Estudo espectroscópico da quebra espontânea de simetria identificada via DFT no estado agregado da molécula de Ftalocianina de Zinco

Abstract

In this work, a spectroscopic characterization study was conducted on the macrocyclic molecule Zinc Phthalocyanine. This molecule's synthesis was discovered in 1907 and, since then, it has been extensively studied in the literature from both theoretical and experimental perspectives. As a result of these characterizations, numerous applications have been developed or found for the molecule. One of these was in photodynamic therapy, where it acts as a photosensor capable of assisting in the production of reactive oxygen, which is responsible for eliminating tumor cells. However, as studies on the molecule advanced, its tendency to form H-type aggregates became known. It was understood that this behavior was detrimental to the use of Zinc Phthalocyanine for photodynamic therapy. Consequently, the pursuit of understanding the behavior of the molecule's aggregate formation was abandoned, until the development of this work. Through new information obtained via DFT (Density Functional Theory) calculations, which predicted an ordered structure for the Zinc Phthalocyanine aggregate, it once again became an object of study. The focus was to investigate the possibility of a symmetry break in the aggregate formed by the molecule. Characterization studies such as Linear Optical Absorption, Photoluminescence, Excitation Photoluminescence, and Raman Scattering were performed to validate the material against what had been previously reported in the literature. Advanced characterization studies, including Emission Ellipsometry, Raman Scattering, and Raman Optical Activity, were conducted to experimentally confirm the predicted symmetry break obtained through DFT calculations. At the end of this work, it was possible not only to validate the theoretical prediction of the DFT but also to measure the preferential orientation with which the formation of the Zinc Phthalocyanine aggregate structure occurs.