Copper ring-disk microelectrodes: fabrication, characterization, and application as an amperometric detector for capillary columns

A novel approach to the fabrication of metal ring-disk (RD) microelectrodes is presented that employs flexible chemical vapor deposition (CVD) and electrode modification techniques. Specifically, the development of a copper ring-disk microelectrode is described utilizing a combination of CVD coating, electroetching, and electroplating. Initially, a 25 μm diameter tungsten wire is concentrically coated by CVD with an insulating layer of silica, a layer of tungsten metal, and finally, a second outer layer of silica. The copper surface was prepared by first creating micrometer cavities by electrochemical etching the tungsten in hydroxide solutions followed by electrodeposition of copper from aqueous solutions of Cu(II). Each step of the process was characterized by scanning electron microscopy, optical microscopy, and cyclic voltammetry, demonstrating the preparation of a viable metal-based dual ring-disk microelectrode system. For the purpose of demonstrating the concept of introducing specific selectivity into the device, amperometric detection of galactose in 0.1 M NaOH was performed at +0.60 V in bulk solution and after flow injection analysis in a capillary column.     

Solventless injecction for packed column supercritical fluid chromatography

The adverse effects of injection solvent strength on microbore packed column SFC band broadening are demonstrated and a solventless injection system that eliminates these effects is introduced. The injection system removes solvent in a GC-like manner using a retention gap and an on-column capillary GC syringe. The analyte is delivered to the analytical column in a solvent-free plug of supercritical fluid mobile phase.     

以万古霉素为流动相添加剂的高效液相色谱法手性分析系统的建立

以丹酰化苯甘氨酸、丹酰化苯丙氨酸、丹酰化丝氨酸、丹酯化丙氨酸为模型化合物，通过对色谱柱类型、缓冲液类型、pH和盐浓度、万古霉素用量、甲醇用量、柱温等色谱参数进行考察，建立了以万古霉素为手性流动相添加剂在普通色谱柱上进行手性分析的色谱系统，并在该系统中成功地拆分了酮洛芬对映体。     

Study of a mathematical model of metal ion complexes in solvent sublation

Separation of metal ion complex, [(C(12)H(8)N(2))(3)Fe(2+)], with surfactant sodium dodecylphrate (DLS) complex from aqueous phase was carried out by solvent sublation, which obeys first-order kinetics. On the base of the complete transport mechanisms, the Langmuir adsorption, and the ion complex equilibrium in the aqueous phase, a mathematical model for the [(C(12)H(8)N(2))(3)Fe(2+)]-surfactant ion complex is obtained with the aid of the Mathematic 4.0 program, 4th Runge-Kutta method, and the Matlab programs. The effects of many parameters, such as K(a), K(l), K(ow), d(i), V(o), V(w), and Q(a), on solvent sublation are investigated. Furthermore, the simulation showed that the model is substantiated for experiments on the solvent sublation of the complex.     

Room-temperature ferroelectric and ferroelastic orders coexisting in a new tetrafluoroborate-based perovskite

The coexistence of multiferroic orders has attracted increasing attention for its potential applications in multiple-state memory, switches, and computing, but it is still challenging to design single-phase crystalline materials hosting multiferroic orders at above room temperature. By utilizing versatile ABX₃-type perovskites as a structural model, we judiciously introduced a polar organic cation with easily changeable conformations into a tetrafluoroborate-based perovskite system, and successfully obtained an unprecedented molecular perovskite, (homopiperazine-1,4-diium)[K(BF₄)₃], hosting both ferroelectricity and ferroelasticity at above room temperature. By using the combined techniques of variable-temperature single-crystal X-ray structural analyses, differential scanning calorimetry, and dielectric, second harmonic generation, and piezoresponse force microscopy measurements, we demonstrated the domain structures for ferroelectric and ferroelastic orders, and furthermore disclosed how the delicate interplay between stepwise changed dynamics of organic cations and cooperative deformation of the inorganic framework induces ferroelectric and ferroelastic phase transitions at 311 K and 455 K, respectively. This instance, together with the underlying mechanism of ferroic transitions, provides important clues for designing advanced multiferroic materials based on organic–inorganic hybrid crystals.

An unprecedented tetrafluoroborate-based perovskite reveals the coexistence of ferroelastic and ferroelectric transitions arising from delicate interplay between stepwise frozen organic cations and cooperative deformation of the framework.     

Comment: 2004's fastest organic and biomolecular chemistry!

In January 2004, the Royal Society of Chemistry launched Organic & Biomolecular Chemistry (OBC) - a journal promising to provide high quality research from all aspects of synthetic, physical and biomolecular organic chemistry. The journal was set to build upon the foundations laid down by its predecessor publications (J. Chem. Soc., Perkin Trans. 1 and J. Chem. Soc., Perkin Trans. 2) as well as complement the subject coverage already published in prestigious general chemistry journals such as Chemical Communications and Chemical Society Reviews. Nearly two years on, just how is the programme developing and what can the community expect to see from the Royal Society of Chemistry (RSC)?     

Rhenium-promoted diastereo- and enantioselective cyclopentannulation reactions: furans as 1,3-propene dipoles

The rhenium furan complexes TpRe(CO)(MeIm)(eta2-2-methylfuran) (1) and TpRe(CO)(MeIm)(eta2-2,5-dmethylfuran) (2) undergo Lewis acid-promoted cyclopentannulation reactions with enones and enals to generate 3-acetylcyclopentene complexes. During the reaction, a rearrangement occurs such that the alpha and beta carbons of the enone are incorporated into the new carbocycle. Treatment of these complexes with an oxidant (H2O2 or silver triflate) liberates the acetylcyclopentene. When a resolved form of the rhenium complex is used, the acetylcyclopentenes can be obtained enantioselectively.     

Gas-phase acidities of disubstituted methanes and of enols of carboxamides substituted by electron-withdrawing groups

The gas-phase acidities DeltaG degrees (acid) of some 20 amides/enols of amides RNHCOCHYY'/RNHC(OH)=CYY' [R = Ph, i-Pr; Y, Y' = CO(2)R', CO(2)R' ', or CN, CO(2)R', R', R' ' = Me, CH(2)CF(3), CH(CF(3))(2)], the N-Ph and N-Pr-i amides of Meldrum's acid, 1,3-cyclopentanedione, dimedone, and 1,3-indanedione, and some N-p-BrC(6)H(4) derivatives and of nine CH(2)YY' (Y, Y' = CN, CO(2)R', CO(2)R' '), including the cyclic carbon acids listed above, were determined by ICR. The acidities were calculated at the B3LYP/6-31+G//B3LYP/6-31+G level for both the enol and the amide species or for the carbon acid and the enol on the CO in the CH(2)YY' series. For 12 of the compounds, calculations were also conducted with the larger base sets 6-311+G and G-311+G. The DeltaG degrees (acid) values changed from 341.3 kcal/mol for CH(2)(CO(2)Me)(2) to 301.0 kcal/mol for PhNHC(OH)=C(CN)CH(CF(3))(2). The acidities increased for combinations of Y and Y' based on the order CO(2)Me < CO(2)CH(2)CF(3) < CN, CO(2)CH(CF(3))(2) for a single group and reflect the increased electron-withdrawal ability of Y,Y' coupled with the ability to achieve planarity of the crowded anion. The acidities of corresponding YY'-substituted systems follow the order N-Ph enols > N-Pr-i enols > CH(2)YY'. Better linear relationships between DeltaG degrees (acid) values calculated for the enols and the observed values than those for the values calculated for the amides suggest that the ionization site is the enolic O-H of most of the noncyclic trisubstituted methanes. The experimental DeltaG degrees (acid) value for Meldrum's acid matches the recently reported calculated value. The calculated structures and natural charges of all species are given, and the changes occurring in them on ionization are discussed. Correlations between the DeltaG degrees (acid) values and the pK(enol) values, which are linear for the trisubstituted methanes, excluding YY' = (CN)(2) and nonlinear for the CH(2)YY' systems, are discussed.     

邻苯二亚胺纤维素水溶液的荧光行为

目前，用于制造光致发光材料的基材均为合成高分子材料，如聚氯乙烯（ＰＶＣ）等热塑性材料以及不饱和聚酯等热固性材料［１］．天然高分子材料发光性能的研究并不多见．而与合成高分子相比，纤维素的结构特征决定了它易参与化学反应，可用以制备各种用途的功能材料，如高...     

Reactions of Thiocarbamoyl compounds with vaska complexes: mechanism and stereochemistry

Bis(dimethylthiocarbamoyl)sulfide, (Me₂NCS)₂S, reacts with (PH₃P)₂MCOCl complexes giving ionic species [Ph₃PM(η²-CSNMe₂)(S₂CNMe₂)CO]X (M = Rh, Ir; X = Cl, PF₆) as kinetic products. On standing solution, [Ph₃PRh(η²-CSNMe₂)(S₂CNMe₂)CO]Cl is slowly transformed into the thermodynamic product Ph₃PRh(η²-CSNMe₂)S₂CNMe₂)Cl. The known reactions of Vaska-type complexes with Me₂NCSCl to give [trans-(Ph₃P)₂Ir(η²-CSNMe₂)COCl]Cl and trans-(Ph₃P)₂Rh(η²-CSNMe₂)Cl₂ probably follow a similar course. (PH₃P)RuNOCl reacts with (Me₂NCS)₂S and Me₂NCSCl in the same way as (Ph₃P)₂IrCOCl, but reacts with (Me₂NCS)₂NPh to give [trans-(Ph₃P)₂Ru(η²-CSNMe₂)NOCl]PF₆. The mechanism and stereochemistry of these reactions are discussed. Reactions were monitored by NMR spectroscopy in an attempt to identify intermediate η¹-thiocarboxamido complexes, but no such species could be detected.