Examinando por Autor "Merino, Gabriel"
Mostrando 1 - 6 de 6
Resultados por página
Opciones de ordenación
Ítem B7Be6B7: A Boron-Beryllium Sandwich Complex(John Wiley and Sons Inc, 2023-08) Dong, Xue; Tiznado, William; Liu, Yu-qian; Leyva-Parra, Luis; Liu, Xin-bo; Pan, Sudip; Merino, Gabriel; Cui, Zhong-huaPlanar boron clusters have often been regarded as “π-analogous” to aromatic arenes because of their similar delocalized π-bonding. However, unlike arenes such as C5H5− and C6H6, boron clusters have not previously shown the ability to form sandwich complexes. In this study, we present the first sandwich complex involving beryllium and boron, B7Be6B7. The global minimum of this combination adopts a unique architecture having a D6h geometry, featuring an unprecedented monocyclic Be6 ring sandwiched between two quasi-planar B7 motifs. The thermochemical and kinetic stability of B7Be6B7 can be attributed to strong electrostatic and covalent interactions between the fragments. Chemical bonding analysis shows that B7Be6B7 can be considered as a [B7]3−[Be6]6+[B7]3− complex. Moreover, there is a significant electron delocalization within this cluster, supported by the local diatropic contributions of the B7 and Be6 fragments. © 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.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 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, OmarA 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.Ítem Planar pentacoordinate s-block metals(Royal Society of Chemistry, 2023-07) Wang, Meng-Hui; Kalita, Amlan J.; Orozco-Ic, Mesías; Yan, Gai-Ru; Chen, Chen; Yan, Bing; Castillo-Toraya, Gabriela; Tiznado, William; Guha, Ankur K.; Pan, Sudip; Merino, Gabriel; Cui, Zhong-HuaThe presence of a delocalized π-bond is often considered an essential criterion for achieving planar hypercoordination. Herein, we show that σ-delocalization could be sufficient to make the planar configuration the most stable isomer in a series of planar pentacoordinate s-block metals. High-level ab initio computations reveal that the global minimum of a series of interalkali and interalkali-alkaline earth clusters (LiNa5, Li5Mg+, Na5Mg+, K5Ca+, CaRb5+, Rb5Sr+, and SrCs5+) adopts a singlet D5h structure with a planar pentacoordinate lithium or alkaline earth metal (AE = Mg, Ca, Sr). These clusters are unusual combinations to stabilize a planar pentacoordinate atom, as all their constituents are electropositive. Despite the absence of π-electrons, Hückel's rule is fulfilled by the six σ-electrons. Furthermore, the systems exhibit a diatropic ring current in response to an external magnetic field and a strong magnetic shielding, so they might be classified as σ-aromatic. Therefore, multicenter σ-bonds and the resulting σ-delocalization stabilize these clusters, even though they lack π-aromaticity. © 2023 The Royal Society of Chemistry.Ítem Revisiting Aromaticity and Chemical Bonding of Fluorinated Benzene Derivatives(Wiley-VCH Verlag, 2015-06) Torres-Vega, Juan J.; Vásquez-Espinal, Alejandro; Ruiz, Lina; Fernández-Herrera, María A.; Alvarez-Thon, Luis; Merino, Gabriel; Tiznado, WilliamThe electron delocalization of benzene (C6H6) and hexafluorobenzene (C6F6) was analyzed in terms of the induced magnetic field, nucleus-independent chemical shift (NICS), and ring current strength (RCS). The computed out-of-plane component of the induced magnetic field at a distance (r) greater than or equal to 1.0 Å above the ring center correlates well (R2>0.99) with the RCS value. According to these criteria, fluorination has two effects on the C6 skeleton; concomitantly, the resonant effects diminish the π electron delocalization and the inductive effects decrease the charge density at the ring center and therefore reduce the magnitude of the paratropic current generated in this region. The equilibrium between both effects decreases aromaticity in the fluorinated benzene derivatives. These results can be extrapolated to determine the aromaticity of any derivative within the series of fluorinated benzene derivatives (C6H(6-n)Fn, where n=1-5). © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.