Examinando por Autor "Islas, Rafael"
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Ítem Análisis del efecto de la incorporación explícita de moléculas de agua en la barrera de activación para el proceso de liberación de hidrógeno molecular a partir del complejo (2,6-BIS [1,1-BIS(2-PIRIDIL)ETIL]-piridina oxo-molibdeno(Universidad Andrés Bello, 2020) Godoy Godoy, Belén Sofía; Martínez Araya, Jorge I.; Islas, Rafael; Chamorro Jiménez, Eduardo; Facultad de Ciencias ExactasEl presente trabajo consiste en determinar computacionalmente la barrera de activación para la producción de dihidrógeno a partir del complejo [PY5Me2Mo(H)(OH)]+ (2,6-bis[1,1-bis(2- piridil)etil]-piridina-oxo molibdeno). Esto último radica en que experimentalmente en un medio acuoso se ha demostrado que dicho compuesto posee la capacidad de producción de dihidrógeno, lo que supone un bajo costo energético en comparación con la descomposición de agua que implica un costo total de 285,8 kJ mol-1 aproximadamente. No obstante, la simulación de disolvente como medio dieléctrico y polarizable (modelo implícito de disolvente) impide cualquier posible interacción entre soluto-solvente. La literatura científica revela que hasta tres moléculas de agua explícitamente incluidas en un modelo mecano-cuántico del mencionado compuesto basado en Mo disminuye la barrera de energía. Pero esos resultados no son concluyentes, ya que no hay certeza de que tres sea el número mínimo de moléculas de agua necesario para una simulación adecuada del agua como disolvente. Teniendo en cuenta los resultados no concluyentes que pueden encontrarse en la literatura científica, el objetivo de esta investigación es encontrar el número mínimo de moléculas de agua que asistan a la reacción molecular de liberación de hidrógeno molecular, sin cambiar la barrera de energía de manera significativa. Para cumplir los objetivos, se realizaron cálculos mecano-cuánticos para estudiar la dependencia de la barrera energética del número de moléculas de agua. Estas moléculas de disolvente se colocaron estratégicamente en el complejo basado en Mo. Los cálculos mecano-cuánticos se basan en la Teoría del Funcional de la Densidad.Ítem Analysis of the electronic delocalization in some isoelectronic analogues of B12doped with beryllium and/or carbon(Royal Society of Chemistry, 2020-06-07) Islas, Rafael; Inostroza, Diego; Arias-Olivares, David; Zúñiga-Gutiérrez, Bernardo; Poater, JordiIn the current work, a new family of isoelectronic analogues to B12is reported. The construction of this family was performed through the isoelectronic substitution principle to generate species such as B11C+, B11Be−, B10BeC, B10C22+, B10Be22−B9Be2C−, and B9BeC2+. The search for the global minimum was realized by utilizing genetic algorithms, while the induced magnetic field, electronic localization function, magnetic current densities, and multicenter aromaticity criteria were calculated to understand their electronic delocalization. Our results show that, in general, C atoms avoid hypercoordination, whereas we have found species with Be atoms located in hypercoordinated positions that are relatively stable. Our analysis of aromaticity indicates that B12has double σ and π disk aromaticity. Mono, double or triple substitution of B by C+or Be−reduces somewhat the aromaticity of the clusters, but less in the case of Be−substitution.Ítem Core-electron contributions to the molecular magnetic response(Royal Society of Chemistry, 2022-04-19) Orozco-Ic, Mesías; Charistos, Nickolas D.; Muñoz-Castro, Alvaro; Islas, Rafael; Sundholm, Dage; Merino, GabrielOrbital contributions to the magnetic response depend on the method used to compute them. Here, we show that dissecting nuclear magnetic shielding tensors using natural localized molecular orbitals (NLMOs) leads to anomalous core contributions. The arbitrariness of the assignment might significantly affect the interpretation of the magnetic response of nonplanar molecules such as C60 or [14]helicene and the assessment of their aromatic character. We solve this problem by computing the core- and σ-components of the induced magnetic field (and NICS) and the magnetically induced current density by removing the valence electrons (RVE). We estimate the core contributions to the magnetic response by performing calculations on the corresponding highly charged molecules, such as C6H630+ for benzene, using gauge-including atomic orbitals and canonical molecular orbitals (CMOs). The orbital contributions to nuclear magnetic shielding tensors are usually estimated by employing a natural chemical shielding (NCS) analysis in NLMO or CMO bases. The RVE approach shows that the core contribution to the magnetic response is small and localized at the nuclei, contrary to what NCS calculations suggest. This may lead to a completely incorrect interpretation of the magnetic σ-orbital response of nonplanar structures, which may play a major role in the overall magnetic shielding of the system. The RVE approach is thus a simple and inexpensive way to determine the magnetic response of the core- and σ-electrons. © 2022 The Royal Society of Chemistry.Ítem Dynamical behavior of Borospherene: A Nanobubble(Nature Publishing Group, 2015-06) Martínez-Guajardo, Gerardo; Cabellos, José Luis; Díaz-Celaya, Andres; Pan, Sudip; Islas, Rafael; Chattaraj, Pratim K.; Heine, Thomas; Merino, GabrielThe global minimum structure of borospherene (B40) is a cage, comprising two hexagonal and four heptagonal rings. Born-Oppenheimer Molecular Dynamics simulations show that continuous conversions in between six and seven membered rings take place. The activation energy barrier for such a transformation is found to be 14.3 kcal·mol-1. The completely delocalized σ - and π-frameworks, as well as the conservation of the bonding pattern during rearrangement, facilitate the dynamical behavior of B40. B40 is predicted to act as a support-free spherical two-dimensional liquid at moderate temperature. In other words, B40 could be called as a nanobubble. © 2015 Macmillan Publishers Limited.Ítem How the Orientation of BN Units Influences the Aromaticity of Some Iminobora-Benzenes(American Chemical Society, 0025-02) Diego, Luz; Arias-Olivares, David; Moreno, Diego V.; Cerpa, Erick; Islas, RafaelIn the current work, the impact of the orientation of the BN units in some proposed isomers of iminobora-benzene (B6C6N6H6) is analyzed. The analysis is oriented toward determining whether the orientation plays an important role in electronic delocalization (aromaticity). The alternation of the BN units generates several isomers, which were built arbitrarily and systematically with the main goal of measuring their respective electronic delocalization. For the analysis of aromaticity, multiple methodologies (AdNDP, AV1245, AVmin, ELF, LOL, MICD, and Bind) were employed, all of which produced consistent trends. Moreover, the alternation of the BN units affects not only electronic delocalization but also relative stability, with relative energy values of up to 85 kcal/mol observed among the isomers. Interestingly, the most aromatic isomer is the least stable isomer, while the most stable isomer is, with some methodologies, the least aromatic. © 2025 The Authors. Published by American Chemical Society.Ítem How the Orientation of BN Units Influences the Aromaticity of Some Iminobora-Benzenes(American Chemical Society, 2025-02) Diego, Luz; Arias-Olivares, David; Moreno, Diego V; Cerpa, Erick; Islas, RafaelIn the current work, the impact of the orientation of the BN units in some proposed isomers of iminobora-benzene (B6C6N6H6) is analyzed. The analysis is oriented toward determining whether the orientation plays an important role in electronic delocalization (aromaticity). The alternation of the BN units generates several isomers, which were built arbitrarily and systematically with the main goal of measuring their respective electronic delocalization. For the analysis of aromaticity, multiple methodologies (AdNDP, AV1245, AVmin, ELF, LOL, MICD, and Bind) were employed, all of which produced consistent trends. Moreover, the alternation of the BN units affects not only electronic delocalization but also relative stability, with relative energy values of up to 85 kcal/mol observed among the isomers. Interestingly, the most aromatic isomer is the least stable isomer, while the most stable isomer is, with some methodologies, the least aromatic. © 2025 The Authors. Published by American Chemical Society.Ítem In Silico Analysis of the Aromaticity of Some Carbo-Metallabenzenes and Carbo-Dimetallabenzenes (Carbo-mers Proposed from Metallabenzenes)(American Chemical Society, 2024-03-09) Arias-Olivares, David; Becerra-Buitrago, Andrés; García-Sánchez, Luis Carlos; Moreno, Diego V.; Islas, RafaelIn the current work, we introduce a novel class of molecules termed carbo-metallabenzenes, and their aromaticity has been comprehensively analyzed. The molecules were strategically designed with the insertion of acetylene (C≡C or C2) units in some selected metallabenzenes. Furthermore, if a second metallic unit is inserted (replacing a sp2 carbon) in the carbo-metallabenzenes rings, a new family of carbo-mers is generated, and this second group has been named as carbo-dimetallabenzenes. The primary objective of this work is to ascertain, through various methodologies, whether these newly proposed molecules retain the aromatic characteristics observed in carbo-benzene. The methodologies employed for bond analysis and aromaticity exploration include the analysis of the molecular orbitals, energy decomposition analysis, electron density of delocalized bonds, magnetically induced current density, and the induced magnetic field (Bind). This study sheds light on that the insertion of the metallic centers reduces the electronic delocalization and their aromaticity is, in some cases, comparable with the electronic delocalization of the inorganic iminobora-borazine and also provides valuable insights into their electronic structure through a multifaceted analysis.Ítem Metallaborazines: To Be or Not to Be Delocalized(American Chemical Society, 2021-08) Islas, Rafael; Arias-Olivares, David; Becerra-Buitrago, Andrés; García-Sánchez, Luis Carlos; Méndez-Ayón, Lya Neftaly; Zuniga-Gutierrez, BernardoIn the current work, the analysis of the electronic delocalization of some metallacycles, based on borazine, was realized by employing magnetic criteria, such as the induced magnetic field and magnetically induced current densities, and electronic criteria, such as adaptative natural density partitioning and the analysis of molecular orbitals. The current metallaborazines were generated from isoelectronic substitutions. The main question is whether the electronic delocalization increases or decreases. The results showed that metal-N bonded borazines could be cataloged as delocalized compounds. On the other hand, the metal-B bonded borazines could be cataloged as nonaromatic (or weak aromatic) compounds based on the results of this analysis.Ítem Simple and Rapid One-Step Electrochemical Synthesis of Nanogranular Cu2O Films(Wiley-Blackwell, 2018-08) Oyarzún, Diego P.; Broens, Martín I.; Linarez Pérez, Omar E.; López Teijelo, Manuel; Islas, Rafael; Arratia-Perez, RamiroIn 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. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimÍtem Testing the effectiveness of the isoelectronic substitution principle through the transformation of aromatic osmathiophene derivatives into their inorganic analogues(Royal Society of Chemistry, 2017) Vásquez-Espinal, Alejandro; Poater, Jordi; Solà, Miquel; Tiznado, William; Islas, RafaelThe objective of the current work is to evaluate the effectiveness of the isoelectronic substitution (IS) principle on a series of complexes with the general formula OsCl2(SX3H3)(PH3)2, where X3 represents the moieties CCC, CCB, CCN, CBN, CNB or NCB, formed by substitution of the carbon atoms in CCC by either the isoelectronic B- or N+ separately, or by both. The SX3H3 moiety forms, together with Os, an aromatic five-membered ring (5-MR) called osmathiophene. The preservation of stability and aromaticity in the resulting systems is used to indicate the effectiveness of the IS principle. The aromaticity of the proposed molecules is analyzed according to the magnetic (induced magnetic field (Bind)) and electronic (through the multicenter index (MCI)) criteria. In addition a chemical bonding analysis on selected species is performed by the adaptive natural density partitioning (AdNDP) method. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.