C120O2的分子结构和光谱性质的理论研究

用INDO系列方法研究双笼氧化物C₁₂₀O₂分子可能异构体的结构,两个氧以桥键形式分别加成到两个碳笼上,在两个碳笼中间形成呋喃型五元环结构,有6/6连接和6/5连接两种C₂v构型.计算表明,C₁₂₀O₂两种构型中6/6连接的C₂v构型更稳定,其光谱与实验值相符.双笼氧化物C₁₂₀O₂的形成既缓解了C₆₀O环氧处的角张力,又比C₁₂₀O分子获得了更强的笼间相互作用,两个C₆₀靠两个呋喃型五元环连接在一起.两个碳笼的多位置直接键连使两碳笼距离较近,有较强的相互作用,但仍各自表现出一定的独立性.C₁₂₀O₂可发生分解生成新的化合物.     

两种C60双氰衍生物的结构、光谱和二阶非线性光学性质的理论研究

用INDO/2和INDO/SCI方法计算了C₆₀(C≡N)₂和C₆₀C(C≡N)₂基态电子结构和电子光谱,所得结果与实验值基本一致.在此基础上,用ZINDO-SOS方法计算了两个分子的二阶非线性光学系数β_ijk和β_μ,并对其结果进行了分析和讨论.结果表明,乙氰基与C₆₀相连的两种碳笼衍生物都有大的非线性光学系数,C₆₀C(C≡N)₂是有希望的非线性光学材料.     

双笼羰基化合物C120CO的理论研究

用INDO系列方法对双笼化合物C₁₂₀CO进行了理论研究,结果表明,C₁₂₀CO中O具有较大的电负性,在此位置可形成氢键.分子内电荷转移较大,非线性光学系数可能较大.C₁₂₀CO的电子光谱与C₁₂₀CH₂和C₁₂₀O的相似.     

探索碳笼分子家族:富勒烯的结构模型构建策略*

以发现C₆₀球笼结构的史实阐述结构模型的制作对探索物质结构奥秘的重要性。以科学家对富勒烯形成机制的探索佐证多角度构建结构模型的合理性,举例介绍搭建C₆₀球棍模型3种方法的操作步骤。探讨一组有结构关联性C_60+10n碳笼分子结构模型构建的思维方法,举例介绍搭建代表分子C₇₀,C₈₀球棍模型的操作步骤。探讨一组有高度对称性的富勒烯结构模型构建的思维方法,举例介绍搭建大直径、高对称富勒烯C₇₂₀球棍模型的操作步骤。结合《普通高中化学课程标准(2017年版)》和教学实践探讨结构模型构建在化学教学中的作用,为富勒烯结构模型的自主构建教学提供范例。     

聚并苯掺杂C60作锂离子电池负极材料的理论与性能研究

在AM1半经验方法水平上,对不同数目的Li⁺位于C₆₀笼内和笼外时形成的复合物进行几何优化,PAS负极材料由于掺杂C₆₀而吸附更多的Li⁺,并且Li⁺容易嵌入到C₆₀中,从理论上解释了聚并苯(PAS)导电性能改善的原因,并对PAS中掺杂C₆₀的最佳比例进行了预测.     

C120O-和C120O2-的电子结构的理论研究

用INDO系列方法对双笼氧化物C₁₂₀O的负离子C₁₂₀O^-和C₁₂₀O^2-的电子结构进行了理论研究.结果表明:C₁₂₀O^-和C₁₂₀O^2-中负电荷平均分布在两个碳笼上,而O的单电子自旋密度几乎为零,离子中两碳笼有较弱的相互作用,C₁₂₀O^2-的基态为三态.     

三种六氯铈(Ⅳ)酸有机盐的研究

合成了2,6-二甲基-γ-吡喃酮、咪唑和吡啶铈(Ⅳ)的氯化物,化学式为(C₇H₈O₂H)₂CeCl₆、(C₃H₄N₂H)₂CeCl₆和(C₄H₉NH)₄CeCl₈.采用差热、热重分析法比较了上述三种化合物的热稳定性,并配合以电导、红外、紫外光谱等手段进行了结构分析.     

自由基C69N及双体(C69N)2结构和电子光谱的理论研究

用INDO系列方法对自由基C₆₉N(Cs)及双体(C₆₉N)₂(C₂h)进行了理论研究,结果表明:笼骨架上N的掺入使C₇₀笼发生畸变,N向笼外突出,与氮相连的碳(6-6环上的C)自旋密度较大,2个C₆₉N自由基在这个碳上以C-C单键连接,形成双体为C₂h对称性,N与附近的3个碳均以单键连接,并不断开。理论计算的电子光谱与实验吻合较好,(C₆₉N)₂易分解为单体C₆₉N.     

中间体C60(CH3)-和产物C60(CH3)2的结构及产物

用INDO系列方法对C₆₀^2-与CH₃反应的中间体C₆₀(CH₃)^-进行理论研究,得到具有Cs对称性的构型。结果表明,CH₃加成到C₁₅上,将使与其相邻的双键碳(C₃₀)的电荷密度和自旋密度达极大值,故加成反应部位在C₃₀处;另外,C₁₅的对位C₁₂(或C₂₇)也较其它部位易于反应,且有两个反应场所,因而产物C₆₀(CH₃)₂可能为六元环上的1,2-加成和1,4-加成两种异构体的混合物。同时对两种加成产物的结构和电子光谱进行了理论研究,指认其电子跃迁,并讨论了其光谱红移的原因。     

CnSi(n=49,50)的理论研究

用量子化学从头算方法研究了C_nSi(n=49,50)的各种可能的构型.结果表明,C₄₉Si为硅取代碳笼C₅₀中一个碳原子而形成的骨架硅杂碳笼,C₄₉Si与C₅₀相比稳定性较低,化学活性较高.C₅₀Si有两种类型结构:Ⅰ为外接型,Ⅱ为四连接型.计算结果表明,对C₅₀Si,外接硅型化合物更稳定,即Ⅰ为主要成分.计算结果与实验结果是一致的.     

C~1~2~0O的分子结构和光谱性质的理论研究

用INDO系列方法对双笼氧化物C~1~2~0O进行了理论研究,结果表明:双笼氧化物C~1~2~0O的形成缓解了C~6~0O中环氧三元环的角张力,并形成了呋喃型五元环将两碳笼连接在一起。两碳笼的直接键连使两笼距离较近,有较弱的相互作用,但仍各自表现一定的独立性,C~1~2~0O可发生分解生成新的化合物,C~1~2~0O的电子光谱与母体分子C~6~0相似。     

Ion-molecule reactions of ammonia clusters with C60 aggregates embedded in helium droplets

Helium nanodroplets are co-doped with C(60) and ammonia. Mass spectra obtained by electron ionization reveal cations containing ammonia clusters complexed with up to four C(60) units. The high mass resolution of Δm/m≈ 1/6000 makes it possible to separate the contributions of protonated, unprotonated and dehydrogenated ammonia. C(60) aggregates suppress the proton-transfer reaction which usually favors the appearance of protonated ammonia cluster ions. Unprotonated C(x)(NH(3))(n)(+) ions (x = 60, 120, 180) exceed the abundance of the corresponding protonated ions if n < 5; for larger values of n the abundances of C(60)(NH(3))(n)(+) and C(60)(NH)(n-1)NH(4)(+) become about equal. Dehydrogenated C(60)NH(2)(+) ions are relatively abundant; their formation is attributed to a transient doubly charged C(60)-ammonia complex which forms either by an Auger process or by Penning ionization following charge transfer between the primary He(+) ion and C(60). The abundance of C(x)NH(3)(+) and C(x)NH(4)(+) ions (x = 120 or 180) is one to two orders of magnitude weaker than the abundance of ions containing one or two additional ammonia molecules. However, a model involving evaporation of NH(3) or NH(4) from the presumably weakly bound C(x)NH(3)(+) and C(x)NH(4)(+) ions is at odds with the lack of enhancement in the abundance of C(120)(+) and C(180)(+). Mass spectra of C(60) dimers complexed with water complement a previous study of C(60)(H(2)O)(n)(+) recorded at much lower mass resolution.     

High resolution and low-temperature photoelectron spectroscopy of an oxygen-linked fullerene dimer dianion: C(120)O(2-)

C(120)O comprises two C(60) cages linked by a furan ring and is formed by reactions of C(60)O and C(60). We have produced doubly charged anions of this fullerene dimer (C(120)O(2-)) and studied its electronic structure and stability using photoelectron spectroscopy and theoretical calculations. High resolution and vibrationally resolved photoelectron spectra were obtained at 70 K and at several photon energies. The second electron affinity of C(120)O was measured to be 1.02+/-0.03 eV and the intramolecular Coulomb repulsion was estimated to be about 0.8 eV in C(120)O(2-) on the basis of the observed repulsive Coulomb barrier. A low-lying excited state ((2)B(1)) was also observed for C(120)O(-) at 0.09 eV above the ground state ((2)A(1)). The C(120)O(2-) dianion can be viewed as a single electron on each C(60) ball very weakly coupled. Theoretical calculations showed that the singlet and triplet states of C(120)O(2-) are nearly degenerate and can both be present in the experiment. The computed electron binding energies and excitation energies, as well as Franck-Condon factors, are used to help interpret the photoelectron spectra. A C-C bond-cleaved isomer, C(60)-O-C(60) (2-), was also observed with a higher electron binding energy of 1.54 eV.     

Theoretical study on the structures and electronic spectra of C120On (n=1,2)

ZINDO series calculations have been carried out to study the double‐cage oxides C₁₂₀O_n (n=1,2). The results show that the formation of a furan ring by the bridge‐bond between the two cages connected the two C₆₀ fullerene units and formed the C₁₂₀O with C_2v symmetry. C₁₂₀O₂ has two isomers with C_2v symmetry depending on either 6–6 or 6–5 connection between the two cages. Two furan rings and a pure four‐member ring form in this molecule. The formation of C₁₂₀O assuages the constraint of epoxide structure in C₆₀O, shortens the distance of the monomers, and produces some finite interaction between the two balls. More bonding in C₁₂₀O₂ shortens the distance of the two cages further and brings about stronger interaction. However, the two cages in C₁₂₀O_n (n=1,2) behave somehow independently that the electronic spectra of C₁₂₀O_n (n=1,2) are similar to those of C₆₀. The 6–6 connection isomer of C₁₂₀O₂ is more stable; its spectra are in good agreement with those of the experiment. The calculated electronic spectra of C₁₂₀O not only are in good agreement with the experiment in the ultraviolet region but also get some weak peaks in the visible region (>400 nm) not observed in experiment. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 291–307, 2000     

Electronic interactions in a new fullerene dimer: C(122)H(4), with two methylene bridges

The isolation of a new fullerene dimer, C(122)H(4), and its structural characterization by (13)C NMR and (1)H NMR spectroscopy and by UV/vis and IR spectroscopy are reported. The structure of this dimer consists of two fullerene cages, which are directly connected through two C-C bonds and two methylene bridges. Consequently, adjacent hexagonal faces of the two fullerene cages are arranged in a face to face manner. Molecular orbital calculations indicate that the proximity of the fullerene cages results in significant through space overlap in both the HOMO and LUMO. As a consequence of this overlap, the electrochemistry of the dimer shows electronic communication with stepwise reduction of each cage.     

Generalized Stone-Wales transformation as the possible origin of ferromagnetism in polymeric C60: a density-functional theory study

Recently, there has been a proposal [Y.-H. Kim et al., Phys. Rev. B 68, 125420 (2003)] suggesting that ferromagnetic interactions in compressed and heated polymeric-C(60) solids could be due to the existence of triplet open cages resulting from successive generalized Stone-Wales transformations within the C(60) cage. Here, by performing B3LYP3-21G and B3LYP6-31G(d) optimizations, we carried out a systematic investigation of the thermodynamics and kinetics of the mechanism of generation of these open cages in their closed-shell singlet, open-shell singlet, and triplet states. We also computed the magnetic interactions induced by the open cages presenting a triplet ground state. Our results indicate that this mechanism is not appropriate to explain the ferromagnetism found in compressed and heated polymeric C(60) for the following reasons: (a) the formation of the only open cage presenting a triplet ground state requires overpassing a highest energy point of 318 kcal/mol, well above other competitive mechanisms reported in the literature; the triplet open cages formed are not stable against their transformation into a diamagnetic intermediate; (c) the magnetic interactions between two adjacent triplet open cages are antiferromagnetic.     

Mechanochemical synthesis of a novel C(60) dimer connected by a silicon bridge and a single bond

[reaction: see text] A novel C(60) dimer connected by a silicon bridge and a single bond was synthesized by the mechanochemical solid-state reaction employing a high-speed vibration milling technique and fully characterized by the (1)H and (13)C NMR, APCI mass, and UV-vis spectroscopy. The presence of the electronic interaction between the two C(60) cages was demonstrated by the electrochemical method.