2 - Royal Society of Chemistry
... The two structures drawn in Figure 1 would be expected to yield at least sixteen ring proton resonances. After 18 hrs irradiation, 50 % conversion to this species was observed and over 50 hrs of spectrometer time were used to characterise this solvent complex. In the 1H NMR spectrum, peaks at 4.08 ...
... The two structures drawn in Figure 1 would be expected to yield at least sixteen ring proton resonances. After 18 hrs irradiation, 50 % conversion to this species was observed and over 50 hrs of spectrometer time were used to characterise this solvent complex. In the 1H NMR spectrum, peaks at 4.08 ...
Full text (no figures)
... temperature chemical stability and the highest creep resistance of any known oxide, leading to its evaluation as a promising fiber material for the preparation of ceramic composites. LaAlO.sub.3 is being used as a substrate material for growth of thin film oxide superconductors. Mullite, an aluminos ...
... temperature chemical stability and the highest creep resistance of any known oxide, leading to its evaluation as a promising fiber material for the preparation of ceramic composites. LaAlO.sub.3 is being used as a substrate material for growth of thin film oxide superconductors. Mullite, an aluminos ...
Metal-Catalyzed Epoxidations of Alkenes with Hydrogen
... IRA-900 resin by ion exchange61 gives a heterogeneous system for the epoxidation of a variety of commercially interesting epoxides; high yields are obtained using only 2 equiv of 30% H2O2 in acetonitrile at 38 °C. None of the systems mentioned above are suitable for preparing acid-sensitive epoxides ...
... IRA-900 resin by ion exchange61 gives a heterogeneous system for the epoxidation of a variety of commercially interesting epoxides; high yields are obtained using only 2 equiv of 30% H2O2 in acetonitrile at 38 °C. None of the systems mentioned above are suitable for preparing acid-sensitive epoxides ...
Crystal structures of IspF from Plasmodium falciparum and
... where Zn2+ is bound and where recognition of the cytidine moiety of substrate occurs. However, conformational flexibility is noted in that area of the active site responsible for binding the methylerythritol component of substrate. Unexpectedly, one structure of BcIspF revealed two molecules of cyti ...
... where Zn2+ is bound and where recognition of the cytidine moiety of substrate occurs. However, conformational flexibility is noted in that area of the active site responsible for binding the methylerythritol component of substrate. Unexpectedly, one structure of BcIspF revealed two molecules of cyti ...
Chem. Mater., 18 (7), 1745-1752
... described to date. Dutreilh et al. reported on a lithium nickel fluorophosphate, Li2NiF(PO4), that adopts an O-F ordered anionic framework.13 Its structure is somewhat similar to that of the title compound with respect to the arrangement of the metal-oxygen (fluorine) octahedra, although it is not i ...
... described to date. Dutreilh et al. reported on a lithium nickel fluorophosphate, Li2NiF(PO4), that adopts an O-F ordered anionic framework.13 Its structure is somewhat similar to that of the title compound with respect to the arrangement of the metal-oxygen (fluorine) octahedra, although it is not i ...
acez and Interfaces - Utrecht University Repository
... A common way of classifying oxides is based on their ----acid-base properties. Metal oxides can then be classified as acidic (e.g., Cr03 and V205), basic (e.g., La203), or amphoteric (e.g., ZnO). In this respect, it is important to know that acidity mostly increases with increasing oxidation state o ...
... A common way of classifying oxides is based on their ----acid-base properties. Metal oxides can then be classified as acidic (e.g., Cr03 and V205), basic (e.g., La203), or amphoteric (e.g., ZnO). In this respect, it is important to know that acidity mostly increases with increasing oxidation state o ...
PDF File
... with the oligonucleotide substrate rSA5 or -1d,rSA5 (Chart 1). Values of kGc X were determined with ribozyme saturating with respect S ([E] ) 50-200 nM; KSd e 0.1 nM) and with saturating GX (2 mM; KGd X e 500 µM under the conditions investigated; Figures 2, 4, and 5 below). To ensure that the chemic ...
... with the oligonucleotide substrate rSA5 or -1d,rSA5 (Chart 1). Values of kGc X were determined with ribozyme saturating with respect S ([E] ) 50-200 nM; KSd e 0.1 nM) and with saturating GX (2 mM; KGd X e 500 µM under the conditions investigated; Figures 2, 4, and 5 below). To ensure that the chemic ...
Structurally simple
... The formation of a strong covalent bond between the Lewis acidic carbon atom of CO2 and a donor atom of a Lewis base leads to the most common examples of CO2 complexes found in the literature. Carbamates, formed through the reaction of CO2 with amines, an interaction taken advantage of in the field ...
... The formation of a strong covalent bond between the Lewis acidic carbon atom of CO2 and a donor atom of a Lewis base leads to the most common examples of CO2 complexes found in the literature. Carbamates, formed through the reaction of CO2 with amines, an interaction taken advantage of in the field ...
Polymerization of methyl acrylate and as comonomer
... form copolymers of ethylene and methyl acrylate. Single-site catalysts represent the most recent generation of Ziegler/Natta catalysts, which in contrast to the latter only form one active catalytic species. Copolymers of ethylene with polar monomers are used as adhesives, paints and compatibilizers ...
... form copolymers of ethylene and methyl acrylate. Single-site catalysts represent the most recent generation of Ziegler/Natta catalysts, which in contrast to the latter only form one active catalytic species. Copolymers of ethylene with polar monomers are used as adhesives, paints and compatibilizers ...
The Influence of Base Metal (M) Oxidation State in Au-M
... 2.4. Catalytic Results of Catalysts Obtained by Co-deposition of Base Metal Oxides with Oxidized Gold Compounds on TiO2 The activity of the co-deposited fresh catalysts, measured at 35 °C (Figure 4) is generally much lower than that of the catalysts prepared by sequential deposition. The copper prom ...
... 2.4. Catalytic Results of Catalysts Obtained by Co-deposition of Base Metal Oxides with Oxidized Gold Compounds on TiO2 The activity of the co-deposited fresh catalysts, measured at 35 °C (Figure 4) is generally much lower than that of the catalysts prepared by sequential deposition. The copper prom ...
Author final version (postprint) - DTU Orbit
... flows was developed in the PhD project with a view to future industrial applications. In particular, the methodology for the tomographic reconstruction of an axisymmetric lab flame temperature profile was developed and tested in the lab using Fourier transform infrared spectroscopy techniques, inclu ...
... flows was developed in the PhD project with a view to future industrial applications. In particular, the methodology for the tomographic reconstruction of an axisymmetric lab flame temperature profile was developed and tested in the lab using Fourier transform infrared spectroscopy techniques, inclu ...
Infrared Spectroscopy: Fundamentals and Applications
... Infrared spectroscopy is a technique based on the vibrations of the atoms of a molecule. An infrared spectrum is commonly obtained by passing infrared radiation through a sample and determining what fraction of the incident radiation is absorbed at a particular energy. The energy at which any peak i ...
... Infrared spectroscopy is a technique based on the vibrations of the atoms of a molecule. An infrared spectrum is commonly obtained by passing infrared radiation through a sample and determining what fraction of the incident radiation is absorbed at a particular energy. The energy at which any peak i ...
Evolution of strategies to prepare synthetic mimics of carboxylate
... provides a convenient simplification of elaborate macromolecules in a real, rather than a virtual, computational, platform [7]. By reducing a metalloprotein to its functional core, it is possible to learn the extent to which the chemistry that occurs at the metal center is predominantly a result of ...
... provides a convenient simplification of elaborate macromolecules in a real, rather than a virtual, computational, platform [7]. By reducing a metalloprotein to its functional core, it is possible to learn the extent to which the chemistry that occurs at the metal center is predominantly a result of ...
Understanding Deviations in Hydrogen Solubility
... systems have provided a more profound understanding of hydrogen absorption in metals and alloys.6,19−24 It has been understood that hydrogen can bind in metal interstitial sites or defects (e.g., vacancies and grain boundaries), where the added electron from hydrogen fills the metal d-band of neighbo ...
... systems have provided a more profound understanding of hydrogen absorption in metals and alloys.6,19−24 It has been understood that hydrogen can bind in metal interstitial sites or defects (e.g., vacancies and grain boundaries), where the added electron from hydrogen fills the metal d-band of neighbo ...
Solution X-ray Absorption Fine Structure Study of the Eu2+ and Sr2+
... were measured using two ionization chambers (filled with air for Eu and with Ar for Sr measurements) with a count rate of 2 s per point, an energy resolution of 1 or 2 eV, a 0.5 or 1 eV step in the XANES region, and a 1 or 2 eV step in the extended x-ray absorption fine structure (EXAFS) region for ...
... were measured using two ionization chambers (filled with air for Eu and with Ar for Sr measurements) with a count rate of 2 s per point, an energy resolution of 1 or 2 eV, a 0.5 or 1 eV step in the XANES region, and a 1 or 2 eV step in the extended x-ray absorption fine structure (EXAFS) region for ...
Spin crossover
Spin Crossover (SCO), sometimes referred to as spin transition or spin equilibrium behavior, is a phenomenon that occurs in some metal complexes wherein the spin state of the complex changes due to external stimuli such as a variation of temperature, pressure, light irradiation or an influence of a magnetic field.With regard to a ligand field and ligand field theory, the change in spin state is a transition from a low spin (LS) ground state electron configuration to a high spin (HS) ground state electron configuration of the metal’s d atomic orbitals (AOs), or vice versa. The magnitude of the ligand field splitting along with the pairing energy of the complex determines whether it will have a LS or HS electron configuration. A LS state occurs because the ligand field splitting (Δ) is greater than the pairing energy of the complex (which is an unfavorable process).Figure 1 is a simplified illustration of the metal’s d orbital splitting in the presence of an octahedral ligand field. A large splitting between the t2g and eg AOs requires a substantial amount of energy for the electrons to overcome the energy gap (Δ) to comply with Hund’s Rule. Therefore, electrons will fill the lower energy t2g orbitals completely before populating the higher energy eg orbitals. Conversely, a HS state occurs with weaker ligand fields and smaller orbital splitting. In this case the energy required to populate the higher levels is substantially less than the pairing energy and the electrons fill the orbitals according to Hund’s Rule by populating the higher energy orbitals before pairing with electrons in the lower lying orbitals. An example of a metal ion that can exist in either a LS or HS state is Fe3+ in an octahedral ligand field. Depending on the ligands that are coordinated to this complex the Fe3+ can attain a LS or a HS state, as in Figure 1.Spin crossover refers to the transitions between high to low, or low to high, spin states. This phenomenon is commonly observed with some first row transition metal complexes with a d4 through d7 electron configuration in an octahedral ligand geometry. Spin transition curves are a common representation of SCO phenomenon with the most commonly observed types depicted in Figure 2 in which γHS (the high-spin molar fraction) is plotted vs. T. The figure shows a gradual spin transition (left), an abrupt transition with hysteresis (middle) and a two-step transition (right). For a transition to be considered gradual, it typically takes place over a large temperature range, even up to several hundred K, whereas for a transition to be considered abrupt, it should take place within 10 K or less.These curves indicate that a spin transition has occurred in a metal complex as temperature changed. The gradual transition curve is an indication that not all metal centers within the complex are undergoing the transition at the same temperature. The abrupt spin change with hysteresis indicates a strong cooperativity, or “communication”, between neighboring metal complexes. In the latter case, the material is bistable and can exist in the two different spin states with a different range of external stimuli (temperature in this case) for the two phenomena, namely LS → HS and HS → LS. The two-step transition is relatively rare but is observed, for example, with dinuclear SCO complexes for which the spin transition in one metal center renders the transition in the second metal center less favorable.There are several types of spin crossover that can occur in a complex; some of them are light induced excited state spin trapping (LIESST), ligand-driven light induced spin change (LD-LISC), and charge transfer induced spin transition (CTIST).