Substituted heterocycles as new candidates for liquid organic hydrogen carriers: In silico design from DFT calculations

A new set of compounds based on N- and S-heterocycles were investigated through Density Functional Theory (DFT) for their use as liquid organic hydrogen carriers (LOHCs). The hydrogenated forms of these compounds could release hydrogen within the most important technical requirements in mobile and stationary applications. In this work, the potential of the 1H-pyrrole/tetrahydro-1H-pyrrole and thiophene/tetrahydrothiophene pairs as possible leader structures to synthesize more sustainable LOHCs from costless oil-refining and oil-hydrotreating by-products is shown. According to DFT-M06-HF results, the 3-allyl-1H-pyrrole/3-allyl-tetrahydro-1H-pyrrole pair presented an adequate theoretical hydrogen storage capacity (3.6 %wt H) and a high theoretical dehydrogenation equilibrium yields (% εd = 67.8%) at 453 K. Therefore, this pair is recommended for hydrogen storage stationary applications. On the other hand, the 2-(thiophen-2-yl)-1H-pyrrole/2-(2,3-dihydrothiophen-2-yl)tetrahydropyrrole pair proved to be suitable for both mobile and stationary applications; the storage capacity of this pair was 3.9 %wt H and the theoretical dehydrogenation equilibrium yields at 453 K (% εd = 28.1%) was considered moderate

Integration of algebra and chemistry concepts with molecular descriptors: A problem-based-learning exercise

A problem-based learning experience integrating mathematical concepts of linear and abstract algebra for undergraduate chemistry students is presented. The pedagogical framework was focused on the conceptual understanding of the vector space, graph theory and matrix algebra as a tool to obtain chemical information. The students were capable to solve a problem of physicochemical properties prediction through the calculation of molecular descriptors of the TOMOCOMD (acronym for TOpological MOlecular COMputational Design) approach. A “scientific congress” was organized by students to expose the results of the research. This evaluation strategy stimulated the self- and co-evaluation. The proposed experience demonstrated an enhanced learning compared to the traditional model.En este trabajo se presenta una experiencia de de aprendizaje basado en problemas que integra conceptos matemáticos de algebra lineal y abstracta para estudiante de pregrado de química. El marco pedagógico se enfocó en el entendimiento conceptual de espacios vectoriales, teoría de grafos y álgebra matricial como una herramienta para obtener información química. Los estudiantes fueron capaces de resolver un problema de predicción de propiedades fisicoquímicas a través del cálculo de descriptores del esquema TOMOCOMD (siglas en inglés de TOpological MOlecular COMputational Design). Los estudiantes organizaron un “congreso científico” para exponer los resultados de la investigación. Esta evaluación estimuló el auto- y co-evaluación. La experiencia propuesta demostró un aprendizaje mayor al ser comparado con el modelo tradicional

Maza,

A theoretical study of the ciprofloxacin interactions with glucuronic acid, arabinose, glucosamine, and rhamnose is presented. The most stable complexes were obtained through genetic algorithms starting from the neutral and zwitterion species of ciprofloxacin. The energy at the semiempirical level PM7 of the optimal structures of the complexes was the genetic algorithm‘s fitness function. The resulting complexes’ geometry was optimized at M062X−D3/6-311++G** level of theory, and non-covalent interactions were assessed through the reduced density gradient and quantum theory of atoms in molecules. The results show that the zwitterion species of ciprofloxacin favorably complex carbohydrates and can induce proton exchange between them. The molecular complexes from proton exchange are the most stable, followed by the complexes formed by the contact of the zwitterion species and the carbohydrate. The complexes formed by both neutral species were the least stable. The medium strength and strong (assisted by charge) hydrogen bonds, the XH⋅⋅⋅π and lone-pair⋅⋅π interactions, were mainly present in the complexes. Proton exchange processes strengthen the interactions mentioned above. © 2022 Wiley-VCH Gmb

Synthesis of (E)-Ethyl-4-(2-(furan-2-ylmethylene)hydrazinyl)benzoate, crystal structure, and studies of its interactions with human serum albumin by spectroscopic fluorescence and molecular docking methods

The authors thank Fondo Nacional de Ciencia Tecnología e Innovación (FONACIT Proyecto de apoyo a Grupos No. G-2005000403). Proyecto 1063, Instituto Venezolano de Investigaciones Científicas (IVIC).A novel hydrazone, (E)-Ethyl-4-(2-(furan-2-ylmethylene)hydrazinyl)benzoate (EFHB), has been synthesized and characterized by FT-IR, NMR and Mass spectroscopy, and X-ray diffraction; compound crystallized as translucent light yellow thin plates. EFHB was studied for their binding to human serum albumin (HSA) using the fluorescence quench titration method. Molecular docking was also performed to get a more detailed insight into their interaction with HSA at the binding site. Addition of this hydrazone to HSA produced significant fluorescence quenching and splitting of emission spectra of HSA through static quenching mechanism with binding constants of about 104 M−1 at 292.15, 298.15, 304.15 and 310.15 K. According to the synchronous fluorescence, tryptophan and tyrosine residues of the protein are most perturbed by the binding process. Thermodynamic parameters ΔG, ΔH, and ΔS were got and the main sort of acting force between EFHB and HSA was studied. Results of molecular docking have shown that EFHB binds to subdomain IIA of HSA mainly by hydrophobic interaction, energy binding are in good agreement with those obtained by fluorescence study (ΔGthe = −7.32 ± 0.09 kcal mol−1 and ΔGexp = −6.76 ± 0.03 kcal mol−1).PostprintPeer reviewe

Synthesis, crystal structure, and non-covalent interactions in ethyl 4-hydrazinobenzoate hydrochloride

The authors thank Fondo Nacional de Ciencia, Tecnología e Innovación (FONACIT Proyecto de apoyo a Grupos No. G-2005000403). Proyecto 1063, Instituto Venezolano de Investigaciones Científicas (IVIC). We thank Dr. Duane Choquesillo-Lazarte (LEC, IACT-CSIC), for the X-ray data collection.The compound ethyl 4-hydrazinobenzoate hydrochloride (E-4HB), C9H13N2O2Cl, has been synthesized and characterized by FT-IR, 1H and 13C NMR and X-ray diffraction. The compound crystallizes as colourless plates in the triclinic space group P-1, with Z' = 2 and cell parameters a = 5.9566 (4) Å, b = 7.4498 (6) Å, c = 23.5349 (17) Å, α = 84.323 (3), β = 84.521 (3), γ = 80.257 (3), V = 1020.95 (13) Å3. The component ions are linked by two N-H...N hydrogen bonds and eight N-H...Cl hydrogen bonds to form complex sheets in which each of the chloride ions accepts hydrogen bonds from four different cations. Calculations on the Non-Covalent Interactions (NCI) amplify the crystallographic conclusions concerning the intermolecular hydrogen bonds.PostprintPeer reviewe

Estudio ONIOM2-DFT de la interacción de N2, O2 y NO con Ce-MOR: sitios activos y termodinámica

A theoretical study of N2, O2, NO and NO+ adsorption with cerium-modified mordenite (Ce-MOR) was carried-out. It was used the two-layer Integrated molecular Orbital + molecular Mechanics methodology (ONIOM2) by combining Density Functional Theory (DFT) and Universal Force Field (UFF) for the high and low level model, respectively. The formation active species of Ce based on the adsorption of CeO+ on crystallographycs positions T1, T2 and T4 in H-MOR. The geometric, vibrational and thermodynamic results indicate that the Ce atom of the CeO+ binds exothermal and spontaneously to two crystallographic non-equivalent oxygens (Om) of MOR (TnOm1Om2 ) according to: T1O1O4, T1O2O3, T2O4O7, T2O5O7 y T4O7O10 (T: Al or Si). The results of the interaction of N2, O2 , NO and NO+ with Ce-MOR indicate that exothermic and spontaneous adsorption occurs only on the active sites located on the main 12 membered ring (12-MR) channel, according to: T1O1O4, T2O5O7 and T4O7O10. In general, the Ce-MOR system stabilizes the electrophilic species [CeO(NO+)], with activity for NOx reactions with nucleophilic reducting agents such as NH3, while it is reported for the CeO(NO) species adsorbed on MOR a dynamic equilibrium between the k1NO, k1ON, k2NO adsorption that could be applicable for NOx catalysis in the absence of reducing agents. On the basis of the thermodynamic reaction functions, it is proposed that the most probable site for the location of the active CeO+ is T2O5O7.Se realizó un estudio teórico para la adsorción de N2, O2, NO y NO+ con mordenita (MOR) modificada con Cerio (Ce). Se empleó una metodología ONIOM de dos capas (ONIOM2, del inglés our own two -layer Integrated molecular Orbital + molecular Mechanics), combinando cálculos UFF (del inglés Universal Force Field) y DFT (del inglés Density Functional Theory) para el bajo y alto nivel, respectivamente. Se estudió la formación de especies activas de Ce basadas en la adsorción de CeO+ sobre las posiciones cristalográficas T1, T2 y T4 en la H-MOR. Los resultados geométricos, vibracionales y termodinámicos indican que el átomo de Ce del CeO+ se enlaza exotérmica y espontáneamente a dos de los oxígenos cristalográficos no equivalentes (Om) de MOR (TnOm1Om2 ) según: T1O1O4, T1O2O3, T2O4O7, T2O5O7 y T4O7O10 (T: Al o Si). Los resultados de la interacción de N2, O2, NO y NO+ con Ce-MOR indican que sólo ocurren adsorciones exotérmicas y espontáneas sobre los sitios activos ubicados sobre el canal principal del anillo de 12 miembros (12-MR) según: T1O1O4, T2O5O7 y T4O7O10. En general, el sistema Ce-MOR estabiliza a las especies electrofílicas [CeO(NO+)], con posible actividad para reacciones deNOx en presencia de reductores nucleofilicos como el NH3; mientras que para las especies CeO(NO) adsorbidas sobre MOR se reporta un equilibrio dinámico entre las adsorciones κ1NO, κ1ON, κ2NO que podrían ser aplicables para catálisis deNOx en ausencia de reductores. Sobre la base de las funciones termodinámicas de reacción se propone que el sitio más probable para la ubicación del CeO+ activo es T2O5O7

Parasitism in bullfighters in the Municipalities Maracaibo of the state, Zulia. Venezuela. Technical Note

La cría del toro de lidia en Venezuela se presenta como una alternativa promisoria, en cuanto al desarrollo de fuentes de empleo y de ingresos, desde el criador hasta la venta de la boletería en las plazas de toros; el toro de lidia, es un rumiante con un alto grado de adaptación, pero susceptible a la acción de diferentes etiologías que habitan en los ambientes agroecológicos donde se cría. En la Plaza de Toros, municipio Maracaibo, estado Zulia se llevó a cabo un muestreo simple de heces para determinar la presencia de parásitos gastrointestinales de 61 toros de lidia, provenientes de cinco ganaderías identificadas de la siguientes manera (LB, RG, P, CH, T), dedicadas a la cría de estos. Las muestras de heces se colectaron directamente del recto de los animales, una vez ubicados en la sala de desposte, utilizándose en cada caso guantes desechables, las muestras fueron analizadas por el método coprológico de sedimentación (Método de Dennis modificado), el método de Willis, Técnica de Mc master para la obtención de los hpg y coprocultivos. La identificación de los huevos de los parásitos se realizó basándose en sus características morfológicas y en el desarrollo de las formas inmaduras (L3) producto del coprocultivo de las muestras, así mismo las muestras positivas a Eimeria spp. Se indujeron a la esporulación de sus ooquistes sometiéndolos a una solución de Dicromato de Potasio al 2,5%. Los resultados revelaron un 100% de animales parasitados, el promedio de huevos/gramo/heces (hpg) fue de 24,62 ± 3,57. Los porcentajes de infestación según el tipo de parásito observado fueron: Haemonchus sp. 45,90%, Oesophagos tomum sp. 59,01%, Eimeria zuernii 14,75%, Eimeria Boris 26,22%, richostrongylus sp. 86,88%, Moniezia sp 1,63%, Bunostomum sp 1,63%, Cooperia sp. 3,27% y Cotylophoron cotylophorum 8,19%. Se concluye que las muestras de heces obtenidas de toros de lidia en la plaza de toros presentaron una infestación de un 100% y un poliparasitismo de 79,8%.721 - 724BimestralThe breeding of the bullfightires in Venezuela it is presented like a promissory alternative, as for the development of employment sources and of revenues, from the breeder until the sale of the ticket office in the squares of bulls, The bull of it fights, it is a rumi¬nant one with a high grade of adaptation, but susceptible to the action of different etiology that you/they inhabit the atmospheres agroecology where it is raised. In the Square of Bulls, municipality Maracaibo, state Zulia was carried out a simple fecal sampling of grounds to determine the positive of parasitism for 61 bullfightires, coming from five Cattle raising (LB, RG, P, CH, T) dedicated to the breeding of bullfightires. The feces samples of grounds were collected directly of the rectum of the animals, once located in the slaughter room, being used in each case disposable gloves, the samples were analyzed by the method sedimentation coprology (Method of modified Dennis), the method of Willis and coprocultive. The identifgication of the eggs was carried out being based on its morphological characteristics and in the development in the ways immature stages (L3) in the coprocultive of the samples, likewise the positive sample to Eimeria spp. was induced to the esporulation its ooquistes subjecting them to a solution of dicromato of potassium to 2,5%. The results revealed 100% of animal parasitsm, the average of eggs / g. / grounds were of 24,62 ± 3,57. The percentages infestation according to the type of parasite observed were: Haemonchus sp. 45,90%, Oesophagos tomum sp. 59,01%, Eimeria zuernii 14,75%, Eimeria bovis 26,22%, Trichostrongylus sp. 86,88%, Moniezia sp. 1,63%, Bunostomum sp. 1,63%, Cooperia sp. 3,27% and Cotylophoron cotylophorum 8,19%. It is conclude that the samples feces of obtained grounds of bullfighters in the square of bulls they presented an infestation of 100% and a poliparasitism of 79,8%

Synthesis, crystal structure, and non-covalent interactions in ethyl 4-hydrazinobenzoate hydrochloride

The compound ethyl 4-hydrazinobenzoate hydrochloride (E-4HB), C9H13N2O2Cl, has been synthesized and characterized by FT-IR, 1H and 13C NMR and X-ray diffraction. The compound crystallizes as colourless plates in the triclinic space group P-1, with Z' = 2 and cell parameters a = 5.9566 (4) Å, b = 7.4498 (6) Å, c = 23.5349 (17) Å, α = 84.323 (3), β = 84.521 (3), γ = 80.257 (3), V = 1020.95 (13) Å3. The component ions are linked by two N-H...N hydrogen bonds and eight N-H...Cl hydrogen bonds to form complex sheets in which each of the chloride ions accepts hydrogen bonds from four different cations. Calculations on the Non-Covalent Interactions (NCI) amplify the crystallographic conclusions concerning the intermolecular hydrogen bonds