Unexpected reactions of [60]fullerene involving tertiary amines and insight into the reaction mechanisms

Thermal reactions of [60]fullerene with amino acid ester hydrochlorides and triethylamine in o-dichlorobenzene at reflux afforded pyrrolidinofullerene derivatives containing the CH(3)CH moiety and originating from triethylamine through an unusual C-N bond cleavage. Detailed investigation of these thermal reactions resulted in the discovery of unprecedented reactions between C(60) and tertiary amines and of reactions of C(60) with tertiary amines and aldehydes, giving cyclopentafullerene derivatives with high stereoselectivity. Plausible reaction mechanisms for the product formation involving the uncommon C-N bond cleavage of tertiary amines were proposed on the basis of extensive experimental results.     

Three novel bismetallacyclopropa[60]fullerene complexes formed via intermediate monometallacyclopropa[60]fullerene diphosphine ligands

The homodinuclear bismetallacyclopropa[60]fullerene complexes (η²-C₆₀)M(μ-η¹,η¹-trans-Ph₂PCHCH PPh₂)₂M(η²-C₆₀) (1, M = Pt; 2, M = Pd) were prepared by reaction of C₆₀ with M(dba)₂ (dba = dibenzylideneacetone) and trans-1,1′-bis(diphenylphosphino)ethylene in 82% and 92% yield, whereas reaction of C₆₀ with Pd(dba)₂ and trans-dppet followed by treatment with C₆₀ and Pt₂(dba)₃ gave rise to the heterodinuclear complex (η²-C₆₀) Pd(μ-η¹,η¹-trans-Ph₂PCHCH PPh₂)₂Pt(η²-C₆₀) (3) in 65% yield. Mechanistic study showed that these reactions involve the intermediates of monometallacyclopropa[60]fullerene diphosphine ligands (η²-C₆₀)M(η¹-trans-Ph₂PCHCHPPh₂)₂ (4, M = Pt; 5, M = Pd). All the mono- and bismetallacyclopropa[60]fullerene complexes 1-5 have been fully characterized by elemental analysis and spectroscopy, as well as for 2 by X-ray crystallography.     

Gas-phase methylation of [60]fullerene

Direct methylation of [60]fullerene via a gas-phase reaction in a CH4/H2 atmosphere was performed using a modified hot filament chemical vapor deposition method. Pressures were varied from 10 to 60 mbar and the substrate was maintained at 690 degrees C. High-resolution matrix-assisted laser desorption ionization (MALDI) mass spectrometry analysis showed signals corresponding to C60H18-2n(H,CH3)n. Collision-induced dissociation experiments confirmed a maximum of 18 ligands possible to the [60]fullerene cage.     

Liquid-crystalline bisadducts of [60]fullerene

A second-generation cyanobiphenyl-based dendrimer was used as a liquid-crystalline promoter to synthesize mesomorphic bisadducts of [60]fullerene. Liquid-crystalline trans-2, trans-3, and equatorial bisadducts were obtained by condensation of the liquid-crystalline promoter, which carries a carboxylic acid function, with the corresponding bisaminofullerene derivatives. A monoadduct of fullerene was also prepared for comparative purposes. All the compounds gave rise to smectic A phases. An additional mesophase, which could not be identified, was observed for the trans-2 derivative. The supramolecular organization of the monoadduct derivative is governed by steric constraints. Indeed, for efficient space filling, adequacy between the cross-sectional areas of fullerene (approximately 100 A(2)) and of the mesogenic groups (approximately 22-25 A(2) per mesogenic group) is required. As a consequence, the monoadduct forms a bilayered smectic A phase. The supramolecular organization of the bisadducts is essentially governed by the nature and structure of the mesogenic groups and dendritic core. Therefore, the bisadducts form monolayered smectic A phases. The title compounds are promising supramolecular materials as they combine the self-organizing behavior of liquid crystals with the properties of fullerene.     

Iodo-controlled selective formation of pyrrolidino[60]fullerene and aziridino[60]fullerene from the reaction between C6) and amino acid esters

The reaction between glycine methyl ester and C60 can be effectively controlled by different iodo-reagents. Addition of DIB ((diacetoxyiodo)benzene) yields the 2,5-bismethoxycarbonyl pyrrolidino[60]fullerene under ultrasonic irradiation; whereas addition of DIB-iodine results in the N-methoxycarbonylmethyl aziridino[60]fullerene under ultrasonic irradiation. The reaction of sarcosine methyl ester with C60 is similar to that of glycine methyl ester under these two conditions. Addition of just iodine to a mixture of sarcosine methyl ester and C60 affords the tetra(amino)[60]fullerene epoxide C60(O)((Me)NCH2COOMe)4. Possible mechanisms are discussed.     

Synthesis of [60]fullerene acetals and ketals: reaction of [60]fullerene with aldehydes/ketones and alkoxides

The reaction of C(60) with propionaldehyde (butyraldehyde or phenylacetaldehyde) and MeONa-MeOH or EtONa-EtOH in anhydrous chlorobenzene in the presence of air at room temperature unexpectedly gave rare fullerene acetals 2aa-cb, while the reaction of C(60) with acetone (acetophenone, cyclohexanone, or cyclopentanone) and MeONa-MeOH or EtONa-EtOH under the same conditions afforded the uncommon fullerene ketals 4aa-db. A possible reaction mechanism for the formation of the fullerene acetals and ketals is proposed based on further experimental results.     

Cycloaddition of diazothioates to [60]fullerene

The cycloaddition of diazothioates to fullerene C₆₀ has been investigated under thermal and catalytic conditions. The reaction between C₆₀ and α-non-substituted diazothioates affords individual pyrazolino[60]fullerenes in contrast to 2-substituted diazothioates which give rise to [2+1] cycloadducts, exclusively.     

Supramolecular [60]fullerene chemistry on surfaces

This critical review documents the exceptional range of research avenues in [60]fullerene-based monolayers showing unique and spectacular physicochemical properties which prompted such materials to have potential applications in several directions, ranging from sensors and photovoltaic cells to nanostructured devices for advanced electronic applications, that have been pursued during the past decade. It illustrates how progress in covalent [60]fullerene functionalisation led to the development of spectacular surface-immobilised architectures, including dyads and triads for photoinduced electron and energy transfer, self-assembled on a wide variety of surfaces. All of these molecular assemblies and supramolecular arrays feature distinct properties as a consequence of the presence of different molecular units and their spatial arrangement. Since the properties of [60]fullerene-containing films are profoundly controlled by the deposition conditions, substrate of adsorption, and influenced by impurities or disordered surface structures, the progress of such new [60]fullerene-based materials strongly relies on the development of new versatile and broad preparative methodologies. Therefore, the systematic exploration of the most common approaches to prepare and characterise [60]fullerene-containing monolayers embedded into two- or three-dimensional networks will be reviewed in great detail together with their main limitations. Recent investigations hinting at potential technological applications addressing many important fundamental issues, such as a better understanding of interfacial electron transfer, ion transport in thin films, photovoltaic devices and the dynamics associated with monolayer self-assembly, are also highlighted.     

Amination of [60]fullerene by ammonia and by primary and secondary aliphatic amines--preparation of amino[60]fullerene peroxides

Ammonia and aliphatic amines react readily in the oxygen-rich regions of the Cs symmetric fullerene peroxides C60(O)(OOtBu)4 (1) and C60(OH)(Br)(OOtBu)4 (2 c). Michael addition-type hydroamination of the 1,4-diene moiety on the central skew-pentagon was observed when 1 was treated with ammonia or with nonbulky primary amines, while sterically demanding primary amines opened the epoxy moiety to form vicinal aminohydroxy fullerene compounds with the amino group on the central pentagon. In 2 c the bromo group was replaced under similar conditions by ammonia and primary amines. Cyclic secondary amines showed different reaction patterns, forming hydrogenation products or aminoketal-fullerenes when treated with 1 and 2 c, respectively. Single-electron transfer (SET) is the key step in all the proposed mechanisms. The compounds were characterized by their spectroscopic data, and in addition, three single-crystal X-ray structures were obtained.     

Arranging pseudorotaxanes octahedrally around [60]fullerene

The formation of both [2]- and [7]pseudorotaxanes, which are obtained by mixing of a dibenzylammonium derivative with mono- and hexakis-adducts of [60]fullerene bearing malonato-benzo[25]crown-8 rings, has been monitored in dichloromethane by both 1D and 2D (1)H NMR spectroscopies.     

Reaction of [60]fullerene with CF3COOHal affords an unusual 1,3-dioxolano-[60]fullerene

Reaction of C₆₀ with acyl hypohalogenites CF₃COOBr or CF₃COOI in the presence of water affords an orthoester-type 1,3-dioxolanofullerene in 40-50% yield. This method cannot be applied for the synthesis of 1,3-dioxolanofullerenes bearing aryl- or alkyl-groups since they undergo non-selective halogenation under the reaction conditions.     

Regioselective triphenylamine-tether-directed synthesis of [60]fullerene bis-adducts

The tether-directed regioselective synthesis of equatorial bis-adducts of [60]fullerene via the 1,3-dipolar cycloaddition reaction of azomethine ylides is reported. A mono-[60]fulleropyrrolidine adduct, derived via 1,3-dipolar cycloaddition of azomethine ylides generated in situ upon thermal condensation of triphenylamine bis-aldehyde and an α-amino acid, was isolated and further reacted to yield, exclusively and selectively, the equatorial bis-adduct, which is structurally characterized by appropriate spectroscopic means.     

亚甲基[6,6]-富勒(fullerene)[60]单羧酸的合成研究

亚甲基[6,6]-fullerene[60]单羧酸是一个具有化学反应活性的fullerene[60]衍生物,可以作它合成得到一些新的具有潜在生化应用价值的水溶性fullerene[60]衍生物。本文详细报道了常规量合成亚甲基[6,6]-fullerene[60]单羧酸的技术。     

Ferric perchlorate-mediated radical reactions of [60]fullerene

Transition-metal-salt-mediated radical reactions of fullerenes have attracted extensive attention as a new and important method for fullerene functionalization. The application of relatively cheap and easily available ferric perchlorate (Fe(ClO 4 ) 3 ) to the synthesis of [60]fullerene (C 60 ) has demonstrated remarkable advantages and afforded a series of novel fullerene derivatives. In this review we present our recent progress in this area and summarize the reactions of C 60 with malonate esters, β-keto esters, nitriles, aldehydes/ketones, and arylboronic acids in the presence of Fe(ClO 4 ) 3 to afford the C 60-fused disubstituted lactones, C 60-fused hemiketal, C 60-fused dihydrofuran, C 60-fused oxazoles, C 60-fused 1,3-dioxolanes, and fullerenyl boronic esters. The possible reaction mechanisms for the above-mentioned reactions are also described in detail.     

Organic and organometallic derivatives of dihydrogen-encapsulated [60]fullerene

Regioselective multi-addition reaction of organocopper and amine compounds onto dihydrogen-encapsulated [60]fullerene, H2@C60, produced a variety of organic and organometallic derivatives of H2@C60. The X-ray crystallographic analysis of dihydrogen-encapsulated bucky ferrocene, Fe(H2@C60Ph5)C5H5, showed the presence of the dihydrogen molecule located almost in the center but slightly away from the ferrocene moiety. The 1H NMR chemical shift values for the encapsulated molecular hydrogen indicated that these values are susceptible to the magnetic environment of the inside as well as the outside of the fullerene cage.     

Reactions of [60]fullerene with 2-azidopyrimidines

The reaction of [60]fullerene with 2-azidopyrimidines affords fullerenoimidazopyrimidines, whose electron affinity is higher than that of nonmodified C₆₀.     

Polymerization of [60]fullerene activated with butyllithium

Fullerene polymerization caused by addition of an alkylating agent was discovered. Alkylation of fullerene with primary or secondary butyllithium gave both mono- and polynuclear products (polyfullerenes). The polymerization rate of the intermediates Bu _n C₆₀Li _n (n < 6) is nearly the same as the rate of the addition of BuLi to fullerene. Molecules C₆₀ can polymerize as well; however, the rate of this reaction is much lower than the polymerization rate of the reactive intermediate species.     

Addition of diphenylphosphinoyl azide to [60]fullerene

The reaction of [60]fullerene with diphenylphosphinoyl azide in toluene or ino-dichlorobenzene in the presence of traces of water affords 2-[N-(diphenylphosphoryl)amino]-1-hydroxy[60]fullerene This reaction in THF gives a mixture of (N-diphenylphosphoryl)[60]fullerenol[1,2-b]aziridine and a product of partial hydrolysis of the bisadduct of phosphorylated azide and fullerene. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2168–2172, November, 1999.