention according to claim 8 is the endohedral fullerene according to claim 7, wherein M is Li.
The invention according to claim 9 is a salt having [M @ C2n] as a cation. The cation has a valence of 1 or more.

M: single or plural metal atoms or atomic group containing them 2n = 60 or 70

The invention according to claim 10 is the salt according to claim 9, which is [M @ C2n] m + · m [SbCl6]-.
m is the valence of the cation.
The salt according to the present claim has an application as an intermediate of the isolated endohedral fullerene. Not only does it have its own use as a research object.
In order to obtain the endohedral fullerene as a neutral substance from the salt, the cation may be reduced by a conventionally known method.
The invention according to claim 11 is the salt according to claim 9 or 10 which is a crystal.
The invention according to claim 12 is the salt according to claim 11 which is a single crystal.

The invention according to claim 13 is the invention according to any one of claims 9 to 12, wherein M is a metal of group 1 to group 4.
The invention according to claim 14 is the salt according to any one of claims 9 to 13, wherein M is an alkali metal.
The invention according to claim 15 is the salt according to claim 14, wherein M is any one of Li, Na, and K.
The invention according to claim 16 is the salt according to claim 15, wherein M is Li.
The invention according to claim 17 is an endohedral fullerene comprising MA @ C60 and MA @ C70, which is larger of MA @ C60 and MA @ C70 in LDI (or LD) -TOF-MS in positive mode There is an endohedral fullerene in which the peak intensity of fullerenes other than MA @ C60 and MA @ C70 with respect to the other peak intensity is 0.5% or less.
MA: Single or plural alkali metal atoms or atomic groups containing them

The invention according to claim 18 is an endohedral fullerene comprising MA @ C60 and MA @ C70, which is larger of MA @ C60 and MA @ C70 in LDI (or LD) -TOF-MS in negative mode It is an endohedral fullerene in which the peak intensity of fullerenes other than MA @ C60 and MA @ C70 is 50% or less with respect to the peak intensity.
MA: Single or plural alkali metal atoms or an atomic group containing them The invention according to claim 19 is the one other than MA @ C60 and MA @ C70 with respect to the larger peak intensity of MA @ C60 and MA @ C70. The endohedral fullerene according to claim 18, wherein the fullerene has a peak intensity of 20% or less.
The invention according to claim 20 is the endohedral fullerene according to any one of claims 17 to 19, wherein the MA is Li.

The invention according to claim 21 is a salt having [MA @ C60] and [MA @ C70] as cations. The cation has a valence of 1 or more.
The invention according to claim 22 is the salt according to claim 21, which is [MA @ C60] k + [MA @ C70] l +. (K + l) [SbCl6]-.
k and l are cation valences.

It is an explanation flow of a method for separating and purifying endohedral fullerenes. It is a positive MS figure of the crystalline salt obtained in the Example. The TCE in the inset refers to a Li @ C60-containing extract material described in Patent Document 3 filed by the present inventors. It is a negative MS figure of the crystalline salt obtained in the Example. The TCE in the inset refers to a Li @ C60-containing extract material described in Patent Document 3 filed by the present inventors. It is a NMR figure by 7Li nuclide of the crystalline salt obtained in the Example. It is a NMR figure by 13C nuclide of the crystalline 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 a mass spectrometry result by the laser desorption type time-of-flight mass spectrometer (LD TOF-MS) of the film | membrane in a prior art example. It is a process flow of separation and purification by solvent extraction in a conventional example. 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 .

Explanation of symbols

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

The endohedral fullerene of the present invention is an endohedral fullerene represented by the following formula in which the peak intensity of empty fullerene is 0.5% or less with respect to the peak intensity of endohedral fullerene in a positive mode mass spectrum (LDI-TOF-MS). .
M @ C2n
M: single or plural metal atoms or atomic group containing them 2n = 60 or 70

In order to produce the isolated endohedral fullerene of the present invention, the following steps are generally performed:
(A) a step of introducing a material having a cluster structure (hereinafter referred to as “cluster material”) consisting of an endohedral fullerene and a plurality of empty fullerenes surrounding the inner fullerene into a solvent;
(B) decomposing the cluster structure and forming an endohedral fullerene cation;
(C) a step of depositing a salt of an endohedral fullerene cation,
(D) A step of separating the solvent and the salt of the encapsulated fullerene cation that has precipitated.

The present inventor conducted experiments on various conditions for various combinations of chemicals to be used, atmosphere, temperature, etc. in the above-described various processes. As a result, the cluster can be decomposed only under certain specific conditions. I found.
The inventor conducted various tests to obtain isolated M @ C2n (2n = 60 or 70).
One of them is to obtain M @ C2n isolated using the cluster structure substance described in Patent Document 3 (hereinafter referred to as “cluster material” unless otherwise specified) as a starting material. Tried.
Further, referring to the technique described in Patent Document 2, it was thought that M @ C2n could be isolated by using a cluster material as a starting material and oxidizing or protonating the starting material.
Specifically, it was thought that M @ C2n could be isolated by reacting the cluster material with an oxidizing agent in a solvent.

However, it was confirmed that M @ C2n cannot be isolated by reacting the cluster material with an oxidizing agent in a solvent.
Then, after earnestly searching why it could not be isolated, I thought that it might be based on the following reason.
1. The cluster material has a structure in which a plurality of empty fullerenes C60 (or C70) surround the metal-encapsulated fullerene M @ C60 (or M @ C70). In this case, the endohedral fullerene and the empty fullerene are bonded not by simple van der Waals force but by charge transfer interaction.

  2. Furthermore, unlike the case of higher-order fullerene, in the case of C60 or C70, the C60 fullerene shell having an anionic property tends to form a C—C covalent bond (Non-patent Document 2). Then, the smaller the number of carbon atoms constituting the fullerene shell, the larger the curvature on the carbon atom, and the original structure that should take a plane as the sp2 orbital is distorted. As a result, the hybrid orbit of carbon atoms has sp3 properties and includes an orbit protruding outward. This outwardly extending track facilitates the formation of CC covalent bonds.

3. The fullerene shell of M @ C60 (or M @ C70) is anionic due to electron transfer from the metal atom, and CC sharing is the same as in the case of C60 (or C70) having the anionic property described above. Form a bond. This action forms a CC covalent bond between M @ C60 (or M @ C70) and C60 (or C70) in the cluster material.
That is, unlike the case of higher-order fullerene, in the case of C60 (or C70), it is considered that a CC covalent bond is formed. The present inventor speculated that this CC covalent bond may be the reason why M @ C60 (or M @ C70) cannot be separated only by adding an oxidizing agent in a solvent.

Based on such assumptions, we eagerly investigated how M @ C60 (or M @ C70) can be isolated from the cluster material.
First, various oxidants were tested, but none of them were isolated. Therefore, it came to be considered that the viewpoint of breaking the C—C bond was necessary instead of the viewpoint of oxidation.

In other words, in order to isolate M @ C60 from a cluster material having a C—C covalent bond, it is necessary to first break the C—C covalent bond and thereby decompose the cluster structure. It was.
In order to cleave the C—C covalent bond, an oxidizing agent having a strong oxidizing power was tried, but it was confirmed that the cluster structure is not necessarily decomposed just because the oxidizing power is strong.

Therefore, an enormous number of experiments were conducted for various elements.
When trying to separate M @ C2n and C2m while performing a huge number of experiments, 2n and 2m are smaller, and the smaller the difference, the more difficult the separation is. In the case of 2n = 2m = 60 It has been experimentally estimated that separation is even more difficult.
This is considered to be for forming a cluster.

In order to isolate M @ C60 from the cluster material, a process of decomposing the cluster structure is required.
As a result of searching for various solvents, oxidizing agents, and other factors, the present inventor has discovered that even if a cluster is oxidized under conditions that satisfy the examples described later, it can be decomposed. However, what is the dominant factor in the degradation of clusters is not fully understood at present.

(Cluster material)
As the cluster material, the material described in Patent Document 3 is preferably used. Details of the synthesis of the cluster material described in Patent Document 3 are as described in Patent Document 4.
When C60 (or C70) exists around M @ C60 (or M @ C70), a cluster structure is formed. Therefore, even a material synthesized by a method such as a laser vapor deposition method, an arc discharge method, an ion implantation method (methods described in Non-Patent Documents 1 and 3), a plasma irradiation method (Patent Document 4) is included in the cluster material.

In addition, the formation of the cluster structure may occur during the synthesis, but the cluster structure may be formed in the purification step even when the cluster structure is not formed during the synthesis. Any of these is a subject of the present invention.
In addition, when introducing into a solvent, it is preferable to remove substances other than the cluster material.

(Decomposition of cluster structure)
In the present invention, decomposition of the cluster structure is essential.
In the decomposition, for example, a decomposition reagent is introduced into a solvent. As the decomposition reagent, for example, an oxidizing agent or a protonating agent is used. As the oxidizing agent, an aminium salt is preferably used.
It was also found that the solvent plays an important role in the decomposition of the cluster structure.

  In particular, it is preferable that the solvent is a mixed solvent of the first solvent, which is a good solvent for the endohedral fullerene, and the second solvent, which is a good solvent for the decomposition reagent, in order to reliably decompose the cluster structure. It is. Although the reason is not clear, it is difficult to oxidize, and it is presumed that when the endohedral fullerene surrounded by the empty fullerene is oxidized, the degradation reagent reaches the inside when it is oxidized.

From the above-mentioned meaning, it is preferable to use a nonpolar solvent as the first solvent, and more specifically, o-dichlorobenzene (hereinafter referred to as “ODCB”) is preferable. On the other hand, the second solvent is preferably a polar solvent that is compatible with the first solvent and dissolves the decomposition reagent. Specifically, acetonitrile (hereinafter also referred to as “AN”) is preferable.
Moreover, as a ratio of a 1st solvent and a 2nd solvent, 1: 1-3: 1 (volume ratio) is preferable. By setting this range, the cluster structure is more reliably decomposed.
The decomposition step may be performed at room temperature (−15 ° C. to 40 ° C.) or under heating, but it is preferably performed under heating from the viewpoint of improving the yield of M @ C60.
90 to 180 degreeC is more preferable. In the case of 90 ° C. or higher, the cluster structure can be decomposed with very good reproducibility. In addition, since 180 degreeC is the boiling point of ODCB which is a good solvent of C60, when using ODCB, less than 180 degreeC is preferable.
As a typical example, in the case of a mixed solvent of acetonitrile, which is a good solvent for an aminium salt, and ODCB, which is a good solvent for C60, the cluster structure can be decomposed more reproducibly at 95 ° C. to 105 ° C.

The time in the decomposition step (heating time when heated) is preferably 1 hour or longer. Decomposition can be more reliably performed by performing for 1 hour or more. In addition, the yield of M @ C60 is improved. The upper limit is preferably 7 days or less. Further, 5 hours to 48 hours is more preferable.
By using an oxidizing agent (one-electron oxidizing agent) as a decomposing reagent, an endohedral fullerene cation can be formed along with decomposition.

(Purification)
Purification of the cation salt of M @ C60 may be performed using, for example, the method described in Patent Document 2.
Moreover, you may perform in the following procedure.
The refining process may separate the necessary components and the impurity components in the solution using the solubility difference.
It is preferable that the separation treatment with the impurities using the difference in solubility uses a difference in solubility of each component in the solvent with respect to two or more kinds of the solvents.
Further, the solvent used in the separation treatment may be one that does not substantially dissolve the endohedral fullerene.

The purification process
A process of dispersing the solution after the decomposition step in a third solvent to separate and recover the first composition as a precipitate;
A first washing treatment in which the first composition is dispersed in a fourth solvent and the remaining decomposition reagent and salts derived from the decomposition reagent are removed and separated and recovered as a second composition; ,
A second cleaning treatment obtained by dispersing the second composition in a fifth solvent and separating a third composition mainly composed of metal-encapsulated fullerene and a counter ion by the decomposition reagent, Have
It is preferable to obtain a cation or a cation salt of the endohedral fullerene.
The third solvent is preferably a solvent that does not substantially dissolve the endohedral fullerenes, empty fullerenes, and salts.
The third solvent is preferably hexane.
The fourth solvent is preferably a solvent that dissolves the residual decomposition reagent and salts derived from the decomposition reagent, and does not substantially dissolve the endohedral fullerene.
It is preferable that the fourth solvent is acetonitrile.
The fifth solvent is preferably a solvent that dissolves empty fullerene and does not substantially dissolve the endohedral fullerene.
It is preferable that the fifth solvent is toluene.

During the purification step, the endohedral fullerene is dissolved in the sixth solvent, the insoluble matter is filtered and then cooled to obtain the endohedral fullerene as an ionic crystal of the endohedral fullerene cation and the counterion anion. It is preferable to include a process.
The sixth solvent is preferably o-dichlorobenzene.
The cooling is preferably performed at a temperature of 0 to 10 ° C. for 20 hours or more.
It is preferable that the separation process using the solubility difference uses a difference in solubility change of each component with respect to the solvent due to a temperature difference.
It is preferable that the separation process based on the difference in solubility utilizes a decrease in the amount of components dissolved by decreasing the solvent.
It is preferable to include a step of obtaining a component containing endohedral fullerene as a solid or liquid by solid-liquid separation from a phase separated into a solid component and a liquid component due to a difference in solubility.
The step of obtaining the component containing the endohedral fullerene as a solid or liquid is preferably filtration.
The step of obtaining the component containing the endohedral fullerene as a solid or liquid preferably includes sedimentation by centrifugation and / or decantation of the supernatant.
Preferably, the purification step is by liquid chromatography that utilizes the distribution of materials between two different phases, the stationary phase and the mobile phase, to fractionate and fractionate only the necessary components.
The liquid chromatography is preferably distribution / adsorption column chromatography.
The liquid chromatography is preferably ion column chromatography.
It is preferable that the liquid chromatography is gel permeation column chromatography (GPC) for fractionation according to particle size.
It is preferable to perform the separation process in the purification step based on the difference in sublimation temperature of the components.

The separation treatment in the purification step is preferably performed by electrophoresis based on the interaction between a charged component and an electric field.
It is preferable that the purification step is separation by particle size difference.
It is preferable that the separation by the particle size difference is by centrifugation.
The separation due to the difference in particle size is preferably by filtration.
In the neutralization step of obtaining the neutral body of the endohedral fullerene, it is preferable that the cation of the endohedral fullerene is reduced with a reducing agent to obtain the neutral body of the endohedral fullerene.
It is preferable to obtain a neutral body of the endohedral fullerene by electrolyzing the cation of the endohedral fullerene.

(Isolated metal-encapsulated fullerene)
Moreover, the isolated endohedral fullerene of the present invention is represented by the following formula in which the peak intensity of empty fullerene is 0.5% or less with respect to the peak intensity of the endohedral fullerene in the positive mode mass spectrum (LDI-TOF-MS spectrum). Is an endohedral fullerene.
M @ C2n
M: Single or multiple metal atoms or atomic groups containing them
2n = 60 or 70

Another isolated metal-encapsulated fullerene is represented by the following formula in which the ratio of the peak intensity of empty fullerene to the peak intensity of the endohedral fullerene is 50% or less in the negative mode mass spectrum (LDI-TOF-MS spectrum). It is an endohedral fullerene.
M @ C2n
M: Single or multiple metal atoms or atomic groups containing them
2n = 60 or 70

  In the mass spectrum, the molecular weight of molecules contained in the material can be measured. Moreover, since the peak corresponding to the molecular weight of the impurity contained is also detected, relative purity can be discussed. There are two types of mass spectra, positive mode and negative mode. Molecules that tend to become positive ions tend to be observed in the positive mode, and molecules that tend to become negative ions tend to be observed relatively strongly in the negative mode. Since the isolated Li @ C60 cation salt contains a Li @ C60 cation, a peak of Li @ C60 (m / z = 727) is strongly observed in the positive mode. Further, since C60 is more easily anionized than Li @ C60, it is relatively easily detected in the negative mode.

In the present invention, the peak of Li @ C60 is strongly observed in the positive mode, and the peak of C60 as an impurity is not substantially observed. Further, even in the negative mode, Li @ C60 that is difficult to be detected as an anion can be strongly observed although the C60 peak is confirmed to be small, for example.
This is clearly seen in the case of the Li @ C60-containing extraction material (hereinafter abbreviated as TCE) described in Patent Document 3. In this extraction material TCE, although a Li @ C60 peak is observed in the positive mode, a considerable amount of the C60 peak is accompanied, and the Li @ C60 peak cannot be confirmed at all in the negative mode measurement.

Regarding the mass spectrum of Li @ C60, there have been reports of the Campbell group so far, but the peak intensity ratio is accompanied by about 1/4 C60 of Li @ C60 (non-patent document 4). It is difficult to say, and there is no report on the spectrum in which the peak of Li @ C60 was observed in the negative mode.
That is, the endohedral fullerene specified by the peaks shown in claims 2, 3, and 4 has not existed conventionally.
This can be realized for the first time by the manufacturing method described above.

(salt)
According to the above production method, the endohedral fullerene-containing composition obtained in the form of a cluster structure is obtained by decomposing the cluster in a solution and then purifying the cation or cation salt therein to obtain the endohedral fullerene. Therefore, it can be used for chemical treatment without re-dissolution by the user.

(The invention's effect)
According to the present invention, it is possible to obtain an isolated M @ C60 or M @ C70 that did not exist conventionally. As a result, it is possible to provide M @ C60 or M @ C70 which is sufficient for physical property research and application.

Example 1
According to the process shown in FIG. 1, M @ C60 was isolated.

S1: Generation process (S11: Synthesis of (cluster material))
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 C60 used as raw material used was C60 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, C60 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 / C60) was set to 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) collected as this composition was used as a starting material, and 2.06 g of this material was prepared.
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: Decomposition process

(S21: Cluster decomposition)
In this step, a recovered material (soot), which is a composition containing Li @ C60 having a cluster structure and a plurality of empty fullerenes, is introduced into a solvent (mixed solvent of the first and second solvents) together with a decomposition reagent, This is a process in which Li @ C60, empty fullerene and other components are released and present in the solution by a chemical reaction.
(I) In a glove box made an anaerobic atmosphere with argon gas, 2.06 g of the recovered product and 7.20 g of an aminium salt as a decomposition reagent were charged into a 200 ml capacity eggplant type flask.
Here, 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 a decomposition reagent is described as “aminium A” according to the following chemical formula.
That is, “aminium A” in this example is a compound name: tris (4-bromophenyl) aminium hexachloroantimonate, and a formula: (4-BrC6H4) 3NSbCl6.
This aminium A was synthesized in-house with reference to the following literature and used.
(Literature) W. Reynolds et al. , J .; Am. Chem. Soc. , 1
987, 109, 4960-4968
(Ii) Next, in the glove box, 103 ml of o-dichlorobenzene (hereinafter referred to as ODCB), which is a nonpolar solvent, is used as the first solvent, and the polar solvent is used as the second solvent. 52 ml of acetonitrile (hereinafter also referred to as AN) was added.
As the solvents, dehydrated o-dichlorobenzene (manufactured by ALDICH) and dehydrated acetonitrile (manufactured by Wako Pure Chemical Industries, Ltd.) were used.
(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 200-ml eggplant flask became a slightly blackish dark black suspension.
(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: Insoluble solid matter removal)
From the suspension after the completion of the decomposition reaction, a solid content insoluble in a solvent (a C60 polymer and other C60-derived components, a Li @ C60 polymer, a polymer in which Li @ C60 and C60 are combined, and an oxidizing agent. The following procedure was carried out for the purpose of removing insoluble components such as unreacted aminium A and most reaction products.
(I) A rotary oil vacuum pump was connected to the suspension eggplant-shaped flask after completion of the above-described decomposition reaction via a liquid nitrogen trap, and acetonitrile was distilled off at room temperature under reduced pressure.
(Ii) Centrifugation was performed to obtain a supernatant in order to suppress a decrease in filtration rate due to filter clogging.
Specifically, the suspension after AN distillation (about 100 ml) in the eggplant-shaped flask was equally divided into four centrifuge tubes with a capacity of 30 ml, and four were placed in a centrifuge (CN-2060 manufactured by HSIANGTAI). At the same time, it was operated at 3000 rpm for 10 minutes.
(Iii) The supernatant of the four centrifuge tubes was filtered with a suction filtration device. A 500 ml Erlenmeyer flask was used for the filtrate receiver.
As a filtration filter, a membrane filter (Omnipore membrane filter, model number JGWP04700, manufactured by Nihon Millipore Co., Ltd., specification, hole diameter 0.2 μm, diameter 47 mmφ, thickness 65 μm) was used.
(Iv) In order to prevent the ODCB solution (the object of the present invention is dissolved) from remaining in the centrifuge tube and the eggplant-shaped flask, the solids in each container (four centrifuge tubes and the eggplant-shaped flask) In order to wash off the minute portion, 150 ml of hexane was subdivided into each container where the solid content remained and shaken well, and then the contents of each container were filtered with a suction filtration device.
The filtrate in the Erlenmeyer flask receiving the filtrate formed a precipitate as the amount of added hexane increased, and became a black-brown suspension.
As hexane, Wako Pure Chemical Industries special grade n-hexane was used.

S3: Purification process

(S31: precipitate formation)
By adding hexane (third solvent), which is a poor solvent for all components dissolved in the filtrate, to the filtrate containing ODCB as the main component, the entire solute containing Li @ C60 cations is precipitated as a solid content. It is a process for obtaining.
(I) In order to further promote precipitation of hexane-insoluble components in the suspension filtrate exhibiting a blackish brown color, 150 ml of hexane was further added to the Erlenmeyer flask to further reduce the dissolved amount. A total of 300 ml was added with the hexane added previously.
(Ii) The Erlenmeyer flask containing the above “filtrate and hexane” was stoppered together, held in the 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 suction filtration device.
As the filtration filter, a membrane filter (Omnipore membrane filter, model number JGWP04700, manufactured by Nihon Millipore Co., Ltd., specification, hole diameter 0.2 μm, diameter 47 mmφ, thickness 65 μm) was used.
During filtration, the solid matter remaining on the inner wall of the glass apparatus such as a filter holder was washed away with hexane in a washing bottle and collected as much as possible.
As a result, a black tar-like filtration residue (hereinafter referred to as “tar-like filtration residue”) as the first composition was obtained on the filter.

(S32: salt removal)
This is a step for dissolving and removing unreacted substances and reactants of the aminium salt, which is an oxidizing agent, from the tar-like 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 does not substantially dissolve Li @ C60 cations and C60 fullerene, is used as the fourth solvent.
(I) In a Erlenmeyer flask with a capacity of 200 ml, a tar-like filtration residue and a filter were put, and 50 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 tar-like filtration residues were dispersed in AN.
(Iii) The suspension was equally divided into two centrifuge tubes with a capacity of 30 ml, and two suspensions were simultaneously set in a centrifuge (CN-2060 manufactured by HSIANGTAI) and operated at a rotation speed of 3000 rpm for 10 minutes.
(Iv) The supernatant of two centrifuge tubes was filtered with a suction filtration device into a filtrate receiving Erlenmeyer flask. Filter solids remained as a residue on the filter ("Filtration 1" treatment).
As a filtration filter, a membrane filter (Omnipore membrane filter, model number JGWP04700, manufactured by Nihon Millipore Co., Ltd., specification, hole diameter 0.2 μm, diameter 47 mmφ, thickness 65 μm) was used.
(V) 30 ml of AN was put into a 200 ml Erlenmeyer flask that was used in the above-mentioned “filtration 1” treatment and had a little solid content, and dispersed with an ultrasonic cleaner for 3 minutes.
(Vi) Disperse the AN solution in the 200 ml Erlenmeyer flask after the dispersion evenly into two centrifuge tubes, disperse with ultrasonic energy for 3 minutes, set the two centrifuge tubes in a centrifuge, and rotate at 3000 rpm. For 10 minutes. As described above, the salts in the solid content remaining in the 200 ml Erlenmeyer flask and the two centrifuge tubes were eluted.
(Vii) The supernatant in the two centrifuge tubes is poured from above the filtered solids on the filter of the suction filtration device after the “filtration 1” treatment, and the filtration solids are washed and the solution in the centrifuge tubes is filtered. (“Filtration 2” treatment).
(Viii) 20 ml of AN was placed in a 200 ml Erlenmeyer flask which was used in the above-mentioned “filtration 2” treatment and had a solid content still slightly fixed, and was dispersed for 3 minutes with an ultrasonic cleaner.
(Ix) Disperse the AN solution in the 200 ml Erlenmeyer flask after the dispersion evenly into two centrifuge tubes, disperse by ultrasonic energy for 3 minutes, set the two centrifuge tubes in a centrifuge, and rotate at 3000 rpm For 10 minutes.
(X) Pour the contents in the two centrifuge tubes from above the filtered solid content on the filter of the suction filtration device after “filtration 2”, and wash the filtered solid content and filter the solution in the centrifuge tube. Performed ("Filtration 3" treatment).
(Xi) The residue solid content obtained by repeated filtration up to “Filtration 3” is the filtration residue solid content that is the second composition.
The amount of AN used in this salt removal treatment was 50 ml for “Filtration 1”, 30 ml for “Filtration 2”, and 20 ml for “Filtration 3” for a total of 100 ml.

(S33: Empty fullerene removal)
In this step, the empty fullerene (C60) 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) The solid residue and the filter residue of the second composition were placed in an Erlenmeyer flask having a capacity of 200 ml, and 50 ml of toluene as the fifth solvent was poured 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 equally divided into two centrifuge tubes with a capacity of 30 ml, and the two suspensions were simultaneously set in a centrifuge (CN-2060 manufactured by HSIANGTAI) and operated at a rotation speed of 3000 rpm for 10 minutes.
(Iii) The contents of two centrifuge tubes were filtered into a filtrate receiving Erlenmeyer flask using a suction filtration device. 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 JGWP04700, specification, pore diameter 0.2 μm, diameter 47 mmφ, thickness 65 μm) was used as a filtration filter.
(Iv) In a 200 ml Erlenmeyer flask, the solid residue of “Filtration 1” and the filter were placed, and 50 ml of fresh toluene was poured therein so that they were immersed. This Erlenmeyer flask was placed in an ultrasonic cleaning machine, and ultrasonic energy was applied for 3 minutes to obtain a suspension in which solid filtration products were dispersed in toluene.
(V) Disperse the suspended toluene solution in the 200 ml Erlenmeyer flask after the dispersion evenly into two centrifuge tubes, disperse with ultrasonic energy for 3 minutes, set the two centrifuge tubes in a centrifuge and rotate Centrifugation was performed at several 3000 rpm for 10 minutes. As described above, unnecessary materials in the solid content remaining in the 200 ml Erlenmeyer flask and the two centrifuge tubes were removed and necessary components were recovered.
(Vii) The solution in the two centrifuge tubes is poured from the top of the filtered solid content on the filter of the suction filtration device after “filtration 1”, and the filtered solid content is washed and the solution in the centrifuge tube is filtered. ("Filtration 2" treatment).
The solid content obtained by repeated filtration up to “Filtration 2” is the solid content of the filtration residue as the third composition.

(S34: Li @ C60 cation extraction)
In this step, the endohedral fullerene cations are dissolved and extracted from the solid residue of the filtration residue, which is the third composition, using a sixth solvent (ODCB). As the sixth solvent, a good solvent for the endohedral fullerene cation is selected.
(I) The third composition filtration residue solid matter and the filter were put into a 200 ml Erlenmeyer flask, and 20 ml of ODCB as the sixth solvent was poured 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 solid was dispersed in ODCB.
(Ii) The suspension was taken in one centrifuge tube with a capacity of 30 ml, set in a centrifuge (CN-2060 manufactured by HSIANGTAI), and operated at a rotation speed of 3000 rpm for 10 minutes.
(Iii) The content of one centrifuge tube was filtered into a filtrate receiving flask with a suction filtration device. The filtrate in which the target substance-encapsulated fullerene cation Li @ C60 salt was extracted and dissolved was placed in a 30 ml vial.
As the ODCB, a special grade ODCB (manufactured by ALDRICH) was used, and as the filtration filter, a membrane filter (Nihon Millipore omnipore membrane filter, model number JGWP02500, specification pore diameter 0.2 μm, diameter 25 mmφ, thickness 65 μm) was used.

(S35: Solid precipitation)
In this step, the endohedral fullerene cations are precipitated as a solid content from the filtrate. Cooling the filtrate reduces the amount of cations dissolved.
(I) The vial bottle containing the filtrate was 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.
(Ii) After standing at cool temperature, precipitation of black powdery solid (referred to as OxAm-C) could be confirmed in the filtrate of the vial.

(S36: Solid recovery)
In this step, the black powdered solid OxAm-C that has precipitated is washed to remove unnecessary materials and collect the necessary solid.
(I) After standing at cool temperature, the filtrate from the vial bottle 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) 100 μl of ODCB was poured into a vial that left most of the black powdery solid on the inner wall and bottom, and the black powdery solid was washed.
(Iii) Subsequently, the supernatant in the vial was poured from above the black residue filtration solids on the filter of the filtration device after decantation filtration, and decantation filtered ("ODCB decantation 1" treatment). .
(Iv) Again, 100 μl of ODCB was newly poured into the vial that left the black powdery solid on the inner wall and bottom, and the black powdery solid was washed again, followed by repeated decantation filtration (“ODCB decantation 2” treatment).
(V) 1 ml of toluene was poured into a vial that left most of the black powdered solid on the inner wall and bottom, and the black powdered solid was washed. Subsequently, the supernatant liquid in the vial was poured from above the black residue filtration solids on the filter of the filtration apparatus after the “ODCB decantation filtration 2” was performed, followed by decantation filtration (“toluene decantation” treatment). .
(Vi) Pour 1 ml of hexane into a vial that has left most of the black powdery solid on the inner wall and bottom, and after washing the black powdery solid, aspirate the contents in the vial 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 decantation, and was suction-filtered. This was repeated three times.
(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 powdery solid after drying contains the inclusion endohedral fullerene cation Li @ C60 + and is referred to as OxAm-C. The weight of OxAm-C obtained here was about 6.7 mg.

(S37: Recrystallization)
The purpose of this step is to obtain high purity by recrystallization of solid OxAm-C containing endohedral fullerene cations and to obtain it as a crystalline solid.
(I) S2: 6.7 mg of OxAm-C was put into a 20 ml vial in the same glove box where the decomposition step was performed, ODCB 6 ml and AN 6 ml were added, and placed in an ultrasonic cleaner to disperse for 3 minutes. .
(Ii) The contents of the vial were filtered with a suction filtration device. The same type of filter was used for each of the above processes. The target product Li @ C60 cation salt is dissolved in the filtrate (received in another 20 ml vial), and the filtered solid content is considered to be an unnecessary substance (impurities).
(Iii) The 20 ml vial containing the filtrate of the mixed solvent of ODCB and AN was put into a desiccator, a rotary oil vacuum pump was connected through a liquid nitrogen trap, and acetonitrile was distilled off at room temperature under reduced pressure.
(Iv) The solution containing the remaining ODCB as a main solvent was allowed to stand in a refrigerator for 3 days.
As a result, a large number of elongated black plate-like crystalline solids (this black plate-like crystalline solid is hereinafter referred to as OxAm-CP) were generated around the inner wall surface of the vial. The crystalline solid had a width of several tens of μm and a length of several mm.

(S38: Crystal recovery)
This is a step for further removing and cleaning impurities (mainly assuming ODCB) in the OxAm-CP crystals and recovering the OxAm-CP crystals (obtained as a solid excluding the solvent).
(I) After standing at a cool temperature, the solution in the vial was poured into the filter holder of the suction filtration device together with the precipitated solid OxAm-CP and filtered. The target product Li @ C60 cation salt is present in the filtered solid OxAm-CP.
(Ii) The solid on the filter was washed with 1 ml of hexane and suction filtered ("hexane washing 1" treatment). Further, the solid was again washed with 1 ml of hexane and suction filtered ("hexane washing 2" treatment).
(Iii) The obtained black solid was taken out together with a filter onto an aluminum foil, placed in a vacuum desiccator, and dried with a diaphragm pump.
The weight of the obtained black plate crystal (OXAM-CP) was 1.5 mg.

  S4: Neutralization process (reduction process)

The neutralization step is a step for reducing the metal-encapsulated fullerene (a salt of Li @ C60 + in this example) obtained as a cation salt and isolating it as a neutral form (Li @ C60 in this example). It is.
(I) 5 mg of OxAm-CP was dissolved in 5 ml of ODCB to obtain a solution.
(Ii) While this solution was stirred, an ODCB solution of the reducing agent bis (pentamethyl-cyclopentadienyl) iron (II) (hereinafter referred to as Fe (Cp *) 2) was gradually added.
Here, the amount of Fe (Cp *) 2 was 4.6 mg which is 3 times equivalent to 5 mg of OxAm-CP.
Molecular weight of OxAm-CP (: Li @ C60 · SbCl6) 1062.1
Molecular weight of Fe (Cp *) 2 326.2
Thus, the amount of reducing agent = (326.2 × 3 × 5) /1062.1=4.6
As a result, the reduction reaction proceeds, and a mixed solution in which Li @ C60 and [Fe (Cp *) 2 +] [SbCl6-] are generated in ODCB is obtained.
(Iii) The mixed solution is added little by little to a flask containing 50 ml of hexane while stirring. As a result, Li @ C60 and [Fe (Cp *) 2+] [SbCl6-] that are substantially insoluble in hexane precipitate and form a suspension.
(Iv) The suspension was suction filtered to obtain a solid content on the filter.
(V) The solid content remaining on the filter was put into 50 ml of acetonitrile and dispersed by stirring.
As a result, [Fe (Cp *) 2+] [SbCl6-], which is an ionic salt, was dissolved in acetonitrile, which is a polar solvent, while Li @ C60 was dispersed in the liquid as a solid.
(Vi) The solution was subjected to suction filtration, the solid content on the filter was collected, and this was suction dried with a vacuum desiccator.
(Vii) The solid obtained by drying was collected in a vial together with an inert gas. This was an isolated Li @ C60 fullerene and the amount of solid obtained was 3 mg.

The following various tests were performed on the black plate crystal OxAm-CP.

(LDI-TOF-MS inspection)
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 @ C60 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 700-800, and the other impurity peaks were weak.

Since Li @ C60 tends to be positive ions, it tends to be observed more strongly in the positive mode than the negative mode. Conversely, C60 tends to be more negative ions than the positive mode.
Actually, in the mass spectrum of OxAm-CP, in the positive mode, a peak at m / z = 720 (C60) with respect to the (A) peak (hereinafter referred to as the (B) peak) was not substantially observed. (The ratio of (B) peak to (A) peak is 0.5% or less), whereas in the negative mode, the (B) peak was weakly observed (the ratio of (B) peak to (A) peak was 20%) Less than.)
Regarding the mass spectrum of Li @ C60, there is a report example of Campbell group so far, but it is accompanied by a large amount of C60 (about 4 times the Li @ C60 in peak intensity ratio), and it is difficult to say that it is isolated. Moreover, there is no report example of the spectrum in which the peak of Li @ C60 was observed in the negative mode.

(NMR inspection)
When 7Li NMR measurement (apparatus name: Bruker AVANCE300, 117 MHz, ODCB) was performed, as shown in FIG. 4, only one peak was given in the vicinity of −11.1 ppm (based on LiCl in heavy water). The peak position of −11.1 ppm is a high magnetic field region as a general Li chemical species, indicating that the Li nuclei are strongly shielded magnetically. This suggests that Li atoms are encapsulated in the C60 shell.
When 13C NMR measurement (apparatus name: Bruker AVANCE 600, 151 MHz, ODCB) was performed, only one peak was given to 142.04 ppm (based on tetramethylsilane in ODCB) as shown in FIG.
In any nuclide, the fact that there is only one peak in the NMR spectrum indicates that this material contains only one lithium species and one carbon species. In particular, the appearance of all carbons equivalently in 13C NMR indicates that the distances between all the carbons in the molecule and Li are equal. That is, the Li atom is at the center inside the C60 shell, and is not located at a biased position inside the C60 shell or outside the C60 shell.
(Elemental analysis)
Table 1 below is a table showing the results of elemental analysis of OxAm-CP.
For C, H, and N analysis, a CHN analyzer MT-6 manufactured by YANACO was used.
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.
Table 1 shows the elemental compositions of the compounds that are likely to be obtained for comparison.
Sample number “OxAm36-CP1” is a typical example of the OxAm-CP sample of this patent.
The composition of "OxAm36-CP1" (obsd. Observed value) and "Li@C60SbCl6.ODCB" (calcd. Theoretical calculation value) are in good agreement (generally, the elemental analysis value and the theoretical composition are 0.00. OxAm-CP is highly likely to be a crystal having a Li @ C60SbCl6 · ODCB composition containing one molecule of ODCB as a solvent.

  In the synthesis step S1, a case where a single fullerene of C60 is used as a starting material and a metal is included in C60 has been described. However, a mixed fullerene of C60 and C70 is used as a starting material, and a metal is used for each. Even in the case of encapsulating M @ C60 and M @ C70, it was possible to obtain isolated encapsulated fullerenes containing M @ C60 and M @ C70, which did not contain fullerenes other than M @ C60 and M @ C70.

Since M @ C60 (or M @ C70) isolated according to the present invention is obtained,
・ The physical properties of M @ C60 (or M @ C70) can be clarified.
・ With the elucidation of physical properties, the scope of application and application development will expand.
-It can be expected as a high-temperature superconducting material, including higher conversion efficiency of organic thin-film solar cells.
Because it is soluble in a solvent ・ Molecular dispersion is possible and molecular functions can be expressed.
-Derivative synthesis becomes easy and various functions can be added.
・ A wide range of application development and applied research is possible.

Claims (22)

An isolated endohedral fullerene represented by M @ C2n.
M: single or plural metal atoms or atomic group containing them 2n = 60 or 70 In the positive mode laser desorption ionization time-of-flight mass spectrum (hereinafter referred to as “LDI (or LD) -TOF-MS”), the peak intensity of other fullerenes is 0.5% or less with respect to the peak intensity of endohedral fullerenes. An endohedral fullerene represented by the following formula.
M @ C2n
M: single or plural metal atoms or atomic group containing them 2n = 60 or 70 An endohedral fullerene represented by the following formula in which the peak intensity of another fullerene is 50% or less with respect to the peak intensity of the endohedral fullerene in LDI-TOF-MS in negative mode.
M @ C2n
M: single or plural metal atoms or atomic group containing them 2n = 60 or 70 The endohedral fullerene according to claim 3, wherein the peak intensity is 20% or less. The endohedral fullerene according to any one of claims 1 to 4, wherein M is a Group 1 to Group 4 metal. The endohedral fullerene according to any one of claims 1 to 5, wherein M is an alkali metal. The endohedral fullerene according to claim 6, wherein M is any one of Li, Na, and K. The endohedral fullerene according to claim 7, wherein M is Li. A salt having [M @ C2n] as a cation. The cation has a valence of 1 or more.
M: single or plural metal atoms or atomic group containing them 2n = 60 or 70 The salt according to claim 9, which is [M @ C2n] m + · m [SbCl6]-.
m is the valence of the cation. The salt according to claim 9 or 10, which is a crystal. The salt according to claim 11, which is a single crystal. The salt according to any one of claims 9 to 12, wherein M is a Group 1 to Group 4 metal. The salt according to any one of claims 9 to 13, wherein M is an alkali metal. The salt according to claim 14, wherein M is any one of Li, Na, and K. The salt according to claim 15, wherein M is Li. MA @ C60 and MA @ C70 containing endohedral fullerenes, MA @ C60 for peak intensity of MA @ C60 or MA @ C70, whichever is larger in LDI (or LD) -TOF-MS in positive mode Endohedral fullerenes with peak intensity of fullerenes other than MA @ C70 of 0.5% or less.
MA: Single or plural alkali metal atoms or atomic groups containing them MA @ C60 and MA @ C70 containing endohedral fullerenes, and MA @ C60 for peak intensity of MA @ C60 or MA @ C70, whichever is larger in LDI (or LD) -TOF-MS in negative mode Endohedral fullerenes with peak intensity of fullerenes other than MA @ C70 of 50% or less.
MA: Single or plural alkali metal atoms or atomic groups containing them The endohedral fullerene according to claim 18, wherein the peak intensity of fullerenes other than MA @ C60 and MA @ C70 with respect to the larger peak intensity of MA @ C60 and MA @ C70 is 20% or less. The endohedral fullerene according to any one of claims 17 to 19, wherein the MA is Li. A salt having [MA @ C60] and [MA @ C70] as cations. The cation has a valence of 1 or more. The salt according to claim 21, which is [MA @ C60] k + [MA @ C70] l +. (K + 1) [SbCl6]-.
k and l are cation valences.

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