Obtenção de um novo ligante salofen derivado do cardanol e seus complexos de Cu(II), Mn(II), Fe(II) e Co(II) com potencial aplicação catalítica

Abstract

The development of new products and processes from the use or transformation of renewable raw materials encourages the development of this work. Based on this idea, this work presents the microwave assisted synthesis, the spectroscopic characterization and voltammetry of the new ligand N,N´-bis(2-hidroxy-4-pentadecilbenzilideno)-1,2-fenilenodiamina (hpbp), a salophen type ligand derived from cardanol and its Cu(II), Mn(II), Fe(II) and Co(II) complexes and the catalytic application in oxidation of R-limonene and reduction of p-nitrophenol. Cardanol, one of the constituents of cashew nut shell (CNSL) and the main by-product of the agricultural industry in Ceará, is a natural and renewable phenolic compound ideal to be used for the synthesis of salophen type ligand, a conjugated tetradentate π ligand capable of coordinating with transition metals. The method of microwave assisted synthesis presented yield 60% in a reaction time of 10 min. The absorption spectroscopy in the infrared (IR) region showed bands in 1618 and in the range of 2917-2845 cm-1 corresponding to imine group and the cardanol alkyl chain, respectively. The (1H and 13C) NMR showed signals in 8,63 and 163,52 ppm confirming the proposed structure. The metal complexes of Mn and Fe were tested as catalysts in the epoxidation of limonene, an olefin from a renewable source of major importance in Brazil and in the food and cosmetics industry, and the Cu complex in the reduction of p-nitrophenol, an industrial contaminant. The catalytic epoxidation showed a conversion of 100% in 5 min of reaction and the kinetic study of reduction of the p-nitrophenol showed the efficiency of the catalyst with reduction of the reaction time, from 60 min to 10 min, using a minimum amount of catalyst , 5 mg, with 5-fold recycles, following a pseudo-first-order model. Thus, the results of this work aim to contribute to the green chemistry using efficient catalysts of renewable source and a synthesis method that minimizes the use of the solvent, reducing environmental impact, saving time and energy and by-product utilization.