研究塑性有机固体的1H NMR方法

塑性有机固体的＾１Ｈ ＭＡＳ ＮＭＲ谱通常由一高分辨谱与一宽线谱组成，其中高分辨谱分量对应于塑性相，而宽线谱分量对应于刚性相。长延迟回波－ＭＡＳ ＮＭＲ实验可测得塑性相的高分辨谱，ＣＲＡＭＰＳ方法可测得整个固体＾１Ｈ体系的高分辨谱，常温下它往往以刚性相的贡献为主要成分。实验结果表明，结合＾１Ｈ ＭＡＳ、回波－ＭＡＳ与ＣＲＡＭＰＳ等三种固态高分辨＾１Ｈ ＮＭＲ技术可望成为深入研究塑性有机固体中塑性相     

Combining multinuclear high-resolution solid-state MAS NMR and computational methods for resonance assignment of glutathione tripeptide

We present a complete set of experimental approaches for the NMR assignment of powdered tripeptide glutathione at natural isotopic abundance, based on J-coupling and dipolar NMR techniques combined with (1)H CRAMPS decoupling. To fully assign the spectra, two-dimensional (2D) high-resolution methods, such as (1)H-(13)C INEPT-HSQC/PRESTO heteronuclear correlations (HETCOR), (1)H-(1)H double-quantum (DQ), and (1)H-(14)N D-HMQC correlation experiments, have been used. To support the interpretation of the experimental data, periodic density functional theory calculations together with the GIPAW approach have been used to calculate the (1)H and (13)C chemical shifts. It is found that the shifts calculated with two popular plane wave codes (CASTEP and Quantum ESPRESSO) are in excellent agreement with the experimental results.     

An investigation of the hydrogen-bonding structure in bilirubin by 1H double-quantum magic-angle spinning solid-state NMR spectroscopy.

The complex hydrogen-bonding arrangement in the biologically important molecule bilirubin IXalpha is probed by using 1H double-quantum (DQ) magic-angle spinning (MAS) NMR spectroscopy. Employing fast MAS (30 kHz) and a high magnetic field (16.4 T), three low-field resonances corresponding to the different hydrogen-bonding protons are resolved in a 1H MAS NMR spectrum of bilirubin. These resonances are assigned on the basis of the proton-proton proximities identified from a two-dimensional rotor-synchronized 1H DQ MAS NMR spectrum. An analysis of 1H DQ MAS spinning-sideband patterns for the NH protons in bilirubin allows the quantitative determination of proton-proton distances and the geometry. The validity of this procedure is proven by simulated spectra for a model three-spin system, which show that the shortest distance can be determined to a very high degree of accuracy. The distance between the lactam and pyrrole NH protons in bilirubin is determined to be 0.186 +/- 0.002 nm (corresponding to a dominant dipolar coupling constant of 18.5 +/- 0.5 kHz). The analysis also yields a distance between the lactam NH and carboxylic acid OH protons of 0.230 +/- 0.008 nm (corresponding to a perturbing dipolar coupling constant of 9.9 +/- 1.0 kHz) and an H-H-H angle of 122 +/- 4 degrees. Finally, a comparison of 1H DQ MAS spinning-sideband patterns for bilirubin and its dimethyl ester reveals a significantly longer distance between the two NH protons in the latter case.     

Identifying guanosine self assembly at natural isotopic abundance by high-resolution 1H and 13C solid-state NMR spectroscopy

By means of the (1)H chemical shifts and the proton-proton proximities as identified in (1)H double-quantum (DQ) combined rotation and multiple-pulse spectroscopy (CRAMPS) solid-state NMR correlation spectra, ribbon-like and quartet-like self-assembly can be identified for guanosine derivatives without isotopic labeling for which it was not possible to obtain single crystals suitable for diffraction. Specifically, characteristic spectral fingerprints are observed for dG(C10)(2) and dG(C3)(2) derivatives, for which quartet-like and ribbon-like self-assembly has been unambiguously identified by (15)N refocused INADEQUATE spectra in a previous study of (15)N-labeled derivatives (Pham, T. N.; et al. J. Am. Chem. Soc.2005, 127, 16018). The NH (1)H chemical shift is observed to be higher (13-15 ppm) for ribbon-like self-assembly as compared to 10-11 ppm for a quartet-like arrangement, corresponding to a change from NH···N to NH···O intermolecular hydrogen bonding. The order of the two NH(2)(1)H chemical shifts is also inverted, with the NH(2) proton closest in space to the NH proton having a higher or lower (1)H chemical shift than that of the other NH(2) proton for ribbon-like as opposed to quartet-like self-assembly. For the dG(C3)(2) derivative for which a single-crystal diffraction structure is available, the distinct resonances and DQ peaks are assigned by means of gauge-including projector-augmented wave (GIPAW) chemical shift calculations. In addition, (14)N-(1)H correlation spectra obtained at 850 MHz under fast (60 kHz) magic-angle spinning (MAS) confirm the assignment of the NH and NH(2) chemical shifts for the dG(C3)(2) derivative and allow longer range through-space N···H proximities to be identified, notably to the N7 nitrogens on the opposite hydrogen-bonding face.     

1H fast MAS NMR studies of hydrogen-bonding interactions in self-assembled monolayers

The structures formed by the adsorption of carboxyalkylphosphonic acids on metal oxides were investigated by (1)H fast magic angle spinning (MAS), heteronuclear correlation (HETCOR), and (1)H double-quantum (DQ) MAS solid-state NMR experiments. The diacids HO(2)C(CH(2))(n)PO(3)H(2) (n = 2, 3, 11, and 15) were adsorbed on TiO(2) and two types of ZrO(2) powders having average particle sizes of 20, 30, and 5 nm, respectively. Carboxyalkylphosphonic acids bind selectively via the phosphonate group, forming monolayers with pendant carboxylic acid groups. Whereas dipolar coupled P-OH protons are detected on TiO(2), there are only isolated residual P-OH groups on ZrO(2), reflecting the relative binding strengths of phosphonic acids on these two substrates. From a comparative (1)H MAS NMR study with an analogous monolayer system, HO(2)C(CH(2))(7)SH coated gold nanoparticles, the hydrogen-bonding network at the monolayer/air interface is found to be quite disordered, at least for SAMs deposited on nonplanar substrates. Whereas only hydrogen-bonded homodimers occur in the bulk diacids, hydrogen bonding between the carboxylic and phosphonic acid groups is present in multilayers of the diacids on the ZrO(2) nanopowder.     

Auger decay of molecular double core-hole state

We report on theoretical Auger electron kinetic energy distribution originated from sequential two-step Auger decays of molecular double core-hole (DCH) state, using CH(4), NH(3), and H(2)CO molecules as representative examples. For CH(4) and NH(3) molecules, the DCH state has an empty 1s inner-shell orbital and its Auger spectrum has two well-separated components. One is originated from the 1st Auger transition from the DCH state to the triply ionized states with one core hole and two valence holes (CVV states) and the other is originated from the 2nd Auger transition from the CVV states to quadruply valence ionized (VVVV) states. Our result on the NH(3) Auger spectrum is consistent with the experimental spectrum of the DCH Auger decay observed recently [J. H. D. Eland, M. Tashiro, P. Linusson, M. Ehara, K. Ueda, and R. Feifel, Phys. Rev. Lett. 105, 213005 (2010)]. In contrast to CH(4) and NH(3) molecules, H(2)CO has four different DCH states with C1s(-2), O1s(-2), and C1s(-1)O1s(-1) (singlet and triplet) configurations, and its Auger spectrum has more complicated structure compared to the Auger spectra of CH(4) and NH(3) molecules. In the H(2)CO Auger spectra, the C1s(-1)O1s(-1) DCH → CVV Auger spectrum and the CVV → VVVV Auger spectrum overlap each other, which suggests that isolation of these Auger components may be difficult in experiment. The C1s(-2) and O1s(-2) DCH → CVV Auger components are separated from the other components in the H(2)CO Auger spectra and can be observed in experiment. Two-dimensional Auger spectrum, representing a probability of finding two Auger electrons at specific pair of energies, may be obtained by four-electron coincidence detection technique in experiment. Our calculation shows that this two-dimensional spectrum is useful in understanding contributions of CVV and VVVV states to the Auger decay of molecular DCH states.     

3-甲基-2(1H)-喹喔啉系列衍生物的电子轰击质谱

用电子轰击质谱（EI－MS）研究了1－烷基－3－甲基－2（1H）－喹喔啉－2－酮（烷基为H，CH3，Et,n-C5H11),1-烷基－3－甲基－6－硝基－2（1H）－喹喔啉－2－酮（烷基为CH3，Et)和1－甲基－3－甲基－6－胺基－2（1H）－喹喔啉－2－酮，结合其结构特征总结出一些裂解规律。讨论了不同取代基对这类化合物熔点的影响，结果表明：在同类喹喔啉化合物中，随着烷基链的增长，样品熔点通常会有所降低，而硝基及胺基的引入会使其熔点升高。     

CH自由基共振增强多光子电离光谱

ＣＨ自由基在燃烧化学、星际化学、化学发光和化学激光研究中占有重要的地位,并且作为最简单的碳氢化合物,ＣＨ自由基是理想的理论计算模型分子,在理论研究领域中也有着重要的地位．因此 ,多年来人们对ＣＨ自由基进行了大量的研究［１ -９］,但是对于ＣＨ自由基,到目前为止大部分局限于低激发态的研究,对于较高激发态的研究报导则很少见．Ｃｈｕｐｋａ等［２ -６］用(２ １)ＲＥＭＰＩ方法获得了ＣＨＤ态的ｖ＝２振动能级光谱．然而后来Ｔｊｏｓｓｅｍ和Ｓｍｙｔｈ［７］测量了同波段的ＲＥＭＰＩ光谱,发现他们测得的光谱谱峰强度与…     

High-pressure delta-Al(OH)3 and delta-AlOOH phases and isostructural hydroxides/oxyhydroxides: new structural insights from high-resolution 1H and 27Al NMR

In order to shed light on the proton distributions and order/disorder in high-pressure delta-Al(OH)3 and delta-AlOOH phases, two-dimensional, high-resolution 1H CRAMPS (FSLG)-MAS NMR and 27Al 3QMAS NMR spectra have been obtained. For delta-Al(OH)3, the 1H CRAMPS-MAS NMR revealed two peaks with an intensity ratio close to 2:1. The 27Al MAS and 3QMAS NMR suggest a single Al site with a well-defined local structure. For delta-AlOOH, the 1H and 27Al NMR indicate the presence of a single H and Al site each. These results are consistent with crystal structures refined from X-ray diffraction. For comparison, 1H MAS and CRAMPS-MAS NMR spectra were also obtained for several other hydroxides/oxyhydroxides, including In(OH)3 and InOOH that have similar structures to delta-Al(OH)3 and delta-AlOOH, respectively. These data not only provide additional insights into the proton distributions in these important crystal structure classes but also together provide a better defined quantitative correlation between 1H chemical shift and hydrogen-bonding O...O distance.     

Visible absorption spectrum of the CH3CO radical

The visible absorption spectrum of the acetyl radical, CH(3)CO, was measured between 490 and 660 nm at 298 K using cavity ring-down spectroscopy. Gas-phase CH(3)CO radicals were produced using several methods including: (1) 248 nm pulsed laser photolysis of acetone (CH(3)C(O)CH(3)), methyl ethyl ketone (MEK, CH(3)C(O)CH(2)CH(3)), and biacetyl (CH(3)C(O)C(O)CH(3)), (2) Cl + CH(3)C(O)H --> CH(3)C(O) + HCl with Cl atoms produced via pulsed laser photolysis or in a discharge flow tube, and (3) OH + CH(3)C(O)H --> CH(3)CO + H(2)O with two different pulsed laser photolysis sources of OH radicals. The CH(3)CO absorption spectrum was assigned on the basis of the consistency of the spectra obtained from the different CH(3)CO sources and agreement of the measured rate coefficients for the reaction of the absorbing species with O(2) and O(3) with literature values for the CH(3)CO + O(2) + M and CH(3)CO + O(3) reactions. The CH(3)CO absorption spectrum between 490 and 660 nm has a broad peak centered near 535 nm and shows no discernible structure. The absorption cross section of CH(3)CO at 532 nm was measured to be (1.1 +/- 0.2) x 10(-19) cm(2) molecule(-1) (base e).     

Precision 1H-1H distance measurement via 13C NMR signals: utilization of 1H-1H double-quantum dipolar interactions recoupled under magic angle spinning conditions

We applied the POST-C7 DQ-dipolar recoupling pulse sequence to the measurement of (1)H-(1)H distances with high precision. The spectral resolution is enhanced by detecting the (1)H magnetization via (13)C signals. A least-squares fitting of the build-up curve of the transferred magnetization to the exact numerical simulations yielded a (1)H(alpha)-(1)H(beta) distance of 248 +/- 4 pm for fully (13)C-labeled L-valine. This distance agrees with the neutron diffraction study. The negative transferred magnetization clearly indicates that the direct DQ (1)H-(1)H dipolar couplings have the largest effect. The signal for the magnetization transfer builds up rapidly by the direct (1)H-(1)H dipolar coupling, and decreases to zero at longer mixing time when the relayed magnetization transfer becomes significant. This large intensity change of the signal leads to the high precision in the distance measurement. We inspected factors that limit the effective bandwidth of the POST-C7 recoupling for the (1)H and (13)C homonuclear spin systems. The spin interactions at times shorter than the cycle time of the C7 sequence were also evaluated to measure the distances. The carbon-detected 2D (1)H DQ mixing experiment was demonstrated for the measurement of multiple (1)H-(1)H distances.     

取代环戊二烯的合成和^1HNMR谱

本文研究了苯基锂和对、间、邻甲苯基锂及对、邻甲氧苯基锂与6,6-二烷基富烯环外双键加成反应的立体效应。在室温下于乙醚溶剂中,6,6-二烷基富烯同上述芳基锂反应,形成取代环戊二烯基锂,经水解给出含或不含手性碳的叔烷基环戊二烯。     

Chain dynamics in partially cross-linked polyethylene by combined rheology and NMR-based molecular rheology

In recent years, ¹H double-quantum NMR (DQ NMR) was established as a suitable molecular-rheology technique to elucidate chain dynamics and to determine entanglement or crosslink densities in linear entangled polymer melts and permanent as well as transient networks. In this work, industrial grade high-density polyethylene, partially cross-linked via electron beam irradiation in the semicrystalline state, is probed in the melt state by low-field DQ NMR and shear rheology. The DQ NMR data is analyzed by two approaches, one assuming the presence of a permanent network and the other considering the potentially complex relaxation spectrum of the studied inhomogeneous systems. A correlation between the DQ NMR results and extent of cross-linking is found. By direct comparison of the rheological results and the NMR-based segmental orientation autocorrelation functions (OACF) via time–temperature superposition (TTS), qualitative consistency between the microscopic and macroscopic observables is established. In this way, the frequency range of shear rheology can be extended by about two decades into the 10 krad/s range. The NMR method is thus a valuable extension of the toolbox of characterization techniques, where gel content measurements by solvent extraction proved to be the least sensitive.     

Crystal Structure of Bis｛1-(2-methoxyethyl)indenyl｝dysprosium Chloride

1　INTRODUCTION　　Organolanthanidecomplexeshavebeenextensivelystudied.However,thestud-iesofindenylrareearthcomplexeswererelativelylimited[1].Althoughaseriesoftri-indenyltetrahydrofuranatolanthanide((C9H7)3Ln·THF)havebeensynthesizedandstudiedbyTsutsuiandGyslingabout30yearsago[2],onlyafewcrystalstruc-turesofindenyllanthanidecomplexeshavebeenreported[1].Moreover,mostofthereportedindenyllanthanidecomplexesweresynthesisedbymetatheticalreactionsofanhydrouslanthanidetrichlorideswithindenyls…     

Near-UV Photodissociation Dynamics of Thiomethoxy Radical via eA2A1 State: H-atom Product Channe

Photodissociation dynamics of jet-cooled thiomethoxy radical (CH3S) via the eA2A1? eX2E transition is investigated near 352 nm. The H-atom product channel is observed directly for the ˉrst time by H-atom product yield spectrum and photofragment translational spectroscopy. The 2132 vibrational level of the eA2A1 state dissociates to the H+H2CS products. The H+H2CS product translational energy release is modest and peaks around 33 kJ/mol; the H-atom angular distribution is isotropic. The dissociation mechanism is consistent with internal conversion of the excited eA2A1 state to the eX2E ground state and subsequent unimolecular dissociation on the ground state to the H+H2CS products.     

A microwave spectroscopic and quantum chemical study of 3-butyne-1-selenol (HSeCH2CH2C[triple bond]CH)

The microwave spectrum of 3-butyne-1-selenol has been studied by means of Stark-modulation microwave spectroscopy and quantum chemical calculations employing the B3LYP/aug-cc-pVTZ and MP2/6-311++G(3df,3pd) methods. Rotational transitions attributable to the H80SeCH2CH2C[triple bond]CH and H78SeCH2CH2C[triple bond]CH isotopologues of two conformers of this molecule were assigned. One of these conformers possesses an antiperiplanar arrangement for the atoms Se-C-C-C, while the other is synclinal and seems to be stabilized by the formation of a weak intramolecular hydrogen bond between the hydrogen atom of the selenol group and the pi electrons of the CC triple bond. The energy difference between these conformers was determined to be 0.2(5) kJ/mol by relative intensity measurements, and the hydrogen-bonded form was slightly lower in energy.     

CCl2(A^1B1)自由基不同振动态的猝灭动力学

对CCl4/Ar混合气体直流脉冲放电产生CCl2自由基，再分别用波长为550.56nm,541.52nm,532.25nm,524.31nm,523.82nm和523.27nm的激光将电子基态CCl2激励到激发态A^1B1的(0,3,0),(0,4,0),(1,3,0),(0,6,0),(1,4,0),(2,2,0)振动态，激发态CCl2(A^1B1)的不同振动态的时间分辨荧光信号显示该信号呈双指数衰减，测得室温下CCl2(A^1B1)不同振动态被NH3,H2O,CH2Br2,NH(CH3)2,NH(C2H5)2,N(C2H5)3,n-C6H14等分子猝灭的实验结果，用三能级模型分析处理实验数据，获得态分辨速率常数kA和ka值，并对实验结果进行了讨论。     

A photoelectron and TPEPICO investigation of the acetone radical cation

The valence shell photoelectron spectrum, threshold photoelectron spectrum, and threshold photoelectron photoion coincidence (TPEPICO) mass spectra of acetone have been measured using synchrotron radiation. New vibrational progressions have been observed and assigned in the X 2B2 state photoelectron bands of acetone-h6 and acetone-d6, and the influence of resonant autoionization on the threshold electron yield has been investigated. The dissociation thresholds for fragment ions up to 31 eV have been measured and compared to previous values. In addition, kinetic modeling of the threshold region for CH3* and CH4 loss leads to new values of 78 +/- 2 kJ mol(-1) and 75 +/- 2 kJ mol(-1), respectively, for the 0 K activation energies for these two processes. The result for the methyl loss channel is in reasonable agreement with, but slightly lower than, that of 83 +/- 1 kJ mol(-1) derived in a recent TPEPICO study by Fogleman et al. The modeling accounts for both low-energy dissociation channels at two different ion residence times in the mass spectrometer. Moreover, the effects of the ro-vibrational population distribution, the electron transmission efficiency, and the monochromator band-pass are included. The present activation energies yield a Delta(f)H298 for CH3CO+ of 655 +/- 3 kJ mol(-1), which is 4 kJ mol(-1) lower than that reported by Fogleman et al. The present Delta(f)H298 for CH3CO+ can be combined with the Delta(f)H298 for CH2CO (-47.5 +/- 1.6 kJ mol(-1)) and H+ (1530 kJ mol(-1)) to yield a 298 K proton affinity for ketene of 828 +/- 4 kJ mol(-1), in good agreement with the value (825 kJ mol(-1)) calculated at the G2 level of theory. The measured activation energy for CH4 loss leads to a Delta(f)H298 (CH2CO+*) of 873 +/- 3 kJ mol(-1).     

Chemistry of cobalt acetate. 7. Electrochemical oxidation of mu3-oxo-centered cobalt(III) acetate trimers

Electrochemical and spectroelectrochemical properties of five cobalt(III) acetate complexes [CoIII3(mu3-O)(CH3CO2)5(OR)(py)3][PF6] are described, where py=pyridine and R=OCCH3 (A), H (B), CH3 (C), CH2CH=CH2 (D), and CH2C6H5 (E). Each is reduced irreversibly as observed by cyclic voltammetry at room temperature and at -40 degrees C in acetonitrile at scan rates up to 20 V s(-1), but oxidized reversibly to a mixed-valence Co(III)2Co(IV) species at approximately 1.23 V vs the ferrocenium/ferrocene couple. Controlled potential coulometry confirmed a one-electron-oxidation process. Spectroelectrochemical oxidation of A at 5 degrees C showed isosbestic points in the electronic absorption spectrum that showed the oxidized complex to be stable in solution for at least 1 h.     

Calorimetric and computational study of 3-buten-1-ol and 3-butyn-1-ol. Estimation of the enthalpies of formation of 1-alkenols and 1-alkynols

The enthalpies of combustion and vaporization of 3-buten-1-ol and 3-butyn-1-ol have been measured by static bomb combustion calorimetry and correlation gas chromatography techniques, respectively, and the gas-phase enthalpies of formation, Delta(f)H degrees (m)(g), have been determined, the values being -147.3 +/- 1.8 and 16.7 +/- 1.6 kJ mol(-1), for 3-buten-1-ol and 3-butyn-1-ol, respectively. High level calculations at the G2 and G3 levels have also been carried out. Relationships between the enthalpies of formation of 1-alkanols, 1-alkenols and 1-alkynols and with the corresponding hydrocarbons have been discussed. From the calculated contributions to Delta(f)H degrees (m)(g) for the substitutions of CH(3) by CH(2)OH, CH(3)CH(2) by CH(2)=CH and CH(3)CH(2) by CH triple bond C, we have estimated the Delta(f)H degrees (m)(g) values for 3-buten-1-ol and 3-butyn-1-ol, in excellent agreement with the experimental ones. Delta(f)H degrees (m)(g) values for 1-alkenols and 1-alkynols up to 10 carbon atoms have also been estimated.