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1.
A semiempirical (AM1) calculation on the structures and stabilities of isomers of the fullerene derivatives C 60O and C 70O is carried out. The ozonolysis reaction mechanism and the thermodynamics of the compounds are studied. The two isomers of C 60O (56 bond and 66 bond) formed by an oxygen atom bridging across a C-C bond have an epoxide-like or an annulene-like structure. According to the ozonolysis reaction mechanism and kinetic factor analysis, the possible products of this ozonolysis reaction are C 60O with oxygen bridging over the 66 bond ( C2v) as an epoxide-like isomer and that with oxygen bridging over the 56 bond ( Cs) as an annulene-like isomer. Further, the sixteen isomers of C 70O (both epoxide-like and annulene-like structures) have been studied with respect to the same reaction mechanism. The most possible product in this ozonolysis reaction contains oxygen bridging across in the upper part (66 bond in C 70O-2 or C 70O-4) as an epoxide-like structure. The other possible product is C 70O-8 (annulene-like structure), in which oxygen bridges across an broken equatorial CC bond in C 70 ( D5h). The vibrational frequency analysis and the electronic structure of the selected C 60O and C 70O isomers are generated for experimental characterisation. The experimental results indicate that C 60O and C 70O may decompose into the odd number fullerenes C 59 and C 69. We therefore studied the structures of C 59 and C 69 also. 相似文献
2.
用INDO系列方法对C 60O 3的可能构型进行研究,结果表明:环氧结构邻近的6-6键易发生进一步的加成反应.其中3个氧原子加在同一个六元环的6-6边上,形成环氧结构最稳定的C 3v构型,第3个氧原子加在2个环氧结构相邻的六元环的6-6边上的C 2、C s构型也相当稳定,C 2、C s构型的部分 13C NMR谱与实验吻合.C 60O 3可能有较好的反应活性,其电子光谱属于理论预测. 相似文献
3.
Effect of solvent polarity on the aggregation behaviour of C 70 has been investigated in several mixed solvents using optical absorption, fluorescence, dynamic light scattering and scanning electron microscopic measurements and compared with those observed for the other fullerene analogue, C 60. It is seen that similar to C 60, aggregation of C 70 also requires the solvent polarity to exceed some critical value. In terms of solvent dielectric constant the critical solvent polarity, required for C 70 aggregation is found to be in the range of 27–31, which is much higher than that required for C 60 aggregation (12–14). The large difference in the critical solvent polarity required for C 60 and C 70 aggregation has been rationalized on the basis of the molecular shapes and the polarizabilities of two fullerene molecules. 相似文献
4.
Both ab initio 6-31G, 3-21G and STO-3G basis sets and semiempirical PM3 and AM1 molecular orbital calculations are carried out on the C 24N 4 molecule of the Td symmetry group. Results on the fully optimized structure which constrained Td symmetry, molecular orbitals and vibrational frequency were obtained by both ab initio and semiempirical methods. The binding energy and various thermodynamic properties were also calculated via the PM3 and AM1 semiempirical methods. All the evidence of this work proves that the C 24N 4 molecule is stable and that its four six-membered rings with a remarkable delocalized C…C bond are similar to the related rings in the C 60 buckminsterfullerene structure. 相似文献
5.
The observation of the surface-enhanced vibrational Raman spectra of vapor-deposited C 60 and C 70 on rough silver films is reported. Both near-monolayer and multilayer films of pure C 60 and of C 60/C 70 mixtures are studied. The films are obtained by evaporating fullerene samples at temperatures of 683–875 K in ultra-high vacuum. Mixed fullerene samples were greatly enriched in C 70 by making use of the slightly different vapor pressures of the two major components at the low end of this temperature range. The spectra contain all the lines of the normal Raman spectra as well as several additional lines caused by a reduction in the stringency of the normal Raman selection rules. These results demonstrate the potential of this technique for detecting small quantities of fullerenes and obtaining their vibrational spectra. 相似文献
6.
IR spectroscopy was coupled with the matrix isolation technique to study the molecular complex formed between C 3O 2 and HCl and its photodissociation. The vibrational frequencies of the complex were compared with those of HCl and C 3O 2 monomers. For C 3O 2, a bent structure was characterized in the solid environment. The vibrational frequencies were calculated in the 4000–400 cm−1 range using an ab initio method at the MP2/6-31G** level for the most stable complex; these frequencies describe the hydrogen interaction with the central carbon atom of C3O2 (T complex). The measured shifts between the vibrational mode frequencies of the complex and monomers were in good agreement with the calculated values. Broad-band UV irradiation ( > 230 nm) of the T complex leads preferentially to ketene chloride and carbon monoxide. Ketene chloride formation can be explained by the reaction between HCl and the carbene C2O, which results from photo-dissociation at the C=CO bond of C3O2. 相似文献
7.
通过将C_9H_(10)O_2-0.5ZnCl_2双酸型低共熔溶剂固载到Al_2O_3上制备了C_9H_(10)O_2-0.5ZnCl_2/Al_2O_3催化剂。该催化剂采用XRD、FT-IR、SEM、EDS、N_2吸附-脱附技术进行了分析。以C_9H_(10)O_2-0.5ZnCl_2/Al_2O_3为催化剂,过氧化氢为氧化剂研究模拟油中芳香族硫化物的脱除性能。考察反应参数如温度、催化剂加入量、O/S物质的量比、硫化物类型等对催化剂脱硫活性的影响。实验结果表明,在模拟油为5 mL、催化剂量为0.2 g、O/S比为8、反应温度为60℃、反应时间为180 min的条件下,模拟油中二苯并噻吩(DBT)脱硫率为99.2%。此外,在模拟油氧化脱硫中催化剂循环使用六次,其氧化脱硫活性略有降低。研究了C_9H_(10)O_2-0.5ZnCl_2/Al_2O_3催化氧化脱硫的反应机理。 相似文献
8.
Research into the controlled formation of nano-structured cluster-based layers on various types of supporting substrates occupies a very prominent place in both the experimental surface physics and in the newly emerging field of computational condensed matter physics, where such processes are modeled via computer-based numerical simulations at the atomic and molecular levels. One area of deep interest is the growth of nano-scale formations of C 60 fullerene on metallic and semi-conducting surfaces, which have potential applications in quantum-scale device fabrication. We review the field of C 60 adsorption on a variety of substrates, and then report on the highly accurate numerical simulations that we have performed to model the adsorption of this molecule on the Si and graphite substrates. We also report on the results of our computations of the scanning tunneling microscopy (STM)-like images of a C 60 molecule adsorbed on a graphite surface to show that no tip-induced states were responsible for the presence of extra features purported to have been observed in an experiment on this system. 相似文献
9.
Deposition of ammonia molecules in fullerene has been investigated theoretically by performing semi-empirical molecular orbital calculation at PM3 level within RHF formalism. C 60 cluster has been doped endohedrally by ammonia molecules. Structural and electronic properties of the systems considered have been studied. It has been found that C 60 cluster can store at most six ammonia molecules. The ammoniacal endofullerenes, (NH 3) n@C 60, have been found stable but endothermic. 相似文献
10.
C 60 is the most important fullerene cage and glycine is the simplest representative of a backbone unit of a protein. In this paper, the structures and the energies of glycine–C 60 complexes were calculated at the B3LYP/6-31G(d) level DFT. It was found that the binding of glycine to C 60 generated a slightly unstable complex via its amino nitrogen, a moderately unstable complex via its hydroxyl oxygen, and a very unstable complex via its carbonyl oxygen. This indicates that fullerene cages might be unable to form stable bindings to proteins via their amino nitrogen, hydroxyl oxygen and carbonyl oxygen active sites. 相似文献
11.
The equilibrium structures and relative stabilities of BN-doped fullerenes C 70−2x(BN) x ( x=1–3) have been studied at the AM1 and MNDO level. The most stable isomers of C 70−2x(BN) x have been found out and their electronic properties have been predicted. The calculation results show that the BN substituted fullerenes C 70−2x(BN) x have considerable stabilities, though they are less stable than their all carbon analog. For C 68BN, the isomers whose BN is located in the most chemically active bonds of C 70 (namely B and A) are among the most stable species, of which B is predicted to be the ground state. The stabilities of C 68BN decrease and the dipole moments increase with increasing the distance between the heteroatoms. For C 66(BN) 2, the lowest energy species is the isomer in which the B–N–B–N bond is formed; For C 64(BN) 3, the most stable species should have three BN units located in the same hexagon to form B–N–B–N–B–N ring. The ionization potentials and the affinity energies of the most stable species of BN-doped C 70 are almost the same as those of C 70 because of the isoelectronic relationship. The ionization potentials and affinity energies depend on the relative position of the heteroatoms in C 68BN, the chemical reactivities of the isomers whose heteroatoms are well separated should differ significantly from their all carbon analog. 相似文献
12.
C6 0 具有 30个等同的可参与化学反应的活泼双键 ,制备并表征富勒烯多加成产物是富勒烯化学中最前沿的课题之一 .Hirsch等[15 ]通过研究C6 0 亚甲基加成反应 ,提出了双加成物立体选择性的一般规律 .我们在C6 0 氧加成方面做了类似的研究工作[6 8].本文选取几类富勒烯环双加成衍生物即富勒烯氧化产物C6 0 O2 [6 ]( 1 )、富勒烯含氮衍生物C6 0 (NH) 2 [5 ]( 2 )、富勒烯含吡咯环衍生物C6 0 (CH2 NHCH2 ) 2 [9]( 3)和富勒醇前体C6 0 (SO4) 2 [10 ]( 4)作为模型分子进行理论研究 ,以探寻富勒烯多加成反应的一般性规律 .… 相似文献
13.
用AM1、PM3及INDO系列方法研究了C 70O 2可能异构体的结构和稳定性.在C 70O稳定构型的基础上,考察了C 70O 2的45种异构体.结果表明,两个O原子加在碳球极端处同一个六元环内不等价的6/6键上形成环氧结构的构型最稳定.在优化构型的基础上,进行电子光谱计算,并与C 70和C 70O进行了比较. 相似文献
14.
We present a theoretical study on the two-photon absorption (TPA) properties of C 60. On the basis of the equilibrium geometry optimized by B3LYP/6-31G method, we employ the ZINDO method combined SOS formula to investigate the second hyperpolarizability and TPA cross section of C 60. The calculated result of the real part of the second hyperpolarizability of C 60 is in good agreement with the previous calculation and the experimental observation. In the 400–1000 nm range of TPA wavelength, we calculated TPA cross sections corresponding to all two photon allowed states. As a result, we find that there is only a TPA cross section maximum—995.7×10 −50 cm 4 s/photon at 518 nm. Another interesting phenomenon is that C 60 possesses the distinct TPA process in contrast to other conjugated molecules in terms of three-state approximation. This paper provides a theoretical basis of further studying TPA properties of C 60. 相似文献
15.
The stabilities of different isomers of C 60Br n have been calculated for n = 2 to 12. A general stereochemical pattern which emerges is the tendency to form strings created by the edge sharing of C 6Br 2 hexagonal faces. Stable structures are formed if these strings form loops, thereby eliminating string ends, which may involve the creation of C 6Br 3 hexagonal faces. A particularly stable structure is formed at C 60Br 6 in which the loop forms a C 10Br 6 fragment with a pentagonal pyramidal arrangement of six bromine atoms. Two isomers of C 60Br 12 are also particularly stable. One isomer contains two of these Br 6 pentagonal pyramids on opposite sides of the molecule, and the other isomer contains a single large loop wrapped around the middle of the molecule. 相似文献
16.
A molecular complex of fullerene C 60 with triptycene, TPC·C 60 is obtained. The complex has a three-dimensional packing of C 60 molecules. According to the IR spectra, the freezing of free rotation of C 60 molecules in the complex is maintained up to 360 K. The XP-spectra of TPC·C 60 show the suppression of π–π * transitions of TPC phenylene rings. The separation of C 60 molecules by TPC ones in TPC·C 60 results in low intensity of the C 60 transitions in the 420–500 nm range in an optical spectrum. This absorption is assumed as that attributed to intermolecular transitions between adjacent C 60 molecules. 相似文献
17.
From C 72 to C 78, the top 20 low-energy isomers screened out from all isomers of each fullerene are optimized and computed by tight-binding Monte Carlo (TBMC), semi-empirical PM3, and ab initio B3LYP/6-31G*//HF/3-21G methods. The comparison results show that the TBMC method can efficiently optimize the structures and correctly predicate the low energy isomers. The relative energies computed by TBMC are in good agreement with the high-lever B3LYP calculation results. Our TBMC and B3LYP results show that the most energetically favorable structure of C 72 is not an isomer satisfying the isolated pentagon rule (IPR), which is different with the result by PM3. The symmetry of the most stable IPR isomer tends to low as the fullerene becomes large and several non-isolated-pentagon structures are found to have low symmetries and low energies close to the most stable isomer. 相似文献
18.
Microwave-assisted extraction (MAE) was examined as an alternative to the traditional Soxhlet method of extracting C 60 and C 70 from fullerene soot. MAE of 0.20 g of fullerene soot with 95:5 toluene–acetonitrile yielded greater than 7.8 mg of C 60 and greater than 0.54 mg of C 70 in 4 min with no further increase in yield after 30 min of irradiation. By comparison, exhaustive Soxhlet extraction of the same size sample with the same solvent yielded 7.1 mg of C 60 and 0.58 mg of C 70 in 340 min. Reextraction by MAE of soot initially extracted by Soxhlet increased the yield of Soxhlet alone. Although MAE was limited to less than 0.5-g sample per extraction vessel, multiple samples were extracted with minimal increased extraction time and no reduction in the amount of material recovered. 相似文献
19.
采用溶胶凝胶法和浸渍法制备了负载于蜂窝陶瓷上的Co/Fe/Al 2O 3/cordierite催化剂,在陶瓷管流动反应器上对其催化C 3H 6选择性还原NO的性能进行了测试。结果表明,该催化剂表现出最优脱硝性能,在模拟烟气条件下,当反应温度为550 ℃时可实现97%的脱硝效率。Co的引入可显著增强Fe/Al 2O 3/cordierite催化剂抗SO 2和H 2O的能力。在模拟烟气中同时引入0.02% SO 2和3% H 2O后,1.5Co/Fe/Al 2O 3/cordierite的脱硝性能受影响甚微,当反应温度高于500 ℃时1.5Co/Fe/Al 2O 3/cordierite催化C 3H 6还原NO的效率均可达到90%以上;相比之下,未经Co修饰的催化剂Fe/Al 2O 3/cordierite脱硝性能受到了严重的抑制,在整个反应温度区间(200-700 ℃)内,其催化C 3H 6还原NO的效率最高不足50%。XRD和SEM表征结果表明,经过适量的Co修饰后的1.5Co/Fe/Al 2O 3/cordierite表面变得更疏松,且形成了以钴铁和钴铝双金属氧化物为主要成分的球状晶粒。H 2-TPR结果表明,相比于Fe/Al 2O 3/cordierite,1.5Co/Fe/Al 2O 3/cordierite有更好的低温还原性能。Py-FTIR结果表明,Co的引入可使催化剂表面的Lewis酸明显增加,且生成了Brønsted酸。N 2吸附-脱附表征结果表明,Co可增大催化剂的比表面积。 相似文献
20.
We study here the reactions between C 60 and planar C 5H 5+ cations that lead to the formation of [C 60C 5H 5] + adduct cations in the chemical ionization source of the mass spectrometer. The structures, stabilities and charge locations of some possible isomers of [C 60C 5H 5] +: σ-adduct, π-complex, [1,4]- and [l,2]-addition cations, are studied by AM1 semiempirical molecular orbital calculations. We find that the most stable is the σ-addition cation. Another interesting and stable structure is the π-complex cation which is bonded by the electrostatic interaction at the inter-ring distance of 1.589 Å with the C5v symmetry. The C 5H 5+ cyclopentadienium cation seems to be an “inverted umbrella” sitting on a five-membered ring of the C 60 cage. 相似文献
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