C70O2可能异构体的结构和电子光谱的理论研究

用AM1、PM3及INDO系列方法研究了C₇₀O₂可能异构体的结构和稳定性.在C₇₀O稳定构型的基础上,考察了C₇₀O₂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C₇₀和C₇₀O进行了比较.     

C50(D5h)衍生物-异质富勒烯C48P2的分子行为理论研究

用半经验的AM1和MNDO方法以及密度泛函B3LYP/3-21G方法对C₅₀(D_5h)的衍生物C₄₈P₂的所有可能的异构体进行了系统的理论研究. 优化了稳定构型, 计算了生成热、HOMO-LUMO能级差、NICS值、红外光谱及电子光谱, 并与C₄₈X₂(X=B, N)的分子行为进行了比较. 计算结果表明: (1) C₄₈P₂的最稳定异构体是异构体C₄₈P₂-78, 该异构体对应于赤道位置六元环内的1,4-取代产物; (2) 决定C₄₈P₂异构体稳定性的主要因素是碳笼的张力, 而稳定性和芳香性之间没有明显的相关性; (3) 相对较稳定的C₄₈P₂异构体的HOMO-LUMO能级差比C₅₀的HOMO-LUMO能级差大; (4) 计算出的红外光谱以及电子光谱可以供实验参考; 计算出的NICS 值也可以用来表征C₄₈P₂各异构体. (5) C₄₈P₂与C₄₈X₂(X=B, N)具有相同的取代选择性规律及稳定性决定因素, 并且相对较稳定的异构体均具有比C₅₀本体大的HOMO-LUMO能级差.     

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.     

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.     

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.     

富勒烯C60硫桥键联四硫富瓦烯衍生物的理论研究

利用半经验AM1法研究了富勒烯C₆₀硫桥键联四硫富瓦烯衍生物和富勒烯C₆₀键联四硫富瓦烯衍生物的几何构型,电子结构.计算结果显示,富勒烯C₆₀硫桥键联四硫富瓦烯衍生物的四硫富瓦烯(TTF)平面与C₆₀发生作用,使其弯曲的程度比富勒烯C₆₀键联四硫富瓦烯衍生物的大,从而形成一种独特的四硫富瓦烯(TTF)平面半包裹C₆₀的空间构型的D-A体系.这很可能是由于C-S单键的灵活性造成的.而且它们的HOMO轨道主要分布在四硫富瓦烯(TTF)部分,而LUMO轨道则主要分布在C₆₀上.预测了富勒烯C₆₀硫桥键联四硫富瓦烯衍生物很有可能在激发态下产生更长寿命的电荷分离态.     

C59O的结构、电子光谱及NMR谱的理论预测

用INDO系列方法对C₆₀的取代产物C₅₉O进行几何构型优化,得到Cs对称性的稳定构型,以此构型为基础,计算并预测了C₅₉O的电子光谱和NMR谱.最后与C₅₉O的等电子分子体C₆₀^2-及C₆₀O进行了比较.     

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。     

C60O3的结构和电子光谱的理论研究

用INDO系列方法对C₆₀O₃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C₃v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C₂、C_s构型也相当稳定,C₂、C_s构型的部分¹³C NMR谱与实验吻合.C₆₀O₃可能有较好的反应活性,其电子光谱属于理论预测.     

C60富勒烯-哌啶硫代荒酸酯稠合体的合成与三线态特征

C₆₀富勒烯与2-(哌啶-硫代荒酸酯)-1,3-丁二烯通过Diels-Alder环加成反应得到C₆₀富勒烯-哌啶硫代荒酸酯稠合体,运用现代波谱技术等确定了产物结构;用半经验方法PM3和AM1计算预测环加成反应性和C₆₀富勒烯-哌啶硫代荒酸酯稠合体的性能.激光光解时间分辨技术初步探究了单加成的C₆₀富勒烯-哌啶硫代荒酸酯稠合体(C₆₀-PX)三线态特征以及与四-(2-噻吩基)-四硫富瓦烯(TT-TTF)分子间的光诱导电子转移反应.     

用原子转移自由基聚合法合成末端含碳笼烯-60的窄分子量分布聚苯乙烯

Ｃ６０是碳笼烯一族的代表,其独特的球笼形空间结构和电子结构决定了其有许多奇异的性质［１］．关于Ｃ６０的化学反应性的研究方兴未艾［２］,其中Ｃ６０的高分子衍生物的合成也是关注所在．迄今关于含Ｃ６０的高聚物的合成已有许多报道［３,４］,而关于窄分布的含Ｃ６０高聚物的合成的研究尚少．Ｆｒｅｙ等［５］将阴离子聚合所得的聚苯乙烯链的末端转变为氨基,再与过量的Ｃ６０发生单电子转移加成反应制得窄分布的以Ｃ６０封端的聚苯乙烯．Ａｓｔｒｕｓ等［６］将活性阳离子聚合所得的六臂星形聚苯乙烯的末端转化为氨基,得到Ｃ６０…     

Structure and stability of the defect fullerene clusters of C60: C59, C58, and C57

We have performed density functional calculations for the structures and stabilities of various isomers of the defect fullerene clusters of C(60): C(59), C(58), and C(57). The C(59_)5-8, C(58_)5-5-7, and C(57_)4-5-9 clusters were calculated to be the most stable isomers of the C(59), C(58), and C(57) clusters, respectively. There are obvious relationships between structure and stability of the defect fullerene clusters. First, an unsaturated carbon atom favors being located at a 6-membered ring rather than a 5-membered ring. Second, the most stable isomers prefer to have newly formed 5-membered rings, rather than newly formed 4-membered rings.     

Theoretical studies on the BN substituted fullerenes C70−2x(BN)x (x=1–3)—isoelectronic equivalents of C70

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 C₆₈BN, the isomers whose BN is located in the most chemically active bonds of C₇₀ (namely B and A) are among the most stable species, of which B is predicted to be the ground state. The stabilities of C₆₈BN decrease and the dipole moments increase with increasing the distance between the heteroatoms. For C₆₆(BN)₂, the lowest energy species is the isomer in which the B–N–B–N bond is formed; For C₆₄(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 C₇₀ are almost the same as those of C₇₀ because of the isoelectronic relationship. The ionization potentials and affinity energies depend on the relative position of the heteroatoms in C₆₈BN, the chemical reactivities of the isomers whose heteroatoms are well separated should differ significantly from their all carbon analog.     

C60加成反应的理论研究

用AM1方法研究了C₆₀与醌并二烯加成反应的机理,并对反应的过渡态及加成产物的构型进行了优化.研究发现,醌并二烯与C₆₀的加成是协同进行的,反应的活化能较低;而氧取代的醌并二烯与C₆₀的加成是协同进行但不同步,反应的活化能较高.前线轨道理论的研究表明反应是由亲二烯体C₆₀的LUMO控制的.     

N@C60的结构和振动光谱的理论研究

用abinitio分子轨道UnrestrictedHartree-Fock(UHF)方法,对N@C₆₀的几何构型进行了全优化.计算结果表明,N基本上以原子的形式存在于笼中,但N原子与碳笼之间存在一定的相互作用,这与实验结果相符.进一步计算了N@C₆₀的振动光谱,并与C₆₀进行了比较分析.     

异质富勒烯C58P2的理论研究

用ＭＮＤＯ半径能方法研究了异质富勒烯Ｃ５８Ｐ２各异构体的结构和相对稳定性。结果表明,１,４－位取代的异构体最稳定,异构体的稳定性随杂原子同距离的增加而降低。Ｃ５５８Ｐ２分子和稳定性比全碳富勒烯Ｃ６０低,但仍具有相当的稳定性,是潜在的合成目标。杂原子磷的掺杂改善了富勒烯的氧化还原性能。考察了各异构体的整体硬度和绝对电负性,产根据绝对电负性的差异预测了富勒烯和异质富勒烯间形成聚合物时的电子转移。     

DFT study on the stabilities of the heterofullerenes Sc3N@C67B, Sc3N@C67N, and Sc3N@C66BN

On the basis of calculations using density functional theory, we investigated the relative stabilities of all isomers of Sc3N@C67B and Sc3N@C67N as well as those of stable isomers of Sc3N@C66BN. As a result, we predict that Sc3N@C68 can be doped substitutionally with a boron atom much better than C60. This effect can be ascribed to the favorable electrostatic attraction between the encased Sc3N cluster and the polar C-B bonds of the fullerene cage, which show the important role played by the encapsulated atoms in stabilizing the fullerene. A difference in the interaction also determines the regiospecificity of Sc3N@C67B. On the contrary, N-doping of the fullerenes forming Sc3N@C67N is much less favorable than that in C60 or C70. A judicious choice of stable isomers of Sc3N@C66BN among a vast number of possible isomers indicates that Sc3N@C68 can also be doped with a pair of B and N atoms better than C60 under the simultaneous existence of B and N sources. Relative stabilities of various isomers of the BN-substituted fullerenes can be understood in terms of the combined electrostatic effects in the B- and N-substitutions of Sc3N@C68 complemented by a specific local preference in the N-substitution and the formation of a B-N bond.     

异质富勒烯C76BN的UV和IR光谱研究

Twenty-tow possible isomers for C76BN were studied by INDO methods. The two most stable geometries are 52,53-C76BN and 29,28-C76BN, in which boron and nitrogen atoms are connected with each other and located at the 6/6 bond near the longest axis of C78(C2v). Electronic spectra of C76BN were investigated with INDO/SCI method. UV absorptions of C76BN are red-shifted compared with those of C78(C2v). The structures and IR spectra for the four stable isomers of C76BN were calculated by AM1 method. It was indicated that the substitution of the BN unit weakens the conjugation of carbon atoms, leading to the decrease of IR frequencies.     

DFT Study on the Structural, Electronic, and Spectroscopic Properties of the Highest Epoxygenated Fullerene C36O18

Theoretical investigation on the highest epoxygenated fullerene C36O18 formed from the initial C36 fullerene with D6h symmetry has been performed at the B3LYP/6-31G(d) level. Their equilibrium structures, thermal stabilities, electronic structures, vertical ionization potentials, vertical electron affinities, vibrational frequencies and 13C NMR chemical shifts have been studied. The calculation results showed that C36O18 isomers have higher LUMO-HOMO energy gaps than the fullerene C36 and should be more stable. Compared with C36 , it is less possible for C36O18 to accept or donate electrons from reduced VEAs and enhanced VIPs. It has been found that C36O18 isomers are not aromatic at all or antiaromatic on analyzing the NICS values. The present study will encourage further theoretical and experimental analyses of this system in future.     

Theoretical Studies on Stabilities of C26BN Isomers

The possible stable stractures of substituted fullerene C26BN formed on the initial C28 cage with Td symmetry have been systematically studied on UHF/3-21g level with constrained syrnmetry(Cs or C1, the charge and multiplicity of all the isomers are zero and five, respectively.The geometry optimization and the vibrational frequencies analysis were performed on the same level with constrained symmetry(Cs or C1. The results show that the most stable isomer of C26BN is formed by boron and nitrogen atoms doping at 5,2-sites.