Determination of Uranium Central-Field Covalency with 34 Resonant Inelastic X-ray Scattering.

Understanding the nature of metal-ligand bonding is a major challenge in actinide chemistry. We present a new experimental strategy for addressing this challenge using actinide 34 resonant inelastic X-ray scattering (RIXS). Through a systematic study of uranium(IV) halide complexes, [UX], where X = F, Cl, or Br, we identify RIXS spectral satellites with relative energies and intensities that relate to the extent of uranium-ligand bond covalency.

The scientific dating of standing buildings.

The techniques of dendrochronology (tree-ring dating) and radiocarbon (14C) dating are described, as they are applied to historic buildings. Both rely on determining the felling dates of the trees used in their construction. For dendrochronology, the construction of master chronologies and the matching of individual ring-width sequences to them is described and, for radiocarbon dating, the use of tree-ring results in calibration.

Development and Evaluation of Topical Gabapentin Formulations.

Topical delivery of gabapentin is desirable to treat peripheral neuropathic pain conditions whilst avoiding systemic side effects. To date, reports of topical gabapentin delivery in vitro have been variable and dependent on the skin model employed, primarily involving rodent and porcine models. In this study a variety of topical gabapentin formulations were investigated, including Carbopol hydrogels containing various permeation enhancers, and a range of proprietary bases including a compounded Lipoderm formulation; furthermore microneedle facilitated delivery was used as a positive control.

100 years of X-ray crystallography.

The developments in crystallography, since it was first covered in Science Progress in 1917, following the formulation of the Bragg equation, are described. The advances in instrumentation and data analysis, coupled with the application of computational methods to data analysis, have enabled the solution of molecular structures from the simplest binary systems to the most complex of biological structures. These developments are shown to have had major impacts in the development of chemical bonding theory and in offering an increasing understanding of enzyme-substrate interactions.

Going the distance: spatial scale of athletic experience affects the accuracy of path integration.

Evidence suggests that athletically trained individuals are more accurate than untrained individuals in updating their spatial position through idiothetic cues. We assessed whether training at different spatial scales affects the accuracy of path integration. Groups of rugby players (large-scale training) and martial artists (small-scale training) participated in a triangle-completion task: they were led (blindfolded) along two sides of a right-angled triangle and were required to complete the hypotenuse by returning to the origin.

Zinc deficiency in Mexican American children: influence of zinc and other micronutrients on T cells, cytokines, and antiinflammatory plasma proteins.

Background: The Third National Health and Nutrition Examination Survey suggested some Mexican American children are at risk of zinc deficiency.

Objective: We measured the effects of zinc and micronutrients or of micronutrients alone on indexes of cell-mediated immunity and antiinflammatory plasma proteins.

Design: Subjects (n = 54) aged 6-7 y were randomly assigned and treated in double-blind fashion in equal numbers with 20 mg Zn (as sulfate) and micronutrients or with micronutrients alone 5 d/wk for 10 wk.

Supramolecular circular helicates formed by destabilisation of supramolecular dimers.

The effect of changes in the angles at the connection points of linear/circular helicates is explored as a route to control the nuclearity and architecture of metallo-supramolecular arrays. This effect is probed by changing the geometry of the metal centre used to assemble bis-pyridylimine ligands that contain a 1,3-bis(aminomethyl) benzene spacer group. Tetrahedral metal ions favour linear dimers, whereas octahedral nickel(II) predominantly gives a triangular circular helicate.

Association between zinc pool sizes and iron stores in premenopausal women without anaemia.

The simultaneous occurrence of Zn and Fe deficiencies in man has been known since the discovery of human Zn deficiency. However, it is not established that low Fe stores per se or Fe-deficiency anaemia infer low Zn status. Therefore our objective was to identify relationships between Zn and Fe status in premenopausal women without anaemia.

Enantiomeric resolution of supramolecular helicates with different surface topographies.

The enantiomeric resolution of an extended range of di-metallo supramolecular triple-helical molecules are reported. The ligands for all complexes are symmetric with two units containing an aryl group linked via an imine bond to a pyridine. Alkyl substituents have been attached in different positions on the ligand backbone.

An estrogen-platinum terpyridine conjugate: DNA and protein binding and cellular delivery.

A platinum metal complex in which terpyridine joins estradiol (via an ethynyl link) to a platinum with a labile ligand (chloride) has been designed, synthesised and its X-ray crystal structure determined. The aim of this work was to link a targeting motif (in this case estrogen) to a metal-based biomolecule recognition unit (the platinum moiety). The target molecule: 17alpha-[4'-ethynyl-2,2':6',2'-terpyridine]-17beta-estradiol platinum(II) chloride (PtEEtpy) has been shown to bind to both human and bovine serum albumin (SA) and to DNA.

Carbene or zwitterion? Competition in organoplatinum complexes.

The reaction of a known dimeric dicarbene complex of platinum with a number of ligands results in four new platinum complexes. The structure of the new complexes is described: one complex must exist as a neutral complex with no charge separation, and the other three are assigned a charge-separated (zwitterionic) structure, rather than a carbene form, on the basis of comparative 13C NMR shifts.

Structure of anhydrous alkali-metal formates.

Single-crystal X-ray diffraction has yielded new crystal structures for cesium formate (CsOOCH) and rubidium formate (RbOOCH). The cesium formate structure has the same unit cell and space group as that published from powder X-ray diffraction data but differs radically in the placement and orientation of the formate ions. The new crystal structure has been successfully modeled with an empirical force field based on pair potentials, whereas it proved impossible to develop a force field that gave an adequate description of the powder structure.

Complexes of 2,6-bis[N-(2'-pyridylmethyl)carbamyl]pyridine: formation of mononuclear complexes, and self-assembly of double helical dinuclear and tetranuclear copper(II) and trinuclear nickel(II) complexes.

The potentially pentadentate ligand 2,6-bis[N-(2'-pyridylmethyl)carbamyl]pyridine (H2L1), readily prepared from reaction of a diester of pyridine-2,6-dicarboxylic acid (H2dipic) and 2-aminomethylpyridine (ampy), shows limited tendency to form 1:1 M:L complexes with labile metal ions, although [CuL1] and [NiL1] were observed as minor species, the latter characterized by a crystal structure analysis. A mononuclear complex formed with inert Co(III) was characterized by a crystal structure as the neutral 1:2 complex [Co(L1)(HL1)] with two ligands acting as tridentate ligands, one coordinated by the central pyridine and its two flanking deprotonated amido groups, and the other by the central pyridine, one amido and one terminal pyridine group, with the remaining poorly coordinating protonated amide remaining unbound along with other terminal pyridine groups. Fe(III) is known to form a symmetrical 1:2 complex, but that complex is anionic due to binding of all four deprotonated amido groups; the unsymmetrical neutral Co(III) complex converts into a symmetrical anionic species only on heating for hours in aqueous base in the presence of activated carbon.

Asymmetric hydrogenation of ketones using a ruthenium(II) catalyst containing BINOL-derived monodonor phosphorus-donor ligands.

[structure: see text] A series of ruthenium(II) complexes containing BINOL-based monodonor phosphorus ligands have been prepared and applied to the asymmetric catalysis of the hydrogenation of aryl/alkyl ketones. The best ligands for this application are those which contain an aromatic groups with either a methoxide or bromide on the ortho position. Using these ligands, alcohols with ee's of up to 99% are formed.

Using noncovalent intra-strand and inter-strand interactions to prescribe helix formation within a metallo-supramolecular system.

The effect of inter-strand and intra-strand interactions is explored in a metallo-supramolecular system in which the metal-ligand coordination requirements may be satisfied by more than one different supramolecular architecture. This is achieved by introducing alkyl substituents onto the spacers of readily prepared bis(pyridylimine) ligands. The alkyl substituents induce twisting within the ligand strand and this intra-strand effect favours formation of helical architectures.

Aggregation of metallo-supramolecular architectures by metallo-assembled hydrogen bonding sites.

Metal-ligand interactions are used not only to design metallo-supramolecular architectures but also to assemble multiple hydrogen bond sites at the periphery of these architectures. The hydrogen bond sites aggregate the architectures into polymeric arrays with the selection of anion determining whether this is self H-bond aggregation or anion-mediated H-bond aggregation.

Association between plasma zinc concentration and zinc kinetic parameters in premenopausal women.

The objective of this study was to measure relationships between plasma zinc (Zn) concentrations and Zn kinetic parameters and to measure relationships of Zn status with taste acuity, food frequency, and hair Zn in humans. The subjects were 33 premenopausal women not taking oral contraceptives and dietary supplements containing iron and Zn. Main outcomes were plasma Zn concentrations, Zn kinetic parameters based on the three-compartment mammillary model using 67Zn as a tracer, electrical taste detection thresholds, and food frequencies.

Binding of phosphate with a simple hexaaza polyammonium macrocycle.

A mixture of dihydrogen phosphate and phosphoric acid has been crystallized with a hexaprotonated 26-membered polyammonium macrocycle, 1,4,7,14,17,20-hexaazacyclohexacosane, as the counterion. The complex crystallizes in the monoclinic space group P2(1)/c with unit cell parameters of a = 10.006(2) A, b = 12.

Spinal cord injury increases iron levels: catalytic production of hydroxyl radicals.

This study used a weight drop impact injury model to explore the role of iron and the reality of iron-catalyzed hydroxyl radical ((*)OH) formation in secondary spinal cord injury (SCI). The time course of total extracellular iron was measured following SCI by microcannula sampling and atomic absorption spectrophotometry analysis. Immediately following SCI, the total iron concentration increased from an undetectable level to an average of 1.

Synthesis and X-ray crystal structure determination of the first Copper(II) complexes of tetraazamacrocycle-glyoxal condensates.

Novel Cu(II) complexes CuLCl(2) (L = 1-4) have been synthesized containing the metal bound to a well-known type of tetracyclic bisaminal formed from the condensation of glyoxal and tetraazamacrocycles (1 = cyclam-glyoxal condensate, 2 = [13]aneN4-glyoxal condensate, 3 = cyclen-glyoxal condensate, 4 = isocyclam-glyoxal condensate). The four-coordinate complexes were characterized by X-ray crystallography, electronic spectroscopy, solid-state magnetic moments, and electron spin resonance spectroscopy. The tetracyclic bisaminals, although having four potential donor atoms, are bound in a cis-bidentate fashion to Cu(II) with two additional cis-chloride donors.

Helical (isotactic) and syndiotactic silver(I) metallo-supramolecular coordination polymers assembled from a readily prepared bis-pyridylimine ligand containing a 1,5-naphthalene spacer.

A ligand in which two pyridylimine binding units are linked by a 1,5-naphthalene spacer is prepared and its silver(I) coordination chemistry investigated. In the solid state, a pair of C-H triplebond N interactions between pyridylimine units link the free ligands into chain structures, with further C-H triplebond N and some -stacking interactions linking these chains into a three-dimensional structure. The spacer constrains the ligand to dinucleate, and with silver(I) the metal coordinates to two pyridylimine units from two separate ligands and this leads to the formation of coordination polymers with a range of different anions.

2-D soft ferromagnet based on [Wv(CN)8]3- and CuII with a Tc of 34 K.

Self-assembly of [Cu(tetren)]2+ (tetren = tetraethylenepentamine) and [W(CN)8]3- in acidic aqueous solution yields the double-layered square grid cyanide-bridged polymer of ((tetrenH5)0.8CuII4[Wv(CN)8](4).7.

Competing supramolecular interactions give a new twist to terpyridyl chemistry: anion- and solvent-induced formation of spiral arrays in silver(I) complexes of a simple terpyridine.

Multiple competing molecular interactions (metal-ligand, pi-stacking and hydrogen-bonding) in the silver(I) complexes of 4'-thiomethyl-2,2':6',2"-terpyridine give rise to a range of different molecular architectures, in which the metal-ligand coordination requirements are satisfied in quite different ways. Polynuclear supramolecular spirals, aggregated mononuclear and aggregated dinuclear units are all structurally characterised. The metallo-supramolecular architecture obtained displays a remarkable dependence both on the choice of non-coordinated anion and the type of solvent used (coordinating or non-coordinating).

Synthesis and Characterization of Functionalized N,N'-Diphenylformamidinate Silver(I) Dimers: Solid-State Structures and Solution Properties.

Functionalized N,N'-diphenylformamidines and their deprotonated silver(I) complexes have been synthesized: silver(I) N,N'-di(4-alkyl)phenylformamidinate (alkyl = methyl, ethyl, n-butyl, and n-hexadecyl) 1-4; silver(I) N,N'-di(4-trifluoromethyl)phenylformamidinate 5, silver(I) N,N'-di(3-methoxy)phenylformamidinate 6, silver(I) N,N'-di(3-methylmercapto)phenylformamidinate 7, silver(I) N,N'-di(2-methoxy)phenylformamidinate 8, silver(I) N,N'-di(2-methylmercapto)phenylformamidinate 9. The effects of increasing the coordination number of the silver(I) centers by donor substituents on the phenyl groups have been investigated by solution and solid-state studies. Variable-temperature proton NMR (223-303 K) for 1-4 shows coupling between the proton attached to the amidinate carbon and the (107/109)Ag centers at room temperature which is unaffected by cooling (2).