Anderson, CO, United States
Anderson, CO, United States

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Zapata-Rivera J.,Rovira i Virgili University | Zapata-Rivera J.,Corporacion University la Costa | Caballol R.,Rovira i Virgili University | Calzado C.J.,University of Seville
Physical Chemistry Chemical Physics | Year: 2015

This work explores the electronic structure aspects involving the complete intermolecular O2 transfer between Ni(ii) and Mn(ii) complexes, both containing N-tetramethylated cyclams (TMC). The energy of the low-lying states of reactants, intermediates and products is established at the CASSCF level and also the DDCI level when possible. The orthogonal valence bond analysis of the wave functions obtained from CASSCF and DDCI calculations indicates the dominant superoxide nature of all the adducts participating in the reaction, and consequently that the whole reaction can be described as the transfer of the superoxide O2 - between Ni(ii) and Mn(ii) complexes, without any additional change in the electronic structure of the fragments. This journal is © the Owner Societies.


Zapata-Rivera J.,Rovira i Virgili University | Zapata-Rivera J.,Corporacion University la Costa | Caballol R.,Rovira i Virgili University | Calzado C.J.,University of Seville | And 2 more authors.
Chemistry - A European Journal | Year: 2014

The recently described intermolecular O2 transfer between the side-on Ni-O2 complex [(12-TMC)Ni-O2]+ and the manganese complex [(14-TMC)Mn]2+, where 12-TMC and 14-TMC are 12- and 14-membered macrocyclic ligands, 12-TMC=1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane and 14-TMC=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, is studied by means of DFT methods. B3LYP calculations including long-range corrections and solvent effects are performed to elucidate the mechanism. The potential energy surfaces (PESs) compatible with different electronic states of the reactants have been analyzed. The calculations confirm a two-step reaction, with a first rate-determining bimolecular step and predict the exothermic character of the global process. The relative stability of the products and the reverse barrier are in line with the fact that no reverse reaction is experimentally observed. An intermediate with a μ-η1:η1-O2 coordination and two transition states are identified on the triplet PES, slightly below the corresponding stationary points of the quintet PES, suggesting an intersystem crossing before the first transition state. The calculated activation parameters and the relative energies of the two transition sates and the products are in very good agreement with the experimental data. The calculations suggest that a superoxide anion is transferred during the reaction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Sousa V.,Corporacion University la Costa | Viego P.R.,University of Cienfuegos | Gomez J.R.,University of Cienfuegos | Quispe E.C.,Autonomous University of Occidente | Balbis M.,Corporacion University la Costa
IEEE Latin America Transactions | Year: 2016

In this work the application of a method to estimate the shaft power of induction motors operating in the presences of unbalanced and harmonics voltages is presented. The method uses the steady state equivalent circuits, with some considerations for the analysis of motor performance, fed with unbalanced and harmonic voltages. The parameters of circuits are determined with low invasiveness, by applying a Bacterial Foraging Algorithm as technique of evolutionary search. With this, the shaft power can be estimated at any operating point. The method was tested in a 12.6 kW motor working in an industrial power supply grid, with harmonics and unbalanced voltage. © 2016 IEEE.


Garzon-Barrero N.M.,University of Sao Paulo | Garzon-Barrero N.M.,Corporacion University la Costa | Shirakawa M.A.,University of Sao Paulo | Brazolin S.,São Paulo Institute for Technological Research | And 3 more authors.
International Biodeterioration and Biodegradation | Year: 2016

The objective of this study was to investigate the performance of alternative sugarcane bagasse particle board (BCP) using castor oil polyurethane resin in comparison with commercial medium density wood particle board (MDP) under natural and accelerated test conditions. The particle boards were evaluated after 12 months of exposure to natural weathering in Pirassununga (21.9965° S, 47.4262° W), Brazil and by an accelerated mold growth test under laboratory conditions. The mold growth was quantified according to the Standards ASTM D 3273-12 (2012) and the results were evaluated by statistical analysis through the Proportional Chances Model (PCM). For both materials, the surface coating with castor oil based bi-component polyurethane resin was less colonized than the non-coated materials; independent of the particleboard type. Additionally, the bending test shows that the sugarcane bagasse particle boards presents better performance of module of elasticity (MOR) (7.7 MPa) in comparison with the commercial wood particle boards (3.6 MPa) after exposed to accelerated tests for mold colonization. The surface coating with castor oil based polyurethane resin reduces mold growth, therefore these results support the potential use of this alternative resin both as a binder and as a surface coating in these particulate materials. The particle boards fabricated with sugarcane bagasse and castor oil resin presented similar mold colonization compared to the commercial wood particle boards. © 2016


Visbal R.,University of Zaragoza | Visbal R.,Corporacion University la Costa | Laguna A.,University of Zaragoza | Gimeno M.C.,University of Zaragoza
Chemistry - A European Journal | Year: 2016

A new and efficient method for the preparation of several imidazolium salts containing an ester group in the C4 position of the aromatic ring through a retro-Claisen reaction pathway between a quinone derivative and several alcohols is described. This new organic transformation proceeds in the absence of a catalyst, but it is greatly catalyzed by different Lewis acids, especially with AgOAc at a very low catalyst loading and in very short reaction times. The process takes place by the nucleophilic attack of the carbonyl groups by the alcohol functionality, thus promoting a double C-C bond cleavage and C-H and C-O bond formation. This reaction represents the first example of this type between a quinone derivative and alcohols. A new and efficient method for the preparation of several imidazolium salts containing an ester group in the C4 position of the aromatic ring through a retro-Claisen reaction pathway is described. This new organic transformation takes place by the nucleophilic attack of an alcohol functionality over the carbonyl groups, thus promoting a double C-C bond activation (see scheme; Mes=mesityl). © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


Espinosa-Fuentes E.,Corporacion University la Costa | Colpas-Castillo F.,University of Cartagena | Meza-Fuentes E.,University of Cartagena | Ropero J.,University of the Atlantic
Propellants, Explosives, Pyrotechnics | Year: 2016

D3 and C2 TATP structures interconvert at room temperature. Herein, an easy method to isolate both conformers is shown that consists of multiple recrystallization steps using different solvent and heating to boiling. Spectroscopic and physical measurements, such as Raman spectroscopy, X-ray diffraction, and melting point analysis, showed that clear and opaque crystals, respectively, represent different conformations of TATP. Additionally, the transition energy between both conformers was estimated using the Raman shifts. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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