In this research work, we examined the decomposition mechanisms of N-substituted diacetamides. We focused on the substituent effect on the nitrogen lone-pair electron delocalization, with electron-withdrawing and electron donor groups. DFT functionals used the following: B1LYP, B3PW91, CAMB3LYP, LC-BLYP, and X3LYP. Dispersion corrections (d3bj) with Becke–Johnson damping were applied when necessary to improve non-covalent interactions in the transition state. Pople basis sets with higher angular moments and def2-TZVP basis sets were also applied and were crucial for obtaining consistent thermodynamic parameters. The proposed mechanism involves a six-membered transition state with the extraction of an α hydrogen. Several conformers of N-diacetamides were used to account for the decrease in entropy in the transition state in the rate-determining state. All calculations, including natural bond orbital (NBO) analyses, were performed using the Gaussian16 computational package and its GaussView 6.0 visualizer, along with VMD and GNUPLOT software. The isosurfaces and IBSIs were calculated using MultiWFN and IGMPlot, respectively.

In this work, we carried out a computational study of the gas-phase thermal decomposition of N-aryl-3-oxobutanamides (β-ketoamides) and the 2-arylhydrazone derivatives. We performed calculations using density functional theory (DFT) at the B97D-GD3BJ/deft2tzvp level, with multivariant analysis including descriptors of global reactivity, e.g., ionization energy (I), electron affinity (A), molecular hardness (η) and electrophilicity (ω). The objective was to elucidate the reaction mechanism. To this end, we modeled the structures of reactants, transition state structures (TSs) and products and studied the effect of substituents on the N-aryl and the 2-aryl aromatic ring on the energy of activation. The synchronicity of the process and the nature of non-covalent interactions were studied to gain insight into the reactivity and selectivity of these molecules. We examined the reactivity of 2-arylhydrazone derivatives, which show reaction rates about three orders of magnitude slower than the parent β-ketoamide. We evaluated two competing mechanisms involving cyclic TSs of six and four members. This study included electronic descriptors, e.g., NBO analysis, IGM/IBSI, Wiberg bond indexes, and intrinsic reaction coordinate calculations (IRCs). We introduce a new descriptor, Dynamic Synchronicity, SyD, for mechanistic and kinetic characterization. To the best of our knowledge, this work is the first comprehensive theoretical study of the system ketoamide/aryl hydrazone. Multivariate statistical methods, i.e., principal component analysis (PCA) and hierarchical cluster analysis (HCA), are useful tools for the selection of the atoms involved in the TSs.

In this research work, we examined the decomposition mechanisms of N-substituted diacetamides. We focused on the substituent effect on the nitrogen lone pair electron delocalization, withdrawing and electron donor groups. DFT functionals used included: B1LYP, B3PW91, CAMB3LYP, LC-BLYP, and X3LYP. Dispersion functions gd3bj were applied when necessary to improve non-covalent interactions in the transition state. Pople with higher angular moments and def2-TZVP basis sets were also applied and were crucial for obtaining consistent thermodynamic parameters. The proposed mechanism involves a six-membered transition state with the extraction of an α hydrogen. Several conformers of N-diacetamides were used to account for the decrease in entropy in the transition state in the rate-determining state. All calculations, including Natural Bond Orbital (NBO) analyses, were performed using the Gaussian16 computational package and its GaussView 6.0 visualizer, along with VMD and GNUPLOT software. The isosurfaces and IBSI indexes were calculated using MultiWFN and IGMPlot, respectively.

We study the nonlinear absorptive and dispersive optical properties of molecular systems immersed in a thermal reservoir interacting with a Four-wave Mixing (FWM) signal. Residual spin-orbit Hamiltonians are considered in order to take into account the internal structure of the molecule. As system parameters in the dissipation processes, transverse and longitudinal relaxation times are considered for stochastic solute-solvent interaction processes. The intramolecular coupling effects on the optical responses are studied using a molecule model consisting of two coupled harmonic curves of electronic energies with displaced minima in nuclear energies and positions. In this study, it was considered the complete frequency space is considered through the pump-probe detuning, not restricting the derivations to only maximums of population oscillations. This approach opens the possibility of studying the behavior of optical responses, which is very useful in experimental design. Our results indicate the sensitivity of the optical responses to parameters of the molecular structure as well as to those derived from the photonic process of FWM signal generation.

In this work, we carried out a computational study of the gas-phase thermal decomposition of N‑aryl‑3‑oxobutanamides (β-ketoamides) and the 2‑arylhydrazone derivatives. We performed calculations using density functional theory (DFT) at B97D‑GD3BJ/deft2tzvp level, with multivariant analysis including descriptors of global reactivity, e.g., ionization energy (I), electron affinity (A), molecular hardness (η) and electrophilicity (ω). The objective was to elucidate the reaction mechanism. To this end, we modeled the structures of reactants, transition states and products and studied the effect of substituents on the N-aryl and the 2-aryl aromatic ring on the energy of activation. The synchronicity of the process and the nature of non-covalent interactions were studied to gain insight into the reactivity and selectivity of these molecules. We examined the reactivity of 2-arylhydrazone derivatives, which show reaction rates about three orders of magnitude slower than the parent β-ketoamide. We evaluated two competing mechanisms involving cyclic transition states of six and four members. This study included electronic descriptors, e.g., NBO analysis, IGM/IBSI, Wiberg bond indexes, and intrinsic reaction coordinate calculations (IRC). We introduce a new descriptor, Dynamic Synchronicity, SyD, for mechanistic and kinetic characterization. To the best of our knowledge, this work is the first comprehensive theoretical study of the system ketoamide/aryl hydrazone. Multivariate statistical methods, i.e., principal component analysis (PCA) and hierarchical cluster analysis (HCA), are useful tools for the selection of the atoms involved in the transition states.

We study the nonlinear absorptive and dispersive optical properties of molecular systems immersed in a thermal reservoir interacting with a four-wave mixing (FWM) signal. Residual spin-orbit Hamiltonians are considered in order to take into account the internal structure of the molecule. As system parameters in the dissipation processes, transverse and longitudinal relaxation times are considered for stochastic solute–solvent interaction processes. The intramolecular coupling effects on the optical responses are studied using a molecule model consisting of two coupled harmonic curves of electronic energies with displaced minima in nuclear energies and positions. In this study, the complete frequency space is considered through the pump–probe detuning, without restricting the derivations to only maximums of population oscillations. This approach opens the possibility of studying the behavior of optical responses, which is very useful in experimental design. Our results indicate the sensitivity of the optical responses to parameters of the molecular structure as well as to those derived from the photonic process of FWM signal generation.