Synergetic effects of the Cu/Pt{110} surface alloy: enhanced reactivity of water and carbon monoxide

We have used synchrotron-based high-resolution X-ray photoelectron spectroscopy in combination with ab initio density functional theory calculations to investigate the characteristics of water and CO adsorption on the bimetallic Cu/Pt{110}-(2 x 1) surface at a Cu coverage near 0.5 ML. Cu fills the troughs of the reconstructed clean surface forming nanowires, which are stable up to 830 K. Their presence dramatically influences the adsorption of water and CO. Water adsorption changes from intact to partially dissociated while the desorption temperature of CO on this surface increases by up to 27 K with respect to the clean Pt{110} surface. Ab initio calculations and experimental valence band spectra reveal that the Cu 3d-band is narrowed and shifted upward with respect to bulk Cu surfaces. This and electron donation to surface Pt atoms cause the increase in the bond strength between CO and the Pt surface atoms. The pathway for water dissociation occurs via Cu surface atoms. The heat of adsorption of water bonding to Cu surface atoms was calculated to be 0.82 eV, which is significantly higher than on the clean Pt{110} surface; the activation energy for partial dissociation is 0.53 eV (not corrected for zero point energy).

The local adsorption geometry and electronic structure of alanine on Cu{110}

The adsorption of alanine on Cu {110} was studied by a combination of near edge X-ray absorption fine structure (NEXAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). Large chemical shifts in the C 1s, N 1s, and O 1s XP spectra were found between the alanine multilayer and the chemisorbed and pseudo-(3 x 2) alaninate layers. From C, N, and O K-shell NEXAFS spectra the tilt angles of the carboxylate group (approximate to 26 degrees in plane with respect to [1 (1) over bar0] and approximate to 45 degrees out of plane) and the C-N bond angle with respect to [1 (1) over bar0] could be determined for the pseudo-(3 x 2) overlayer. Using this information three adsorption geometries could be eliminated from five p(3 x 2) structures which lead to almost identical heats of adsorption in the DFT calculations between 1.40 and 1.47 eV/molecule. Due to the small energy difference between the remaining two structures it is not unlikely that these coexist on the surface at room temperature. (c) 2006 Elsevier B.V. All rights reserved.

A new cyano-bridged one-dimensional (GdFeIII)-Fe-III coordination polymer with o-phenanthroline as the blocking ligand: synthesis, structure, and magnetic properties

Synthesis, structural characterization, and magnetic properties of a new cyano-bridged one-dimensional iron (III)-gadolinium (III) compound, trans-[Gd(o-phen)(2)(H2O)(2)(mu-CN)(2)Fe(CN)(4)], - 2no-phen (o-phen = 1,10-phenanthroline), have been described. The compound crystallizes in the triclinic P (1) over bar space group with the following unit cell parameters: a = 10.538(14) angstrom, b = 12.004(14) angstrom, c = 20.61(2) angstrom, alpha = 92.41(1)degrees, beta = 92.76(1)degrees, gamma = 11 2.72(1)degrees, and Z = 2. In this complex, each gadolinium (III) is coordinated to two nitrile nitrogens of the CN groups coming from two different ferricyanides, the mutually trans cyanides of each of which links another different Gd-III to create -NC-Fe(CN)(4)-CN-Gd-NC- type 1-D chain structure. The one-dimensional chains are self-assembled in two-dimensions via weak C-H center dot center dot center dot N hydrogen bonds. Both the variable-temperature (2-300 K, 0.01 T and 0.8 T) and variable-field (0-50 000 Gauss, 2 K) magnetic measurements reveal the existence of very weak interaction in this molecule. The temperature dependence of the susceptibilities has been analyzed using a model for a chain of alternating classic (7/2) and quantum (1/2) spins. (c) 2005 Elsevier B.V. All rights reserved.

The synthesis and characterisation of two new iron thioantimonates: [Fe(en)(3)](2)Sb2S5 center dot 0.55H(2)O and [Fe(en)(3)](2)Sb4S8

Two new iron thioantimonates, [Fe(en)(3)](2)Sb2S5 (.) 0.55H(2)O (1) and [Fe(en)(3)](2)Sb4S8 (2). were synthesised under solvothermal conditions from the reactions of Sb2S3, FeCl2 and S in the presence of ethylenediamine at 413 and 438 K, respectively. The products were characterised by single-crystal X-ray diffraction, elemental analysis and SQUID magnetometry. Compound 1 is unusual in containing isolated Sb2S54- anions formed from two corner-sharing SbS33- trigonal pyramids. These units are arranged in rippled layers, 4 A apart, parallel to the bc-plane. Octahedrally coordinated [Fe(en)(3)](2+) cations lie in depressions within these anionic layers. In compound (2), repeated corner linking of SbS33- trigonal pyramids generates SbS2- chains, which may be considered as a polymerised form of the Sb2S54- anions in 1. The SbS2- chains are separated by [Fe(en)(3)](2+) cations. In both compounds, there is an extensive network of hydrogen bonds between the nitrogen atoms of the ethylenediamine ligands and the sulfur atoms of the anions and, in the case of 1, the uncoordinated water molecule. (c) 2005 Elsevier Ltd. All rights reserved.

2D parallel interpenetration of [M-2(bpp)(4)X-4] [M, Fe(II)/Co(II); bpp, 4,4 '-trimethylenedipyridine; X, SCN-SeCN- and N-3(-)] complexes: pseudohalide-dependent conformation of bpp

Three coordination complexes of Co(II)/Fe(II) with 4,4'-trimethylenedipyridine (bpp) and pseudohalides (SCN-, SeCN- and N-3(-)) have been synthesized. The complexes have been characterized by X-ray single crystal structure determination. They are isomorphous having 2D layers in which two independent wavy nets display parallel interwoven structures. Pseudohalide binds metal centers through N terminal and occupies the trans axial positions of the octahedral metal coordination environment. Pseudohalide remains pendant on both sides of the polymeric layer and help the stacking through hydrogen bonding. The conformation of bpp in the interpenetrated nets is observed to be dependent on the choice of pseudohalide. (C) 2008 Elsevier Inc. All rights reserved.

New polynuclear Mo-Fe complexes with ferrocenylamidobenzimidazole ligands

The reaction between [Mo(eta(3)-C3H5)(CO)(2)(NCMe)(2)Br] (1) and the ferrocenylamidobenzimidazole ligands FcCO(NH(2)benzim) (L1) and (FcCO)(2)(NHbenzim) (L2) led to a binuclear (2) and a trinuclear (3) Mo-Fe complex, respectively. The single-crystal X-ray structure of [Mo(eta(3)-C3H5)(CO)(2)(L2)Br] [L2 = {[(eta(5)-C5H5)Fe(eta(5)-C5H4CO)](2)(2-NH-benzimidazol-yl)}] shows that L2 is coordinated to the endo Mo(eta(3)-C3H5)(CO)(2) group in a kappa(2)-N,O-bidentate chelating fashion whereas the Mo-II centre displays a pseudooctahedral environment with Br occupying an equatorial position. Complex 2 was formulated as [MO(eta(3)-C3H5)(CO)(2)(L1)Br] on the basis of a combination of spectroscopic data, elemental analysis, conductivity and DFT calculations. L1 acts as a kappa(2)-N,N-bidentate ligand. In both L1 and L2, the HOMOs are mainly localised on iron while the C=O bond(s) contribute to the LUMO(s) and the next highest energy orbitals are Fe-allyl antibonding orbitals. When the ligands bind to Mo(eta(3)-C3H5)(CO)(2)Br, the greatest difference is that Mo becomes the strongest contributor to the HOMO. Electrochemical studies show that, in complex 2, no electronic interaction exists between the two ferrocenyl ligands and that the first electron has been removed from the Mo-II-centred HOMO. (c) Wiley-VCH Verlag GmbH & Co. KGaA.

A ferromagnetic linear trinuclear Ni(II)-Schiff base complex supported by phenoxo and cinnamato bridges

A new linear trinuclear nickel(II) complex, [Ni-3(salme)(2)(OCn)(4)] (Hsalme = 2-[(3-methylamino-propylimino)-methyl]-phenol, OCn = cinnamate), showing weak ferromagnetic coupling (J = 1.8(1) cm(-1)) through phenoxo and a novel tridentate bridging mode (1 kappa(OO)-O-2':2 kappa O') of the cinnamate ligand has been synthesized and structurally characterized by X-ray crystallography. (C) 2009 Elsevier B.V. All rights reserved.

A stable pure hydroxyl layer on Pt{110}-(1x2)

The adsorption of water and coadsorption with oxygen on the missing-row reconstructed Pt{110}-(1x2) surface was studied by using temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy. Coadsorbed oxygen below saturation (<0.65 +/- 0.05 ML) leads to the formation of 014, which occupies sites near the ridge Pt atoms, In contrast to the more closely packed Pt{111} Surface, OH appears not to form hydrogen bonds with coadsorbed water molecules and is stable after the desorption of water tip to about 205 K (as determined by TPD). Because OH and atomic oxygen compete for adsorption sites, water dissociation is only observed for oxygen coverages below saturation. In the absence of coadsorbed oxygen, water stays intact at all temperatures and forms a strongly bound layer of 2 ML coverage oil the clean Pt{110}-(1x2) surface at temperatures between 140 and 175 K.

Facile photoinduced charge separation through a cyanoacetylide bridge in a heterobimetallic Fe(II)-Re(I) complex

Photoinduced Fe-to-bpy charge transfer in [{Cp(dppe)Fe}-(mu-C CC N){Re(CO)(3)(bpy)}]PF6 has been observed by ps-TRIR spectroscopy, supported by UV-Vis/IR spectroelectrochemistry and DFT calculations.

Quantitative model for the kinetics of lyotropic phase transitions involving changes in monolayer curvature

We present a kinetic model for transformations between different self-assembled lipid structures. The model shows how data on the rates of phase transitions between mesophases of different geometries can be used to provide information on the mechanisms of the transformations and the transition states involved. This can be used, for example, to gain an insight into intermediate structures in cell membrane fission or fusion. In cases where the monolayer curvature changes on going from the initial to the final mesophase, we consider the phase transition to be driven primarily by the change in the relaxed curvature with pressure or temperature, which alters the relative curvature elastic energies of the two mesophase structures. Using this model, we have analyzed previously published kinetic data on the inter-conversion of inverse bicontinuous cubic phases in the 1-monoolein-30 wt% water system. The data are for a transition between QII(G) and QII(D) phases, and our analysis indicates that the transition state more closely resembles the QII(D) than the QII(G) phase. Using estimated values for the monolayer mean curvatures of the QII(G) and QII(D) phases of -0.123 nm(-1) and -0.133 nm(-1), respectively, gives values for the monolayer mean curvature of the transition state of between -0.131 nm(-1) and -0.132 nm(-1). Furthermore, we estimate that several thousand molecules undergo the phase transition cooperatively within one "cooperative unit", equivalent to 1-2 unit cells of QII(G) or 4-10 unit cells of QII(D).

Challenging students in Further Education: themes arising from a study of innovative FE provision for excluded and disaffected young people

The paper draws on a research project on innovative provision in an FE college for excluded and disaffected young people. The college offers places on vocational courses to students who are still of compulsory school age who have been excluded by or have persistently failed to attend or achieve in school. One set of themes to emerge relates to the experiences of the students: the role of personal relationships and, especially, relationships with teachers, in the breakdown of school placements; the importance both of good relationships with tutors, often expressed as 'being treated like an adult', and of a vocational and practical curriculum in successful re-engagement at college; and positive but highly instrumental and employment related attitudes to education. Another set of themes relates to the practical and organisational difficulties and the way that a lack of flexibility in 14-19 provision, especially while students are still of compulsory school age, creates difficulties for programmes of this kind. Finally the paper considers the tensions between pressures for accountability and outcome-driven measures and the aims of increasing participation and using education to address issues of social inclusion.

Global and local expression of chirality in serine on the Cu{110} surface

Establishing a molecular-level understanding of enantioselectivity and chiral resolution at the organic−inorganic interfaces is a key challenge in the field of heterogeneous catalysis. As a model system, we investigate the adsorption geometry of serine on Cu{110} using a combination of low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The chirality of enantiopure chemisorbed layers, where serine is in its deprotonated (anionic) state, is expressed at three levels: (i) the molecules form dimers whose orientation with respect to the substrate depends on the molecular chirality, (ii) dimers of l- and d-enantiomers aggregate into superstructures with chiral (−1 2; 4 0) lattices, respectively, which are mirror images of each other, and (iii) small islands have elongated shapes with the dominant direction depending on the chirality of the molecules. Dimer and superlattice formation can be explained in terms of intra- and interdimer bonds involving carboxylate, amino, and β−OH groups. The stability of the layers increases with the size of ordered islands. In racemic mixtures, we observe chiral resolution into small ordered enantiopure islands, which appears to be driven by the formation of homochiral dimer subunits and the directionality of interdimer hydrogen bonds. These islands show the same enantiospecific elongated shapes those as in low-coverage enantiopure layers.

Low-temperature partial dissociation of water on Cu(110)

The low-temperature reactivity of water (D2O) adsorbed on clean and oxygen pre-covered Cu(1 1 0) was studied using high resolution X-ray photoelectron spectroscopy (HRXPS) and low energy electron diffraction (LEED). On the clean surface partial dissociation to hydroxyl was observed already at 95 K. Upon annealing to 220 K hydrogen bonded water-hydroxyl chains are formed. Upon further annealing water desorbs leaving behind a layer of hydroxyl, most of which desorbs recombinatively eventually. With pre-adsorbed oxygen water reacts to hydroxyl lifting the added-row reconstruction even below 225 K. Upon annealing this adsorbate layer passes through essentially the same stages as without pre-adsorbed oxygen.

Spectroscopy of ultrathin epitaxial rutile TiO[sub 2](110) films grown on W(100)

Epitaxial ultrathin titanium dioxide films of 0.3 to similar to 7 nm thickness on a metal single crystal substrate have been investigated by high resolution vibrational and electron spectroscopies. The data complement previous morphological data provided by scanned probe microscopy and low energy electron diffraction to provide very complete characterization of this system. The thicker films display electronic structure consistent with a stoichiometric TiO2 phase. The thinner films appear nonstoichiometric due to band bending and charge transfer from the metal substrate, while work function measurements also show a marked thickness dependence. The vibrational spectroscopy shows three clear phonon bands at 368, 438, and 829 cm(-1) (at 273 K), which confirms a rutile structure. The phonon band intensity scales linearly with film thickness and shift slightly to lower frequencies with increasing temperature, in accord with results for single crystals. (c) 2007 American Institute of Physics.

Interaction of nitrogen dioxide (NO2) with a monolayer of oleic acid at the air–water interface – A simple proxy for atmospheric aerosol

The reactions between atmospheric oxidants and organic amphiphiles at the air water interface of an aerosol droplet may affect the size and critical supersaturation required for cloud droplet formation. We demonstrate that no reaction occurs between gaseous nitrogen dioxide (1000 ppm in air) and a monolayer of an insoluble amphiphile, oleic acid (cis-9-octadecenoic acid), at the air water interface which removes material from the air water interface. We present evidence that the NO2 isomerises the cis-9-octadecenoic (oleic) acid to trans-9-octadecenoic (elaidic) acid. The study presented here is important for future and previous studies of (1) the reaction between the nitrate radical, NO3, and thin organic films as NO2 is usually present in high concentrations in these experimental systems and (2) the effect of NO2 air pollution on the unsaturated fatty acids and lipids found at the air liquid surface of human lung lining fluid.