Correlações entre constantes espectroscópicas, propriedades termodinâmicas e solubilidade do fulereno c60 em alcanos

Abstract

The fullerenes solubility studies is it of fundamental importance in view of the possibility of their application in the most diverse areas. The present work is dedicated to investigate the solubility of C60 fullerene in alkanes. The system formed by the fullerene and the solvent was considered an approximation of a diatomic system. The Rydberg analytical function was used to describe the potential of the electronic part. The spectroscopic constants were obtained by two different methodologies, the Dunham method and the Discrete Variable Representation method. Through the spectroscopic constants the thermodynamic properties are calculated by the partition function. Analyzes of the spectroscopic and thermodynamic properties for the C60-methane, C60-propane, C60-pentane, C60-heptane, C60-nonane, C60-undecane and C60-tridecane systems were carried out. For a greater reality from these analyzes, was investigated some functional and bases sets for the electronic structure calculations. It was also investigated which system configuration its most suggested. The calculated values ​​for the dissociation energy showed tendency to increase as the number of atoms in system. The spectroscopic constants calculated by the Dunham method and the Discrete Variable Representation method present satisfactory agreement. The entropy variation for the analyzed systems has a value lower than the enthalpy change, behind this analysis can affirmed that the thermodynamic properties obtained show that the spontaneity is influenced mainly by the enthalpy variation. It was also observed that the enthalpy change is governed by the energy variation of the system and that the largest relative contribution to the energy variation is provided by the dissociation energy values. To finish the work was done the solubility analysis was carried out versus spectroscopic and thermodynamic parameters. Such analysis indicates correlation between solubility, spectroscopic constants and thermodynamic properties.