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1.
Two solvates of fluorinated derivatives of C60 fullerene were studied by single-crystal X-ray diffraction analysis. The crystals of fluorinated fullerene solvate C60F18·C6H5Me belong to the monoclinic system with the unit cell parameters a = 11.532(2) , b = 21.501(3) , c = 16.261(2) , = 101.798(5)°. The fluorinated fullerene molecule with the approximate symmetry C 3v occupies a general position. The crystals of fluorinated fullerene solvate C60F48·2C6H3Me3 belong to the cubic system (a = 23.138(2) ). The C60F48 molecule occupies the special position with the S 6 symmetry. The experimental molecular geometry agrees with the results of quantum-chemical calculations.  相似文献   

2.
New molecular complexes of fullerene C60 · Ph4E (E = Si, Ge, and Sn) were synthesized, and their crystal structures were determined. All molecular complexes are isostructural single-phase systems. The planes of the benzene rings in the Ph4E molecules are virtually parallel to the six-membered fragments of the fullerene molecule.  相似文献   

3.
The stereoselectivity of the formation of hybrid amino acid derivatives of fullerene (AADF) C60 was studied. The energies of the model addition reactions C60 + n C2H6 ? Me n -C60-Me n (1) and C60 + n EtNC4H7Me ? Et n -C60-(NC4H7Me) n (2) (n = 1–3) were calculated by the DFT method B3LYP/6-31G*. The most stable products of reaction (1) are hexamethylated fullerene derivatives in which five Me groups are arranged in the form of a regular pentagon. Among the AADF obtained by reaction (2), 1,4-disubstituted fullerene isomers are most stable. The molecular structures of such isomers were calculated for six biologically active hybrid AADF; the solvent contact areas of these molecules were evaluated.  相似文献   

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Low-temperature orientationally ordered structures of two-dimensional C60   总被引:1,自引:0,他引:1  
Orientationally ordered structures of two-dimensional (2D) C(60) at low temperature have been investigated theoretically and experimentally. Using total energy optimization with a phenomenological potential, we find the ground state is a close packed hexagonal lattice in which all the molecules have the same orientation. Several local minima of the potential energy surface are found to be associated with other 1 x 1 lattices as well as 2 x 2 lattices. The energies of the orientational domain boundaries of the 1x1 lattices are also computed, and two kinds of which yield negative values. A majority of these theoretical findings are confirmed by our low-temperature scanning tunneling microscopy study of a 2D C(60) array supported on a self-assembled monolayer.  相似文献   

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The modeling of the molecular and electronic structures of the following mono- and biosmium complexes of fullerene C60 was performed by quantum chemical methods (MNDO/PM3 and DFT/PBE): (??2-C60)[Os(PPh3)2(CO)CNMe], (??2,??2-C60)[Os(PPh3)2(CO)(CNMe)]2, (??2-C60)[Os(PH3)2(CO)H], (??2,??2-C60)[Os(PH3)2(CO)H]2, (??2-C60)[Os(PH3)2(CO)CNMe], (??2,??2-C60)[Os(PH3)2(CO)CNMe]2, and (5-C60H5)[Os(C5H5)], (5, 5-C60H10)[Os(C5H5)]2.The osmium atoms in the first six complexes are ??2-coordinated by fullerene C60. In the last two complexes, the ??5-coordination mode is observed. The structures of the radical anions of these complexes were calculated. The energies of the frontier orbitals were evaluated. The acceptor properties of the complexes are discussed. The electron affinities were estimated in two ways: from the energy of the lowest unoccupied molecular orbital (LUMO) and as the energy difference between the neutral molecule and its radical anion.  相似文献   

9.
The electronic and vibrational structures of C60 and C70 have been calculated at the PM3 semiempirical level. C60 has a partially delocalized structure, while C70 has both a localized set and a delocalized set of MOs. As with AM1 and MNDO, PM3 predicts the heat of formation of C70 to be greater than that of C60, and that C70 is the thermodynamically more stable species. Calculation of the normal modes was accelerated over 40 times by limited use of symmetry theory.  相似文献   

10.
Two icosahedral structures, a truncated icosahedron and a truncated dodecahedron, have been examined for the C60 cluster. Optimized geometries by INDO calculations are: in the former, 1.449 Å (for pentagonal edges) and 1.397 Å; in the latter, 1.41 Å (for triangular edges) and 1.345 Å. At these geometries, HOMO-LUMO gaps are 9.23 and 8.86 eV, respectively.  相似文献   

11.
Using a pairwise additive atom-atom intermolecular potential to describe the interaction between C60 molecules, we calculated the lowest-energy structures of (C60)N clusters up to N = 15 and compared the results with predictions derived using Girifalco’s spherical potential. The cluster binding energies calculated on the basis of the former potential are in all cases significantly higher than those obtained from the latter. Moreover, the atom-atom potential predicts that small fullerene clusters have structures based on icosahedral packing, a finding which, for N = 14 and 15, contrasts with the results obtained using Girifalco’s approximation.  相似文献   

12.
111-oriented p-type Si wafer with a resistivity of 1-5 Omega cm was implanted with Fe+ and then annealed at 1100 degrees C in N2 for 60 min, followed by anodization in a solution of HF to form porous structure with beta-FeSi2 nanocrystallites. Photoluminescence (PL) spectral measurements show that a strong PL peak appears in the range of 610-670 nm. The position of the PL peak remains unchanged, but its intensity increases with the storage time in air until about three months and then saturates. C60 molecules were chemically coupled on the porous structure through a kind of silane coupling agent to form a nanocomposite. It is revealed that the stable PL peak monotonically shifts to a pinning wavelength at 570 nm. Experimental results from PL, PL excitation, Raman scattering, and x-ray diffraction measurements clearly show that the pinned PL originates from optical transition in C60-related defect states, whereas the photoexcited carriers occur in the beta-FeSi2 nanocrystallites formed during anodization. This work opens a new way to tailor nanometer environment for seeking optimal luminescent properties.  相似文献   

13.
In this paper, a new simple method is presented for the estimation of the toxicity of nitroaromatic compounds including some well-known explosives. This method can predict the 50% lethal dose concentration for rats (LD 50) as the estimation of toxicity in vivo. The prediction of LD 50 of nitroaromatics through a new general correlation is based on the number of alkyl and nitro groups per molecular weight of the nitroaromatic compound as a core function. The existence of some specific structural parameters can decrease or increase the predicted results on the basis of the core function. The predicted results of various nitroaromatic compounds afford reliable prediction of LD 50 with respect to experimental data. Prediction of toxicity for 28 nitroaromatic compounds, where the experimental data were available, and new nitroaromatic derivatives produce comparable results to those of several models of Quantitative Structure Activity Relation (QSAR).  相似文献   

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The interaction of oxygen molecules with a fullerene surface has been studied using high resolution electron energy loss spectroscopy and temperature programmed desorption. Vibrational excitation of the adsorbed oxygen is observed at 190 meV, an energy value comparable with that for molecular oxygen in the gas phase. We take this to indicate physisorption of molecular oxygen on the C(60) surface. Thermal desorption results also show that the bonding of oxygen molecules to the C(60) overlayer is comparable to that on a graphite surface. A detailed study of the energy dependence of the vibrational excitation reveals an inelastic electron resonance scattering process. The angular dependence of the resonant vibrational excitation exhibits features distinctively different from those for molecular oxygen physisorbed on the related graphite surface, at a comparable coverage. One possible reason is that the corrugated surface potential, due to the curvature of the C(60) molecules, promotes the preferential ordering of the physisorbed oxygen molecules perpendicular to the surface plane of the C(60) overlayer.  相似文献   

16.
We report classical and tight-binding molecular dynamics simulations of the C(60) fullerene and cubane molecular crystal in order to investigate the intermolecular dynamics and polymerization processes. Our results show that, for 200 and 400 K, cubane molecules remain basically fixed, presenting only thermal vibrations, while C(60) fullerenes show rotational motions. Fullerenes perform "free" rotational motions at short times (approximately < 1 ps), small amplitude hindered rotational motions (librations) at intermediate times, and rotational diffusive dynamics at long times (approximately > 10 ps). The mechanisms underlying these dynamics are presented. Random copolymerizations among cubanes and fullerenes were observed when temperature is increased, leading to the formation of a disordered structure. Changes in the radial distribution function and electronic density of states indicate the coexistence of amorphous and crystalline phases. The different conformational phases that cubanes and fullerenes undergo during the copolymerization process are discussed.  相似文献   

17.
Intermediate neglect of differential overlap (INDO ) calculations were used to study two structures of C60NH: one of C, geometry with a bridging NH across the bond between two fused six-membered rings in C60 and the other of Cs geometry with a bridging NH across the bond between a five- and a six-membered ring. We calculated the most stable isomer of C60NH to be of C, symmetry. It was found that the C isomer has a protonated aziridine structure with a bridging C? C bond length of 0.1520 nm. The electronic spectra of both isomers of C60NH were calculated. Comparisons were made with the isoelectronic molecules C60O and C60CH2, cases in which the calculated electronic spectra for the most stable isomers C60O (C) and C60CH2 (C) are in good agreement with recent experimental results. © 1995 John Wiley & Sons, Inc.  相似文献   

18.
The methodology for the prediction of aqueous solubilities of solid organic compounds, and their temperature dependence, based on the Conductor-like Screening Model for Real Solvents (COSMO-RS/COSMOtherm) procedure, is presented and evaluated. The predictive capability of the quantum chemistry based program and the applied methodology was tested on the most common solid carboxylic acids. From the temperature dependence of the solubilities, the mean apparent enthalpies of solution were derived. The results obtained for a set of 27 carboxylic acids, consisting of aromatic carboxylic acids, dicarboxylic acids, as well as hydroxycarboxylic acids, are in good agreement with the experimental solubility data and their dependence with the temperature. The mean apparent enthalpies of solution, although of the same order of magnitude of the experimentally values, seem to be systematically underestimated.  相似文献   

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20.
We report the details of our study to synthesize a new endohedral fullerene, H2@C60, in more than 100 mg quantities by closure of the 13-membered ring orifice of an open-cage fullerene using four-step organic reactions. The 13-membered ring orifice in a previously synthesized open-cage fullerene incorporating hydrogen in 100% yield was reduced to a 12-membered ring by extrusion of a sulfur atom at the rim of the orifice, and the ring was further reduced into an eight-membered ring by reductive coupling of two carbonyl groups also at the orifice. Final closure of the orifice was completed by a thermal reaction. Purification of H2@C60 was accomplished by recycle HPLC. A gradual downfield shift of the NMR signal for the encapsulated hydrogen observed upon reduction of the orifice size was interpreted based on the gauge-independent atomic orbital (GIAO) and the nucleus-independent chemical shift (NICS) calculations. The spectral as well as electrochemical examination of the properties of H2@C60 has shown that the electronic interaction between the encapsulated hydrogen and outer C60 pi-system is quite small but becomes appreciable when the outer pi-system acquires more than three extra electrons. Four kinds of exohedral derivatives of H2@C60 were synthesized. The tendency in the shift of the NMR signal of the inner hydrogen was found to be quite similar to that observed for the 3He NMR signal of the corresponding derivatives of 3He@C60.  相似文献   

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