二维配位聚合物[K2(5-nbdc)2Cd(Ⅱ)·imH·H2O]∞的合成和晶体结构(英)

The crystal structure of the title complex, [K₂(5-nbdc)₂Cd(Ⅱ)·imH·H₂O]_∞ (5-nbdc=5-nitro-1,3-benzenedicarbonate, imH=imidazole) has been determined by X-ray diffraction analysis. The crystal data are: tetragonal, space group P4₁, M_r=694.93 for CdC₁₉H₁₂N₄O₁₃K₂, a=1.018 6(10) nm, b=1.018 6(10) nm, c=2.436 7(5) nm; Z=4, V=2.528 2(6) nm³, F(000)=1 376, D_c=1.826 Mg·m^-3, μ=1.267 mm^-1. The title polymeric complex exhibits a two-dimensional framework, in which adjacent Cd(Ⅱ) ions are bridged by μ-O₄-5-nitro-1,3-benzenedicarbonate groups forming one-dimensional chains that are further linked by μ-O₃-5-nitro-1,3-benzenedicarbonate groups into two-dimensional anion rectangle sheets with large 32-membered rings. The strong π-π stacks of the benzene rings link these adjacent sheets into a three-dimensional van der Waals network. CCDC: 245527.     

Simplified chemical and radiochemical synthesis of 2-arachidonoyl-glycerol, an endogenous ligand of cannabinoid receptors

Endocannabinoids have emerged as a new class of lipid mediators, with manifold roles in the central nervous system and in the periphery. Several studies have identified 2-arachidonoyl-glycerol (2-AG) as a major endogenous agonist of cannabinoid receptors. Here, the chemical synthesis of 2-AG is reported, along with the synthesis of its tritium-labeled derivative. These unlabeled and radiolabeled compounds are suitable tools for unravelling some metabolic routes and biological activities of 2-AG in various cells and tissues.     

Syntheses based on (N,N-difluoroamino)dinitroacetonitrile

High reactivity of the nitrite group in (NN-difluoroamino)dinitroacetonitrile was demonstrated. Based on its reaction with HN₃, a new preparative method for the synthesis of 5-[(N,N-difluoroamino)dinitromethylltetrazole was developed; some derivatives of the latter compound have been obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8. pp. 2056–2058, August, 1996.     

Modification of polybenzimidazole: Synthesis and thermal stability of poly(N1-methylbenzimidazole) and poly(N1,N3-dimethylbenzimidazolium) salt

Poly(N₁,N₃-dimethylbenzimidazolium) (PDMBI) salt and poly(N₁-methylbenzimidazole) (PMMBI) were synthesized by methylation of commercial polybenzimidazole [poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole (PBI)]. First, the N-lithium salt of polybenzimidazole was formed by treating polybenzimidazole solution of 1-methyl-2-pyrolidinone (NMP) with lithium hydride at 80°C for 18 h. Ninety percent substitution of PMMBI was obtained by treating the N-lithium salt of PBI with equimolar ratio of iodomethane at room temperature. Upon addition of excess iodomethane to the lithium salt of PBI at 80°C, a polymer was formed that showed 100% substitution on the N₁ nitrogen and about 30% substitution of the methyl group on the N₃ nitrogen in the form of N₁,N₃-dimethylbenzimidazolium iodide salt [PDMBI (30%)]. The content of the benzimidazolium iodide salt was increased to about 90% by dissolving PDMBI (30%) in dimethyl sulfoxide (DMSO) and re-treating with excess iodomethane at 80°C overnight. The modified PBI polymers were characterized by NMR and FTIR. The modified PBI differed in solubility from PBI. PMMBI could be easily dissolved in NMP and PDMBI in DMSO at room temperature. The solution of PDMBI could be mixed with water in all proportions without precipitation. PDMBI could be also dissolved directly in a mixture of DMSO and water (1 : 1). Typical polyelectrolyte behavior of viscosity was found in solution of PDMBI (30%) and PDMBI (90%) when DMSO and a mixture of DMSO and water were used as solvents. A salt effect on viscosity was also found in the mixed solvent solution. Thermogravimetric analysis (TGA) showed that the methyl group on the imidazole ring was unstable above 180°C under nitrogen. When PDMBI was heated under nitrogen, one of the methyl groups was lost with the counterion to result in a neutral PMMBI. © 1993 John Wiley & Sons, Inc.     

On-line multidimensional chromatography using packed capillary liquid chromatography and capillary gas chromatography

The introduction of selected fractions from a liquid chromatograph into a gas chromatograph has been described; however, analyses were performed by off-line experiments requiring collection and reinjection of the separate fractions or by on-line procedures where disadvantageously, only a fraction of the separated peak or a well resolved component in a mixture could be introduced into a gas chromatograph. This disadvantage is overcome by the apparatus and method described in this paper, which utilizes a multidimensional chromatography system employing a high efficiency, packed capillary LC column coupled on-line to a capillary gas chromatograph. The liquid chromatograph (so designed) can act as a highly efficient clean-up or chemical class fractionation step prior to introduction into the gas chromatograph, significantly reducing sample preparation times in many applications. Thus minor components in a complex matrix can be determined without prior sample clean-up, an example of which is the determination of polychlorinated biphenyls in a complex hydrocarbon matrix.     

Synthesis of siloxane stationary phases for capillary gas chromatography and supercritical fluid chromatography

A comparison is made between dichlorosilanes and cyclic siloxanes as starting materials in the synthesis of stationary phases for capillary gas chromatography (CGC) and supercritical fluid chromatography (SFC). Siloxanes containing one or more of the side groups methyl, vinyl, phenyl, and cyanoethyl in various ratios were synthesized and compared. These phases were characterized by chromatographic (gel permeation, GPC), spectroscopic (IR, ¹H NMR, ²⁹Si NMR), and thermal (DSC) methods. Coated fused silica columns were evaluated with respect to polarity, crosslinkability with several free-radical initiators, and thermal stability. A new liquid phase, 7% cyanoethyl, 7% phenyl, 1% vinyl methyl polysiloxane is shown to be more polar than OV-1701, more temperature stable, easily crosslinked and suitable for use in supercritical fluid chromatography.     

含时变分S 矩阵解得一般形式

推导出含时S散射矩阵变分表达式经基函数展开并优化后的解的一般形式。     

Excess and partial excess molar volumes of mixing of N,N-dibutyl-2-ethylhexamide with dodecanol

Excess and excess partial molar volumes of mixing of the system N,N-dibutyl-2-ethylhexylamide (DBEHA) + dodecanol (DDA) were determined at 25, 35, 45, 55 and 65°C. The excess molar volumes exhibit a maxima at each temperature at approximatelyx _DBEHA = 0.3 and a minima close tox _DBEHA = 0.9. The values of the excess volumes in general increase with the temperature. The partial excess molar volumes are calculated from the smoothed data and the results are discussed in the light of postulated amide-alcohol interactions.     

Antiferromagnetic complexes involving metal---metal bonds III. Synthesis, structure and magnetic properties of heterotrinuclear complexes of the type M(CO)5L (M = Cr, Mo and w) containing [(C5H5CrSCMe3)2S] as unusual antiferromagnetic ligand L

Isostructural heterotrinuclear complexes (C₅H₅CrSCMe₃)₂S · M(CO)₅ (II–IV) were isolated from photochemical reactions between the antiferromagnetic complex (C₅H₅CrSCMe₃)₂S (I) (with the Cr---Cr bond 2.689 Å long and with the exchange parameter −2J = 430 cm⁻¹) and metal hexacarbonyls, M(CO)₆, where M is Cr, Mo, or W. According to the X-ray structural data on III and IV, complex I plays the role of an unusual antiferromagnetic ligand L bound to M through the sulphide bridge (M–S 2.58(2) Å). Its geometry remains practically unaffected by the complex formation (the Cr---Cr bond length in III and IV is 2.73(1) Å). The exchange parameter, −2J (410, 440 and 440 cm⁻¹ in II to IV, respectively), also shifts only insignificantly from that of I, which probably means that indirect exchange via the sulphide bridge in I is of minor importance compared with the direct Cr---Cr exchange. The Cr---Cr bond length may thus be correlated with the observed overall exchange coupling.     

Glass capillary columns for separation of free organic acids

Glass capillary columns have been prepared without acidic additive in the stationary phase, from which free organic acids elute as sharp and symmetrical peaks. The required surface in the borosilicate glass capillary was generated by a combination of leaching with aqueous HCl and deposition of colloidal silica particles; it can be coated with stationary phases have a broad range of polarity. Aqueous samples containing free organic acids can also be analyzed in such columns in an isothermal mode.