粉状白钨酸的研究——Ⅲ.从粉状白钨酸制备偏钨酸铵和偏钨酸有机铵盐以及它们的性质研究

本文继活性粉状白钨酸的制得,用其制备偏钨酸钠后,进一步报道了以粉状白钨酸为出发点的偏钨酸铵(NH_4)_6[H_2(W_3O_(10))_4]·nH_2O、偏钨酸乙基铵、二乙基铵、三乙基铵和四乙基铵盐的合成及部分性质研究。同法还制得偏钨酸三正丁基铵,经化学分析其组成接近[(n-C_4H_9)_3NH]_6·[H_2(W_3O_(10))_4],与文献报道的“酸式盐”[(n-C_4H_9)_3NH]_5H[H_2(W_3O_(10))_4]不同。     

硼化合物的研究——Ⅺ.氢硼酸π-环戊二烯基-烷撑双(二苯基膦)合镍(Ⅱ)的合成和性质

本文以C_5H_5NiPPh_3Cl与Ph_2P(CH_2)_nPPh_2为起始物合成了C_5H_5NiPh_2P(CH_2)nPPh_2Cl·C_6H_6,再进一步与氢硼酸季铵盐反应,合成了12个氢硼酸π-环戊二烯基-烷撑双(二苯基膦)合镍(Ⅱ)化合物。对这些化合物进行了元素分析、红外光谱鉴定,并测定了氯化物的~1H NMR谱。所有含硼化合物于室温下对空气是稳定的,而它们的热稳定性与阳离子中螯合环的大小和氢硼酸根结构有关,即氢硼酸根相同的化合物,热稳定性随着螯合环的增大而降低;阳离子相同时,热稳定性次序是:[C_5H_5NiPh_2P(CH_2)_nPPh_2]_2B_(12)H_(12)>[C_5H_5NiPh_2P(CH_2)_nPPh_2]_2B_(10)H_(10)>C_5H_5NiPh_2P(CH_2)_nPPh_2B_(11)H_(14)>C_5H_5NiPh_2P(CH_2)_nPPh_2B_3H_8。     

多氟烯烃~(19)F化学位移与亲核反应性的关系

由于多氟烯烃化合物中氟原子的强的电子效应,使得烯基氟的~(19)F化学位移参数与该烯烃的电荷密度分布有密切的联系。它在一定程度上反映了多氟烯烃在亲核反应中的化学反应性。这在某种意义上来说加深了对多氟烯烃结构及化学反应性的认识。一、多氟烯烃电荷密度与~(19)F化学位移的关系 Spiesecke和Schneider在1961年首次发表了C_5H_5~-,C_6H_6,C_7H_7~+上碳原子的π电子电荷密度与~(13)C、~(1)H化学位移的关系。他们测定了C_5H_5~-,C_6H_6,C_7H_7~+的~(13)C、~1H的化学位移,再根据早就为人们所熟知的Huckel分子轨道理论计算得到的共轭分子π电荷的     

粉状白钨酸研究 Ⅸ.含W-N键的钨同多酸盐[Py_2W_(12)O_(38)]~(-4)的合成

继不久前McCarronⅢ自MoO_3·2H_2O和吡啶制得了[(C_5H_5N)_2MO_ 8O_(26)]~(4-)之后,我们通过粉状白钨酸与吡啶水溶液反应成功地制备了一种无色的晶体(C_5H_5NH)_4[(C_5H_5N)_2W_(12)O_(38)]·6H_2O。从反应混合物中还分离到一个黄色的副产物,其组成经分析为(C_5H_5N)_(0.85)·WO_3。与Johnson用黄钨酸制备的层状化合物(C_5H_5N)·WO_3属同一物相。粉状白钨酸在无水吡啶中放置两周后可得到另一种化学式为(C_5H_5NH)HW_4O_(13)·3H_2O的吡啶化合物,经IR和DTA研究可初步说明该化合物与粉状白钨酸(微晶态)之间的联系,并因此推测白钨酸的组成可能为H_2W_4O_(13)·nH_2O。     

包括d轨道的NMR化学位移的INDO/GIAO微扰理论

本文推广了计算~(18)C化学位移的INDO/GIAO方法,以进行~(15)N、~(17)O以及过渡元素配合物的~(18)C化学位移计算。通过N,O及Fe的INDO参数的优化选择,计算的~(15)N、~(17)O以及配合物(C_5H_5)Fe(CO)_2CN,(C_5H_4)_2Fe(COH)_2及(C_5H_4)_2Fe(CH_2OH)_2的~(18)C化学位移符合实验结果,同时发现计算的原子净电荷ρ(M)和σ~d(M)之间存在良好的线性关系。     

硼化合物研究(ⅩⅩⅢ)——硼氢化钾与二茂铁甲基三烃基氯化铵的反应

我们曾研究了硼氢化钾与四乙基氯化铵在一定量水存在下的热解反应,制得了B_(10)H_(10)~(2-)、B_(12)H_(12)~(2-)等多面体硼氢化合物,并提出了热解反应的历程。在少量水存在下,通过三烷基苄基氯化铵与硼氢化钾反应,合成了四氢硼酸三烷基苄基铵R_3(C_6H_5CH_2)NBH_4。但热解该类型四氢硼酸盐时,得不到B_(10)H_(10)~(2-)、B_(10)H_(12)~(2-)等多面体硼氢化合物,而是苄基与氮相连的C—N键断裂形成的R_3N·BH_3配合物和甲苯。本文研究C_5H_5FeC_5H_4CH_2NMe_2(R)Cl与KBH_4在水溶液中     

苯基或联苯基桥连双环戊二烯基铼羰基化合物的合成、结构及催化性能（英文）

两个单桥连的双环戊二烯(C_5Me_4H)E(C_5Me_4H)(E=C_6H_4,(C_6H_4)_2)分别与Re_2(CO)_(10)在均三甲苯中加热回流,得到了2个双核配合物(E)[(η~5-C_5Me_4)Re(CO)_3]_2(E=C_6H_4(1),(C_6H_4)_2(2))。通过元素分析、红外光谱、核磁共振氢谱和碳谱对配合物1和2的结构进行了表征,用X射线单晶衍射分析测定了配合物的结构。同时对2个配合物在芳香族化合物Friedel-Crafts酰基化反应中的催化活性进行了研究。     

铁羰基化合物的研究(η~5-C_5H_5)Fe(CO)_2CH_2COOR的合成

在我们实验室里采用环戊二烯基羰基铁的钠盐[(η~5-C_5H_5)Fe(CO)_2]Na和氯代乙酸酯ClCH_2COOR(R=C_2H_5,C_3H_7,C_4H_9,C_5H_(11))直接反应合成了铁羰基化合物(η~5-C_5H_5)Fe(CO)_2CH_2COOR(Ⅰ).并通过IR、~1H NMR、~(13)C NMR以及MS的分析,确定了(Ⅰ)的结构.η~5-环戊二烯基(2-烷氧基-2-氧代乙基)二羰基合铁(Ⅰ)的合成路线如下:     

铍-铍金属链夹心配合物D_(4d)[Be_n(C_4H_4)_2]~(2-)及[Be_n(C_4H_4)_2]Li_2(n=2~8)（英文）

采用密度泛函理论方法(B3LYP和BP86)在6-311+G(d,p)基组水平上系统研究了新颖的铍-铍金属链夹心配合物D_(4d)[Be_n(C_4H_4)_2]~(2-)及[Be_n(C_4H_4)_2]Li_2(n=2~8)的几何结构、电子结构、成键特征及热力学稳定性。结果表明,具有交错式D4d对称性的D_(4d)[Be_n(C_4H_4)_2]~(2-)及[Be_n(C_4H_4)_2]Li_2为体系势能面上的真正极小。自然键轨道(NBO)、分子中的原子(AIM)及分子轨道分析表明,该系列夹心配合物中铍-铍间主要以共价键为主,而配体与铍-铍链之间则主要以离子键为主。核独立化学位移(NICS)分析表明配体在该系列配合物中具有π芳香性。稳定的夹心配合物锂盐[Be_n(C_4H_4)_2]Li_2(n=2~8)有望通过C4H4Li2/C5H-5配体交换反应进行制备,该系列配合物将进一步丰富多核夹心配合物研究领域。     

铵盐离子对中有机阴离子交换排序的研究

本文用测定ClO_4~-离子选择性电极电势选择性系数K_(ij)~(pot)的方法,研究了七种长链季铵大阳离子与十余种有机阴离子在水、油两相中交换能力的排序。即: C_2O_4~-相似文献   

粉状白钨酸的研究(Ⅻ)——某些聚钨酸有机铵盐的合成和性质

以粉状白钨酸和三种有机铵--乙二胺、乙醇胺和异丙胺为原料,分别合成了偏钨酸盐和仲钨酸盐。通过紫外,红外光谱、核磁共振谱以及极谱测定,研究了三种不同类型有机胺聚钨酸盐的组成与性质,发现乙醇胺和异丙胺的偏钨酸盐具有光敏性。     

Toward direct determination of conformations of protein building units from multidimensional NMR experiments part II: a theoretical case study of formyl-L-valine amide

Chemical shielding anisotropy tensors have been determined for all twenty-seven characteristic conformers of For-L-Val-NH2 using the GIAO-RHF formalism with the 6-31 + G* and TZ2P basis sets. The individual chemical shifts and their conformational averages have been compared to their experimental counterparts taken from the BioMagnetic Resonance Bank (BMRB). At the highest level of theory applied, for all nuclei but the amide proton, deviations between statistically averaged theoretical and experimental chemical shifts are as low as 1-3%. Correlated chemical shift plots of selected nuclei, as function of the respective phi, psi, chi1, and chi2 torsional angles, have been generated. On two-dimensional chemical shift-chemical shift plots, for example, 1H(NH)-15N(NH) and 15N(NH)-13Calpha, regions corresponding to major conformational clusters have been identified, providing a basis for the quantitative identification of conformers from NMR shift data. Experimental NMR resonances of nuclei of valine residues have been deduced from 18 selected proteins, resulting in 93 1Halpha-13Calpha chemical shift pairs. These experimental results have been compared to relevant ab initio values revealing remarkable correlation between the two sets of data. Correlations of 1Halpha and 13Calpha values with backbone conformational parameters (phi and psi) have also been found for all pairs (e.g. 1Halpha/phi and 13Calpha/phi) but 1Halpha/psi. Overall, the appealing idea of establishing backbone folding of proteins by employing chemical shift information alone, obtained from selected multiple-pulse NMR experiments (e.g. 2D-HSQC, 2D-HMQC, and 3D-HNCA), has received further support.     

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.     

Studies on asterosaponins—V : A novel steroid conjugate, 5α-pregn-9(11)-ene-3β,6α-diol-20-one-3-sulfate,from a starfish saponin,asterosaponin A

A new crystalline steroid conjugate was obtained by partial acid hydrolysis of asterosaponin A, a steroidal saponin from the starfish, Asterias amurensis. The structure of the conjugate was established as 5α-pregn-9(11)-ene-3β,6α-diol-20-one-3-sulfate (2) on the basis of elemental analysis, IR and PMR spectra measurement and chemical reaction. Solvolysis of compound 2 yielded 5α-pregn-9(11)-ene-3β,6α-diol-20-one. Oxidation with chromium trioxide-pyridine complex followed by solvolysis afforded a new steroid, 5α-pregn-9(11)-ene-3β-ol-6,20-dione, whose structure was deduced by the measurement of ORD curve and PMR spectra. Thus, the location of carbohydrate moiety in asterosaponin A has been assigned to 6α-hydroxy group of the steroid conjugate.     

氨在丝光沸石位置(VI)上的吸附

The adsorption of NH3 on (AO)3SiO*HAl(OA)2OSi(OA)3 cluster from the structure of site (VI) of mordenite Zeolite has been calculated by an adsorption model of hydrogen-bond form, quantum chemical method, CNDO/2 scheme. Variations of adsorption distance between NH3 and O* in the cluster were directly related to initial adsorption heats of NH3 on O*H group, jump frequency of the proton between NH3 and O* and frequency shift of IR band with O*H group. Adsorption distance of NH3 on O*H group has been calculated, the range was about 2.5 to 2.75A, and the most favourable adsorption distance with strong acid strength was 2.5A. It was related to the maximum initial adsorption heat which was 33.80 kcal/mol, the lowest activation energy of proton mobility between NH3 ane O*, and the largest frequency shift of IR bands with O*H group. This result qualitatively corresponded to experimental observations. It showed that the various representations of acidic strength are equivalent to each other which could be explained on basis of adsorptin model of hydrogen bond form.     

PMR Study of Molecular Complex Equilibrium in Solution 4-Substituted Nitrobenzenes with Aromatic Donors

4-Substituted nitrobenzenes, 4-X-C₆H₄NO₂ (where X=-Cl, -Br, -COCH₂, -CHO), complexed with methyl benzenes in inert solvent cyclohexane have been studied by PMR spectroscopy. Equilibrium constant and the chemical shift of pure complex were determind through observation of the A₂B₂ spectrum of ring protons in the electron acceptor compounds. Equilibrium constant and chemical shift of pure complex were evaluated separately on the basis of either chemical shift A or B. Unequal chemical shift of pure complex was obtained and used to discuss the geometry of complex.     

Synthesis and spectral properties of porphyrinquinone derivatives based on deuteroporphyrin IX

A series of diquinone derivatives of deuteroporphyrin IX, having different bond lengths between the chromophores, have been prepared. Deuteroporphyrin IX was condensed with modified hydroxyl-containing quinones by the mixed anhydride method. PMR spectroscopy was used to show that the magnetic anisotropy of the porphyrin ring has a strong effect on the chemical shift of the protons of the quinone ring and its neighboring substituents.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 608–616, May, 1988.     

Proton magnetic resonance studies of actinomycin-related peptides containing N-methyl groups

The PMR spectra of several cyclic and acyclic dipeptide derivatives representing portions of the actinomycin structure have been studied. In the spectra of the acyclic compounds temperature-dependent duplicity resulted from the equilibration of conformers possessing cis and trans peptide bonds. The lanthanide shift reagent Eu(FOD)₃ was utilized to distinguish N-methyl groups in the two conformations and observations were made on the steric dependence of the observed shifts. The origin of the wide variation in chemical shift of N-methylvalyl α-protons is discussed in relation to the conformation of actinomycin.     

Electronic structure, molecular electrostatic potentials, vibrational spectra in substituted calix[n]arenes (n = 4, 5) from density functional theory

Electronic structure, molecular electrostatic potential, and vibrational frequencies of para-substituted calix[n]arene CX[n]-R (n = 4, 5; R = H, NH(2), t-Bu, CH(2)Cl, SO(3)H, NO(2)) and their thia analogs (S-CX[n]-R; with R = H and t-Bu) in which sulfur bridges two aromatic rings of CX[n] have been derived from the density functional theory. A rotation around CH(2) groups connecting the phenol rings engenders four, namely, cone, partial cone, 1,2-alternate, and 1,3-alternate CX[n]-R conformers. Of these, the cone conformer comprising of large number of O1-H1···O1' interactions turns out to be of lowest energy. Normal vibration analysis reveal the O1-H1 stretching frequency of unsubstituted CX[n] shifts to higher wavenumber (blue shift) on substitution of electron-withdrawing (NO(2) or SO(3)H) groups, while electron-donating substituents (NH(2), t-Bu) engender a shift of O1-H1 vibration in the opposite direction (red shift). The direction of frequency shifts have been analyzed using natural bond orbital analysis and molecular electrostatic potential (MESP) topography. Furthermore, calculated (1)H NMR chemical shift (δ(H)) in modified CX[n] hosts follow the order: H1 > H3/H5 > H7(a) > H7(b). The δ(H) values in CX[4] are in consonant with the observed (1)H NMR spectra.     

Experimental and theoretical study of~(13)C shielding tensors in new-style molybdenum complex

~~Experimental and theoretical study of~(13)C shielding tensors in new-style molybdenum complex~~