Análise QTAIM e IQA de reações de Diels-Alder entre o ciclopentadieno e alguns cianoetilenos ao longo de caminhos IRC completos

Abstract

Eight variations of the Diels-Alder reaction were analyzed along their entire Intrinsic Reaction Coordinates (IRCs) through the lens of the Quantum Theory of Atoms and Molecules (QTAIM) and the Interaction Quantum Atoms (IQA) approach ± a methodology which will be referred to as “IQA@IRC” in this work. For each reaction, the structures for reactants, transition state structures (TSS) and products were optimized, characterized as stationary points and their respective IRCs were calculated using the software Gaussian16 at the B3LYP/6-311G(d,p) level of theory. Afterwards, still using Gaussian16, each geometry from the IRC was used to generate a wavefunction file, from which results regarding properties related to QTAIM and IQA were obtained through the software AIMAll. Several properties were computed and then plotted in scatter diagrams, such as bonding properties in critical points, IQA atomic energy contributions, QTAIM atomic charges, charge transfer variations and bonding parameters on BCPs. The proposed methodology showed that the IQA energy of each atom vary in a distinct way from that of the global energy. Additionally, the bonding parameters presented results coherent to chemical insight, and in agreement with the (a)synchronicity of the reactions herein studied, demonstrating the feasibility of the IQA@IRC procedure to act as a complimentary tool for detailed analyses of reaction mechanisms. Despite the additional computational effort required for such analyses, the significant amount of data and insight gathered strongly suggests that the benefits of this methodology outweigh its costs.