C~nSi(n=28,29)各种可能结构的理论研究

利用量子化学从头计算方法研究了C~nSi(n=28,29)各种可能的结构,研究结果表明:C~2~9Si为硅取代碳笼(Fullerens)中一个碳原子而形成的骨0架硅杂碳笼(Fullerenes),而且C~2~9Si最稳定结构是通过硅取代碳笼(C~3~0)最稳定结构中一个碳原子而得到.C~2~9Si比C~3~0有较低的稳定性和较高的化学活性.C~2~8Si有两种类型结构:(I)外接,(Ⅱ)缺位(hole-defect)型,即硅四连接型.计算结果表明,对C~2~8Si,外接硅型化合物更稳定,即(I)为主要成份.而且C~2~8Si最稳定结构是由C~2~8最稳定结构外接硅而形成.计算结果与实验观测一致。     

C~4~0, C~4~0^+, Nb@C~4~0^+, NbC~3~9^+, Nb@C~4~0H~4^+的 量子化学研究

用量子化学从头计算方法研究了C~4~0,C~4~0^+,Nb@C~4~0^+,NbC~3~9^+,Nb@C~4~0H~4^+的几何构型、电子结构和C~2~8一样,C~4~0(T~d)基态也为^5A~2态,笼骨架上具有四个悬挂键。计算结果表明C~4~0和C~4~0^+比NbC~3~9^+和Nb@C~4~0^+稳定,与实验结果一致。     

C~4~0, C~4~0^+, Nb@C~4~0^+, NbC~3~9^+, Nb@C~4~0H~4^+的 量子化学研究

用量子化学从头计算方法研究了C~4~0,C~4~0^+,Nb@C~4~0^+,NbC~3~9^+,Nb@C~4~0H~4^+的几何构型、电子结构和C~2~8一样,C~4~0(T~d)基态也为^5A~2态,笼骨架上具有四个悬挂键。计算结果表明C~4~0和C~4~0^+比NbC~3~9^+和Nb@C~4~0^+稳定,与实验结果一致。     

C~6~0O异构体的研究

本文用臭氧氧化C~6~0的苯溶液,用HPLC分析产物,室温下氧化产物只得到一个C~6~0O异构体组分峰。低温下产物得到两个C~6~0O异构体组分峰。多出的一个峰经实验与理论的研究,表明它很可能是异构体C~6~0O(C~s)。     

C~6~0SiH~2的结构和电子光谱的量子化学研究

用INDO系列方法研究了C~6~0SiH~2的两种结构: 一是SiH~2加在两个六元环之间的键上形成C~2~v构型; 另一是SiH~2加在一个五元环和一个六元环之间的键上形成C~s构型。从总能量和LUMO-HOMO能级差看, C~6~0SiH~2的稳定结构应是C~2~v构型, 其中桥C(15)-C(30)的键长为0.1508nm, 键序为0.9369, 说明不开环, 形成类环丙烷结构。文中计算了两种构型的电子吸收光谱和NMR谱, 此类计算是基于对C~6~0SiH~2的等电子体C~6~0O和C~6~0CH~2的研究之上, 且后两者的研究结果与实验相一致。     

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.     

C~3~6二聚体的结构和稳定性的理论研究

用密度泛函理论(DFT)B3LYP方法,在3-21G水平上系统研究了C~3~6二聚体(C~3~6)~2的可能的稳定结构及其稳定性。结果表明,两个C~3~6的腰带六元环面对面以两根C－C键连接具有D~2~h对称性的结构的能量最低。在所研究的二聚体(C~3~6)~2中,C~3~6笼间键长在0.151～0.169nm之间,表明C~3~6单体间均以共价键结合。(C~3~6)~2的稳定性以及笼间键长与成键原子的位置密切相关。本文还给出了计算所得的电子结构,并讨论了其对(C~3~6)~2性质的影响。     

C~5~9HN的电子结构、UV-vis光谱及非线性光学性质的理论研究

对一种碳笼骨架氮取代化合物C~5~9HN用INDO系列方法进行了理论研究,得到了C~5~9HN的电子结构、分子稳定性、UV-vis光谱及二阶非线性光学系数。     

C~6~0, C~7~0的烷基化

本文利用低价稀土化物(S~mI~2或YbI~2)与C~6~0、C~7~0及卤代烃(烯丙基溴、氯苄)的混合溶液反应,制得烯丙基化、苄基化的富勒烯。发现与C~6~0相接的苄基数可以从1到14,验证了Krusic等人的结果。此外,还发现C~6~0可以进行烯丙基化,得到(CH~2=CHCH~2)~nC~6~0(n=1-10),C~7~0可以进行苄基化,C~7~0上至少可以接13个苄基,实验证明这类反应是对富勒烯进行烷基化的一种简便、有效的方法。     

异质富勒烯C~5~9Si与C~6~9Si的理论研究

利用MNDO,AM1和PM3半经验量子化学计算方法对硅杂富勒烯C~5~9Si和C~6~9Si进行了系统的理论研究.计算了稳定构型、生成热、前沿轨道能级差、电离势、电子亲和势、绝对电负性和整体硬度.结果表明,硅杂富勒烯的稳定性虽然低于全碳富勒烯,但也具有相当的稳定性.C~5~9Si的稳定性比已经合成的C~5~8X~2(X=B,N)高,C~6~9Si与C~7~0的稳定性差异也很小,因此在适宜条件下文中所讨论的硅杂富勒烯是应该能够合成的.在C~6~9Si各异构体中,取代位置在赤道的异构体具有最低的能量和最大的前沿轨道能级差,也是最稳定的异构体.与全碳勒烯C~6~0和C~7~0相比,C~5~9Si和C~6~9Si具有较小的电离势和电子亲和势,表明硅杂富勒烯容易被氧化,而被还原的难度要些,但是仍容易发生还原反应而生成负离子.因此硅原子的掺杂能够使富勒烯的氧化还原性能得以改善.C~5~9Si和C~6~9Si更容易与亲电试剂反应,而发生亲核反应的活性要相对小一些.硅杂富勒烯C~5~9Si和C~6~9Si的绝对电负性和硬度都小于相对应的全碳富勒烯,对电子的束缚力要相对小一些。     

C120NH的电子光谱和结构的理论研究

用INDO系列方法对双笼化合物C₁₂₀NH进行了理论研究,并预测C₁₂₀NH的形成缓解了C₆₀NH中亚胺基三元环处的角张力,从而较稳定;两碳笼直接键连使其相互间有较弱的相互作用,N仍具有较强的捕获质子能力,且有一定选择性;C₁₂₀NH的电子光谱与母体C₆₀及C₁₂₀O和C₁₂₀CH₂相似.     

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.     

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     

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.     

Quantum chemical density-functional theory calculations of the structures of defect C60 with four vacancies

Quantum chemical density-functional theory (DFT) calculations have been carried out for the six isomers obtained by removing four adjacent atoms from C60. The most stable isomer consists of twelve 5-member and eighteen 6-member rings, indicating that the removal of some atoms from C60, which contains twelve 5-member rings and twenty 6-member rings, does not always generate larger holes. Each of the other five isomers contains at least one 4-member ring and one larger ring (7-, 8-, 9-, or 10-member ring) besides the 5- and 6-member rings. All isomers have similar structures for singlet and triplet spin multiplicities but with different stabilities. The ground states for two of the isomers are triplets, whereas the ground states for the other isomers are singlets. Furthermore, a comparison between the various isomers allowed one to examine the effect of the structure on the stability of fullerene cages.     

C60O2可能异构体的结构,电子光谱和NMR谱的理论研究

用ＩＮＤＯ系列方法研究Ｃ６０Ｏ２可能异构体的结构，两个氧原子分别加在两个六元环相邻边或五六元环相邻边形成环氧结构，为Ｃｓ对称性，得６种可能构型，计算表明，两个氧原子加在同个六元环的六六元环相邻边所形成环氧结构Ｃｓ构型最稳定，环氧处Ｃ－Ｃ键不断开，与实验结果一致，其电子光谱计算结果亦与实验值相吻合，这种Ｃｓ构环氧结构所在六元环上的另一个Ｃ－Ｃ键有大的键序，为高活性位置，因此Ｃ６０Ｏ２可能有较好的化学     

Reversible dimerization of [5,6]-C60O

The recently discovered [5,6]-open isomer of C(60)O has been found to undergo facile dimerization to form a new C(2) symmetry isomer of C(120)O(2), which can be photodissociated with relatively high efficiency to regenerate monomeric [5,6]-C(60)O. High yield dimerization of [5,6]-C(60)O proceeds spontaneously in toluene solution near room temperature. On the basis of (13)C NMR spectroscopy, ab initio quantum computations, and HPLC retention patterns, the resulting C(120)O(2) product has been deduced to be a nonpolar dimer of C(2) symmetry in which the C(60)O moieties are linked by two single bonds between sp(3)-hybridized carbon atoms adjacent to oxygen atoms. Photophysical properties of this dimer have also been measured and compared to those of C(120), the [2 + 2]-dimer of C(60). The ground-state absorption spectrum of C(120)O(2) in toluene is slightly red-shifted relative to that of C(120), with a distinctive peak at 329 nm and an S(1)-S(0) origin band at 704 nm. Its fluorescence spectrum shows two major peaks at 718 and 793 nm. In room-temperature toluene, the measured triplet state intrinsic lifetime of this C(120)O(2) isomer is 34 +/- 2 micros, a value somewhat shorter than that of C(120) (44 micros). C(120)O(2) undergoes photodissociation from its triplet state to regenerate monomeric [5,6]-C(60)O with quantum yields of 2.5% at 24 degrees C and 43% at 70 degrees C. It can therefore serve as a stable reactant for photolytic production of [5,6]-C(60)O. As a simple fullerene adduct that reacts under mild conditions, [5,6]-C(60)O may prove useful in special synthetic applications. Solutions of [5,6]-C(60)O are also unique because they can provide mixtures of a fullerene monomer and its dimer in a dynamic balance controllable by adjustment of concentration, temperature, and optical irradiation.     

杂氮三环化合物X射线研究——Ⅲ.1-氯甲基-2,8,9-三氧杂-5-氮杂-1-硅三环[3,3,3,0~(1.5)]十一烷-3-酮的结构测定

题目所指化合物属单斜晶系,P2_1/c空间群,晶胞参数a=6.751(1),b=11.274(3),c=13.134(4),β=100.390(3)°,晶胞含分子数Z=4.用直接法和Fourier综合解得粗结构,取1490个可观测独立反射数据,经最小二乘修正,偏离因子R为0.056。三个五员环(Si,O,C,C,N)中各最大扭角分别为33.2°,23.0°,35.1°,其中最小者(23.0°)属于含羰基的环。