Estimativa dos pKa da Rutina empregando modelos semi-empíricos de cálculo mecânico-quântico

Abstract

In this study, molecular and thermodynamic properties of rutin molecule in the gas phase and in water, with the inclusion of discrete water molecules in specific locations, were studied by means of quantum mechanical calculations, using a tool specifically the semi-empirical methods AM1 and PM6 for the theoretical calculation of pKa. The inclusion of discrete molecules of water aimed a better description of solute-solvent interaction with minimal computational requirements. The results suggest that the theoretical values compared with the experimental results obtained a relative success using the Cosmo solvation model, with insertion of discrete water molecules. This methodology provided a relatively low computational investment with more simplified mathematical relationships, and did not use correction equations for the calculation of pKa. This work presented in some cases results similar to those presented in the literature with ab-initio calculations, with errors of 0.53 units of PKA (Pliego, 2003). The semi-empirical method PM6 was the more satisfactory, reaching an error of 0.63 pKa units for the calculation of pKa1 and 0.76 pKa units for pKa2.