1H and 13C NMR spectral data of bioactive cage‐like polycyclic compounds

Bioactive cage‐like polycyclic compounds have attracted the attention of several research groups because of their unique appearance and their biological activities. Their structures were established on the basis of ¹H NMR and ¹³C NMR spectroscopic data. The ¹H and ¹³C signal assignments and most homonuclear hydrogen coupling constants were assigned by use of techniques such as 1D ¹H and ¹³C NMR and 2D gCOSY, non‐edited gHSQC and gHMBC. The gNOESY experiments proved the endo‐stereochemistry. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and characterization of crystalline structures based on phenylboronate ligands bound to alkaline earth cations

We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)(3)(-) coordinated to metal cations: [Ca(PhB(OH)(3))(2)], [Sr(PhB(OH)(3))(2)]·H(2)O, and [Ba(PhB(OH)(3))(2)]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution (1)H, (11)B, and (13)C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydroxyl groups were identified in the structures: those involved in hydrogen bonds, and those that are effectively "free" and not involved in hydrogen bonds of any significant strength. To position precisely the OH protons within the structures, an NMR-crystallography approach was used: the comparison of experimental and calculated NMR parameters (determined using the Gauge Including Projector Augmented Wave method, GIPAW) allowed the most accurate positions to be identified. In the case of the calcium compound, it was found that it is the (43)Ca NMR data that are critical to help identify the best model of the structure.     

Collision-induced dissociation of MCl(+) adducts (M = Mg, Mn, Zn, Co, Ni and Cu) and Cu(+) and Ag(+) adducts of dithioalkyl ketene acetals

Electrospray ionization mass spectra of equimolar solutions of dithioalkyl ketene acetals 1 and 2 and metal chlorides (MgCl(2), MnCl(2), ZnCl(2), CoCl(2), NiCl(2) and CuCl(2)) produced abundant ligated metal ion adducts [1 + MCl](+) and [2 + MCl](+). In addition, CuCl(2) also gave rise to Cu(+) adducts. The ligated metal ion adducts upon collision-induced dissociation (CID) showed characteristic fragmentation pathways reflecting the favoured site of coordination. The results show that MgCl(+) prefers oxygen over sulfur, whereas the reverse is true for ZnCl(+) adducts, exemplified by the preferred fragmentation of [1 + MgCl](+) as elimination of MgCl(OH), while that of [1 + ZnCl](+) is expulsion of ZnCl(SCH(3)). Co and Ni chloride adducts tend to give stable metal coordinated species. Cleavage of the dithiolane ring followed by elimination of C(2)H(4)S is the preferred pathway during the CID of [2 + MCl](+) adducts. The CuCl(+) adducts of 1 and 2 showed reduction of Cu((I)) to Cu((0)) resulting in the M(+)(*)ions of 1 and 2. Abstraction of *CH(3) resulting in elimination of CuCH(3) was observed during CID of Cu(+) adducts of 1 and 2. A comparative study of the corresponding Ag(+) adducts revealed a similar behaviour.     

The inclusion behavior of benzo-15-crown-5 with hydrated transition metal picrates

Six kinds of benzo-15-crown-5 (L) adducts having the stoichiometric formula M(Pic)₂ · L · xH₂O (M=Mn, Cu, x=2; M=Co, Ni, Zn, Cd, x=4; Pic means picrate anion) have been synthesized and characterized by EA, IR, UV and molar conductance. The X-ray crystal structural analysis of the benzo-15-crown-5 adduct with hydrated copper(II) picrate revealed that the benzo-15-crown-5 molecule virtually acts as a second-sphere ligand, which associates with the copper(II) ion by hydrogen bonding of the coordinating water molecule. By the comparison of the IR, UV spectra and molar conductance of the new adducts prepared, it can be deduced that the other adducts exhibit the similar coordination environment to that of the copper adduct.     

One-pot syntheses, coordination, and characterization of application-specific biodegradable ligand-polymers

Syntheses and chelation of tailored biodegradable polymers to rhenium for medicinal applications are described. A group of bifunctional ligand-initiators consisting of a chelating end for metal complexation and a hydroxyl end suitable to initiate polymerization was utilized in the ring-opening polymerization of l-lactide. The resulting biodegradable ligand-polymers were equipped with a tridentate donor set to coordinate specific metal ions. All synthesized compounds were characterized by IR spectroscopy, 1D/2D NMR spectroscopy and MALDI-TOF mass spectrometry, confirming successful polymerization and coordination to the [Re(CO)(3)](+) core. The pliability of designing application-specific polymers with respect to the nature of the metal ion facilitates extending the application of these biodegradable polymers to early detection of diseases (imaging) and radiotherapy of cancers.     

Hydrogen bond directed self-assembly of core-substituted naphthalene bisimides with melamines in solution and at the graphite interface

A series of red and blue highly fluorescent core-substituted naphthalene bisimide dyes has been synthesized and they have been investigated as supramolecular building blocks. NMR and UV-Vis titration experiments of these dyes with complementary melamines revealed the formation of triple hydrogen bonds (DAD-ADA arrays) in solution. At stoichiometric ratios, ditopic melamine receptors could dissolve otherwise insoluble bisimides by means of hydrogen bonding, even in aliphatic solvents. At the solution/graphite interface, one-dimensional chains of hydrogen bonded naphthalene bisimides and two-dimensional adlayers of ditopic melamines are formed for the pure compounds but little evidence for heterocomplexes between the two complementary building blocks could be obtained.     

非手性席夫碱-异丙氧基铝引发外消旋丙交酯的立构选择性聚合

摘要以非手性的席夫碱-异丙氧基铝(Ⅱ)引发外消旋丙交酯(rac-LA)的立构选择性聚合. 其聚合动力学研究结果表明, 聚合反应对于单体符合一级反应动力学. 所得聚合物的数均分子量与单体转化率成正比, 并且分子量分布很窄, 表明该聚合反应具有良好的可控性. 此外所得的聚外消旋乳酸是tm为179 ℃的结晶性聚合物. 13C NMR和同核去偶1H NMR谱表明, 所得的聚乳酸是一种立构嵌段聚合物, 平均嵌段长度为11个乳酸单元.     

MgCl2/R'nAl(OR)3-n: an excellent activator/support for transition-metal complexes for olefin polymerization

A new and effective method for the activation, and simultaneously, immobilization of bis(phenoxyimine) early-transition-metal complexes for olefin polymerization (known as FI catalysts), which makes use of MgCl(2)/R'(n)Al(OR)(3-n) as an activator/support, has been developed. Ti-, Zr-, and V-FI catalysts combined with this MgCl(2)-based compound can form highly active MgCl(2)-supported single-site catalysts capable of demonstrating superior catalytic properties, compared to the corresponding homogeneous methylaluminoxane- (Ti- and Zr-FI catalysts) or alkylaluminum-activation systems (V-FI catalysts), in terms of their catalytic activity, molecular weight, stereoselectivity, and comonomer incorporation. Additionally, these new catalysts can produce polymers of significant morphology with high efficiency. Notably, the MgCl(2)-based compounds can also effectively activate and immobilize the early-to-late transition-metal complexes that have emerged recently. Thus, the application of MgCl(2)-based compounds as activators/supports for transition-metal complexes for olefin polymerization provides a conceptually new strategy for the development of methylaluminoxane- and borate-free, high-performance, single-site catalysts capable of controlling polymer morphology.     

Enhanced 13C resolution in semi-selective HMbC: a band-selective, constant-time HMBC for complex organic structure elucidation by NMR

A semi-selective 2D HMBC experiment is described which yields high-resolution in the indirect carbon-13 dimension by suppressing homonuclear proton coupling modulations and so provides an NMR technique suitable for the structure elucidation of organic compounds which exhibit particularly crowded carbon-13 spectra.     

Monitoring Conformational Changes in an Enzyme Conversion Inhibitor Using Pure Shift Exchange NMR Spectroscopy

We report the acquisition of 2D NMR EXSY spectra with ultrahigh resolution, which allows for probing the slow conformational exchange process in a pharmaceutical compound. The resolution enhancement is achieved by implementing interferogram based PSYCHE homonuclear decoupling to generate a pure shift proton spectrum along the direct domain of the resulting data. The performance of this pure shift EXSY pulse sequence is compared to the standard experiment recorded under identical conditions. It is found that although being less sensitive and requiring a longer acquisition time, the quality of pure shift spectra allows for extracting exchange rates values that are coherent with the ones determined by standard approach, on a temperature range that demonstrates the robustness of the chosen homonuclear decoupling method. The resolution enhancement provided by the simplification of proton line shape allows for probing a higher number of proton sites whose analysis would have been biased using a standard method. These results open the way to a thorough and accurate study of chemical exchange processes based on a multi-site analysis of 2D pure shift EXSY spectra     

3-Methoxycarbonyl-4-phenyl-2-pyrrolidone in reactions with benzalmalonate and its analogs

3-Methoxycarbonyl-4-phenyl-2-pyrrolidone reacts with benzalmalonate and related compounds as an N-nucleophile affording adducts as an easily resolvable diastereoisomeric mixture. Structure of the synthesized compounds is studied by IR and ¹H, ¹³C NMR spectroscopy. Structural parameters and configurations of the stereoisomers of one among the series of synthesized compounds was determined by X-ray structural analysis. The pyrrolidone ring of these compounds is shown to be present in an envelope conformation. The supramolecular structures in crystal are formed mainly on account of intermolecular hydrogen bonds of C-H?O type and π?π interactions.

     

Using pure shift HSQC to characterize microgram samples of drug metabolites

Difficulties in isolating samples from complex biological matrices and sensitivity limitations have long stymied the utilization of heteronuclear 2D NMR for the characterization of drug metabolites. Small diameter cryogenic NMR probes have largely ameliorated sensitivity limitations and the recently reported pure shift HSQC 2D NMR pulse sequence offers a further and marked improvement in both resolution and sensitivity. Using a 7.4 μg sample of the commercially available metabolite 3-hydroxy carbamazepine dissolved in 30 μL of deuterated solvent and a 600 MHz NMR equipped with a 1.7 mm cryogenic NMR probe, it was possible to acquire high signal-to-noise pure shift HSQC data in just over 30 min. A conventional HSQC spectrum acquired with identical parameters had approximately half the signal-to-noise of the pure shift HSQC spectrum. Collapsing the vicinal homonuclear couplings in the pure shift HSQC spectrum also significantly improves resolution. A practical, real world application of the technique is illustrated with the chromatographically isolated metabolite 3-hydroxy amiodarone from incubation with CYP2J2 recombinant enzyme. High quality pure shift HSQC data were recorded in slightly over 14 h for a 3 μg sample of the metabolite.     

A versatile template for the formation of [2]pseudorotaxanes. 1,2-Bis(pyridinium)ethane axles and 24-crown-8 ether wheels

Linear 1,2-bis(pyridinium)ethane 'axles' and macrocyclic 24-membered crown ether 'wheels' (, and ) combine to form [2]pseudorotaxanes. These interpenetrated adducts are held together by N+...O ion-dipole interactions, a series of C-H...O hydrogen bonds and pi-stacking between electron-poor pyridinium rings of the axle and electron-rich catechol rings of the wheel. 1H NMR spectroscopy was used to identify the structural details of the interaction and to determine the thermodynamics of the binding process in solution. Analysis of nine of these adducts by single crystal X-ray crystallography allowed a detailed study of the non-covalent interactions in the solid state. A wide variety of structural changes could be made to the system. The versatility and potential of the template for the construction of permanently interlocked structures such as rotaxanes and catenanes is discussed.     

Crystal structures of Ziegler-Natta catalyst supports

The crystal structures of three MgCl(2)·nEtOH complexes with n=1.5, 2.8, and 3.3 have been fully determined. Such complexes are the fundamental precursors for Ziegler-Natta polymerization catalysts used to produce polyolefins on a multimillion-ton scale worldwide. The ab initio structure solution showed that the structure of MgCl(2)·nEtOH complexes with n=1.5 and 2.8 are based on ribbons of metal-centered octahedra, whereas for n=3.3 this chainlike arrangement breaks into a threadlike structure of isolated octahedra linked by hydrogen bonds. A clear correlation between catalyst performance and the crystal structure of precursors has been found, and reveals the fundamental role of the latter in determining catalyst properties. The direct knowledge of building blocks in the precursor structures will help to develop more accurate models for activated catalysts. These models will not require the arbitrary and oversimplified assumption of locating the catalyst active sites on selected cut surfaces of the α-MgCl(2) crystal lattice.     

Hydrothermal synthesis, structures, and photoluminescent properties of benzenepentacarboxylate bridged networks incorporating zinc(II)-hydroxide clusters or zinc(II)-carboxylate layers

The first coordination compounds of partially or wholly deprotonated benzenepentacarboxylic acid (H5L) were synthesized in the presence or absence of auxiliary 2,2'-bipyridyl (2,2'-bpy) and 1,10-phenanthroline (phen) ligands, and their crystal structures and photoluminescent properties were characterized. Their formulas are [Zn6(mu3-OH)2(L)2(H2O)6]n (1), [Zn5(mu3-OH)2(HL)2(2,2'-bpy)2]n (2), [Zn2(HL)(phen)2(H2O)2]n (3), and [Zn5(L)2(phen)4(H2O)3]n.2nH2O (4). Both 1 and 2 are three-dimensional (3D) zinc(II)-hydroxide cluster based coordination frameworks. 1 contains distorted chairlike hexanuclear Zn6(mu3-OH)2 cluster units as secondary building blocks. Each Zn6(mu3-OH)2 unit connects six others through the three-connected nodes of L5- ligands into a 3D rigid and condensed coordination network, whereas in 2, each pentanuclear Zn5(mu3-OH)2 unit connects the other six ones through the three-connected [HL]4- nodes into a 3D network in the simple cubic packing mode. 3 has two-dimensional (2D) Zn(II)-carboxylate supramolecular layers constructed from a one-dimensional (1D) coordination chain structure by hydrogen bonds of the water and mu5-[HL]4- bridges, whereas 4 has 2D coordination layers composed of Zn(II) and mu8-L5- bridges. The adjacent coordination assemblies in 3 and 4 are further extended by hydrogen bonds and pi...pi interactions into 3D supramolecular architectures. 1-4 are photoluminescent active materials, and their photofluorescent properties are closely related to their intrinsic structure arrangements.     

拉曼光谱研究CaCl2和MgCl2对水结构的影响

测试了CaCl2、MgCl2溶液(浓度小于1.0 mol•L-1)的OH伸缩振动区域的拉曼光谱.对所得到的拉曼光谱进行了计算机去卷积处理,并由此计算了不同溶液中水的四面体结构的百分数.研究表明,CaCl2、MgCl2对水中四面体结构有破坏作用，且CaCl2的破坏作用比MgCl2大.与17O核磁共振结果对比与分析,认为CaCl2、MgCl2虽然破坏水中的四面体结构,但通过促进含氢键数少的水分子形成氢键,故从总体上促进水的缔合结构.     

MgCl_2晶型对丙烯聚合MgCl_2载体催化剂活性的影响

ＭｇＣｌ_２晶型对丙烯聚合ＭｇＣｌ_２载体催化剂活性的影响张明辉，肖世镜中国科学院化学研究所，北京，１００８０）关键词丙烯聚合、ＭｇＣｌ２、载体催化剂近年来，有关ＭｇＣＩ。载体催化剂的研究报道和综述文章不少，但涉及载体晶型对催化剂结构性能的影响却少见．...     

Characterization and quantification of microstructures of a fluorinated terpolymer by both homonuclear and heteronuclear two‐dimensional NMR spectroscopy

Fluoropolymers are usually insoluble in organic solvents. Insolubility of fluoropolymers limits basic characterization such as microstructural investigations. In the family of fluoropolymers, terpolymer of tetrafluorethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (VDF), named THV is one of the newest members. There are nine grades of THV available. Among the nine grades, THV‐221 G is an ideal model polymer for basic characterization purposes. THV‐221 G is soluble in solvents such as acetone and ethyl acetate. In the current report, both homonuclear and heteronuclear 2D NMR experiments were employed in solution on THV‐221 G. The homonuclear gradient correlation spectroscopy NMR measurement revealed that THV has two adjacent TFE units in addition to TFE‐HFP sequence orders. The fraction of the microstructures is quantified by the analysis of 1D solution ¹⁹F NMR spectrum. Further, the gradient heteronuclear single quantum coherence experiment helped with the clarification of chemical environments of the units TFE, HFP, and VDF. The 1D solution ¹³C NMR spectrum was helpful in clarifying sequence assignments of VDF. It is concluded that THV is a random polymer with a limited fraction of TFE‐TFE and TFE‐HFP sequence orders in addition to head‐to‐tail polymerization of VDF unit. Copyright © 2014 John Wiley & Sons, Ltd.