Updated Abraham model correlations for correlating solute transfer into dry butanone and dry cyclohexanone solvents

Updated Abraham solvation parameter model correlations are derived for describing the partitioning and solubility behaviour of organic nonelectrolyte solutes and inorganic gases in both anhydrous butanone and cyclohexanone solvents. The butanone and cyclohexanone correlations are based on data sets that contain 103 and 72 experimental data points, respectively. The derived correlations for butanone describe the experimental partitioning and solubility behaviour to within a standard deviation of 0.145 log units. A slightly smaller standard deviation of 0.135 was observed between the experimental and back-calculated values for the cyclohexanone solvent correlation equations.     

Crystal structure,physical, and photophysical properties of a ruthenium(II) bipyridine diazafluorenone complex

The complex [Ru(bpy)₂(dafo)](PF₆)₂, where bpy is 2,2-bipyridine and dafo is diazafluorenone crystallizes in the space group P2₁/n witha=9.505(3) Å,b=14.002(4) Å andc=25.783(8) Å. The coordination geometry of the Ru atom is that of a distorted octahedron with a RuN₆ core. The two Ru-N bond distances to the dafo ligand are 2.13(1) and 2.15(1) Å; the four Ru-N bond distances to the bipyridine ligands are 2.03(1), 2.05(1), 2.06(1), and 2.07(1) Å. The three shortest Ru-N distances aretrans to the three longest Ru-N distances. The complex is oxidized and reduced reversibly at 1.41 and –0.65 V vs. SSCE, respectively. It displays absorptions at 438 nm (1.6×10⁴), 285 nm (6.2×10⁴), and 240 nm (4.1×10⁴) and a broad emission centered at 626 nm in water at room temperature. The emission lifetime is 420 ns and the emission quantum yield is 5.3×10^–4.     

Determination of ampicillin in New Zealand white rabbit plasma using column switching technique and HPLC

Summary The purpose of this study was to develop a simple and fast analytical method for quantitation of ampicillin in rabbit plasma, suitable for analysis of large numbers of samples collected from experimental animals. The concentration of ampicillin in rabbit plasma was determined utilizing ion-pair reverse-phase high performance liquid chromatography (HPLC) with UV detection and a column switching technique. Plasma samples were treated with a perchloric acid solution to precipitate proteins and centrifuged to pellet the precipitated proteins. Cephalexin was used as an internal standard. The C₁₈ precolumn was placed in the injector loop of the Rheodyne injector. Samples were injected with the injector in the load position and the precolumn was washed free from interfering compounds. When the injector was switched to the inject position, the mobile phase was passed through the precolumn taking relatively pure compounds onto the analytical column. The limit of quantitation was established to be 400 ng mL^–1 of plasma. The standard curves were linear over the range of ampicillin concentrations assayed, 400 to 10,000 ng mL^–1 of rabbit plasma, and had a mean regression coefficient of 0.9962 (±0.0043). Intra-day variability was determined using six replicates of controls (low and high) analyzed on a single assay. The percent of relative accuracy for low and high controls were 5.67 and 1.12, respectively. Inter-day variability was determined over a four day period analyzing replicates of each control. The percent of relative accuracy for low and high controls were 4.33 and 1.63, respectively.     

Selection of a pentameric host in the host-guest complexes [[[[P(mu-NtBu)]2(mu-NH)]5].I]-[Li(thf)4]+ and [[[P(mu-NtBu)]2(mu-NH)]5].HBr.THF

The structures of the host-guest complexes [[[[P(mu-NtBu)]2(mu-NH)]5]I]-.[Li(thf)4]+ [2.I[Li(thf)4]] and [[[P(mu-NtBu)]2(mu-NH)]5].HBr.THF (2.HBr.THF) show that increased distortion of the framework of the pentameric macrocycle [[[P(mu-NtBu)]2(mu-NH)]5] (2) occurs with the larger halide ions. Theoretical studies show that the thermodynamic stabilities of the model host-guest anions [2.X]- (X=Cl, Br, I) are in the order Cl- approximately Br->I-, that is, the reverse of the templating trend observed experimentally. These studies support the view that the selection of the pentamer 2 over the tetramer [[[P(mu-NtBu)]2(mu-NH)]4] (1) is kinetically controlled, a conclusion which is also consistent with the previous observation that the frameworks of 1 and 2 are not in dynamic equilibrium with each other.     

Hairpin versus extended DNA binding of a substituted beta-alanine linked polyamide

A series of alpha-substituted beta-alanine (beta) linked polyamides (DbaPyPyPy-beta*-PyPyPy) were prepared and examined. This resulted in the observation that while most substituents disrupt DNA binding, (R)-alpha-methoxy-beta-alanine (beta((R)-OMe)) maintains strong binding affinity and preferentially adopts a hairpin versus extended binding mode, providing an alternative hairpin linker to gamma-aminobutyric acid (gamma). A generalized variant of a fluorescent intercalator displacement assay conducted on a series of hairpin deoxyoligonucleotides containing a systematically varied A/T-rich binding site size was developed to distinguish between the extended binding of the parent beta-alanine 1 (DbaPyPyPy-beta-PyPyPy) and the hairpin binding of 3 (DbaPyPyPy-beta((R)-OMe)-PyPyPy).     

Binary electrocatalysts for organic oxidations

The electro-oxidation of formaldehyde and methanol has been studied on a number of binary platinum electrocatalysts. These comprised mixed electro-deposits of Pt with Sb, As, Bi, Hg, Re, Te or Sn and a range of homogeneous Pt-Rh alloys of different, known, surface composition. These systems were found to exhibit an enhanced activity over that of platinum alone, and this behaviour was correlated with the ease of adsorption of oxygen on the added metal. The activities for organic oxidation were compared with predictions of a model involving reaction between adsorbed oxygen and organic species on the metal surface. The proposed mechanism accounts for the behaviour of both homogeneous and heterogeneous alloy systems.     

Synthesis and deprotonation of P-H-functionalised phosph(III)azanes; borohydride dependency on the formation of cis- or trans-[HP(mu-NtBu)2PNtBuH

The reaction of [ClP(muNtBu)2PNtBuH] (1) with LiBsBu3H yields trans-[HP(muNtBu)2PNtBuH] (2), by contrast, reaction with LiBEt3H yields cis-[HP(mu-NtBu)2PNtBuH] (3). Compounds and represent the first examples of P-H-functionalised cyclophosph(III)azanes. Deprotonation of with BnNa (Bn=benzyl) gives the first example of a secondary phosphine-functionalised cyclodiphosph(III)azane anion [HP(mu-NtBu)2PNtBu]- (4).     

Study of an actinomycin complex by mass spectrometry-mass spectrometry

The characterization of components within actinomycin complexes may often be complicated by the lack of material and standards of known actinomycins. Mass spectrometry-mass spectrometry can be employed both as a separatory device and as a means of structural analysis. This technique has been applied to an actinomycin complex obtained from a previously unidentified Streptomyces strain. The method involved initial work on a known material, in this case actinomycin D, and application to the unknown material. Three major components within the unknown complex were characterized as actinomycins D, F(8), and F(9).