Synthesis of ordered mesoporous NiO with crystalline walls and a bimodal pore size distribution

A mesoporous solid with crystalline walls and an ordered pore structure exhibiting a bimodal pore size distribution (3.3 and 11 nm diameter pores) has been synthesized. Previous attempts to synthesize solids with large ordered mesopores by hard templating focused on the preparation of templates with thick walls (the thick walls become the pores in the target materials), something that has proved difficult to achieve. Here the large pores (11 nm) do not depend on the synthesis of a template with thick walls but instead on controlling the microporous bridging between the two sets of mesopores in the KIT-6 template. Such control determines the relative proportion of the two pore sizes. The wall thickness of the 3D cubic NiO mesopore has also been varied. Preliminary magnetic characterization indicates the freezing of uncompensated moments or blocking of superparamagnetism.     

Easily prepared chiral scorpionates: tris(2-oxazolinyl)boratoiridium(i) compounds and their interactions with MeOTf

Optically active C 3-symmetric monoanionic ligands are uncommon in organometallic chemistry. Here we describe the synthesis of readily prepared tris(4 S-isopropyl-2-oxazolinyl)phenylborate [To (P)] and fluxional, zwitterionic four- and five-coordinate iridium(I) compounds [Ir(To (P))(eta (4)-C 8H 12)] ( 4) and [Ir(To (P))(CO) 2] ( 5). The highly fluxional nature of 4 and 5 makes structural assignment difficult, and the interaction between the iridium(I) center and the [To (P)] ligand is established by solid-state and solution (15)N NMR methods that permit the direct comparison between solution and solid-state structures. Although iridium cyclooctadiene 4 is a mixture of four- and five-coordinate species, the dicarbonyl 5 is only the five-coordinate isomer. The addition of electrophiles MeOTf and MeI provides the oxazoline N-methylated product rather than the iridium methyl oxidative addition product. N-Methylation was unequivocally proven by through-bond coupling observed in (1)H- (15)N HMBC experiments.     

A pH-metric, UV, NMR, and X-ray crystallographic study on arsenous acid reacting with dithioerythritol

The aqueous solutions of arsenous acid with the meso and racemic forms of 1,4-dithiol-butane-2,3-diol, namely, dithioerythritol (dte) and dithiothreitol (dtt), respectively, were titrated pH-metrically in different molar ratios. The p K a values determined for As(OH) 3, and dtt were in good accordance with the literature data, and we determined for the first time the p K a value of dte. The deprotonation steps of both M (As(OH) 3 considered as a central metal ion) and H 2L components dte and dtt (considered as ligands) appeared at a higher pH in the titration curves of the ternary systems (M, H 2L, H (+)) than in the individual component. This unusual observation is explained by the condensation reactions between the reagents taking place in the pH < 8 range. In the solutions of c As(III) > 5.10 (-3) M, the precipitate formed upon mixing the arsenous acid and H 2L solutions in neutral medium, and the formation of the precipitate shifted toward acidic pH on the increase of the total concentrations. This indicated that pH-metry can follow the reactions only in an indirect way. Useful, but not satisfactory, information can be obtained by means of this method alone. Combined with NMR and UV spectroscopic measurements it is revealed that depending on the As(III)/H 2L molar ratio, different complexes form in the solutions. In the species with 1:2 composition, one of the ligands is strongly bound to the arsenic(III) probably via its two thiolate, while the second one is attached only weakly. The crystal structure of an As(III)-dte crystal of 1:1 composition, grown from ethanolic solution, shows that As(III) binds the ligand through its three p-orbitals in a manner similar to that expected in aqueous solution. While the uptake of the second ligand cannot be detected by pH-metry, the decomposition of thioether bonds above pH approximately 10 is confirmed by the change in UV spectra at approximately 265 nm to be a base-consuming process. In such alkaline solutions, most probably, rearrangement of the bonding scheme occurs, resulting in ligands being bound to the arsenic(III) through the oxygen donor atoms.     

Imidazole-substituted oxoverdazyl radical as a mediator of intramolecular and intermolecular exchange interaction

The 3-(2'-imidazolyl)-1,5-dimethyl-6-oxoverdazyl radical (imvd(*)) and the corresponding tetrazane H3imvd were prepared and structurally characterized, the former as two different hydrates. Reaction of imvd(*) with [M(hfac)2] led to the formation of monometallic complexes [M(hfac)2(imvd(*))] (M = Ni and Mn). They were characterized by single-crystal X-ray diffraction. In the solid state, all four radical-containing compounds exhibit imidazole-oxoverdazyl pi stacking. Following the structural analysis, imvd(*) behaves as an antiferromagnetic (AF) coupled chain with J = -100 cm(-1) (H = -J summation operator SiS(i+1)). The magnetic behavior of [M(hfac)2(imvd(*))] complexes is interpreted with a four-coupled spin model with a metal ion radical intramolecular interaction (JMn = -62.5 cm(-1) and JNi = 193 cm(-1); H = -JSMSimvd) and an AF intermolecular interaction (JMn' = -12.6 cm(-1) and JNi' = -4.3 cm(-1)) related to imidazole-oxoverdazyl pi stacking.     

Surface characterisation of chemically reduced electrolytic manganese dioxide

In this work a titration technique has been used to characterize the amphoteric surface properties of a series of chemically reduced electrolytic manganese dioxide (EMD) samples (MnO 1.97 to MnO 1.50). The surface of the EMD was found to consist of independent acidic and basic hydroxyl groups, which were able to be characterised by their respective equilibrium constants and site concentrations. For this chemically reduced series Kb varied from (1.81-8.43)x10(-10) as reduction proceeded, with the corresponding basic site concentration varying from (0.20-2.50)x10(-4) mol/m2 over the pH range considered. Ka was ranged from (1.23-9.23)x10(-6) over the reduction range considered. The increase in Kb suggested a weakening of the MnO bond via the introduction of the larger Mn3+ ions which will increase the length of this bond. Weakening the MnO bond results in a corresponding strengthening of the OH bond giving the surface hydroxyl group a basic nature which is supported by the increasing basic site concentration. For the samples with an x in MnOx value above 1.71 the total number of acidic sites decreased which supports the increase in the concentration of basic sites; however, below 1.71, the surface concentration of acidic sites increases slightly, which can be rationalised by the fact that the pyrolusite domains within the EMD (with relatively stronger MnO bonds) are accessible at this stage of the reduction. The number of surface oxide sites (Ns) and surface hydroxyl sites (Ns(OH)) were calculated crystallographically, and from the sum of the acid and basic hydroxyl groups determined by titration. Both methods produced data with the same order of magnitude, as well as indicated the expected increase in the number of surface hydroxyl groups with increasing degree of reduction. Electrochemical analysis of the samples in 9 M KOH showed the expected decrease in capacity with an increase in the degree of reduction. It also showed a decrease in the amount of charge contributed to the overall homogeneous reduction by Mn4+ ions in surface defects and within the ramsdellite domains over the entire x in MnOx range. However, the amount of charge contributed from the pyrolusite domains remained unchanged until after a x in MnOx value of 1.71.     

Decarboxylative isomerization of N-Acyl-2-oxazolidinones to 2-oxazolines

N-Acyl-2-oxazolidinones are ring-opened by lithium iodide and decarboxylated in the presence of a mild proton source. Further reaction with an amine base provides 2-oxazolines. The transformation is general for oxazolidinones unsubstituted in the 5 position and occurs under mild conditions (25-50 degrees C). These results complement the existing methods for this transformation by allowing lower temperatures and/or avoiding metal catalysts.     

Rapid Construction of a Benzo‐Fused Indoxamycin Core Enabled by Site‐Selective C−H Functionalizations

Methods for functionalizing carbon–hydrogen bonds are featured in a new synthesis of the tricyclic core architecture that characterizes the indoxamycin family of secondary metabolites. A unique collaboration between three laboratories has engendered a design for synthesis featuring two sequential C?H functionalization reactions, namely a diastereoselective dirhodium carbene insertion followed by an ester‐directed oxidative Heck cyclization, to rapidly assemble the congested tricyclic core of the indoxamycins. This project exemplifies how multi‐laboratory collaborations can foster conceptually novel approaches to challenging problems in chemical synthesis.     

A practical and cost-effective mutation scanning-based approach for investigating genetic variation in Cryptosporidium

In the present study, we used a mutation scanning-targeted sequencing approach to assess variation in part (pgp60) of the 60 kDa glycoprotein (gp60) gene among Cryptosporidium samples from humans in Victoria, Australia. Two nuclear ribosomal loci (the small subunit rRNA gene and the second internal transcribed spacer) were used to identify the samples as Cryptosporidium hominis (n = 74), Cryptosporidium parvum (n = 23) or Cryptosporidium meleagridis (n = 1). In total, nine distinct pgp60 sequences were identified (three C. hominis, five C. parvum and one C. meleagridis). Phylogenetic analyses of the pgp60 sequence data, employing well-defined reference sequences for comparison, allowed the genotypic and subgenotypic classification of samples. The C. hominis samples were classified as Ib A10G2R2, Id A15G1R2, and a new genotype, designated Ib2, was identified subgenotypically as A18G1R4. The C. parvum samples were classified as IIa A18G3R1, IIa A20G3R1, IIa A22G3R1, IIa A23G3R1 and IIc A5G3R2. These findings suggested that the C. hominis metapopulation is largely homogeneous, consisting of a single dominant genotype, Ib A10G2R2, whereas the C. parvum metapopulation is considerably more heterogeneous, with no single dominant genotype. The greater level of genetic heterogeneity found among the C. parvum samples, despite the smaller sample size, may relate to the zoonotic infection pattern of this species, which would be reflective of a greater number of possible infection sources. The present mutation scanning approach, coupled with targeted sequencing of genetically distinct representatives, is a practical, cost-effective tool for large-scale population genetic and epidemiological studies of Cryptosporidium and other eukaryotic organisms.     

Detecting deviations from pure EOF during CE separations

CE separations are known for their high separation efficiencies. In systems with EOF, the high efficiencies benefit from the flat, plug profile that is characteristic of EOF. When a velocity gradient is present, such as in separations which have nonuniform buffer ionic strength, surface adsorption or differences in the height of the ends of the capillary, a parabolic flow component is introduced. This deviation from purely EOF yields increased peak dispersion and a subsequent decrease in separation performance. This work details a rapid method for detecting deviations from ideal plug flow during the course of a separation using the radially averaged flow profile of a photobleached fluorophore added to the BGE. By comparing the ratio of two different data analysis procedures, deviations from ideal plug flow can be detected. This method allows rapid measurement of flow character and does not interfere with the concurrent separation. We demonstrate easy detection of the onset of hydrodynamic flow induced by both gravity siphoning and an ionic strength buffer discontinuity. A brief analysis of the radially averaged peak shapes is also presented.     

Comparison of liposomes formed by sonication and extrusion: rotational and translational diffusion of an embedded chromophore

We report on the physical and optical characterization of liposomes formed by extrusion and sonication, two widely used methods for vesicle preparation. We also address the issue of whether the properties of bilayers formed from liposomes prepared by the two techniques differ at the molecular and mesoscopic levels. We used the phospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), with and without cholesterol, to form liposomes, incorporating 1-oleoyl-2-[12-[(7-nitro-2-1,3-benzoxadiazol-4-yl)amino]dodecanoyl]-sn-glycero-3-phosphocholine (18:1-12:0 NBD-PC) as an optical probe of dynamics. We measured the physical morphology of liposomes by transmission electron microscopy (TEM) and dynamic light scattering (DLS), and the rotational and translational diffusion of 18:1-12:0 NBD-PC by time correlated single photon counting (TCSPC) and fluorescence recovery after pattern photobleaching (FRAPP), respectively. We find that, despite apparent differences in average size and size distribution, both methods of preparation produced liposomes that exhibit the same molecular scale environment. The translational diffusion behavior of the tethered chromophore in planar bilayer lipid membranes formed from the two types of liposomes also yielded similar results.