Patent Publication Number: US-2011065944-A1

Title: New reactions of fullerenes

Description:
FIELD 
     This disclosure relates to new reactions of fullerenes with primary amines in the presence of a peroxide. 
     BACKGROUND 
     Fullerenes are a third allotrope of carbon. Unsubstituted fullerenes are insoluble in water and soluble only in a small number of aromatic solvents. Some fullerene derivatives have been found to exhibit biological activities. For instance, certain endohedral metallofullerenes have been found to be suitable as magnetic resonance imaging (MRI) contrast agents. However, due to the limited solubility, the applications of the fullerene derivatives are still restricted, particularly, as biological tools. 
     SUMMARY 
     An exemplary embodiment is directed to a process for producing a fullerene derivative, comprising reacting a fullerene compound with a primary amine in the presence of a peroxide, to form the fullerene derivative. 
     The present disclosure describes a convenient process producing fullerene derivatives with improved solubility, which makes it possible to use these fullerene derivatives as MRI contrast agents, fullerene therapeutics, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a reaction scheme of C 60  with a secondary amine. 
         FIG. 2  shows the reaction products of t-butyl peroxide radical with C 60 . 
         FIG. 3  illustrates a reaction scheme of fullerene peroxide with nucleophile NaOCH 3 . 
         FIG. 4  shows crystal structures of fullerene radical addition products. 
         FIG. 5  illustrates successive addition scheme of radical R to a fullerene structure. 
         FIG. 6  shows a mass spectrum of C 60 -perfluorohexyl radical addition product. 
         FIG. 7  illustrates a reaction scheme of radical addition to fullerene C 60  via copper ion. 
         FIG. 8  shows an X-ray crystal structure of C 60 (CF 3 ) 12 . 
         FIGS. 9(   a ) and ( b ) show stick models of Gd 3 N@C 80  structures. 
         FIG. 10  illustrates a reaction scheme of radical addition of CF 3 I to Sc 3 N@C 80 . 
         FIG. 11  is a photograph of the gel electrophoresis data of C 70 -monoethyleneglycol amine adduct (C 70 -MEG), Hydrochalarone-1 (Gd 3 N@C 80 -MEG) and Hydrochalarone-3 (Gd 3 N@C 80 -TEG). 
         FIGS. 12(   a ) and ( b ) show IR spectra of C 70 -MEG before and after D 2 O addition. 
         FIGS. 13(   a ) and ( b ) show  1 H NMR spectra of MEG and undialyzed C 70 -MEG in D 2 O. 
         FIG. 14  shows the elemental analysis of Hydrochalarone-3. 
         FIGS. 15  ( a ) and ( b ) show IR spectra of C 70 -MEG and Hydrochalarone-3. 
         FIGS. 16  ( a ) and ( b ) show IR spectra of Hydrochalarone-1 and Hydrochalarone-3. 
         FIG. 17  shows UV/Vis spectrum of Hydrochalarone-6 in water. 
         FIGS. 18(   a ) and ( b ) show IR spectra of GdTMS-decylamine and Hydrochalarone-1. 
         FIGS. 19  ( a ) and ( b ) show  1 H NMR spectra of MEG-TFA in D 2 O and YTMS pre-dialysis. 
         FIG. 20  shows  1 H NMR spectrum of post-dialysis Y Hydrochalarone-1 in D 2 O. 
         FIGS. 21  ( a ) and ( b ) show TGA spectra of Hydrochalarone-6 and unfunctionalized Gd 3 N@C 80 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Various studies have been conducted on water-solubilization of fullerenes. The addition of polar groups to the fullerene to render the molecule water-soluble was reported in a study by Friedman. Friedman, S. H., et al.,  Inhibition of the HIV -1  Protease by Fullerene Derivatives: Model Building Studies and Experimental Verification , J. Am. Chem. Soc. (1993) 115, 6506-6509. In another example, the addition of hydroxyl groups was described by Chiang who reacted C 60  with aqueous acids to provide a polyhydroxyl fullerene compound. Chiang, L. Y., et al.  Multi - hydroxy Additions onto C   60    Fullerene Molecules  J. Chem. Soc. Chem. Comm. (1992) 1791. 
     An early review of other methods was reported by Nakamura: Yomago, S., Nakamura, E. et al.  In vivo Biological Behavior of a Water - miscible Fullerene - C 14  Labeling, Absorption, Distribution, Excretion, and Acute Toxicity  Chemistry and Biology, (1995), 2(6), 385-389. Lamparth et al. described the synthesis of C 60  malonic acids by the reaction of fullerene with diethyl bromomalonate, followed by saponification of the formed malonates in the presence of NaH. The resulting C 60  malonic acids are soluble in basic to neutral water and insoluble in aqueous acids. Lamparth et al.,  Water - soluble Malonic Acid Derivatives of C   60    with a Defined Three - dimensional Structure , J. Chem. Soc., Chem. Commun. 1994, 1727-28. Further, Sawamura et al. reported the preparation of water soluble anionic fullerenes, i.e., pentaaryl and pentamethylfullerene anions R 5 C 60   −  by the reaction of fullerene with an organocopper reagent. Sawamura et al.,  Pentaorgano[ 60 ]fullerene R   5   C   60   −   . A Water Soluble Hydrocarbon Anion , Chem. Lett. 2000, 1098-99. 
     Addition reactions of aliphatic amines to fullerenes have also been explored. It was found that some primary and secondary amines add readily and repeatedly across C 60  fullerene producing complex reaction mixtures composed of numerous structures and isomers. Eudl et al.,  Fullerenes: Synthesis, Properties and Chemistry of Large Carbon Clusters , Ed.: G. S. Hammond and V. J. Kuck, ACS Symp. Ser. 1992, 48 (11), 161-175. Other studies showed that certain secondary amines, such as N,N′-dimethylethylenediamine, piperazine and morpholine, can result in well-defined addition products. Kampe et al.,  Diamino and Tetramino Derivatives of Buckminsterfullerene C   60 , Angew. Chem., Int. Ed. Engl. 1992, 32, 1174-76; Schick et al.,  Reaction of [ 60 ]fullerene with morpholine and piperidine: preferred  1,4- additions and fullerene dimer formation , J. Chem. Soc., Chem. Commun. 1995, 2023-24. 
     Amine additions to fullerenes are well known and have been reviewed. See e.g. Miller, G P  Reactions between aliphatic amines and [ 60 ]fullerene: a review  C. R. Chemie 9, 952-959 (2006). In addition, the reaction of secondary amines (HNR 2 ) with fullerenes catalyzed by molecular oxygen in air has been reported ( FIG. 1 ). See e.g. Nakamura,  Regioselective Oxygenative Tetraamination of [ 60 ]Fullerene. Fullerene-mediated Reduction of Molecular Oxygen by Amine via Ground State Single Electron Transfer in Dimethyl Sulfoxide , J. Org. Chem., 70, 4826-4832 (2005). Nakamura states that “ . . . primary amines give no isolable products” in this reaction. 
     A similar pattern addition of organic peroxides such as tert-butyl hydroperoxide has been extensively studied by Gan ( FIG. 2 ). See e.g. Gan,  Fullerene peroxides , C R Chimie, 9, 1001-1004 (2006). Gan comments that “nucleophiles react with fullerene peroxides according to either SN1 or SN2′ or SN2″ pathway.” The only example described therein is the addition of CH 3 O −  (methoxide) that displaces a peroxide to give one or more adducts. The assigned structures and pathways are shown in  FIG. 3 . 
     Yang reported the opening of holes in fullerene using peroxides. Two cage-open fullerene derivatives 2 and 4 gave X-ray crystal structures as shown in  FIG. 4 . Yang, et al.,  Controlled region - and chemoselective addition of isothiocyanate to the dione moiety of a cage - opened fullerene - mixed peroxide derivative , Chem. Comm. 1980-1982 (2008). 
     More recently, Nakamura reported the addition reaction of secondary amines to C 60  which was catalyzed by cumene hydroperoxide. Nakamura et al.,  Synthesis of Oxy Aminated [ 60 ] and [ 70 ] Fullerenes with Cumene Hydroperoxide as Oxidant , Chem. Lett. 36, 20-21 (2007). 
     Based on Nakamura&#39;s work, all of these addition processes require that the fullerene first reacts with the amine to form a charge transfer complex, which is then oxidized by the molecular oxygen or peroxide. 
     The present inventor has found a new reaction that secondary amines do not participate in. Furthermore, neither molecular oxygen nor cumene hydroperoxide affects the reaction. In particular, the reaction proceeds with a specifically preformed and reactive amine radical. For example, a reaction involving aminopropyl-surface-modified silica as the amine was performed. Butanone peroxide was added to the silica-bound amine, then washed off through filtering and rinsing of the silica. This activated silica reacted readily with a number of fullerenes in solution when a mixed-fullerene solution was added. These data suggest that the key step in the reaction is the formation of a novel nitrogen-centered radical. 
     The terms “fullerene” and “fullerene compound,” as used herein, denote a compound containing a fullerene cage network, and include both an empty fullerene compound with no additional atoms within its cage network and an endohedral metallofullerene. The term “endohedral metallofullerene,” as used herein, denotes a fullerene compound where one or more metal atoms are encapsulated inside a fullerene cage network. Accepted symbols for elements and subscripts to denote numbers of elements are used herein. Generally, all elements to the right of an @ symbol are part of the fullerene cage network, while all elements listed to the left of the @ symbol are contained within the fullerene cage. For example, under the notation Gd 3 N@C 80 , the Gd 3 N trimetallic nitride is situated within a C 80  fullerene cage. 
     The term “TRIMETASPHERE®” (TMS) denotes a member of a family of endohedral metallofullerenes which contain a trimetallic nitride compound in the fullerene cage. One example Gd 3 N@C 80  is referred to as GdTMS. Some examples of TRIMETASPHERE® are discussed in U.S. Pat. Nos. 6,303,760 and 6,471,942, and U.S. Patent Application Publication No. 2004/0054151. 
     The term “fullerene derivative,” as used herein, denotes a fullerene-containing product obtained in the reaction described herein. 
     The present disclosure describes new reactions of fullerene compounds with amines in the presence of a peroxide. 
     Soon after the discovery of fullerene C 60 , its chemistry as a “radical sponge” was recognized and extensively studied. C 60  is a highly conjugated olefin with carbon-carbon bonds that can react avidly with radicals to produce increasingly more stable allylic radicals and eventually multiple adducts. The unique feature of all these fullerenes is the presence of six 5-membered rings (each closed fullerene structure must have six five membered rings) that can accept five radical (R.) groups to produce the very stable cyclopentadienyl radical ( FIG. 5 ). See e.g. Krusic et al.,  Radical Reactions of C   60 , Science, 254, 1183-85 (1991). 
     The addition of alkyl radicals to fullerenes was extensively investigated by the Dupont group. For example, heating perfluorohexyl iodine with C 60  at 178° C. gave addition of 8-11 groups to the sphere ( FIG. 6 ). Fagan, P J et al.,  Production of Perfluoroalkylated Nanospheres from Buckminsterfullerene , Science, 262, 404-407 (1993). 
     More recently, the controlled addition of radicals to fullerenes has been adapted as a reliable process using radical-producing reagents such as organocuprates ( FIG. 7 ). Matsuo, Y. and Nakamura, N.,  Selective Multiaddition of Organocopper Reagents to Fullerenes  Chem. Rev., 108, 3016-3028 (2008). 
     While much of the regiochemistry of radical fullerene additions takes place at the unique fullerene pyracylene bonding patterns of interconnecting carbons, another pathway involves 1,4-addition on benzene rings. For example, Kareev has reported successive CF 3 .radical additions to C 60  which result in a product with adducts that was completely characterized by X-ray crystallography ( FIG. 8 ). See Kareev et al.,  X - ray structure and DFT study of C   1 - C   60 ( CF   3 ) 12   . A high - energy, kinetically - stable isomer prepared at  500° C., Chem. Commun., 2007, 1650-1651 
     Addition chemistry of TRIMETASPHERE® (“TMS”) C 80  compounds is often different from empty cage fullerenes, since the fullerene pyracylene bonding pattern is not present in C 80 . There are, however, benzene rings that can participate in 1,4-addition reactions. In fact, if one examines the distribution of benzene rings on the surface of a TMS, a “belt” of 12 rings are arrayed in a biphenyl-type linkage. Every other benzene ring is situated over a Gd metal atom ( FIG. 9 ) and indeed appears to participate in η6-bonding arrangements.  FIG. 9(   a ) is an X-Ray structure of Gd 3 N@C 80 , and  FIG. 9(   b ) is a Gd 3 N@C 80  model with top and bottom atoms cut away to reveal arrangement of the internal trimetallic nitride and surrounding belt of benzene rings. 
     The addition of radicals to TMS compounds takes place via 1,4-addition on benzene rings around this “biphenyl-belt”. Shustova has recently reported the addition of trifluoromethyl radical to Sc 3 N@C 80 . While the product mixture contains mainly a series of Sc 3 N@C 80 (CF 3 ) n  where n=8-12, they were able to isolate and characterize the bis adduct as shown in  FIG. 10 . Note that the addition preferentially occurred in a 1,4-pattern on the benzene ring in between two η6-bonded scandium atoms ( FIG. 10 ). Shustova, N, B. et al,  Radical Trifluoromethylation of Sc   3   N@ C   80 , J. Am. Chem. Soc. 129 (38), 11676-11677 (2007). 
     Fullerene Compounds 
     The fullerene compound described herein may contain a fullerene cage represented by C m . m represents an integer, in particular, an even value, from about 60 to about 200. In one embodiment, m is 60, 68, 70, 74, 78, 80, 82, 90, 92, and 94. Further, m is preferably an integer from about 60 to about 88. The fullerene cage may optionally have one or more substituents. The substituents on the fullerene cage are not particularly limited, so long as they do not interfere with the reaction described herein. 
     When an endohedral metallofullerene is used as the fullerene compound, the metal atom(s) encapsulated inside a fullerene cage network are not particularly limited. When multiple atoms are encapsulated inside a fullerene cage network, they may be the same or different. In one embodiment, the endohedral metallofullerene contains at least one paramagnetic metal and particularly, an element having one or more unpaired electrons. In a preferred embodiment, a rare earth element, a group IIIB element in the periodic table of elements or the like can be used as the encapsulated atom. Examples of suitable rare earth elements and group IIIB elements may include, but are not limited to, gadolinium (Gd), scandium (Sc), erbium (Er), holmium (Ho), yttrium (Y), lanthanum (La), thulium (Tm), dysprosium (Dy), terbium (Tb) and ytterbium (Yb). 
     In one embodiment, the fullerene comprises C 60 , C 70 , or Gd 3 N@C 80 . It was found that C 60  and C 70  react about 4-fold faster than Gd 3 N@C 80  under the same reaction conditions. 
     Amines 
     The amines which are suitable for the reaction described herein can be quite diverse and include ammonium, alkyl amines, amino acids, poly ether amines, etc. Hydroxyl group-containing amines are generally not preferred due to potential oxidation reactions of the hydroxyl group by the peroxide. In an embodiment, the amine group in the amine is attached to a primary or secondary carbon atom. Preferably, such amine group is attached to a primary carbon atom. 
     In an embodiment, the amine described herein comprises a primary amine. Examples of suitable primary amine compounds may include compounds represented by RNH 2 . In one embodiment, R may represent H, NH 2 (CH 2 ) a CH 3  and NH 2 (CH 2 CH 2 O) a CH 3  wherein a is an integer of 1 or more, and preferably, 1 to 20. In an embodiment, a is 1, 3, 5 or 11. Specifically, the primary amine compounds may be represented by the formula RNH 2  wherein R is H, ethyl, propyl, hexyl, dodecyl, —CH(CH 2 OCH 3 ) 2 , —(CH 2 ) 4 —NH 2 , —(CH 2 ) 10 —NHBoc, —(CH 2 ) 2 —COOH, —CH(COOCH 2 CH 3 )(CH 2 ) 2 Ph, —CH 2 -18-crown-6, -glyme-OCH 3 , -glyme-NHBoc, -triglyme-OCH 3 , -triglyme-NHBoc, -hexaglyme-OCH 3  and -hexaglyme-NHBoc (glyme refers to a repeating ethylene glycol unit). 
     Peroxides 
     The peroxide described herein preferably contains butanone peroxide. Other suitable peroxides, such as cumene hydroperoxide, can also be used. Moreover, when water is used as the solvent for the reaction described herein, hydrogen peroxide may be used as the peroxide. 
     Solvents 
     The solvent for this reaction may comprise an organic solvent, such as toluene, xylene, benzene and ortho-dichlorobenzene. In addition, certain partially reacted fullerene products have a reasonable solubility in water, and can be further reacted in water. These solvents may be used individually or in combination thereof. In an embodiment, the solvent contains xylene. 
     Reactions of Fullerene Compounds 
     The present inventor has discovered a new reaction type that provides a favorable route to functionalization of fullerene compounds. The reaction is based on a unique activated nitrogen-centered radical species generated from an amine and a peroxide. 
     The term “Hydrochalarone,” as used herein, refers to the class of compounds resulting from the reaction of the fullerenes, peroxide and amine. Hydrochalarone-1, Hydrochalarone-3 and Hydrochalarone-6 refer to the compounds obtained by using, as the amine, monoethylene glycol (MEG), triethylene glycol, and hexaethylene glycol, respectively. 
     Although not wishing to be bound by any theory, it is believed that the reaction of a peroxide, such as butanone peroxide, with an amine, such as a primary amine, leads to formation of an RN(OH). reactive intermediate that has stability of at least several minutes but not many hours. In the presence of a fullerene compound, the RN(OH). reacts rapidly with the benzene rings on the fullerene cage, forming a fullerene radical, which, in turn, may react with other radical or non-radical species present in the reaction mixture. 
     The resulting substituted fullerene molecules may be repeatedly reacted with the existing radical species, thereby forming multi-substituted fullerene molecules, polymers or both. Further substitutions may occur at any available position of the substituted fullerene, e.g., a carbon atom on the fullerene cage or any site on the substituent thereof. 
     In such a reaction, the concentration of the fullerene can range from about 0.25 mg/mL to about 5.0 mg/mL, based on the volume of the solvent used. In an embodiment, the fullerene can be used in a concentration of about 1 mg/mL to about 2 mg/mL, based on the volume of the solvent. 
     Generally, the amine compound and the peroxide can be used in large excess of the fullerene compound. In an embodiment, the fullerene:amine molar ratio can range from about 1:50 to about 1:750 and preferably, about 1:500. The amine:peroxide molar ratio can range from about 1:1 to about 1:10, preferably, about 1:5, and more preferably, about 1:3. It should be noted that butanone peroxide contains three peroxide units. In a particular embodiment, the fullerene:amine: effective peroxide unit molar ratio is about 1:500:1000. When water is used as the solvent, the amounts of the amine compound and the peroxide may be relatively higher. 
     The reaction of the fullerene compound may be conducted at ambient conditions and the reaction proceeds at a varied rate depending on the nature of fullerene, amine, peroxide and/or solvent. The reaction process can be monitored by the formation of precipitate of the product from the reaction mixture. 
     The reaction temperature may be raised to accelerate the reaction rate, if necessary or desired. In this case, the reaction temperature is preferably set below the boiling point of the amine and/or solvent used therein. In an embodiment, the reaction can be carried out at ambient temperature to about 80° C. 
     When a C 80  TRIMETASPHERE® is used, the reaction is preferably run at 75° C. On the other hand, when a C 60  or C 70  TRIMETASPHERE® is used, the reaction runs relatively fast at ambient temperature and does not need heating. When using Gd 3 N@C 80 , the reaction yield can be determined by ashing a sample of a known quantity of the product and determining the Gd 2 O 3  concentration therein. The Gd 2 O 3  concentration can be determined by measuring relaxivity and comparing the measured value to a previously determined concentration/relaxivity calibration curve. 
     When an empty fullerene is used, the reaction is substantially complete in about 10 minutes to about 60 minutes at ambient temperature. When Gd 3 N@C 80  is used, the reaction is substantially complete in about 10 minutes to about 60 minutes at 75° C. and from about 1 hour to about 16 hours at ambient temperature. The isolated reaction yields of Gd 3 N@C 80  can range from about 60% to about 80%, with the remainder being aggregated partially reacted materials. The crude reaction products may be purified by various methods, such as precipitation, dialysis and column chromatography. 
     In one specific reaction of NH 2 (CH 2 CH 2 O) 3 CH 3  with Gd 3 N@C m  in the presence of butanone peroxide, mono- and/or multi-substituted fullerene derivatives may be formed. It is possible that the resulting reaction products may contain, in addition to the —N(OH)R addition product(s), the —ONHR addition product(s), the —NHR addition product(s) or a mixture of two or more of these products. It is also possible that the intermediate fullerene radicals polymerize, thereby forming one or more polymers in the reaction mixture. 
     Further, in the reaction mixture, the number of substituents on each fullerene cage may vary, depending, to some extent, on the nature of fullerene, substituents and reaction conditions. Thus, it is likely that any particular reaction may generate a mixture of fullerene derivatives having different types and/or numbers of substituents on the fullerene cages thereof. 
     When a fullerene derivative having more than one types of substituents is desired, different amines may be employed simultaneously (“one-pot reaction”) or in sequence, which may vary and can be optimized by those skilled in the art. 
     The fullerene derivatives obtained in the reaction described herein may have a relatively high solubility in water and/or other organic solvents, such as ether. Generally, an amine having fewer hydrocarbon groups and/or one or more heteroatoms, such as oxygen and nitrogen, tends to result in a fullerene derivative having a relatively higher water solubility. On the other hand, an amine having more hydrocarbon groups tends to result in a fullerene derivative having improved ether solubility. For instance, the solubility of Gd 3 N@ C 80 /NH 2 CH 2 CH 2 OCH 3  adduct (“Hydrochalarone-1”) in water is about 100 mg/mL. This figure is roughly two orders of magnitude above the highest values for the known fullerenes and their derivatives. In an embodiment, the fullerene derivative described herein has a water solubility of greater than about 40 mg/mL. Further, the solubility of Gd 3 N@C 80 /NH 2 (CH 2 ) 11 CH 3  adduct in ether is greater than about 10 mg/mL. Depending on the end uses, it is possible to fine tune the water/ether solubility of the fullerene derivatives described herein by employing a suitable amine in the reaction. 
     The improved solubility makes the fullerene derivatives described herein suitable for various applications. Particularly, the improved water solubility allows the fullerene derivatives described herein to be compatible with biological systems and thus useful in the biological fields. In addition, the endohedral metallofullerene derivatives described herein preferably have a relaxivity of greater than about 40 mM −1 s −1 , which makes them potentially useful as MRI contrast agents. 
     The increased solubility is believed to be attributable to the attachments on the fullerene cage. In addition, a charge residing on the cage may also be accountable for the increased water solubility. For example, gel electrophoresis experiments show that Gd 3 N@C 80 /NH 2 (CH 2 CH 2 O) 3 CH 3  adduct (“Hydrochalarone-3”) bears a negative charge ( FIG. 11 ). In one embodiment, the endohedral metallofullerene compound may have one or more negative charges and counter cation(s). The counter cation may be any positively charged species present in the medium. Specific examples of the cations may include, but are not limited to, H +  and protonated amine reagent used in the reaction, e.g., protonated MEG. 
     Specifically,  FIG. 11  shows gel electrophoresis results of C 70 -monoethyleneglycol amine (C 70 -MEG) (left), Hydrochalarone-1 (Gd 3 N@C 80 -MEG) (middle) and Hydrochalarone-3 (Gd 3 N@C 80 -TEG) (right) moving toward cathode (bottom). The gel electrophoresis was conducted according to Novex® Tris-Glycine polyacrylamide gel chemistry (Novex® 10% Tris-Glycine Gel 1.0 mm, 10 well). Novex® Tris-Glycine polyacrylamide gel chemistry is based on the Laemmli system (1) with minor modifications for maximum performance in the pre-cast format. These gels do not contain SDS and can therefore be used to accurately separate both native and denatured proteins. Novex® Tris-Glycine Gels are made with high-purity, strictly quality-controlled reagents: Tris base, HCl, acrylamide, bisacrylamide, TEMED, APS, and highly purified water. They do not contain SDS. Tris-Glycine Running Buffer without SDS is used as buffer. The testing sample is prepared by combining 25 uL of each sample with 5 uL of glycerol per well. The current is loaded @ 50 Volts (20 minutes) and then increased to 120 Volts (30 minutes) once loaded. 
     The present invention is further illustrated by the following specific examples but is not limited hereto. 
     EXAMPLES 
     Unless specified, all the commercially available materials were used herein without further purification. All the measurements including weight and temperature were uncorrected. 
     Example 1 
     Reaction of an Empty Fullerene with NH 2 CH 2 CH 2 OCH 3    
     C 60  (15 mg) was dissolved in xylene (10 mL) by means of sonication for 30 seconds. To this solution were added NH 2 CH 2 CH 2 OCH 3  (300 mg) and butanone peroxide (750 mg of a 31% commercially available solution in 2,2,4-trimethyl-1,3-pentanediol diisobutyrate). The mixture was shaken at ambient temperature for 1 hour. During the course of the reaction, the solution turned from purple to yellow and a brown precipitate formed. The solution was decanted leaving the brown oil. The oil was washed with toluene (5 mL×2) and ether (5 mL×2), then dissolved in water (10 mL) and filtered through a 100 nm filter, yielding the product in solution. The resulting solution may be further purified by dialysis using 1000 MWCO tubing. Alternatively, the product may be precipitated with isopropanol from a methanol solution to yield a brown powder. 
     The same reaction was also conducted by substituting C 70  for C 60 . IR spectra of C 70 -monoethyleneglycol amine (C 70 -MEG) before addition of D 2 O and after heating in D 2 O ( FIGS. 12(   a ) and ( b ), respectively) show lack of H/D exchange with heating treatment. 
     Further,  1 H NMR spectra of MEG ( FIG. 13(   a )) and undialyzed C 70 -MEG ( FIG. 13  ( b )) show the presence of MEG-H +  cation with C 70 -MEG in the reaction mixture. 
     Example 2 
     Reaction of an Empty Fullerene with Decyl Amine NH 2 (CH 2 ) 11 CH 3    
     To a solution of C 60  (36 mg) in xylene (20 mL) were added NH 2 (CH 2 ) 11 CH 3  (2.1 g) and butanone peroxide (4.2 g of a 31% commercially available solution in 2,2,4-trimethyl-1,3-pentanediol diisobutyrate). The reaction was observed by a rapid color change to yellow-brown. The crude product was purified by silica chromatography, using diethyl ether as eluant. The obtained product was an ether-soluble dark brown oil (see  FIG. 18(   a )). 
     Example 3 
     Reaction of an Endohedral Metallofullerene with NH 2 (CH 2 CH 2 O) 3 CH 3    
     Gd 3 N@C g 0 (10 mg), NH 2 (CH 2 CH 2 O) 3 CH 3  (250 mg) and butanone peroxide (1500 mg of a 31% commercially available solution in 2,2,4-trimethyl-1,3-pentanediol diisobutyrate) were mixed with xylene (10 mL). The resulting mixture was agitated at 75° C. for 1 to 2 hours. At this time, the reaction mixture became nearly colorless but with precipitate. The colorless solvent was decanted and the remaining oil was washed with toluene and ether. The oil was then dissolved in water. The aqueous extract was passed through a Sephadex column twice (eluting at the solvent front) and/or dialyzed with 1000 MWCO tubing. Rotavapping the aqueous solution can be difficult; however, warming under a steady nitrogen stream yielded a black powdery product (“Hydrochalarone-3”). The relaxivity of the product was measured to be 130 mM −1 s −1 , and the solubility was greater than 50 mg/mL in water. 
     Elemental analysis for Hydrochalarone-3 indicates a product with 12 pendent groups having the formula C 164 H 192 O 48 N 13 Gd 3  ( FIG. 14 ). It is noted that in elemental analysis of TRIMETASPHERE®s, incomplete combustion of the cage is a persistent problem. For example, samples of pure, unfunctionalized materials, such as Sc 3 N@C 80 , routinely result in low carbon analysis. This is undoubtedly due to the high stability of these materials, as reflected in the TGA. 
       FIGS. 15(   a ) and  15 ( b ) are IR spectra of C 70 -MEG and Hydrochalarone-3 (low peroxide preparation), which show the peak at about 1452 cm −1  associated with hydroxylamines. 
     Further, Hydrochalarone-1 and Hydrochalarone-6 can be prepared in the same manner.  FIGS. 16(   a ) and  16 ( b ) are IR spectra of Hydrochalarone-1 and Hydrochalarone-3.  FIG. 17  is UV/Vis of Hydrochalarone-6 in water.  FIGS. 18(   a ) and  18 ( b ) are IR spectra of GdTMS-decylamine and Hydrochalarone-1 showing C—O stretch (at about 1100 cm −1 ) in a non-ether amine product. It is noted that GdTMS-decylamine is ether soluble while Hydrochalarone-1 is water soluble. 
       FIGS. 19(   a ) and ( b ) are  1 H NMR spectra of MEG-TFA in D 2 O and YTMS-MEG pre-dialysis showing the presence of MEG-H +  with YTMS-MEG in the reaction mixture.  FIG. 20  is a  1 H NMR spectrum of post-dialysis Y Hydrochalarone-1 in D 2 O wherein MEG-H P  has been removed by dialysis. 
       FIGS. 21(   a ) and ( b ) are TGA of Hydrochalarone-6 and unfunctionalized Gd 3 N@C 80 , which show weight loss vs. temperature.  FIG. 21(   b ) shows that the unfunctionalized TMS starts to decompose around 200° C. and is completely decomposed at 400° C., while the Hydrochalarone derivative cage doesn&#39;t decompose until around 600° C. The rapid weight loss at around 600° C. is believed to due to the decomposition of the fullerene cage, based on the mass before the weight loss relative to the final mass, which is Gd 2 O 3 . 
     Example 4 
     Reaction of Hydrochalarone-3 in Water 
     Hydrochalarone-3 (2 mg) was dissolved in water (1 mL). To this solution were added NH 2 (CH 2 CH 2 O) 3 CH 3  (41 mg) and H 2 O 2  (23 mg). The mixture was allowed to react for 20 hours and the color thereof faded. Measurement of water proton relaxation parameter T 1  (Maran Ultra relaxometer) showed a change from 256 ms to 395 ms, indicating an increase in the number of substitution on the carbon cage. 
     Example 5 
     Solid Phase Reaction with Fullerenes 
     Silica modified to have 3-aminopropyl groups appended to its surface was suspended in xylene and treated with butanone peroxide. The solid was then filtered and washed with xylene. With free peroxide thus removed, the solid was added to a solution containing a mixture of fullerenes that included C 60 , C 70 , and metalloendohedral fullerenes of the general formula M 3 N@C 80 . Within one hour, the C 60  and C 70  were removed from solution. This experiment demonstrates that the reaction takes place using a reactive intermediate generated by reaction of the amine and peroxide rather than direct reaction of the amine with the fullerene. 
     While various embodiments have been described with reference to specific embodiments, variations and modifications may be made without departing from the spirit and the scope of the invention. Such variations and modifications are to be considered within the purview and scope of the invention as defined by the appended claims. 
     All of the above-mentioned references are herein incorporated by reference in their entirety to the same extent as if each individual reference was specifically and individually indicated to be incorporated herein by reference in its entirety.