Complete basis set extrapolated potential energy, dipole, and polarizability surfaces of alkali halide ion-neutral weakly avoided crossings with and without applied electric fields

Complete basis set extrapolations of alkali halide (LiF, LiCl, NaF, NaCl) energy, dipole, and polarizability surfaces are performed with and without applied fields along the internuclear axis using state-averaged multireference configuration interaction. Comparison between properties (equilibrium separation, dissociation energy, crossing distance, diabatic coupling constant, dipole, and polarizability) derived from the extrapolated potential energy (or dipole) surfaces are made with those obtained from direct extrapolation from the basis set trends. The two extrapolation procedures are generally found to agree well for these systems. Crossing distances from this work are compared to those of previous work and values obtained from the Rittner potential. Complete basis set extrapolated crossing distances agree well with those derived from the Rittner potential for LiF, but were significantly larger for LiCl, NaF, and NaCl. The results presented here serve as an important set of benchmark data for the development of new-generation many-body force fields that are able to model charge transfer.     

Polytriazoles as copper(I)-stabilizing ligands in catalysis

Polytriazolylamines were synthesized by the copper(I)-catalyzed ligation of azides and alkynes. The C3-symmetric derivative, TBTA, was shown to be a powerful stabilizing ligand for copper(I), protecting it from oxidation and disproportionation, while enhancing its catalytic activity.     

The stannylation of carbonyl-stabilised phosphorus ylids,and tin-assisted elimination reactions

The interaction of organotin halides with lithium salts of mono-substituted phosphorus ylids and also with disubstituted ylids is described.     

Functionalized nanoparticles for liquid atmospheric pressure matrix-assisted laser desorption/ionization peptide analysis

Nanoparticles for the extraction of peptides and subsequent analysis using atmospheric pressure matrix-assisted laser desorption/ionization (APMALDI) have been evaluated. The atmospheric pressure source allows for particles to be directly introduced in the liquid matrix, minimizing sample loss and analysis time. Described in this work are two sample preparation procedures for liquid APMALDI analysis: a C18 functionalized silica nanoparticle for hydrophobic extractions, and an aptamer functionalized magnetite core nanoparticle for rapid, affinity extractions. The C18 particles provide a non-selective support for rapid profiling applications, while the aptamer particles are directed towards reducing the complexity in biological samples. The aptamer functionalized particles provide a more selective analyte-nanoparticle interaction whereby the tertiary structure of the analyte becomes more critical to the extraction. In both cases, the liquid APMALDI matrix provides a support for ionization, and acts as the releasing agent for the analyte-particle interaction. Additionally, analyte enrichment was possible due to the large surface-to-volume ratio of the particles. The experiments conducted with functionalized nanoparticles, in an atmospheric pressure liquid matrix, present a basis for further methodologies and utilities of silica nanoparticles to be developed.     

Sodium p‐nitro­benzoxasulfamate monohydrate

The title compound, alternatively named sodium 6‐nitro‐3H‐1,2,3‐benzoxa­thia­zole 2,2‐dioxide monohydrate, Na⁺·C₆H₃­N₂O₅S^?·H₂O, consists of chains of NaO₇ units, with the seven donor‐O atoms coming from two water mol­ecules and five p‐­nitro­benzoxasulfamate anions. The seven‐coordinate geometry around the Na⁺ ion is described as monocapped trigonal prismatic, but with a large distortion from ideal geometry. Each triangular face is defined by one O atom each from a water mol­ecule, a nitro group and a sulfonyl group. An O atom from a sulfonyl group caps one of the square faces of the trigonal prism in an unsymmetrical fashion. The water mol­ecules and one sulfonyl O atom are involved in bridging adjacent units, as is the nitro group of the anion. The sulfamate ions adopt an antiparallel alignment between the NaO₇ units and are connected to each other by C—H?O and π–π interactions. The three‐dimensional crystal structure is stabilized by a network of strong O—H?N hydrogen bonds.     

Effects of injector geometry and sample matrix on injection and sample loading in integrated capillary electrophoresis devices

The double-T injector design employed in many microchip capillary electrophoresis devices allows for the formation of very small (50-500 pL) sample plugs for subsequent analysis on-chip. In this study, we show that sample plugs formed at the channel junction can be geometrically defined. The channel width and injector symmetry prove to be of great importance to good performance. A unique pushback of solvent into the side channels can be induced when the side channels have a very low resistance to flow, and this helps to better define the injected sample plug. Samples and running buffers of differing ionic strength (e.g., 10 mM KCl buffer and 20 mM KCl sample) can yield widely variable results in terms of plug shape and amount injected (variations of 1.5 to 10x). Applying bias voltages to all the intersecting channels aids in controlling the plug shape. However, when the ionic strengths of buffer and sample are not matched, the actual amount injected (up to 10x variations) can be inconsistent with the appearance of the plug formed in the injector (up to only 30 % variations). Operating at constant pH and ionic strength produced the most consistent results. This report examines the effects of altering the injector geometry and solution ionic strengths, and presents the results of using bias voltages to control plug formation. The observed results should provide a benchmark for modeling of the fluid dynamics in channel intersections.     

Solvation largely accounts for the effect of N-alkylation on the properties of nickel(II/I) and chromium(III/II) cyclam complexes

The source of the effect of N-alkylation on the redox properties of Ni(II/I) and Cr(III/II) cyclam complexes has been investigated using DFT calculations. The structures of the anhydrous and hydrated complexes were optimized in the gas phase, and single point calculations were performed in a polarized continuum. The main results are the following: the decrease in outer sphere solvation upon N-alkylation is the major source of the relative stabilization of the lower oxidation state complexes by the tertiary amine ligands; tertiary amine nitrogen donors are stronger sigma-donors than the secondary amines, as predicted from the inductive effect of alkyls; steric strain elongates the metal-nitrogen bonds in the tertiary complexes and decreases the ligand strain energies; and the site of water binding to the complexes differs because of their different electronic structures (i.e., in the Ni complexes, the water molecules bind to the M[bond]N[bond]H sites, whereas in the Cr complexes they bind to the central metal cation). Outer sphere hydrogen bonding of water to the ligands in the coordination sphere lowers the ionization potentials by charge delocalization.     

Greenhouse gas abatement — toward Pareto-optimal decisions under uncertainty

This paper examines the economic logic of integrated assessment — balancing the costs against the benefits of greenhouse gas abatement. Stylized facts are employed in a multiregion computable general equilibrium model with a public good. The percentage shares of global emissions are determined outside the model — based upon some form of international agreement — and emission rights are tradeable between regions. The analysis is confined to Pareto-optimal (cooperative) solutions. We focus on the sensitivity of initial decisions to low-probability, high-consequence scenarios associated with cumulative emissions. For simplicity, there are only two regions, two tradeable goods, two time periods, and two states-of-world. With the particular form of public good model adopted here (production rather than utility function impacts), it turns out that a Pareto-optimal hedging strategy is indepedent of the emission shares allocated to each region. Equity issues may be separated from those of economic efficiency. Similar results extend to cases in which there are additional regions, tradeable goods, time periods, and states-of-world.Presented at the Conference on the Economics of Global Environmental Change, Birmingham University, May 9–11, 1994. This research was funded by the Electric Power Research Institute (EPRI). The views presented here are solely those of the individual authors, and do not necessarily represent the views of EPRI or its members.