A facile access to enantiomerically pure [60]fullerene bisadducts with the inherently chiral trans-3 addition pattern

The Bingel reaction between C(60) and an enantiopure bismalonate tether equipped with two acetonide moieties led to the synthesis and successful column chromatographic isolation of the enantiomerically pure (f,s)C and (f,s)A bisadducts with the inherently chiral trans-3 addition pattern. Acidic deprotection of the acetonide groups gave access to novel chiral fullerene compounds which combine the inherent chirality of the fullerene core with the functional glycol groups located on the tether.     

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.     

Dihydronaphthyl-based [60]fullerene bisadducts for efficient and stable polymer solar cells

Dihydronaphthyl-based [60]fullerene bisadduct derivative, NC(60)BA, was synthesized at mild temperature in high yield. NC(60)BA not only possesses a LUMO energy level 0.16 eV higher than PC(61)BM but also has amorphous nature that can overcome thermal-driven crystallization. The fabricated P3HT:NC(60)BA-based polymer solar cells exhibit superior photovoltaic performance and thermal stability compared to PC(61)BM-based devices under the same conditions.     

Regio- and stereoselective synthesis of enantiomerically pure [60]fullerene tris-adducts with an inherently chiral e,e,e addition pattern

The synthesis and flash column chromatographic separation of enantiomerically pure tris-adducts of C60 with an e,e,e-addition pattern is achieved via cyclopropanation with chiral D3-symmetrical cyclo-tris(malonate) tethers.     

Unusual addition patterns in trifluoromethylation of [60]fullerene

From pyrolytic trifluoromethylation of [60]fullerene with CF3CO2Ag at 300 degrees C we have isolated ca. sixty C60(CF3)n isomers (numbers in parentheses) as follows: n = 2(1), 4(8), 6(13), 8(21), 10(11), 12(5), 14(4), twenty-one of which have been characterised by 19F NMR. Compounds with addition levels up to n = 20 have also been identified. With increasing value of n, yields decrease and the separation of compounds of similar HPLC retention time but different addend levels becomes more difficult. Many of the 19F NMR spectra show combinations of quartets and septets (the latter tending to be more downfield) due to 'linear' addend arrays. The spectra are consistent with addition across both 6:6- and 5:6-ring junctions [double (1.2) and single (1.6) bonds, respectively], giving corresponding coupling constants for adjacent addends of ca. 14.5 and 12.0 Hz respectively, the differences being attributable to the different 1.2- and 1.6-bond lengths. The 13C NMR spectrum of C60(CF3)2 shows the CF3 groups are in either a 1.4- or 1.6-relationship; the UV-vis band appears at 442 nm. Other unsymmetrical tetra-adducts are comprised of isolated pairs of CF3 groups. The exceptionally large number of derivatives and isomers, (much greater than in any other fullerene reaction), no dominant product, and unusual addition pattern indicates that thermodynamic stability is not of primary importance in governing product formation. EI mass spectrometry of trifluoromethylfullerenes is characterised by loss of CF3 groups, the more highly addended compounds also showing fragmentation by CF2 loss, attributable to steric compression. The CF3 group shows strong IR bands at ca. 1260 and 1190 cm-1. The compounds are stable to aq. acetone, which contrasts to the behaviour of fluorofullerenes. Trifluoromethylation by the Scherer radical (C9F19.) gave addition of up to eight CF3 groups, together with hydrogen in some products. During EI mass spectrometry of some of these, loss of HF attributable to CF3 and H adjacency can occur, giving CF2-containing derivatives.     

Regioselective synthesis and properties of novel [60]fullerene bisadducts containing a dibenzocrown ether moiety

The reactions of [60]fullerene with bis-o-quinodimethane precursors 3, 4, and 5 containing a dibenzo-18-crown-6, 24-crown-8 and 30-crown-10 moiety, respectively, were investigated. Both 3 and 4 provided trans-4 bisadducts 6a and 7a, respectively, as major product, though the selectivity in the latter was lower than that in the former. As minor product, 6b (cis-2) was produced from 3, while 7c (e) as well as 7b (cis-2) were produced from 4. Precursor 5 exclusively afforded e bisadduct 8 without any other regioisomers. These bisadducts showed different ionophoric properties from one another; for instance, 6a and 7b exhibited a high complexing ability toward the K+ ion, while 6b hardly showed complexation with any alkali metal ions. The selectivity coefficients (K(Na,K)(pot)) of 6a and 7b toward K+ over Na+ ion, determined with an ion-selective electrode, were much higher than that of dibenzo-18-crown-6.     

烯醇硅醚对[60]富勒烯的亲核加成反应

在空气气氛和非极性溶剂(甲苯)中1-(4'-甲氧基苯基)-1-三甲基硅氧基乙烯与[60]富勒烯反应得到了非预计的环丙基骈[60]富勒烯衍生物(5).在无氧和极性非质子性溶剂(THF)中进行上述反应,得到了1,2-取代[60]富勒烯亲核加成产物(3)。对反应的机理作了合理的阐述。     

Regioselective synthesis and zone selective deprotection of [60]fullerene tris-adducts with an e,e,e addition pattern

D(3h)-symmetrical tripodal tris(malonate) tethers have been used for the synthesis of [60]fullerene tris-adducts with an e,e,e addition pattern bearing topologically distinct polar and equatorial addend zones that can selectively be deprotected.     

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.     

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.     

Photoactivated [3+2] addition of 6,7-seco-angustilobine B to fullerene [C60

A synthesis of a new alkaloid-fullerene conjugate (1) is reported. The reaction was carried out by photoinduced [3+2] cycloaddition of the Alstonia indole alkaloid, 6,7-seco-angustilobine B (2), to fullerene[C60] (3) under aerobic conditions. The major monoaddition photoadduct (1) was characterized unambiguously by UV, IR, MALDI-TOFMS and NMR experiments. A mechanism highlighted by sequential photoinduced electron transfer andradical recombination pathways is also proposed. No significant enhancement in inhibition against M. tuberculosis H37Rv was observed for 1 compared with its parent compounds 2 and 3.     

Probing the spatial requirements for [60]fullerene-[60]fullerene π-stacking and the syn addition of [60]fullerenes across acenes

The reaction between 2 equiv of [60]fullerene and 6,8,15,17-tetraphenylheptacene-7,16-quinone leads to both cis and trans-bis[60]fullerene adducts. This result contrasts sharply with the highly diastereoselective syn additions of [60]fullerenes across 6,13-diphenylpentacene and 6,8,15,17-tetraphenylheptacene. The importance of spatially dependent [60]fullerene-[60]fullerene π-stacking interactions in promoting a syn addition of [60]fullerenes is discussed.     

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.     

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.     

Novel addition in trifluoromethylation of [70]fullerene

Pyrolytic trifluoromethylation of [70]fullerene with CF₃CO₂Ag at 300 °C results in the addition of up to 12 CF₃ groups to the fullerene cage. Forty-six C₇₀(CF₃)_n derivatives (numbers in parentheses) were separated by two-stage high pressure liquid chromatography (HPLC) as follows: n = 2(2), 4(16), 6(9), 8(14) 10(5), some being characterised by NMR. The range of derivatives is much greater than for other [70]fullerene reactions, and as with [60]fullerene trifluoromethylation, no single derivative is dominant, indicating that kinetic stability mainly controls product formation. NMR spectra show most derivatives to be unsymmetrical, with combinations of quartets and septets (overlapping quartets) due to contiguous (‘linear’) addend arrays, having significantly different coupling constants of the ‘terminal’ quartets of between 9.1 and 17.7 Hz. These differences, together with those observed previously in trifluoromethylation of [60]fullerene are consistent with addition across both 6:6- and 5:6-ring junctions. Of the two C₇₀(CF₃)₂ isomers, one has either C_s or C₂ symmetry, the other has C₁ symmetry, whilst the C₇₀(CF₃)₄ derivatives fall into four categories: (i) symmetrical compounds (one gives only two singlets in the NMR); (ii) unsymmetrical compounds that show a ‘linear’ coupling sequence; (iii) unsymmetrical compounds having a remote pairs of adjacent groups; (iv) compounds having a coupled array of three CF₃ groups, together with a remote group suggesting sterically-driven migration. The first evaluation of differential NMR couplings across 6:6- and 5:6-bonds in a fullerene has been made using C₆₀F₆ as a model.     

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.     

Preferential separation of fullerene[84] from fullerene mixtures by encapsulation

The encapsulation of fullerenes with a cyclotriveratrylene derivative, capable to self assemble into a dimer by means of three strong 4-ureidopyrimidinone quadruple hydrogen bonds is described. The system shows preference for C84, allowing its easy enrichment directly from fullerene mixtures.     

First isolation and characterization of eight regioisomers for [60]fullerene-benzene bisadducts

[reaction: see text]. The [2 + 2] cycloaddition between [60]fullerene and benzyne generated from 4,5-dimethoxyanthranilic acid (4) afforded bisadducts 5 along with the monoadduct. All of the eight possible regioisomers were first isolated by HPLC and then characterized on the basis of MS, NMR, UV-vis, and CD spectroscopies.     

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.