Identification and quantification of nucleosides and nucleobases in Geosaurus and Leech by hydrophilic-interaction chromatography

A simple hydrophilic-interaction chromatography (HILIC) method was developed for the identification and quantification of 14 nucleosides and nucleobases, namely cytosine, uracil, cytidine, guanine, hypoxanthine, xanthine, uridine, thymine, inosine, guanosine, thymidine, 2′-deoxyadenosine, 2′-deoxyinosine and 2′-deoxyuridine in two traditional Chinese medicines, Geosaurus and Leech. The separation was achieved on a TSKgel Amide-80 column (150 mm × 2.0 mm, 3.0 μm) with a mixture of acetonitrile and 10 mM aqueous ammonium acetate as the mobile phase at a flow rate of 0.2 mL/min. The temperature was set at 30 °C and UV detection wavelength was set at 260 nm. All calibration curves showed good linearity (R² > 0.9957) within the test ranges. The overall intra- and inter-day RSD ranged from 0.4 to 3.4% and from 0.7 to 3.3%, respectively. The LOD and LOQ were in the range of 0.07-30.49 ng/mL and 0.26-60.98 ng/mL, respectively. The repeatability of the method was in the range of 2.2-5.8% for Geosaurus and 1.4-5.5% for Leech. The recoveries of the samples were in the range of 91.4-100.9% for Geosaurus, and 91.9-99.3% for Leech. The established method was applied successfully for the analysis of nucleosides and nucleobases in 22 commercially available samples collected from different regions in China and Japan. Our data showed that HILIC had advantages as a useful tool for the study of the bioactive components in Geosaurus and Leech as well as their quality control, and could therefore be used for the determination of the analytes in pharmaceutical products and biological fluids.     

Carbomolybdate clusters formed by carbonyl insertion into molybdenum-oxygen bonds. Structural investigation of the [RMo4O15X] core (R = ---C9H4O, X = OCH3; R = ---C14H10, X = ---C7H5O2; R = C14H8, X = ---OH)

[C₄H₉)₄N]₂[Mo₂O₇] reacts with a variety of organic species containing α-diketone groups to give tetranuclear complexes of general composition [RMo₄O₁₅X]³⁻. The complexes [(C₄H₉)₄N]₃[(C₉H₄O)Mo₄O₁₅(OCH₃)] (I), [(C₄H₉)₄N]₃[(C₁₄H₁₀)Mo₄O₁₅(C₆H₅CO₂)] (11) and [(C₄H₉)₄N]₃[(C₁₄H₈)Mo₄O₁₅(OH)] (III) were synthesized from the reactions of dimolybdate with ninhydrin, benzil and phenanthraquinone, respectively. Complex II may also be prepared from dimolybdate and benzoin in acetonitrile-methanol solution, from which it co-crystallizes with the binuclear species [(C₄H₉)₄N]₂[Mo₂O₅(C₆H₅C(O)C(O)C₆H₅)₂] · CH₃CN · CH₃OH (IV). Complexes I–III exhibit the tetranuclear core, previously described for the α-glyoxal derivatives [(C₄H₉)₄N]₃[(HCCH)Mo₄O₁₅X], where X = F⁻ or HCO₂⁻. The ligands may be formally described as diketals, formed by insertion of ligand carbonyl subunits into molybdenum-oxygen bonds. The structures I–III differ most dramatically in the identity and coordination mode of the anionic ligand X⁻ which occupies a position opposite the diketal moiety relative to the [Mo₄O₁₁]²⁺ central cage. Thus, I exhibits a doubly bridging methoxy group in this position, while II possesses a benzoate ligand with an unusual μ₃-O,O′coordination mode. Complex III presents a hydroxy-group unsymmetrically bonded to three of the molybdenum centres. The stereochemical consequences of the various coordination modes are discussed. Crystal data: Compound I, monoclinic space group Pc, a = 24.888(2), b = 12.897(3), c = 24.900(3) Å, β = 101.94(2)°, D_calc = 1.28 g cm⁻¹ for Z = 4. Structure solution and refinement based on 8695 reflections with F_o 6σ(F_o) (Mo-K_α, λ = 0.71073 Å) converged at a conventional discrepancy factor of 0.060. Compound II, orthorhombic space group Pbca, a = 20.426(6), b = 26.916(6), c = 32.147(7) Å, V = 17673.2(20) ų, D_calc = 1.33 g cm⁻³ for Z = 8; 5224 reflections, R = 0.076. Compound III, tetragonal space group I4₁/a, a = b = 48.129(6), c = 13.057(2) Å, V = 30246.2(12) ų, D_calc = 1.35 g cm⁻³ for Z = 16; 5554 reflections, R = 0.053. Compound IV, orthorhombic space group Pnca, a = 16.097(4), b = 16.755(4), c = 25.986(7) Å, V = 7008.1(13) ų, Z = 4, D_calc = 1.18 g cm⁻³ ; 2944 reflections, R = 0.061.     

Review: Recent applications of scanning electrochemical microscopy to the study of charge transfer kinetics

Scanning electrochemical microscopy (SECM) has been proven to be a valuable technique for the quantitative investigation and surface analysis of a wide range of processes that occur at interfaces. In particular, there is a great deal of interest in studying the kinetics of charge transfer characteristics at the solid/liquid and liquid/liquid interface. This overview outlines recent advances and applications of SECM to the investigation of charge transfer reactions at the solid/liquid interface and liquid/liquid interface.     

Standard enthalpy of formation of 3,4,5-trimethoxybenzoic acid

The energy of combustion of crystalline 3,4,5-trimethoxybenzoic acid in oxygen at T=298.15 K was determined to be -4795.9±1.3 kJ mol^-1 using combustion calorimetry. The derived standard molar enthalpies of formation of 3,4,5-trimethoxybenzoic acid in crystalline and gaseous states at T=298.15 K, Δ_fH_m ^Θ (cr) and Δ_fH_m ^Θ (g), were -852.9±1.9 and -721.7±2.0 kJ mol^-1, respectively. The reliability of the results obtained was commented upon and compared with literature values. This revised version was published online in August 2006 with corrections to the Cover Date.     

Self-assembly in palladium(II) and platinum(II) chemistry: the biomimetic approach

The self-assembly of complex cationic structures by combination of cis-blocked square planar palladium(II) or platinum(II) units with bis(pyridyl) ligands having bridging amide units has been investigated. The reactions have yielded dimers, molecular triangles, and polymers depending primarily on the geometry of the bis(pyridyl) ligand. In many cases, the molecular units are further organized in the solid state through hydrogen bonding between amide units or between amide units and anions. The molecular triangle [Pt(3)(bu(2)bipy)(3)(mu-1)(3)](6+), M = Pd or Pt, bu(2)bipy = 4,4'-di-tert-butyl-2,2'-bipyridine, and 1 = N-(4-pyridinyl)isonicotinamide, stacks to give dimers by intertriangle NH.OC hydrogen bonding. The binuclear ring complexes [[Pd(LL)(mu-2)](2)](CF(3)SO(3))(4), LL = dppm = Ph(2)PCH(2)PPh(2) or dppp = Ph(2)P(CH(2))(3)PPh(2) and 2 = NC(5)H(4)-3-CH(2)NHCOCONHCH(2)-3-C(5)H(4)N, form transannular hydrogen bonds between the bridging ligands. The complexes [[Pd(LL)(mu-3)](2)](CF(3)SO(3))(4), LL = dppm or dppp, L = PPh(3), and 3 = N,N'-bis(pyridin-3-yl)-pyridine-2,6-dicarboxamide, and [[Pd(LL)(mu-4)](2)](CF(3)SO(3))(4), LL = dppm, dppp, or bu(2)bipy, L = PPh(3), and 4 = N,N'-bis(pyridin-4-yl)-pyridine-2,6-dicarboxamide, are suggested to exist as U-shaped or square dimers, respectively. The ligands N,N'-bis(pyridin-3-yl)isophthalamide, 5, or N,N'-bis(pyridin-4-yl)isophthalamide, 6, give the complexes [[Pd(LL)(mu-5)](2)](CF(3)SO(3))(4) or [[Pd(LL)(mu-6)](2)](CF(3)SO(3))(4), but when LL = dppm or dppp, the zigzag polymers [[Pd(LL)(mu-6)](x)](CF(3)SO(3))(2)(x) are formed. When LL = dppp, a structure determination shows formation of a laminated sheet structure by hydrogen bonding between amide NH groups and triflate anions of the type NH-OSO-HN.     

12兆瓦热电气多联产装置的开发

介绍了为解决某钢铁企业的中热值煤气，蒸汽和电的短缺而开发的一台12MW的热电气多联产装置，在该系统中，把一台流化床气化炉和一台75t/h循环流化床锅炉结合在一起，从而实现煤气和蒸汽联产，在详细介绍了该装置的设计思想和结构特点的同时，用所建的热电气多联产模型对该装置包括煤气产量，煤气成分，煤气热值和系统运行温度等在内的性能参数进行了预测。     

Highly Direct alpha-Selective Glycosylations of 3,4-O-Carbonate-Protected 2-Deoxy- and 2,6-Dideoxythioglycosides by Preactivation Protocol

A new efficient pre-activation method for the highly alpha-stereoselective glycosylation of 2-deoxysugars and 2,6-dideoxysugars has been developed using 2-deoxy- and 2,6-dideoxythioglycosides as glycosyl donors. The approach allows a wide range of glycosyl acceptors and donors to be used; the alpha-selectivity is very good to excellent.     

Chemiluminescence flow system for the determination of Fe(II) and Fe(III) in water

A novel chemiluminescence (CL) flow system has been developed for the sequential determination of Fe(II) and Fe(III) in water. Fe(II) was detected by its catalytic effect on the CL reaction between luminol immobilized on an anion exchange resin column and dissolved oxygen; Fe(III) was determined by difference measurement after on-line conversion to Fe(II) in a reducing mini-column packed with Cu plated Zn granules. For both ions, the calibration graph was linear in the range 1 × 10^–9 to 1 × 10^–6 g/mL, and the detection limit was 4 × 10^–10 g/mL. A complete analysis could be performed in 1.5 min with a relative standard deviation of less than 5%. The system could be reused for over 200 times and has been applied successfully to the determination of Fe(II) and Fe(III) in natural water samples. Received: 13 March 1997 / Revised: 3 June 1997 / Accepted: 6 June 1997     

Regioselective synthesis of 1,2,3-triazole derivatives via 1,3-dipolar cycloaddition reactions in water

Reaction of an arylacetylene with an azide in hot water gave 1,4-disubstituted 1,2,3-triazoles in high yields, while similar reaction between a terminal aliphatic alkyne and an azide (except m-nitroazidobenzene) afforded a mixture of regioisomers with the ratio of 1,4- to 1,5-isomers ranging from 3:1 to 28.6:1. Reactions of m-nitroazidobenzene with either arylalkynes or aliphatic alkynes formed only 1,4-disubstituted derivatives in excellent yields.     

Electronic structure and molecular orbital study of the first excited state of the high‐efficiency blue OLED material bis(2‐methyl‐8‐quinolinolato)aluminum(III) hydroxide complex from ab initio and TD‐B3LYP

Bis(2‐methyl‐8‐quinolinolato)aluminum(III) hydroxide complex (AlMq₂OH) is used in organic light‐emitting diodes (OLEDs) as an electron transport material and emitting layer. By means of ab initio Hartree–Fock (HF) and density functional theory (DFT) B3LYP methods, the structure of AlMq₂OH was optimized. The frontier molecular orbital characteristics and energy levels of AlMq₂OH have been analyzed systematically to study the electronic transition mechanism in AlMq₂OH. For comparison and calibration, bis(8‐quinolinolato)aluminum(III) hydroxide complex (Alq₂OH) has also been examined with these methods using the same basis sets. The lowest singlet excited state (S₁) of AlMq₂OH has been studied by the singles configuration interaction (CIS) method and time‐dependent DFT (TD‐DFT) using a hybrid functional, B3‐LYP, and the 6‐31G* basis set. The lowest singlet electronic transition (S₀ → S₁) of AlMq₂OH is π → π* electronic transitions and primarily localized on the different quinolate ligands. The emission of AlMq₂OH is due to the electron transitions from a phenoxide donor to a pyridyl acceptor from another quinolate ligand including C → C and O → N transference. Two possible electron transfer pathways are presented, one by carbon, oxygen, and nitrogen atoms and the other via metal cation Al³⁺. The comparison between the CIS‐optimized excited‐state structure with the HF ground‐state structure indicates that the geometric shift is mainly confined to the one quinolate and these changes can be easily understood in terms of the nodal patterns of the highest occupied and lowest unoccupied molecular orbitals. On the basis of the CIS‐optimized structure of the excited state, TD‐B3‐LYP calculations predict an emission wavelength of 499.78 nm. An absorption wavelength at 380.79 nm on the optimized structure of B3LYP/6‐31G* was predicted. They are comparable to AlMq2OH 485 and 390 nm observed experimentally for photoluminescence and UV‐vis absorption spectra of AlMq₂OH solid thin film on quartz, respectively. Lending theoretical corroboration to recent experimental observations and supposition, the reasons for the blue‐shift of AlMq2OH were revealed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004