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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. Source


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. Source


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. Source


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. Source

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