Analysis of the topology of the electron density and the reactivity descriptors of biomolecules with insecticide activity

Modifications of the phytosanitary control in fruit in the pre- and post-harvest processes by exogenous application of biomolecules with insecticide activity have motivated the theoretical-experimental investigation of biomolecular systems. Essential oils such as limonene, monoterpenes like 3-carene, and halogenated monoterpenes like mertensene have shown interesting insecticide activity. In this work, a complete characterization of the topology descriptors of the electron density of these 3 compounds has been carried out in the gas phase using the Quantum Theory of Atoms in Molecules formulation. In addition, the global and local descriptors of the reactivity have been quantified by means of Density functional theory, using the hybrid functional of correlation and exchange B3LYP. To determine the reactivity descriptors in terms of the ionization potential (I) and electron affinity (A), two methods were used: (1) the Koopmans’ theorem with the DZ basis set and (2) the vertical difference of the total electronic energy method with a TZ basis set. In this last approach, an electron is aggregated with or removed from the neutral molecule. Both methods showed the same trends in the properties calculated by topology of electron density as well as those obtained by global and local reactivity.