Nanopartículas de cobre auto-suportadas em vidros borofosfatos para reações click

Abstract

This paper comprises the synthesis, characterization and application of borophosphate glasses that act as heterogeneous supports for the growth of copper nanoparticles (CuNPs). The glass matrix (borophosphate glass) was obtained by the conventional melting-cooling way with a molar ratio of NaH2PO4/H3BO3 equal to 2, adding 10 mol% of Al2O3 in order to increase the chemical resistance against moisture. Subsequently, doping was carried out on the surface of the glass matrix using 12 mol% Cu+ ions. After doping, the glass was subjected to thermal treatment in a hydrogen gas H2 reducing atmosphere, a process by which Cu+ ions react with H2 at 430 ℃ in a relative short time of 45 minutes, inducing migration of copper ions from inside the vitreous matrix towards the surface of the material forming copper nanoparticles via the bottom-up process. Then, an investigation about the catalytic properties of copper nanoparticles as well as their self-adhesion on the support made of borophosphate glass was conducted. For this, a synthetic methodology was developed for the application of CuNPs involving conventional heating at 80 ℃C between a terminal alkaline and organic azide to obtain 1,2,3-triazole derivatives. The class of 1,2,3-triazole heterocycle compounds act as synthetic intermediates of drugs with important biological activity. However, the synthetic routes described in the literature for obtaining these products have disadvantages, since they use solvents, non-recoverable catalysts, long reaction periods with high temperature and formation of two regioisomers. That said, the search for sustainable methodologies that provide for environmental damage reduction has attracted attention in scientific research, especially those about the principles established by Green Chemistry. The reactions established for the catalyst application are based on the click chemistry approach, known for being fast and stereospecific reactions. The catalytic activity of copper doped borophosphate glass proved to be efficient for organic reactions with good to excellent yields. The use of the catalyst favored the exclusive formation of the regioisomer of interest (1,2,3-triazole-1,4- disubstituted). The physical nature of the vitreous support allowed the catalyst to be easily isolated from the liquid phase and extracted using simple separation methods. In addition, the catalyst showed potential for recycling, being possible to reuse it for another five cycles in a row, presenting subtle yield decreases.