NMR and MO Studies on the Molecular Structure of a Fluoranthene-Benzene Complex

Summary. Fluoranthene (FA) forms a 1:1 van der Waals complex with benzene in cyclohexane. The ¹H NMR spectrum of this complex shows that the FA moiety in the complex state has five kinds of hydrogen atoms and that the ¹H NMR peaks assigned to the protons attached to the naphthalene skeleton are largely shifted to higher magnetic field on complex formation with benzene. These observations indicate that the complex takes the structure of C_S symmetry, in which the benzene molecule mainly interacts with the electronic system localized on the naphthalene moiety of FA. The present ab initio calculations reproduce well the ¹H NMR spectral shifts mentioned above and the experimentally predicted C_S structure of the complex. According to the PPP calculations for the electronic absorption spectral changes on the complex formation, the FA-benzene complex is considered to take a sandwich type structure.     

一种新颖分子振荡元件的核磁共振研究

一种新颖分子振荡元件的核磁共振研究孙小强，何明阳，扬扬，孟启，何光裕（江苏石油化工学院应用化学系，常州，２１３０１６）关键词分子元件；核磁共振；超分子利用超分子自我识别、自我组装原理，在分子水平上研制、开发具有调控功能的分子元件已成为当前科研工作的前...     

X-Ray Structure and Proton NMR Study of a Hexacoordinated Lithium Complex

The structure of the lithium complex with1,3,5-tris[oxymethylene(N,N-dicyclohexyl)carboxyamido]cyclohexanehas been determined by the X-ray method.The compound is triclinic, space group P¯1,a = 15.623(3), b = 19.279(4),c = 19.295(4)Å = 102.32(3), = 92.45(3), = 105.67(3)0, V = 5436(2)Å3, Z = 4. Itscomposition is represented by the formulaC48H82N3O6LiI 0.5H2O. The lithium cationis encapsulated in a polar pseudo-cavity of six oxygen atoms of the ligandmolecule and displays a distorted trigonal prism coordination. The conformationof the ligand in the solid state complex has been compared with the conformationof the complex in solution determined by 1H-NMR measurements.Supplementary data relevant to this publication have been deposited with the British Library, No. SUP 82224 (21 pages).     

Synthesis,Crystal Structure of Cis—dioxo—catecholatotungsten（VI） Complex and Its NMR Studies on the Interaction with ATP

Cis-dioxo-catecholatotungsten(VI) complex anion[W^(VI)O2-(OC6H4O)2]^2- was obtained with discrete protonated ethylenediamine (NH2CH2CH2NH3)^ cations by the reaction of tetrabutyl ammonium decatungstate with catechol in the mixed solvent of CH3OH,CH3CN and ethylenediamine,and compared with its molybdenum anaogue [Mo^(V) O2(OC6H4O)2]^3- by crystal structure,UV,EPR,The results of the UV and EPR spectra show that tungsten is less redox active than molybdenum since the molybdenum is reduced from Mo(VI) to Mo(V) but tungsten stays in the original highest oxidized state Mo(VI) when they are crystallized from the solution above.It is worthy to note that [W^(VI)O2(OC6H4O)]^2- shows the same coordination structure as its molybdenum analogue in which the metal center exhibits distorted octahedral coordination geometry with two cis-dioxocatecholate ligands and might have the related coordination structure feature with the cofactor of flavoenzyme because [Mo^(V)O2(OC6H4O)2]^3- presented essentially the same EPR spectra as flavoenzyme.The NMR studies on the interaction of the title complex with ATP reveal that the reduction of W(VI) to W(V) occurs when the title complex is dissolved in D2O and the W(V) is oxidized again when ATP solution is mixed with original solution and the hydrolysis of the catecholato ligand take places at mean time being monitored by ^1H NMR and ^13C NMR spectra.     

双过氧钒配合物与吡啶类配体相互作用的NMR研究

为探讨单齿/双齿吡啶类配体对反应平衡的影响,在模拟生理条件下(0.15mol·L-1NaCl溶液),应用多核(1H、13C和51V)多维(COSY,HSQC和HMBC)以及变温NMR技术研究双过氧钒配合物[OV(O2)2(D2O)]-/[OV(O2)2(HOD)]-(简写为bpV)与系列吡啶类配体的相互作用,研究结果表明bpV与有机配体的反应性从强到弱的顺序为:2,2′-联吡啶2,2′-联吡啶-4,4′-二甲酸根吡啶异烟酸根,这说明双齿吡啶类配体配位能力强于单齿配体,而不带羧基的吡啶类配体(单齿或双齿)配位能力强于所对应的带羧基的取代吡啶,竞争配位导致一系列新的6配位(配体为吡啶或异烟酸根)或7配位(配体为2,2′-联吡啶或2,2′-联吡啶-4,4′-二甲酸根)的过氧钒物种[OV(O2)2LL′]n-(LL′=吡啶类配体,n=1,2,3)生成。     

高分子多尺度结构与动力学的固体NMR研究

高分子材料中的微观结构和动力学特征决定了材料的最终物理化学性能,并具有典型的时间和空间上的多尺度特性。在不同时空尺度上表征凝聚态下高分子中多尺度的结构、动力学及其动态演变等问题,进而阐明其结构-性能间的关系一直是高分子科学研究中的挑战性课题。目前,固体NMR技术已成为从原子至100nm的空间和10-9～10s的时间尺度上研究固态高聚物体系中多层次结构和复杂运动并阐明其结构与性能关系的有力工具。本文将综述我们近年来系统构建的多尺度固体NMR实验技术,及其在阐明高分子链结构、链间相容性和相互作用、界面相结构及相区尺寸、以及从高频到超慢链运动等问题中的应用。     

Molecular Structure of the Ethylenediammonium Complex of a Tetracarboxy-macrocyclic Receptor Molecule

The crystal and molecular structure of the complex formed by the ionized bistartro-[18]-crown-6 receptor molecule 1 with the ethylenediammonium cation, is described. The macrocycle is roughly planar, the carboxy groups of each tartaric acid residue being in a diaxial relationship and extending above and below this plane. This conformation allows ‘lateral’ interactions with bound species to occur. The substrate is sandwiched between two macrocycles, with one of its NH heads anchored to the polyether core, and the other one in contact with the two carboxy groups of the neighboring molecule.     

Solvothermal Synthesis and Structure Studies of a Mixed-valence Oxochloromolybdenum Complex

Emerald green crystals of a new mixed-valence oxochloromolybdenum complex,Mo(OH)2(2,2′-bipy)Cl2.[MoO(2,2′-bipy)Cl3]2, were obtained in an attempt to synthesize the Mo-S cluster compounds under solvothermal conditions. The title compound was characterized by EPR and X-ray single-crystal diffraction techniques. Crystallographic data: orthorhombic, space group Fdd2, a = 12.684(1), b = 21.518(2), c = 29.096(3)A, Mr = 1103.97, V= 7941(1)A^3, Z= 8, Dc =1.843 g/cm^3,μ= 1.514 mm^-1, F(000) = 4304, R = 0.0654 and wR = 0.1544 for 1944 observed reflections with 1 ≥/ 2σ(I). The compound consists of two different neutral molecules, Mo^IV-(OH)2(2,2′-bipy)Cl2 and MoVO(2,2′-bipy)Cl3. Both Mo^IV and Mo^V ions are in a distorted octahedral environment. The Mo(1)^IV atom is surrounded by two Cl^- ions and two O atoms from OH^- and two N atoms from a 2,2′-bipy ligand. The Mo(2) atom is surrounded by three Cl^- ions, one O^2- anion and two N atoms from another 2,2“-bipy ligand. The bipyridine occupies two cis-equatorial sites, while the Cl^- ions are located at the axial and equatorial positions.     

双过氧钒配合物与3-取代吡啶相互作用的NMR研究

为探讨有机配体上取代基团对反应平衡的影响, 在模拟生理条件下(0.15 mol/L NaCl溶液), 应用多核(1H、13C和51V)多维(DOSY)以及变温NMR技术研究双过氧钒配合物[OV(O2)2(D2O)]－/[OV(O2)2(HOD)]－(简写为dpV)与3-取代吡啶的相互作用, 并首次报道了一些物种的NMR化学位移. dpV与有机配体的反应性从强到弱的顺序为: 吡啶＞烟酸 根＞烟酸甲酰胺≈烟酸甲酯, 这说明吡啶环上取代基影响反应平衡. 竞争配位导致一系列新的6配位的过氧钒物种生成. 密度泛函计算结果合理地解释了实验结果, 并表明溶剂化效应在反应中起重要作用.     

Ab Initio MO Studies on the Reaction Mechanism for Carbonyl Insertion Catalyzed by Carbonyl Cobalt Complex

IntroductionSome of ah l'nito MO studies on elementary reactions catalyzed by organometallic compounds have been published[' 41, which are of momentous significance for better understanding the catalytic action and developing the catalytic agent. At the same time, there still aremany unknown aspects that remain to be studied. Carbonyl insertion is one of the key reac.tlons, and it can go in three possible pathsL'--'j, i. e., carbonyl migration, ethyl migrationand concerted reaction paths. Th…     

SAPO—5分子筛的结构研究

用X射线单晶衍射方法测定了晶体尺寸为150μm×100μm的SAPO-5分子筛的晶体结构.结果表明,SAPO-5属六方晶系,空间群P_6cc,晶胞参数a=1.3802nm,c=0.8503nm,权重偏离因子R_w=0.043.F~-离子位于2个四元环中间.电子探针分析结果表明,硅只取代磷进入SAPO-5分子筛骨架.     

可利用酸碱控制的分子器件：准轮烷的“开”与“关”

4,4‘－二氨基二苯醚衍生物（A）和缺电子联吡啶大环（CPQT）发生π-π堆积作用进行自组装形成准轮烷;准轮烷的“开”与“关”可以利用酸碱调控。此过程可利用体系的氢的化学位移变化来进行跟踪。     

Theoretical Studies on the Structure and Spectrum of Imidazole-Chloranil Charge Transfer Complex

UV-Vis absorption spectra of the molecular complex formed by imidazole (Im) and chloranil (CA) were measured in chloroform. The stoichiometry of the imidazole-chloranil (Im-CA) complex was determined as 1:1 by applying Benesi-Hildebrand's equation and Job's continuous variation method. Density function theory (DFT) and MP2 calculations were performed to study the structures and the binding energies of the Im-CA complex. The calculations located four conformations (denoted as S1-S4) for the Im-CA complex, two edge(Im)-to-face(CA) linked and two edge(Im)-to-edge(CA) linked. It was found that the edge-to-face conformers are more stable than the edge-to-edge ones. The bonding characteristics of these conformers were investigated with natural population analysis (NPA), topological analysis of electron density, and natural bond orbital (NBO) analysis. It was revealed that the edge-to-face conformers are charge-transfer (CT) complexes whereas the edge-to-edge conformers are the hydrogen bond complexes. For the most stable conformation of the Im-CA complex (S1), the charge transfer interaction of the imidazole n(N15) lone pair orbital with the chloranil ∏*(C1=O7) orbital plays a crucial role in the Im-CA binding, and the binding is further strengthened by the O7… H20 hydrogen bond. The electronic excitation energies of the complex (S1) were calculated with time-dependent DFT (TDDFT), and the observed UV-Visible spectrum of the complex was analyzed based on the computed results.     

Molecular Structure of ortho-Fluoronitrobenzene Studied by Gas Electron Diffraction and Ab Initio MO Calculations

The molecular structure of ortho-fluoronitrobenzene (o-FNB) has been investigated by gas-phase electron diffraction and ab initio MO calculations. The geometrical parameters and force fields of o-FNB were calculated by ab initio and DFT methods. The obtained force fields were used to calculate vibrational amplitudes required as input parameters in an electron diffraction analysis. Within the experimental error limits, the geometrical parameters obtained from the gas-phase electron diffraction analysis are mostly in agreement with the results obtained from the ab initio calculations. The main results are: the molecular geometry of o-FNB is nonplanar with a dihedral angle about C–N of 38(3)°. The r _g (C–F) bond is shortened to 1.307(13) Å in comparison with r _g (C–F) = 1.356(4) Å in C₆H₅F.     

NMR和分子力学法研究溶液中有机分子结构

在分子力学能量优化项中加入由ＮＭＲ实验得到的几何参数二面角（相应于~３Ｊ_（ＨＨ）耦合常数）及质子间距所构造的约束函数，使分子力学计算得到的能量极小点的分子构象，其耦合常数（~３Ｊ_（ＨＨ））及质子间距同ＮＭＲ实验结果相符合。文中以（±）－３－（４＇－甲苯基）－１－氮杂双环［２．２．２］－３－辛醇为例，采用自编的ＮＭＲ参数约束的分子力学计算程序ＭＭ２ＮＪ对其构象进行了计算。所得结果与Ｘ射线衍射法比较，有较好的一致性     

复杂缔合体系NMA-H2O的1H NMR研究

N-甲基乙酰胺(NMA)是最简单的肽键模型分子,广泛地被用来研究氢键相互作用.采用外标法测量了不同温度下NMA-H₂O缔合体系的¹H NMR数据,通过磁化率校正得到了混合物的准确化学位移数据.然后用量子化学计算的结果确定体系的缔合形式,运用化学缔合理论建立模型,对模型进行降维,减少模型参数;再采用最小二乘法,联合遗传算法(GA)和Levenberg-Marquardt算法对模型参数进行全局寻优,求解得到了缔合平衡常数和缔合平衡的ΔH和ΔS.此外,还采用密度泛函理论(DFT)计算了NMA-H₂O的几种主要缔合形式在298 K的ΔH,计算结果与化学缔合模型得到的结果和文献吻合较好.     

2D NMR Studies on the Structure of Urushiol of Chinese Lacquer

The urushiol diacetate was successfully separated by centrifugal rotation TLC on the silica gel coated with silver nitrate.The structure and configuration of key component of.urushiol (64.6%) were determined successfully by using 1H and 13C conventional method,DEPT technique,homo- and heteronuclear chemical shift correlation 2D-NMR,2D-J NMR,hftteronuclear relayed coherencetransfer 2D-NMR,and relaxation time T1 investigation.The as-signment of resonances for 1H and C were confirmed.There is plentyof evidence which shows that the key component of urushiol is3-(8'Z,11'E,13'Z-pentadecatrienyl)catechol.The results show that RELAY 2D-NMR new technique can be successfully applied to determining the structure of complicated unknown compounds.     

类蜘蛛丝聚合物结构及分子运动的固体核磁共振研究

运用固体核磁共振(NMR)技术研究了聚丙氨酸多肽片段(Ala)5与高分子齐聚物聚苯乙烯(PS, 分子量2000)及聚异戊二烯(PI, 分子量2210)共聚而成的类蜘蛛丝蛋白聚合物——聚苯乙烯-co-聚丙氨酸聚合物(PS-co-PAL)和聚异戊二烯-co-聚丙氨酸聚合物(PI-co-PAL)的结构及分子运动. 聚合物13C CP/MAS NMR(交叉极化/魔角旋转核磁共振)谱及其旋转坐标系中自旋-晶格弛豫时间(T1ρ(13C))的结果表明, 此两种聚合物中多肽片段(Ala)5具有相同的化学位移, 即相似的化学环境和二级结构, 并具有相近的T1ρ(13C), 即类似的聚集态结构. 聚合物的宏观力学性质明显不同: 常温下, PS-co-PAL呈硬颗粒状, PI-co-PAL呈橡胶状且易拉伸. 结果说明聚合物力学性质与高分子链段的性质密切相关. PI-co-PAL聚合物的PI链段, 其骨架—CH2CH—的T1ρ为(5.3±0.4) ms, 而PS-co-PAL聚合物的PS链段, 其骨架—CH2CH—的T1ρ为(47.0±5.5) ms, 说明二聚合物中PI链段较PS链段更为柔软. 另外, 基于密度泛函理论(DFT)的化学位移计算证明, 聚合物PS-co-PAL和PI-co-PAL中多肽片段(Ala)5的二面角均为(-131°, 142°), 说明它们以β-折叠构象存在.