Bonding in Metal Hexacarbonyls

A detailed analysis of the valence molecular orbitals (MO) in Cr(CO)6, Mo(CO)6, and W(CO)6is presented. A generalized bonding scheme, which includes participation of metal p electrons in the metal–ligand bond, emerges from our results. The metal p electrons are also responsible for effecting mixings between different sets of carbonyl 5σ and 1π orbitals. In these hexacarbonyls, this ‘‘σ’’+‘‘π’’ metal–ligand bonding contribution is quantitatively as significant as the well known σ donation and π‐back‐donation components. The MO’s obtained with the Dirac scattered‐wave (DSW) method are also used to determine the importance of relativistic effects in this series. The DSW results show that even in W(CO)6, relativistic effects are qualitatively unimportant. Extensive comparisons with existing theoretical and experimental data are made for both ground‐state and transition‐state calculations

ADSORPTION ESSAYS OF PALLADIUM IN MODIFIED SILICA GEL WITH THIOURONIUM GROUPS: EXPERIMENTAL AND THEORICAL STUDIES

Indexación: Web of Science; ScieloThe silylant 3-cloropropyltriethoxysilyl was anchored over silica gel in anhydrous conditions in order to react with thiourea to obtain modified silica gel with thiouronium. The aim to obtain an inorganic support that is able to hijack metals from the VIII group such as palladium. The product was characterized by Sbet and FTIR infrared spectroscopy. For the determination of the structure in the modified silica gel NMR spectra of silicon and carbon were preformed in solid state. The coordination form of the modified silica gel to the metal was studied computationally in the context of the DFT theory, using the ADF code. This was a collaborative work with "Fundación Chile" for the recuperation of precious metals from the mining industry.http://ref.scielo.org/gk7rm

Simple and rapid one-step electrochemical synthesis of nanogranular Cu2O films

In the present work, we report a simple experimental strategy for the one-step electrochemical synthesis of nanogranular Cu2O films by copper anodization in fluoride-containing ethylene glycol media. Microscopic exploration using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM), shows the formation of spherical shape grains with sizes ranging from 20 to 40 nm. Raman and X-Ray Photoemission Spectroscopy (XPS) results indicate that only CuI oxide is obtained. A band gap energy Eg=2.01 eV is estimated from UV–vis reflectance spectroscopy indicating that an indirect transition mechanism between semiconductor bands takes place. These evidences indicate that the present synthesis of nanogranular Cu2O films is a promising method for obtaining improved properties of materials for the design of photoelectronic devices.Fil: Oyarzún Jerez, Diego Patricio. Universidad Andrés Bello; ChileFil: Broens, Martin Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Linarez Pérez, Omar Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Lopez Teijelo, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Islas, Rafael. Universidad Andrés Bello; ChileFil: Arratia-Perez, Ramiro. Universidad Andrés Bello; Chil

Optimizing the electrocatalytic activity of surface confined Co macrocyclics for the electrooxidation of thiocyanate at pH 4

We have studied the trends in catalytic activity of several Co macrocyclics confined on the surface graphite electrodes for the oxidation of thiocyanate. A plot of log i (at constant E) versus the formal potential of the catalyst gives a volcano correlation, indicating that the Co(II/I) redox potential needs to be tuned, in order to achieve maximum reactivity. Graphite electrodes modified with Co phthalocyanine at pH 4 exhibit linear amperometric response for thiocyanate concentration in the range 10−7 and 10−3 M. Theoretical calculations show that electrocatalytic activity (as log i at constant E) plotted versus the energy of the LUMO of the Co complex also gives a volcano correlation

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements