Synthesis and characterization of tetrakis-silylated C60 isomers

A photochemical reaction of C(60) with disilane in a 2:3 ratio affords the isomer mixture of the tetrakis-adduct of C(60)((t)BuPh(2)Si)(4) as the major product. The use of a three-stage HPLC separation system isolated three of their isomers. Their structural assignments were based on FAB mass, UV-vis, NMR, and cyclic voltammetry (CV) measurements. The CV analysis showed that the terakis-adduct has lower oxidation and higher reduction potentials than the bis-adduct C(60)((t)BuPh(2)Si)(2) and the parent C(60).     

Tube and cage C(60)H(60): a comparison with C(60)F(60)

Tube C(60)H(60) (5) with fused five-membered rings is more stable than the cage isomer (1) with isolated five-membered rings. Introduction of endo C-H bonds into structure 5 results in further stabilization, but the most stable tube structure with four endo C-H bonds (7) is higher in energy than the most stable cage structure with ten endo C-H bonds (3) by 74.2 kcal/mol. A comprehensive comparison of C(60)H(60) with C(60)F(60) has been made.     

New isomers of trifluoromethylated fullerene: C60(CF3)12 and C60(CF3)14

HPLC separation of the products of high-temperature reaction of a sublimed mixture of C₆₀–C₇₀ (10: 1) with CF₃I in a sealed ampoule allowed isolation and determination of molecular structures (X-ray crystallography and ¹⁹F NMR) of two new isomers of C₆₀(CF₃)₁₂ and one isomer of C₆₀(CF₃)₁₄. These isomers are characterized by low relative formation energies, which suggests that the trifluoromethylation process is basically under the thermodynamic control.     

Poly(trifluoromethyl)fullerene radical anions. An ESR/Vis-NIR Spectroelectrochemical Study of C60F2,4 and C60(CF3)2,10

Cyclic voltammograms are reported for C(60)(CF(3))(n) derivatives for the first time. The compounds studied were 1,9-C(60)(CF(3))(2) and 3 isomers of C(60)(CF(3))(10), including the structurally characterized derivative 1,3,7,10,14,17,23,28,31,40-C(60)(CF(3))(10) (C(60)(CF(3))(10)-3). The compound 1,9-C(60)(CF(3))(2) exhibited 3 reversible reductions; C(60)(CF(3))(10)-3 exhibited 2 reversible reductions; the other 2 isomers of C(60)(CF(3))(10) each exhibited 1 reversible reduction. ESR and near-IR spectroelectrochemical experiments were performed to characterize some of the C(60)(CF(3))(n)(-) and C(60)(CF(3))(n)(2-) species generated by cyclic voltammetry. The ESR spectrum of the C(60)(CF(3))(10)-3(-) radical anion consisted of an envelope of 25 lines centered at g = 2.0032 (the apparent a value is ca. 0.5 G), evidence of coupling between the unpaired electron and a significant number of the CF(3) fluorine atoms. The most significant finding is that this radical anion has a half-life in solution at 25 degrees C of about 7 min.     

Isolation of individual capsaicinoids from a mixture and their characterization by (13)C NMR spectrometry

Individual compounds were isolated from a laboratory mixture of capsaicinoids by a multi-stage approach. First, the capsaicinoids were fractionated into capsaicins and non-capsaicins by argentation solid phase extraction (SPE) on a silver-charged propyl sulfonate resin. Second, compounds in each fraction were isolated by semi-preparative liquid chromatography on a C₃₀ phase in aqueous methanol. Third, the individual components of the original mixture were concentrated by reversed phased (C₁₈) SPE. The structure of each purified compound was confirmed by ¹³C NMR spectrometry and spectral comparison to known standards, purchased or synthesized locally. The chemical shifts of 15 capsaicinoid standards were measured on a 600 MHz instrument, and their assignments to particular carbons were made by reference to Distortionless Enhancement by Polarization Transfer (DEPT) NMR experiments and NMR spectral prediction software.     

Synthesis of water-soluble cystine C60 derivative with catalyst and its active oxygen radical scavenging ability

A novel water-soluble cystine C_(60)derivative was synthesized in the presence of the catalyst,tetrabutylammonium hydroxide (TBAH).The product was characterized by FT-IR,UV,~1H NMR,~(13)C NMR,MS and elemental analysis.Furthermore,the scavenging ability to superoxygen anion radical O_2~(·-)and hydroxyl radical ~·OH was studied by chemiluminescence.It was found that cystine C_(60)derivative showed an excellent efficiency in eliminating superoxygen anion radical and hydroxyl radical.The 50% inhibition concentration(IC_(50))for superoxygen anion radical and hydroxyl radical were 0.167 and 0.008 mg/mL,respectively.     

The Interaction of C60, C70, and C60(CN)2 radical anions with cobalt(II) tetraphenylporphyrin in solid multicomponent complexes

A method for the synthesis of the multicomponent ionic complexes: [Cr(I)(C(6)H(6))(2) (.+)][Co(II)(tpp)(fullerene)(-)].C(6)H(4)Cl(2), comprising bis(benzene)chromium (Cr(C(6)H(6))(2)), cobalt(II) tetraphenylporphyrin (Co(II)(tpp)), fullerenes (C(60), C(60)(CN)(2), and C(70)), and o-dichlorobenzene (C(6)H(4)Cl(2)) has been developed. The monoanionic state of the fullerenes has been proved by optical absorption spectra in the UV/vis/NIR and IR ranges. The crystal structures of the ionic [[Cr(I)(C(6)H(6))(2)](.+)](1.7)[[Co(II)(tpp)(C(60))](2)](1.7-). 3.3 C(6)H(4)Cl(2) and [[Cr(I)(C(6)H(6))(2)] (.+)](2)[Co(II)(tpp)[C(60)(CN)(2)]](-)[C(60)(CN)(2) (.-)]).3 C(6)H(4)Cl(2) are presented. The essentially shortened Co.C(fullerene) bond lengths of 2.28-2.32 A in these complexes indicate the formation of sigma-bonded [Co(II)(tpp)][fullerene](-) anions, which are diamagnetic. All the ionic complexes are semiconductors with room temperature conductivity of 2 x 10(-3)-4 x 10(-6) S cm(-1), and their magnetic susceptibilities show Curie-Weiss behavior. The neutral complexes of Co(II)(tpp) with C(60), C(60)(CN)(2), C(70), and Cr(0)(C(6)H(6))(2), as well as the crystal structures of [Co(II)(tpp)](C(60)).2.5 C(6)H(4)Cl(2), [Co(II)(tpp)](C(70)). 1.3 CHCl(3).0.2 C(6)H(6), and [Cr(0)(C(6)H(6))(2)][Co(II)(tpp)] are discussed. In contrast to the ionic complexes, the neutral ones have essentially longer Co.C(fullerene) bond lengths of 2.69-2.75 A.     

Isolation and characterization of a neutral imino-semiquinone radical

The neutral imino-semiquinone, 4,6-di-tert-butyl-2-tert-butylimino-semiquinone (isqH.), can be prepared by a conproportionation of the parent aminophenol and iminoquinone compounds. The neutral radical species has been characterized in the solid state by X-ray diffraction and in solution by EPR and UV-vis absorption spectroscopy. The stability of the open-shell radical is derived from the basicity of the tert-butylimino group and the intramolecular hydrogen bond.     

Stability of (C60)2 and epoxide dimers, (C60)2ON, and their anions

The PM3, AM1, and MINDO3 semiemperical methods are used to calculate the the energy difference between C60ON and C60ON- and the bond dissociation energy necessary to cleave neutral and negatively charged (C60)2 dimers and epoxide dimers, (C60)2ON, to their respective monomers C60, and C60ON/2. The results show that the anions of the dimers are significantly more stable than neutral dimers. This result may explain the higher thermal stability of the observed ferromagnetic phase in photolyzed C60. which has been attributed to epoxide dimers and oligomers. It also provides an explanation for the origin of unpaired electron spin necessary for ferromagnetism.     

Novel synthesis and characterization of five isomers of (C(70))(2) fullerene dimers.

The synthesis and characterization of dimers and polymers, wherein two or more cages are linked, represent an important frontier in the chemistry of fullerene derivatives. A simple and novel method that requires no special apparatus has been developed for the dimerization of [70]fullerene to (C70)2. Upon grinding [70]fullerene in a mortar and pestle in the presence of K2CO3, five structural isomers of (C70)2 have been produced. These isomers are separated from one another via high performance liquid chromatography and are characterized by 13C NMR, UV-vis-NIR absorption and mass spectroscopy.     

Synthesis of water-soluble C_(60) derivatives and their scavenging free radical activity

Four piperazine-appended [60] fuilerenes (1a-1d) were synthesized and characterized. Their activities of scavenging radical were studied via UV-Vis and EPR. The results indicate that light irradiation is of advantage to increase the activity of scavenging radical.     

Isolation and characterization of a carbene derivative of La@C82

The photochemical reaction of La@C82 with 2-adamantane-2,3-[3H]-diazirine affords adduct 2, La@C82(Ad), in a quantitative and highly selective manner. The structure of compound 2 is confirmed by ESR, MS, and UV-vis-NIR spectroscopies, and the first X-ray crystallographic characterization of an endohedral monometallofullerene derivative is reported.     

Isolation and characterization of unsymmetrical C(60)Me(5)O(3)H, a cage-opened bisepoxide ketone: tautomerism involving a fullerene cage bond

Bisepoxide ketone C(60)Me(5)O(3)H, possessing a nine-membered hole in the cage, has been isolated from the reaction of C(60)Cl(6) with methyllithium followed by hydrolysis. It is a tautomer of the recently isolated bisepoxide fullerenol, this tautomerism being the first example involving a cage C-C bond, and may be driven by cage strain. Like the fullerenol, the ketone gives a high C(58)(+) fragmentation ion intensity during EI mass spectrometry.     

Ab initio Hartree–Fock–Slater calculation of Tetrathiafulvalene (TTF) and the TTF1+ and TTF2+ ions

The electronic structures of TTF, TTF¹⁺, and TTF²⁺ are described by means of an ab initio Hartree–Fock–Slater procedure with a double-zeta STO basis. Electronic and photoemission spectra, bonding, and charge distributions are discussed and compared to experiments and previous calculations.     

A liquid crystalline supramolecular complex of C60 with a cyclotriveratrylene derivative

Cyclotriveratrylene (CTV) derivatives substituted with 9 (1) or 18 (2) long alkyl chains have been prepared. Whereas no liquid crystalline behavior has been observed for 1, the CTV derivative 2 has mesomorphic properties. Indeed, at room temperature compound 2 exhibits a nematic phase characterized by cybotactic groups with a local lamello-columnar order. Both CTV derivatives 1 and 2 are able to form supramolecular complexes with C60 in the solid state. In both cases, the 2:1 host-guest species have been obtained as brown compounds. No liquid crystalline behavior was observed for the supramolecular complex [C60 is included in (1)2]. In contrast, observation of the brown product obtained from C60 and the CTV derivative 2 directly after preparation by polarized optical microscopy revealed a fluid birefringent phase at room temperature. When the sample is heated above 70 degrees C, the birefringence of the texture under the microscope disappears and the X-ray diffraction pattern is transformed into a pattern characteristic of a cubic phase. For the first time in thermotropic liquid crystals, the space group of this cubic phase can be assigned as I4(1)32.     

Embracing C(60) with multiarmed geodesic partners.

1,3,5,7,9-Pentakis(4-methoxyphenylthio)corannulene (3), 1,3,5,7,9-pentakis(2-naphthylthio)corannulene (4), and 1,3,6,8-tetrakis(4-methoxyphenylthio)corannulene (5b) have been synthesized by chlorination of corannulene with ICl in CH(2)Cl(2) at 25 degrees C and subsequent nucleophilic aromatic substitution with the appropriate sodium thiophenolate in DMEU at 25 degrees C. (1)H NMR titration studies demonstrate that these novel bowl-shaped hosts form 1:1 complexes with C(60) in toluene-d(8) solution with association constants of 454, 368, and 280 M(-1), respectively.     

Synthesis and characterization of difluoromethylene-homo[60]fullerene, C60(CF2)

Refluxing of the o-DCB solution of C60 with CF2ClCOONa and 18-crown-6 leads to formation of C60(CF2)n (n = 1-3); the monoadduct C60(CF2) has been found to consist of the main [6,6]- and minor [5,6]-isomers, both having an open structure.