Search results for "topological analysis"
showing 10 items of 13 documents
Energetic study of bifurcated hydrogen bonds in secondary structures of salts composed with dicarboxylic acids and ethylamine
2020
Abstract The nature of bifurcated hydrogen bonds prompted us to analyze the energy of supramolecular motifs on the example of new structures of carboxylic acids salts with amines, which guarantee a multitude of such interactions. Experimental and theoretical studies of four dicarboxylic salts with primary amine: ethylammonium succinate hydrate (1), tartrate hydrate (2) phthalate hydrate (3) and terephthalate (4) has been investigated along with study of the strength of interactions between the anions and cations. The complete topological analysis of the charge density for all new structures allowed designation of the estimated Cumulative Dissociation Energy (eCDE).
A Bader’s topological approach for the investigation of the high pressure stability field of the Mg-perovskite phase
2014
Characterization of the pressure induced Ringwoodite toMg-perovskite and Mg-wüstite phase transition by Catastrophe Theory
2010
The pressure-induced ringwoodite to Mg-perovskite and periclase post-spinel phase transition: a Bader’s topological analysis of the ab initio electro…
2011
In order to characterize the pressure-induced decomposition of ringwoodite (c-Mg2SiO4), the topological analysis of the electron density q(r), based upon the theory of atoms in molecules (AIM) developed by Bader in the framework of the catastrophe theory, has been performed. Calculations have been carried out by means of the ab initio CRYSTAL09 code at the HF/DFT level, using Hamiltonians based on the Becke- LYP scheme containing hybrid Hartree– Fock/density functional exchange–correlation terms. The equation of state at 0 K has been constructed for the three phases involved in the post-spinel phase transition (ringwoodite -> Mg-perovskite + periclase) occurring at the transition zone–lower…
Theoretical study on the molecular mechanism of the [5 + 2] vs. [4 + 2] cyclization mediated by Lewis acid in the quinone system
2013
[EN] The thermal and Lewis acid (LA) catalyzed cyclizations of quinone 1 involved in the synthesis of Colombiasin A and Elipsaterosin B have been theoretically studied using DFT methods at the B3LYP/6-311G(d,p) computational level. B3LYP calculations suggest that the formal endo [4 + 2] cycloadduct allowing the synthesis of Colombiasin A is preferentially formed under thermal conditions, while in the presence of the BF3 LA catalyst the formal [5 + 2] cycloadduct is seen, allowing the synthesis of Elipsaterosin B. The BF3 LA catalyst not only accelerates the nucleophilic attack on the C2 carbon of the quinone framework through a more polar C-C bond formation, but also provokes a different el…
Understanding the regioselectivity in hetero Diels–Alder reactions. An ELF analysis of the reaction between nitrosoethylene and 1-vinylpyrrolidine
2013
[EN] The regioselectivity in the hetero Diels-Alder reaction between nitrosoethylene 1 and 1-vinylpyrrolidine 2 has been studied by a comparative ELF bonding analysis along the IRC of the endo/ortho and endo/meta regioisomeric channels at the B3LYP/6-31G*. level. Along the most favorable endo/ortho regioisomeric channel, the C-C sigma bond is first formed by coupling of two pseudoradical centers located at the most electrophilic carbon of 1 and the most nucleophilic center of 2. Formation of these relevant pseudoradical centers, which depend on the total charge transfer process along the polar reaction, and not on the approach mode of each reagent, is well characterized by analysis of the a…
Pressure stability field of Mg-perovskite under deep mantle conditions: A topological approach based on Bader's analysis coupled with catastrophe the…
2019
Abstract The pressure stability field of the Mg-perovskite phase was investigated by characterizing the evolution of the electron arrangement in the crystal. Ab initio calculations of the perovskite structures in the range 0–185 GPa were performed at the HF/DFT (Hartree-Fock/Density Functional Theory) exchange–correlation terms level. The electron densities, calculated throughout the ab-initio wave functions, were analysed by means of the Bader's theory, coupled with Thom's catastrophe theory. To the best of our knowledge the approach is used for the first time. The topological results show the occurrence of two topological anomalies at P~20 GPa and P~110 GPa which delineate the pressure ra…
Bader's analysis of the electron density in the Pbca enstatite - Pbcn protoenstatite phase transition
2011
The Bader’s topological analysis of the electron density obtained via ab initio quantum mechanical simulation at Hartree–Fock and DFT level has been performed for experimentally in situ heated structures of enstatite–protoenstatite MgSiO 3 . The measurements have been performed in the temperature range 1200–1400 K. The work was aimed at characterizing both the evolution of the electron arrangement in the crystal and that of the crystal-structure at the enstatite–protoenstatite phase transition in terms of topology of the electron density, with particular care about the Mg–O and the O–O bonds. The observed breaking of some chemical bonds with increasing temperature and/or due to the phase tr…
Topological analysis of chemical bonding in the layered FePSe3 upon pressure-induced phase transitions
2020
The authors acknowledge the assistance of the University Computer Center of Saint-Petersburg State University in the accomplishment of high-performance computations. A.K. is grateful to the Latvian Council of Science project no. lzp-2018/2-0353 for financial support. Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.
Gold(I) Complexes of Ferrocenyl Polyphosphines: Aurophilic Gold Chloride Formation and Phosphine-Concerted Shuttling of a Dinuclear [ClAu···AuCl] Fra…
2016
International audience; A smart steric control of the metallocene backbone in bis- and poly(phosphino)ferrocene ligands favors intramolecular aurophilic interactions between [AuCl] fragments in polynuclear gold(I) complexes. We synthesized and characterized by multinuclear NMR and X-ray diffraction analysis mono-, di-, and polynuclear gold complexes of constrained ferrocenyl diphosphines, which bear either bulky tert-butyl groups or more flexible siloxane substituents at the cyclopentadienyl rings. The complexes meso-1,1'-bis-(diphenylphosphino)-3,3'-di-tert-butylferrocene (4-m), rac-1,1'-bis[bis-(5-methy1-2-furyl)phosphino]-3,3'-di-tert-butyfferrocene (5-r), and rac-1,1'-bis ( diphenylphos…