Síntese e Caracterização de fotossensibilizadores baseados em Ftalocianinas de Zn(II) assimétricas tipo A3B

Abstract

In the present work, we present the synthetic development of asymmetric metallophthalocyanines for application as photosensitizers in order to improve the photocatalytic efficiency of titanium dioxide. In this context, the synthesis of 2-carboxy, 8,15,22-triaminophthalocyanine Zinc(II) and 2-carboxy,9,16,23-triaminophthalocyanine of Zinc(II), and their isomers, have been proposed. phthalocyanine Zinc(II) derivative containing three amino groups and one carboxylate group in their peripheral positions. The synthesis resulted in a mixture of isomers in 75% yield. The characterization of the asymmetric phthalocyanine Zinc(II) mixtures was performed by spectroscopic measurements in the ultraviolet-visible (UV-Vis), infrared (IV) and nuclear magnetic resonance (1H NMR) spectrometric measurements mass and thermogravimetric analysis and differential thermal analysis (TG/DTA). The similarity between these isomers and the tendency of aggregation presented by phthalocyanines are a great challenge for the separation, even using modern techniques of high performance liquid chromatography (HPLC). From the theoretical calculations realized it was possible to observe great similarity in the polarity between the isomers. Analysis by HPLC allowed observing three of the eight possible isomers. In the theoretical study performed for 2-carboxy,9,16,23-triaminophthalocyanine of Zinc(II) and its isomers, it was observed that the LUMO orbital of these phthalocyanines is associated with the Q band, only a slight increase in the electron density on the oxygen of the carboxyl group. This is appreciably improved when these phthalocyanines are anchored to an anatase fragment, suggesting, unlike expected, only a discrete displacement of the electron density to TiO2. On the other hand, the singlet-triplet excitation energies, estimated from TDDFT calculations, suggest an efficient population of the T1 state both for these phthalocyanines in solution and anchored to Anatase, revealing, based on the estimated energies, the possibility of these species sensitize the generation of singlet oxygen, similar to the experimental evidence. This opens the possibility of applying these phthalocyanines, associated or not to semiconductor oxides, both in photocatalytic processes and in photodynamic therapy.