Estudo teórico do mecanismo de isomerização do pentaaminonitritocobalto(iii) usando dinâmica molecular de car-parrinello e metadinâmica

Abstract

Isomerization of pentaamminenitritocobalt complex (III) – nitrito isomer [Co(NH3)5ONO]2+ and nitro isomer [Co(NH3)5NO2] 2+ - were discovered by Jorgensen in 1983 and later confirmed by Werner. Since then, the complexes play an important role in Coordination Chemistry. Most of the literature about these complexes brings the isomerization process in an experimental way, carried out through Visible Ultraviolet (UV-Vis), Infrared Spectroscopy (IR), Single-Crystal X-Ray Diffraction and, recently, Nuclear Magnetic Resonance (NMR), and Differential Scanning Calorimetry (DSC) Thermal Analysis. However, the study through quantum chemical methods, such as Density Functional Theory (DFT), is still presented discreetly. Therefore, a more thorough study is necessary to investigate the phenomenon of isomerization and its mechanisms of reaction, through alternative and reliable computational methods. By the use of theoretical and computational methods, this work is aimed at carrying out the study of isomerization mechanisms for reaction of solid and gaseous states of inorganic complexes of the pentaamminenitritocobalt (III) compounds, using the Molecular Dynamic of Car-Parrinelo (MDCP) associated to the formalism of the DFT and Metadynamic (MTD). It is thus intended to determine the energies of fundamental states of the compounds involved in the reaction of the isomerization of pentaamminenitritocobalt (III), the energy and the molecular structure of the activated complex. It is, moreover, intended to run the simulation of MDCP in the pentaamminenitritocobalt (III) isomer in the gaseous phase and in aqueous solution. The results of the simulation of MDCP in the study of pentaamminenitritocobalt (III) and pentaamminenitrocobalt (III) show that hydration significantly alters the geometric parameters of these compounds. These alterations suggest a strong interaction of the molecules of the compounds with water molecules, through hydrogen bonds. The results discussed in this work are consistent with theorical data described in other articles by A. Eslami and N. Hasini, I. Ciofini and C. Adomo, among others mentioned in this work.