[60]富勒烯衍生物的对称性、碳笼结构与C NMR谱

本文全面综述了多种[60]富勒烯衍生物的结构,阐述了(13)~C NMR谱在[60]富勒烯衍生物结构表征中的应用,重点讨论了不同对称性[60]富勒烯衍生物的(13)~C NMR谱图特征.通过[60]富勒烯部分(13)~C共振线的化学位移、数目和相对强度,可以确定[60]富勒烯衍生物的对称结构和加成方式.对于C_s、C_(2v)和C_(3v)对称性的[60]富勒烯衍生物,镜面上的碳原子的相对化学位移很大程度上取决于他们距加成位置的距离.因此,(13)~C NMR谱在碳笼具体结构的确定中具有不可替代的作用.     

[60]富勒烯与1,1′-联茚的Diels-Alder加成物的合成与结构表征

通过Diels-Alder环加成反应,发现可控制反应条件,使1,1′-联茚与C60反应,并高产率地得到具有新颖结构的单加成物.用HPLC,FT-IR,FD-MS及1H NMR,13C NMR,HMQC,HMBC等多种波谱技术对其结构进行表征,测得它的两个sp3杂化的桥头碳的化学位移为δC:70.91,证明生成的衍生物为[6,6]闭式环加成.13C NMR谱共给出38个信号,表明C601,1′-联茚衍生物分子具有Cs对称性;此外,还发现单加成衍生物C601,1′-联茚热稳定性好,在四氢呋喃、丙酮等极性溶剂中溶解性好,很适合于在LB膜及光限幅性能方面的研究.     

富勒烯C60-多芳胺类衍生物选择性加成反应的研究

多芳胺是良好的电子给体,富勒烯C60作为电子受体的光诱导分子内和分子间电荷转移现象[1,2]引起人们普遍关注,尤其是设计合成长寿命电荷分离态的富勒烯C60-多芳胺基类衍生物研究[3,4]是热点课题之一.由于聚吡咯/聚芳胺的氧化还原电位较低[5],我们设想包含吡咯/芳胺给体的富勒烯C60衍生物能延长电荷分离态的寿命.本文用1,3-偶极环加成反应[6]对富勒烯C60与多芳胺化合物的选择性加成反应进行了研究,在不同条件下得到了单加成产物和三加成产物,用FAB-MS,UV-vis,IR,1H NMR,13C NMR,HPLC等方法确定了其分子结构.并且利用半经验AM1量子化学方法在理论上研究了它们的优化构型(如图1)、电子结构,结果表明,富勒烯C60-多芳胺基类衍生物的前沿轨道主要由富勒烯C60部分决定,富勒烯C60母体与功能化基团三苯胺基之间存在较强的分子内电荷转移,这为富勒烯C60衍生物作为光电分子器件材料的应用提供了理论和实验依据.     

新型富勒烯衍生物的激光质谱结构表征

对3种电化学方法合成的新型结构富勒烯衍生物进行了激光质谱表征,确认了1,2加成以及[5,6]开环富勒烯衍生物结构.质谱结果发现了富勒烯以及富勒烯衍生物与氧的结合峰,核磁共振结果进一步证明了富勒烯衍生物的结构,为含有C60结构衍生物的研究提供了有力的表征手段.     

一些富勒烯C60双加成物稳定性的理论研究

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 .…     

醋酸锰作用下二烯丙基叔胺与[60]富勒烯的自由基环加成反应

二烯丙基叔胺与[60]富勒烯在醋酸锰作用下发生自由基环加成反应,生成[60]富勒烯并吡咯烷衍生物.醋酸锰的用量和反应温度等因素对反应有一定影响.反应可能先由Mn(Ⅲ)与烯丙胺经单电子氧化产生自由基,再与[60]富勒烯加成并进一步环化.研究中得到的各产物的结构均通过波谱学方法表征.     

新型富勒烯-吖啶二酮衍生物的合成

通过环加成、水解和酯化三步反应在富勒烯上引入吖啶二酮结构合成了一种新型的富勒烯-吖啶二酮衍生物,其结构经UV,1H NMR,13C NMR,IR和MS表征。     

^1^3C-（19F）NMR去耦方法

一、引言含有等性氟的化合物往往可直接测得(13)~C-(19)~F的耦合常数。早期以连续波方式工作的核磁共振仪,由于灵敏度的限制,不能直接测量(13)~C核的化学位移和(13)~C-(19)~F的耦合常数,而采用测量(19)~F NMR谱的(13)~C的卫星线,求得(13)~C-(19)~F的自旋耦合常数。自FT核磁共振仪闻世后,才能直接测量(13)~C-(19)~F的自旋耦合常数和(13)~C的化学位移。但对含有多种非等性氟的多氟化合物的(13)~C谱,谱线复杂,相互重叠,如不去掉氟对碳的耦合,对指定谱线的归属和确定相应的耦合常数会有一定的困难。目前对(13)~C-{(19)~F}NMR去耦实验技术尚未见公开发表。由于(19)~F的化学位移范围较大(300ppm),且J_(C-F)     

二萜生物碱的~(13)C核磁共振谱

本文通过对186个二萜生物碱及其衍生物的~(13)C NMR谱数据的分析比较,就以下几方面作了归纳总结:①信号归属的方法;②常见取代基OCH_3、NCH_3、、NCH_2CH_3、OCOCH_3、的化学位移范围;③季碳和某些特定碳的化学位移规律。某些特定结构,如C_(20)二萜生物碱中的噁唑烷环以及C_(20)差向异构体等的~(13)C NMR谱特征;④C_(19)二萜生物碱中不同位置上取代基(H→OH、H→OMe、OH→OAc、OH→OMe、OH→C=O)效应和立体化学效应。这些归纳总结有助于此类化合物结构的阐明。     

2′,5′-二氢-1′H-吡咯骈[3′,4′:1,2]][60]富勒烯衍生物的合成

以甘氨酸乙酯盐酸盐与取代的苯甲醛为原料,制得了一系列亚胺,然后用亚胺与C(60)反应,得到带有不同取代基的吡咯烷骈[60]富勒烯衍生物.经~1H NMR,~(13)C NMR,FT-IR,UV-vis以及TOF-SIMS等方法对所得化合物结构进行了表征,并进行了产物的生物活性测试.     

1H and 13C NMR chemical shift assignments of spiro-cycloalkylidenehomo- and methanofullerenes by the DFT-GIAO method

The (1)H and (13)C NMR chemical shifts of spiro-cycloalkylidene[60]fullerenes were assigned using experimental NMR data and the Density Functional Theory (DFT)-Gauge Independence Of Atomic Orbitals method (GAIO) calculation method in the Perdew Burke Ernzerhof (PBE)/3z approach. The calculated values of the (13)C NMR chemical shifts adequately reproduce the experimental values at this quantum chemistry approach. Similar assignments will be helpful for (13)C NMR spectral analysis of homo- and methano[60]fullerene derivatives for structure elucidation and to determine the influence of fullerene frames on substituents and the influence of substituents on fullerene cores.     

Facile, scalable, regioselective synthesis of C3v C60H18 using organic polyamines

[chemical structure: see text]. Organic polyamines are efficient reagents for the regioselective hydrogenation of [60]fullerene. When [60]fullerene is heated in diethylenetriamine, a known C60H18 isomer with C3v symmetry is produced and isolated in good purity without the need for chromatographic separation. The reaction can be scaled upward to multigram levels without impacting yield or quality of product.     

Structural reassignment of the mono- and bis-addition products from the addition reactions of N-(Diphenylmethylene)glycinate esters to [60]fullerene under Bingel conditions

The addition of N-(diphenylmethylene)glycinate esters (Ph2C=NCH2CO2R) to [60]fullerene under Bingel conditions gives [60]fullerenyldihydropyrroles and not methano[60]fullerenyl iminoesters [C60C(CO2R)(N=CPh2)] as previously reported. Unequivocal evidence for the structure of C60C(CO2Et)(N=CPh2) was provided by INADEQUATE NMR studies on 13C enriched material. New mechanistic details are proposed to account for the formation of [60]fullerenyldihydropyrroles and their reductive ring-opening reactions.     

Synthesis of a single isomer of the bis-adduct of isocyanurato-substituted azide with [60]fullerene

A single di(azahomo)[60]fullerene isomer was prepared for the first time by the reaction between [60]fullerene and isocyanurato-substituted azide. The structure of the product was established by ¹H and ¹³C NMR, UV, and IR spectroscopy.     

Rearrangement of the cyclohexadiene derivatives of C60 to bis(fulleroid) and bis(methano)fullerene: structure,stability, and mechanism

The cyclohexadiene derivative of C(60) rearranges photochemically to bis(fulleroid) (two [6,5] open structure) and bis(methano)fullerene (two [6,6] closed structure). During this process, a [6,5] open/[6,6] closed intermediate is observed. The isolated intermediate undergoes photochemical rearrangement to bis(fulleroid) and bis(methano)fullerene. On the other side, it undergoes retrorearrangement to the starting material in the dark. The structure and energetics of these C(60) derivatives have been studied at the AM1, PM3, RHF, and B3LYP levels of theory. It is found that bis(fulleroid) bearing four tert-butoxycarbonyl substituents is 5.8 kcal/mol (B3LYP) more stable than the corresponding bis(methano)fullerene. The isolated intermediate having the [6,5] open/[6,6] closed structure is 6.7 kcal/mol more favorable than the previously proposed two [6,5] closed intermediate, and the formation of this compound is well explained by the di-pi-methane rearrangement. (13)C NMR calculation at the B3LYP level reproduced the experimental chemical shifts with very good accuracy for each molecular system. Theoretical studies mainly at the unrestricted B3LYP level on singlet and triplet state potential energy surfaces on fullerene derivatives support the di-pi-methane rearrangement mechanism. The previously proposed symmetrical [4+4]/[2+2+2] and the novel proposed unsymmetrical di-pi-methane pathways may coexist during the reaction.     

Structure and dynamics of homoleptic beryllocenes: a solid-state 9Be and 13C NMR study

The correlation between anisotropic 9Be NMR (quadrupolar and chemical shielding) interactions and the structure and dynamics in [Cp2Be], [Cp2*Be], and [(C5Me4H)2Be] is examined by solid-state 9Be NMR spectroscopy, as well as by ab initio and hybrid density functional theory calculations. The 9Be quadrupole coupling constants in the three compounds correspond well to the relative degrees of spherical ground-state electronic symmetry of the environment about beryllium. Theoretical computations of NMR interaction tensors are in excellent agreement with experimental values and aid in understanding the origins of NMR interaction tensors and their correlation to molecular symmetry. Variable-temperature (VT) 9Be and 13C NMR experiments reveal a highly fluxional structure in the condensed phase of [Cp2Be]. In particular, the pathway by which the Cp rings of [Cp2Be] 'invert' coordination modes is examined in detail using hybrid density functional theory in order to inspect variations of the 9Be NMR interaction tensors. The activation energy for the 'inversion' process is found to be 36.9 kJ mol(-1) from chemical exchange analysis of 13C VT CP/MAS NMR spectra. The low-temperature (ca. -100 degrees C) X-ray crystal structures of all three compounds have been collected and refined, and are in agreement with previously reported structures. In addition, the structure of the same Cp2Be crystal was determined at 20 degrees C and displays features consistent with increased intramolecular motion, supporting observations by 9Be VT NMR spectroscopy.     

NMR spectrometric studies of complexation of [60]fullerene with series of anisoles

Detailed (1)H and (13)C NMR spectrometric studies have been carried out to gain insight into the nature of molecular interactions of the electron donor-acceptor (EDA) complexes of [60]fullerene with a series of anisoles, namely, anisole, m-bromoanisole, and p-bromoanisole. [60]Fullerene has been shown to form 1:1 adducts with the above series of anisoles. Formation constants (K) for all the complexes have been determined from the systematic variation of the NMR chemical shifts of specific protons of the anisoles in the presence of [60]fullerene. The K values of [60]fullerene/anisole, [60]fullerene/m-bromoanisole, and [60]fullerene/ p-bromoanisole complexes yield good estimates of the Hammett rho constant for the complexation reaction. To the best of our knowledge, this paper reports for the first time a very fruitful technique by which the concentrations of EDA complexes can be estimated from systematic variations of the (13)C NMR signal.     

Fullerene-derivatized amino acids: synthesis, characterization, antioxidant properties, and solid-phase peptide synthesis

A series of [60]fullerene-substituted phenylalanine (Baa) and lysine derivatives have been prepared by the condensation of 1,2-(4'-oxocyclohexano)fullerene with the appropriately protected (4-amino)phenylalanine and lysine, respectively. Conversion of the imine to the corresponding amine is achieved by di-acid catalyzed hydroboration. The reduction of the imine is not accompanied by hydroboration of the fullerene cage. The [70]fullerene phenylalanine derivative has also been prepared as have the di-amino acid derivatives. The compounds were characterized by MALDI-TOF mass spectrometry, UV/Vis spectroscopy, and cyclic voltammetry. 1H and 13C NMR spectroscopy allowed the observation of diastereomers. Fullerene-substituted peptides may be synthesized on relatively large scale by solid-phase peptide synthesis. The presence of the C60-substituted amino acid in a peptide has a significant effect on the secondary structures and self-assembly properties of peptides as compared to the native peptide. The antioxidant assay of Baa and a Baa-derived anionic peptide was determined to be significantly more potent than Trolox.     

Trends in chemical shift dispersion in fullerene derivatives. Local strain affects the magnetic environment of distant fullerene carbons

13C NMR chemical shift assignments for 1,2-C60H2 (1) and a series of 13C-labeled fullerene derivatives with three-, four-, and five-membered annulated rings (2-4) were assigned using 2D INADEQUATE spectroscopy and examined for trends that correspond to the changes in strain in the fullerene cage. Chemical shifts of equivalent carbons from 1-4 show that eight carbons trend downfield (carbons 5, 7, 8, 9, 11, 15, 16, 17) and the remaining six carbons (4, 6, 10, 12, 13, 14) trend upfield with increasing ring size. While the average chemical shift is nearly constant, the dispersion is greatest when the local strain is the least, in 1,2-C60H2 (1). 13C chemical shifts are not well correlated with trends in ring size, with strain as measured by the pyramidalization angle of nearby carbons, or with the geometry of the fullerene cage. We interpret the results as evidence that subtle geometrical changes lead to modulation of the strength of ring currents near the site of addition and, in turn, the magnetic field generated by these ring currents affects the chemical shift of carbons on the far side of the fullerene core. These results highlight ring currents as being critically important to the determination of 13C chemical shifts in fullerene derivatives.