Examinando por Autor "Chamorro, Eduardo"

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    A simple topology-based model for predicting the activation barriers of reactive processes at 0 K
    (Royal Society of Chemistry, 2023-05) Ayarde-Henríquez, Leandro; Guerra, Cristian; Duque-Noreña, Mario; Chamorro, Eduardo
    This work reveals an underlying correlation between the topology and energetic features of matter configurations/rearrangements by exploiting two topological concepts, namely, structural stability and persistency, leading thus to a model capable of predicting activation energies at 0 K. This finding provides some answers to the difficulties of applying Thom's functions for extracting energetic information of rate processes, which has been a limitation for exact, biological, and technological sciences. A linear relationship between the experimental barriers of 17 chemical reactions and both concepts was found by studying these systems’ topography along the intrinsic reaction coordinate. Such a procedure led to the model , which accurately predicts the activation energy in reacting systems involving organic and organometallic compounds under different conditions, e.g., the gas-phase, solvent media, and temperature. This function was further recalibrated to enhance its predicting capabilities, generating the equation for this procedure, characterized by a squared Pearson correlation coefficient (r2 = 0.9774) 1.1 times higher. Surprisingly, no improvement was observed.
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    Conceptual density functional theory: status, prospects, issues
    (Springer, 2020-02) Geerlings, Paul; Chamorro, Eduardo; Kumar Chattara, Pratim; De Proft, Frank; L. Gázquez, José; Liu, Shubin; Morell, Christophe; Toro‑Labbé, Alejandro; Vela, Alberto; Ayers, Paul
    This paper results from a round table discussion at the CCTC2018 Conference in Changsha City, Hunan, China, in December 2018. It presents a report on the status, prospects, and issues of conceptual density functional theory (CDFT). After a short exposition on the history of CDFT, its fundamentals, philosophy, and successes are highlighted. Then ten issues for reflection on the future of conceptual DFT are formulated and discussed, ending with one or more summarizing statements on the present status of various concepts/principles/practices and proposed directions for future research. The issues include the further analysis of the energy functional, E[N,v], extended to include effects of temperature, solvent, and mechanical forces, basic requirements for physically acceptable response functions as reactivity descriptors, the use of the grand canonical ensemble, the relevance of CDFT for chemical kinetics and thermodynamics, the domain of validity of CDFT-based principles, the combination of CDFT with reaction path calculations, information-theoretic descriptors, and the treatment of excited states and time dependence. The final issue advocates the transition of CDFT from an interpretative to a predictive mode; we believe this is of utmost importance for promoting CDFT as a viable alternative to wave function-based methods for the practicing chemist, a separate issue treated in the final section. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
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    Conceptual density functional theory: status, prospects, issues
    (Springer, 2020-02-01) Geerlings, Paul; Chamorro, Eduardo; Chattaraj, Pratim Kumar; De Proft, Frank; Gázquez, José L.; Liu, Shubin; Morell, Christophe; Toro-Labbé, Alejandro; Vela, Alberto; Ayers, Paul
    This paper results from a round table discussion at the CCTC2018 Conference in Changsha City, Hunan, China, in December 2018. It presents a report on the status, prospects, and issues of conceptual density functional theory (CDFT). After a short exposition on the history of CDFT, its fundamentals, philosophy, and successes are highlighted. Then ten issues for reflection on the future of conceptual DFT are formulated and discussed, ending with one or more summarizing statements on the present status of various concepts/principles/practices and proposed directions for future research. The issues include the further analysis of the energy functional, E[N,v], extended to include effects of temperature, solvent, and mechanical forces, basic requirements for physically acceptable response functions as reactivity descriptors, the use of the grand canonical ensemble, the relevance of CDFT for chemical kinetics and thermodynamics, the domain of validity of CDFT-based principles, the combination of CDFT with reaction path calculations, information-theoretic descriptors, and the treatment of excited states and time dependence. The final issue advocates the transition of CDFT from an interpretative to a predictive mode; we believe this is of utmost importance for promoting CDFT as a viable alternative to wave function-based methods for the practicing chemist, a separate issue treated in the final section.
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    Elucidating the N−N and C−N Bond-breaking Mechanism in the Photoinduced Formation of Nitrile Imine
    (John Wiley and Sons Inc, 2023-06) Guerra, Cristian; Ayarde-Henríquez, Leandro; Rodríguez-Núñez, Yeray A.; Ensuncho, Adolfo; Chamorro, Eduardo
    In this study, we revealed the significance of chemical bonding for the photochemically induced mechanism of 2-phenyl tetrazole derivatives generating nitrile imines. The correlated electron localization function shows that the formation of imine nitrile involves two key bond events: (i) the heterolytic C−N breakage taking place in the T1 state and (ii) the homolytic N−N rupture occurring in the T2 excited state. In particular, a cation-radical specie results from the C−N cleavage, whereas the N−N rupture creates a biradical resonant form of imine nitrile. Additionally, we noticed that the substantial pair delocalization of the C−C-N bonded structure could play a significant role in the conversion of the biradical imine nitrile into both the propargylic and allenic forms via the T1→S0 deactivation. © 2023 The Authors. ChemPhysChem published by Wiley-VCH GmbH.
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    Introduction to celebrating Latin American talent in chemistry
    (Royal Society of Chemistry, 2021-12) Merino, Gabriel; Fernández-Herrera, María A.; Soler-Illia, Galo J. A. A.; Zarbin, Aldo J. G.; Zuin, Vânia G.; Chamorro, Eduardo; de Oliveira, Luciana G.; Mesko, Márcia Foster; Fraga, Cesar; Ibarra Alvarado, Ilich A; Dupont, Jairton; Nogueira, Ana Flávia; Graeff, Carlos F. O.; Pastore, Heloise Oliveira; da Silva Júnior, Eufrânio N.; Azzaroni, Omar
    A year ago, amid the pandemic, we proposed that the RSC should compile a collection of Latin American contributions to chemistry. The central aim of this collection is to showcase the quality of the research work being carried out in this area. The project was quite well received, and several journals joined. This is not a unique project in this sense; there have been other recent collections with the purpose of highlighting the chemistry developed in Latin America.1–5 However, the current situation of chemistry in each region deserves an analysis of its respective historical context. So, we have taken advantage of this space first to provide a very general historical overview of chemistry in Latin America and then to analyze certain numbers that offer us a picture of where we stand as a consequence of our history. We apologize for focusing on only three countries in a region that includes 46 countries (Latin America and the Caribbean), but we are sure that the stories and problems are similar.
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    Reactividad química en el contexto de la teoría de los funcionales de la densidad
    (Universidad Andrés Bello, 2007) Cárdenas Valencia, Carlos; Chamorro, Eduardo; Fuentealba, Patricio; Facultad de Ecología y Recursos Naturales
    La teoría de los funcionales de la densidad (DFT) establece un marco en donde construir una teoría de reactividad química simple, transparente y que guarda relación directa con conceptos empíricos de la química. La reactividad química es la respuesta de un sistema molecular frente a diferentes perturbaciones. En DFT, esta respuesta es caracterizada mediante descriptores de reactividad química que constituyen los coeficientes de una expansión en series de Taylor de una perturbación del estado fundamental de los reactivos. Esta perturbación puede afectar cualquiera de las variables fundamentales del sistema y la respuesta del sistema puede ser tanto electrónica como en las posiciones nucleares. Tales respuestas constituyen en sí mismas los así llamados esquemas de reactividad electrónica y nuclear, respectivamente. En esta tesis se extendió el formalismo de reactividad nuclear al caso de polarización de espín, con el fin de incluir todos los efectos de espín en la respuesta nuclear. También se construyó un método preciso para evaluar la función nuclear de Fukui y cualquier índice definido en· términos de una derivada respecto al número de electrones. Los métodos aproximados más comunes usados para evaluar la función nuclear de Fukui fueron contrastados con el nuevo esquema de cálculo. Por otro lado, se desarrollo y exploró la utilidad de un esquema de reactividad química descrito en el marco del formalismo de Kohn y Sham, en el cual muchas de las aproximaciones usadas para evaluar los índices estándar de reactividad son exactas. De esta manera, se establecieron las bases fisicas sobre las que se fundamentan estas aproximaciones, lo cual permite entender mejor los límites de los modelos teóricos que soportan. Finalmente, este trabajo de tesis abordó el desarrollo y aplicación de modelos de reactividad adecuados para explorar los patrones locales de reactividad en sistemas extendidos. Estos modelos se construyeron a partir de la densidad de estados, la cual es un resultado estándar de un cálculo ab initio. Estos modelos fueron aplicados exitosamente en la racionalización de la naturaleza reactiva de ciertos nanotubos de carbono y superficies de óxidos alcalinotérreos.
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    Revisiting the bonding evolution theory: a fresh perspective on the ammonia pyramidal inversion and bond dissociations in ethane and borazane
    (Royal Society of Chemistry, 2023-10-04) Ayarde-Henríquez, Leandro; Guerra, Cristian; Duque-Noreña, Mario; Chamorro, Eduardo
    This work offers a comprehensive and fresh perspective on the bonding evolution theory (BET) framework, originally proposed by Silvi and collaborators [X. Krokidis, S. Noury and B. Silvi, Characterization of elementary chemical processes by catastrophe theory, J. Phys. Chem. A, 1997, 101, 7277-7282]. By underscoring Thom's foundational work, we identify the parametric function characterizing bonding events along a reaction pathway through a three-step sequence to establish such association rigorously, namely: (a) computing the determinant of the Hessian matrix at all potentially degenerate critical points, (b) computing the relative distance between these points, and (c) assigning the unfolding based on these computations and considering the maximum number of critical points for each unfolding. In-depth examination of the ammonia inversion and the dissociation of ethane and ammonia borane molecules yields a striking discovery: no elliptic umbilic flag is detected along the reactive coordinate for any of the systems, contradicting previous reports. Our findings indicate that the core mechanisms of these chemical reactions can be understood using only two folds, the simplest polynomial of Thom's theory, leading to considerable simplification. In contrast to previous reports, no signatures of the elliptic umbilic unfolding were detected in any of the systems examined. This finding dramatically simplifies the topological rationalization of electron rearrangements within the BET framework, opening new approaches for investigating complex reactions. © 2023 The Royal Society of Chemistry.