A novel method for resonant inelastic soft X‐ray scattering via photoelectron spectroscopy detection

A method for measuring resonant inelastic X‐ray scattering based on the conversion of X‐ray photons into photoelectrons is presented. The setup is compact, relies on commercially available detectors, and offers significant flexibility. This method is demonstrated at the Linac Coherent Light Source with ～0.5 eV resolution at the cobalt L₃‐edge, with signal rates comparable with traditional grating spectrometers.     

Excess thermodynamic quantities of D<Subscript>2</Subscript>O water calculated from its Raman O−D stretching spectra

Excess thermodynamic functions of D₂O water have been calculated from the vibrationally decoupled O−D stretching spectra of very dilute solutions of HOD in H₂O. Comparison of the results with reference calorimetric data for water showed a good correspondence for excess heat capacity above the melting point of ice. The excess enthalpy at the melting point also coincides well with latent heat of melting.     

New approaches to hyperbranched poly(4‐chloromethylstyrene) and introduction of various functional end groups by polymer‐analogous reactions

A facile way for the synthesis of hyperbranched poly(4‐chloromethylstyrene) [P(4‐CMS)] with adjustable molar mass by classic atom transfer radical polymerization (ATRP) and mechanistically similar procedures is presented. Subsequently, the chlorine functional groups have been modified to obtain polymers with different polarities. On the one hand, the polymer was end‐capped with unpolar groups (e.g., methyl, phenol ether) to obtain chemically inert substances. On the other hand, more complex functional groups have been introduced through azide groups by 1,3‐dipolar cycloaddition reaction (“click chemistry”). Furthermore, a method for the introduction of ester groups under mild conditions using cesium carboxylates is presented, which also allowed the preparation of so‐called hyperstars by attaching COOH functionalized polystyrene chains onto the P(4‐CMS) as core molecule. All these reactions were carried out in high or very high yields. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2224–2235, 2010     

Unusual Reactions of (+)‐Car‐2‐ene and (+)‐Car‐3‐ene with Aldehydes on K10 Clay

The reactions of (+)‐car‐2‐ene ( 1 ) and (+)‐car‐3‐ene ( 2 ) with aldehydes in the presence of montmorillonite clay were studied for the first time (Schemes 3 and 5). The major products of these reactions are optically active, substituted hexahydroisobenzofurans, probably formed as a result of an attack of the protonated aldehyde at the cyclopropane ring. Quite unexpectedly, the products are cis‐configured at the ring‐fusion site; the fact was established by means of quantum‐chemical calculations and NMR data. It appeared that the behavior of the 2 : 3 mixture 1 / 2 in reactions with aldehydes in the presence of K10 clay differed substantially from the reactivities of the corresponding individual monoterpenes.     

X-ray diffraction and Mössbauer spectroscopy studies of LiFe0.5Ti1.5O4 – A new primitive cubic ordered spinel

LiFe_0.5Ti_1.5O₄ was synthesized by solid-state reaction carried out at 900 °C in flowing argon atmosphere, followed by rapid quenching of the reaction product to room temperature. The compound has been characterized by X-ray powder diffraction (XRD) and ⁵⁷Fe Mössbauer effect spectroscopy (MES). It crystallizes in the space group P4₃32, a = 8.4048(1) Å. Results from Rietveld structural refinement indicated 1:3 cation ordering on the octahedral sites: Li occupies the octahedral (4b) sites, Ti occupies the octahedral (12d) sites, while the tetrahedral (8c) sites have mixed (Fe/Li) occupancy. A small, about 5%, inversion of Fe on the (4b) sites has been detected. The MES data is consistent with cation distribution and oxidation state of Fe, determined from the structural data.The title compound is thermally unstable in air atmosphere. At 800 °C it transforms to a mixture of two Fe³⁺ containing phases – a face centred cubic spinel Li_(1+y)/2Fe_(5−3y)/2Ti_yO₄ and a Li_(z−1)/2Fe_(7−3z)/2Ti_zO₅ – pseudobrookite. The major product of thermal treatment at 1000 °C is a ramsdellite type lithium titanium iron(III) oxide, accompanied by traces of rutile and pseudobrookite.     

Alkaline earth metal ions mediated self-assembly in the presence of 1,10-phenanthroline, nitrate and tetrafluoroborate anions

1,10-Phenanthroline (phen) was reacted with various combinations of two and in one of the cases with three alkaline earth metal cations taken in equimolar ratio. In all the competitive reactions it was obtained only one product free of any impurities, which is in accordance with the theory of self-assembly processes. The compound [Ca(phen)2(H2O)2(NO3)]NO3 was synthesized in all the reactions where Ca(2+) was involved. In contrast, none of the reactions led to the preparation of a strontium complex. Two of the reactions, in which participated Be(2+), resulted in the compound (phen)3(H+)2(NO(-)(3))2. The second group of competitive reactions was carried out with 1,10-phenanthroline and a given alkaline earth metal cation in the presence of the anions NO(3)(-) and BF(4)(-). These led to the compounds Mg(phen)4(BF4)2(H2O)3, [Ca(phen)2(H2O)2(NO3)]BF4, Sr(phen)4(OH)(BF4)(H2O) and Ba(phen)3.5(BF4)2(H2O). All the newly synthesized substances were characterized by elemental analysis, IR- and FAB-mass-spectra.     

The syn-oriented 2-OH provides a favorable proton transfer geometry in 1,2-diol monoester aminolysis: implications for the ribosome mechanism

A computational study of 1-formyl 1,2-ethanediol aminolysis predicts a stepwise mechanism involving syn-2-OH-assisted proton transfer. The syn-oriented 2-OH takes over the catalytic role of the external water or amine molecule previously observed in 2-deoxy ester aminolysis. It provides more favorable, that is, more linear, proton transfer geometry for the rate-limiting transition state resulting in an almost billion-fold rate acceleration of the overall reaction. These findings provide structural basis for explanation of the efficiency of the proton shuttling mechanism and imply double proton transfer catalysis by peptidyl tRNA A76 2'-OH as a possible catalytic strategy used by ribosome.     

Structure, stability, electronic and magnetic properties of Ni4 clusters containing impurity atoms

Using a gradient-corrected density functional method, we studied computationally how single impurity atoms affect the structure and the properties of a Ni4 cluster. H and O atoms coordinate at a Ni-Ni bond, inducing small changes to the structure of bare Ni4 which is essentially a tetrahedron. For a C impurity, we found three stable structures at a Ni4 cluster. In the most stable geometry, the carbon atom cleaves a Ni-Ni bond of Ni4, binding to all Ni atoms. Inclusion of the impurity atom leads to a partial oxidation of the metal atoms and, in the most stable structures, reduces the spin polarization of the cluster compared to bare Ni4. An H impurity interacts mainly with the Ni 4s orbitals, whereas the Ni 3d orbitals participate strongly in the bonding with O and C impurity atoms. For these impurity atoms, Ni 3d contributions dominate the character of the HOMO of the ligated cluster, in contrast to the HOMO of bare Ni4 where Ni 4s orbitals prevail. We also discuss a simple model which relates the effect of a H impurity on the magnetic state of metal clusters to the spin character (minority or majority) of the LUMO or HOMO of the bare metal cluster.     

Predicting adsorption enthalpies on silicalite and HZSM‐5: A benchmark study on DFT strategies addressing dispersion interactions

We evaluated the accuracy of periodic density functional calculations for adsorption enthalpies of water, alkanes, and alcohols in silicalite and HZSM‐5 zeolites using a gradient‐corrected density functional with empirical dispersion corrections (PBE‐D) as well as a nonlocal correlation functional (vdW‐DF2). Results of both approaches agree in acceptable fashion with experimental adsorption energies of alcohols in silicalite, but the adsorption energies for n‐alkanes in both zeolite models are overestimated, by 21?46 kJ mol^?1. For PBE‐D calculations, the adsorption of alkanes is exclusively determined by the empirical dispersion term, while the generalized gradient approximation‐DFT part is purely repulsive, preventing the molecule to come too close to the zeolite walls. The vdW‐DF2 results are comparable to those of PBE‐D calculations, but the latter values are slightly closer to the experiment in most cases. Thus, both computational approaches are unable to reproduce available experimental adsorption energies of alkanes in silicalite and HZSM‐5 zeolite with chemical accuracy. © 2014 Wiley Periodicals, Inc.