Modifying electronic communication in dimolybdenum units by linkage isomers of bridged oxamidate dianions

Reactions of Mo(2)(O(2)CCH(3))(DAniF)(3), DAniF = N,N'-di-p-anisylformamidinate, with oxamidate dianions [ArNC(O)C(O)NAr](2-), Ar = C(6)H(5) and p-anisyl, give pairs of isomeric compounds where the [Mo(2)] units are bridged by the oxamidate anions. For the alpha isomers, the C-C unit of the dianion is nearly perpendicular to the Mo-Mo bonds, and these are essentially perpendicular to each other. For the beta isomers, the corresponding C-C unit and the Mo-Mo bonds are essentially parallel to each other. Each type of isomer is stable in solution. The electronic communication as measured by the DeltaE(1/2) for the oxidation of each of the Mo(2) units is significantly better for the beta isomers. This is supported also by the appearance of what is conventionally called an intervalence charge-transfer band in the near infrared region upon oxidation of the beta isomers but not the alpha isomers. Molecular mechanics and DFT calculations help explain the relative conformations in the alpha isomers and the relative energy differences between the alpha and beta isomers.     

Separation and determination of seven fluoroquinolones by pressurized capillary electrochromatography

In this paper, pressurized CEC was used for the separation and determination of seven fluoroquinolones (FQs). The effect of different experimental conditions, such as the concentration and pH of the buffer, the organic modifier concentration, the surfactant and ion-paring agents added to the electrolyte, and applied voltage were studied. All the seven FQs were baseline separated using mobile phase containing 27% v/v ACN, 5 mmol/L Na2HPO4 buffer (pH 4.0 adjusted using citric acid), 11 mmol/L SDS, and 0.01% TEA v/v at detection wavelength of 287 nm and at an applied voltage of -10 kV. The calibration curves were linear (r>0.9991) over a concentration range of 1.0-50.0 mg/L for norfloxacin (NFLX); 2.5-50.0 mg/L for fleroxacin (FLX), ciprofloxacin (CPFX), and lomefloxacin (LMX); and 5.0-50.0 mg/L for enoxacin (ENX), ofloxacin (OFLX), and gatifloxacin (GFLX). The detection limits (S/N = 3) for ENX, OFLX, FLX, NFLX, CPFX, LMX, and GFLX were 0.5, 0.8, 0.4, 0.2, 0.4, 0.5, and 1.0 mg/L, respectively. The method is simple, rapid, and reproducible. It was successfully applied to the analysis of fish muscle samples spiked with FQs. Mean recoveries ranged from 81.6 to 97.6%.     

Trapping tetramethoxyzincate and -cobaltate(II) between Mo24+ units

Two compounds of a new type, [Mo(2)](CH(3)O)(2)M(CH(3)O)(2)[Mo(2)] where [Mo(2)] is an abbreviation for Mo(2)[(p-MeOC(6)H(4))NCHN(p-MeOC(6)H(4))](3) and M = Zn (1) and Co (2), are reported. Discrete [M(OR)(4)](2-) ions, either as such or in the mu(2),eta(4) role, have not heretofore been described. In these compounds they have distorted tetrahedral structures and bridge two [Mo(2)] groups in much the same way as did SO(4)(2-), MoO(4)(2-), and WO(4)(2-) ions in other recently reported compounds (Cotton, F. A.; Donahue, J. P.; Murillo, C. A. Inorg. Chem. 2001, 40, 2229). The (1)H NMR spectrum of 1 and the visible spectrum and magnetic properties of 2 are consistent with these structures. The M(OCH(3))(4) bridges are moderately effective in coupling the two [Mo(2)] redox centers. Compounds 1 and 2 may also be viewed as having Zn(II) and Co(II) centers tetrahedrally coordinated by the bidentate ligand [Mo(2)[(p-MeOC(6)H(4))NCHN(p-MeOC(6)H(4))](3)(OMe)(2)](-). From that point of view they may be compared with Zn(DPM)(2) and Co(DPM)(2) (3), where DPM is the anion of dipivaloylmethane. For purposes of comparison, 3 has been fully characterized structurally, spectroscopically, and magnetically. Close analogies between 2 and 3 are shown to exist.     

Theoretical Study of the C_(60)O_3 Isomers

WiththepreparationandisolationofC,,O.'moreandmoreattentionwaspaidtotheirstructuresandpropertiest').WooddetectedC,,O.firstwhentheypreparedC,,byvaporizinggraphite").Fromthenon,thelaboratoriesallovertheworldhavepreparedC6,O.byvariousmethodssuchasPhotoxidationt2-4),Electrochemicaloxi-dation[si,Ozonizationt7.83andChemicaladditiont6'12-14iandsoon.Accordingtothefollow-uptheoreticalstudiesforC,,O.,itisindicatedthattherearetwoisomersofC,,O:eithertheoxygenatomislocatedoverthe6/6bondtogeneratethe6/…     

3-(4-氯苯基)-6-取代苯氧乙酰氨基均三唑并[3,4-b]-1,3,4-噻二唑类化合物的合成

将取代苯氧乙酰氨基引入到3,6-二取代均三唑并噻二唑的分子骨架中, 设计合成了8个未见文献报道的3-(4-氯苯基)-6-取代苯氧乙酰氨基均三唑并[3,4-b]-1,3,4-噻二唑类化合物5a～5h, 结构经元素分析、IR和¹H NMR等测试得到确证.     

Theoretical studies on the band structures of superconducting solid compounds: Nb3X (X=Si, Ge, Sn, Pb)

The band structures of several analogous superconducting A-15 type solid compounds, Nb3X (X=Si, Ge, Sn, Pb), have been calculated by use of the tight-binding method within the Extended Huckel approximation (EHT). By analysis of their energy bands, densities of states and crystal orbital overlap populations, the dependence of the superconducting transition temperatures (Tc) on the electronic structures and bondings is qualitatively elucidated.     

酵母核糖核酸在碳纳米管修饰电极上的电化学行为及其分析测定

研究了酵母核糖核酸（yRNA）在碳纳米管（MWNT）修饰电极上的电化学行为，优化了测定参数，在此基础上建立了一种直接测定yRNA的电分析测试方法。yRNA在碳纳米管修饰电极上于磷酸盐缓冲溶液中在0．758V处产生不可逆的氧化电流峰，峰电流与yRNA的质量浓度在1～10mg／mL之间有良好的线性关系，线性回归方程为：Iρ=0．0813ρ＋0．1807，相关系数r为0．9980，检出限为0．6mg／mL。     

Synthesis and Crystal Structure of[Fe_2V (μ_3-O) (μ-O_2CCH_3)_6 (THF)_3]Cl· 3H_2O

lmTR0DUCTI0NTrivanadium(III)ox0-carb0xylat0complexeshaveattractedmuchinterestre-cently"~".Manyc0mp0unds0fthiskindhavebeensynthesizedandtheirstructural,physicalandspectr0sc0picpr0pertieshavebeenstudied.Butnone0fthiskindofcom-plexeswithmixedmeta1shavebeensynthesized.Hereinwereportthecrystalstruc-tureofthefirstmixedmeta1carboxylatocomp0undofvanadium.2EXPERIMENTAL2.1Synthesis0.l6g(lmmol)VCl3,0.32g(2mmol)FeCl3and0.48g(6mm0l)NaCO,CH,wasdisso1vedinaso1uti0n0ft0luerie(20ml),THF(lOml),ac…     

REMGa3Ge and RE3Ni3Ga8Ge3 (M = Ni, Co; RE = rare-earth element): new intermetallics synthesized in liquid gallium. X-ray, electron, and neutron structure determination and magnetism

New quaternary intermetallic phases REMGa(3)Ge (1) (RE = Y, Sm, Tb, Gd, Er, Tm; M = Ni, Co) and RE(3)Ni(3)Ga(8)Ge(3) (2) (RE = Sm, Gd) were obtained from exploratory reactions involving rare-earth elements (RE), transition metal (M), Ge, and excess liquid Ga the reactive solvent. The crystal structures were solved with single-crystal X-ray and electron diffraction. The crystals of 1 and 2 are tetragonal. Single-crystal X-ray data: YNiGa(3)Ge, a = 4.1748(10) A, c = 23.710(8) A, V = 413.24(2) A(3), I4/mmm, Z = 4; Gd(3)Ni(3)Ga(8)Ge(3), a = 4.1809(18) A, c = 17.035(11) A, V = 297.8(3) A(3), P4/mmm, Z = 1. Both compounds feature square nets of Ga atoms. The distribution of Ga and Ge atoms in the REMGa(3)Ge was determined with neutron diffraction. The neutron experiments revealed that in 1 the Ge atoms are specifically located at the 4e crystallographic site, while Ga atoms are at 4d and 8g. The crystal structures of these compounds are related and could be derived from the consecutive stacking of disordered [MGa](2) puckered layers, monatomic RE-Ge planes and [MGa(4)Ge(2)] slabs. Complex superstructures with modulations occurring in the ab-plane and believed to be associated with the square nets of Ga atoms were found by electron diffraction. The magnetic measurements show antiferromagnetic ordering of the moments located on the RE atoms at low temperature, and Curie-Weiss behavior at higher temperatures with the values of mu(eff) close to those expected for RE(3+) free ions.     

阴离子交换色谱-积分脉冲安培法测定鱼粉和玉米粉水解液中氨基酸

将高效阴离子交换色谱．积分脉冲安培直接检测法应用于鱼粉和玉米粉水解液中的氨基酸的分析测定。该方法使用Dionex AminoPac PA10阴离子交换柱为分析柱，控制柱温为35℃，以NaOH和NaAc的强碱性溶液为淋洗液，在合适的梯度条件下，可以实现对17种常见氨基酸的高效分离。在强碱性条件下，获得良好分离的各个氨基酸可在配有金工作电极的电化学检测器上以积分脉冲安培法获得高灵敏度的检测。在优化的测定条件下，该方法对这17种氨基酸的检出限在0．21—3．38pmol之间；峰面积校正曲线的线性范围为2—3个数量级；5次平行测定的峰面积的相对标准偏差RSD在0．32％—4．7％之间。该方法应用于玉米粉和鱼粉水解液中氨基酸含量的测定，结果良好。对玉米粉和鱼粉水解液标准加入的回收率分别在81．9％—108．0％和90．0％～108．0％之间。