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
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2020
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es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
El 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.
The current work consists of computationally determining the activation barrier for the production of dihydrogen from the complexes [PY5Me2Mo(H)(OH)]+ (2,6-bis[1,1-bis(2- pyridyl)etil]- pyridine oxo-molybdenum). The latter lies in the fact that experimentally in a watery environment, it has been demonstrated that such compound can produce dihydrogen, thus leading to a low energetic cost compared to the decomposition of water that implies an amount of 285,8kJmol-1 approximately. Nevertheless, the solvent simulation as a dielectric and polarizable medium (implicit model of solvent) prevents any possible solute-solvent interplay. The scientific literature reveals that up to three water molecules explicitly included in a quantum mechanical model of the aforementioned Mo-based compound decreases the energy barrier. But those results are not conclusive since there is no certainty about three is the minimum number of water molecules required for a proper simulation of water as a solvent. Bearing in mind the non-conclusive results that can be found in the scientific literature, the aim of this research is finding the minimum number of water molecules that keep assisting the molecular hydrogen release reaction, without changing the energy barrier significantly. To fulfill the objectives, quantum-mechanical calculations were carried out in order to study the dependence of the energy barrier upon the number of water molecules. These solvent molecules were strategically placed in the Mo-based complex. Quantum-mechanical calculations are based on the Functional Theory of Density.
The current work consists of computationally determining the activation barrier for the production of dihydrogen from the complexes [PY5Me2Mo(H)(OH)]+ (2,6-bis[1,1-bis(2- pyridyl)etil]- pyridine oxo-molybdenum). The latter lies in the fact that experimentally in a watery environment, it has been demonstrated that such compound can produce dihydrogen, thus leading to a low energetic cost compared to the decomposition of water that implies an amount of 285,8kJmol-1 approximately. Nevertheless, the solvent simulation as a dielectric and polarizable medium (implicit model of solvent) prevents any possible solute-solvent interplay. The scientific literature reveals that up to three water molecules explicitly included in a quantum mechanical model of the aforementioned Mo-based compound decreases the energy barrier. But those results are not conclusive since there is no certainty about three is the minimum number of water molecules required for a proper simulation of water as a solvent. Bearing in mind the non-conclusive results that can be found in the scientific literature, the aim of this research is finding the minimum number of water molecules that keep assisting the molecular hydrogen release reaction, without changing the energy barrier significantly. To fulfill the objectives, quantum-mechanical calculations were carried out in order to study the dependence of the energy barrier upon the number of water molecules. These solvent molecules were strategically placed in the Mo-based complex. Quantum-mechanical calculations are based on the Functional Theory of Density.
Notas
Unidad de Investigación (Licenciado en Química)
Proyecto FONDECYT 1181504.
Proyecto FONDECYT 1181504.
Palabras clave
Moléculas de Agua, Análisis, Liberación de Hidrógeno