Confinamento eletrônico em hidrocarbonetos policíclicos aromáticos.

Abstract

The polycyclic aromatic hydrocarbons (PAHs) are componds that contain one or more benzene rings together. Therefore, exist in these molecular systems the called ressonance [pi] electrons that could be more weakly connected. This ressonance it is one of the determining aspects of the aromacity molecular. The ressonance is related the fusion structure on one compond and to displaced electrons that has distributed the character of the multiple bonds. The PAHs’s ressonance [pi] electrons can be seen how free electrons confined in the region molecule. The quantum theory brings a intrinsic model for the eletronic confinement, in this case the molecular external ambient is not considered. For another approach, the extrinsic model we consider the molecular external ambient. The intrinsec model approach can be studied leading to the solution of the electronic spectra of molecules fot this confinement. In the present work we consider that in PAH we can have more than one confinement region. As a direct consequence we have more possibilities, for example for the first transition state. The PAH present electronic transitions in the region of the UV-Vis spectra, which we seek in this work to correlate with the confinement theories. Using only the particle model in which the results are obtained through intrinsic and extrinsic confinement. Other than the level energies, the energy differences in the two approaches are the same. We apply the intrinsic [pi] electron model to benzene, naphthalene, anthracene, tetracene, pentacene, hexacene, heptacene, octacene, nonacene and decacene molecules. We were able to predict one peak for benzene, one peak for pentacene and five peaks for the tetracene spectrum. It was possible to predict the maximum UV-Vis wavelengths for the studied PAHs. For this model, the application in PAH was consistent with the results found in the literature. We compared these wavelength results from the UV-Vis spectrum using the theoretical quantum chemistry method of the confined particle model and the computacional ZINDO method.