ATRP Fotocontrolada: uso de complexo de Fe(III) como catalisador fotoredox
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Data
2022-07-01
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Universidade Estadual Paulista (Unesp)
Resumo
Houve um grande aumento no interesse pelo desenvolvimento de novos sistemas de polimerização radicalar controlada (CRP) nos últimos anos. Com base nisto, este trabalho apresenta uma síntese de um novo complexo de Fe(III) com ligantes carbenos N-heterocíclicos (NHC). Os precursores, o ligante e o complexo foram caracterizados por espectroscopia de absorção na região do UV-Vis, espectroscopia vibracional na região do infravermelho (FTIR), voltametria cíclica e ressonância magnética nuclear (RMN 1H). O complexo [Fe(Pmb)2Br] foi usado com mediador foto-redox na reação de foto-ATRP (Polimerização Radicalar por Transferência de Átomo) do metacrilato de metila (MMA) em diferentes proporções molares [MMA]/[EBPA]/[FeIII]. O estudo cinético do sistema de polimerização apresentou um perfil de pseudo-primeira ordem. Na proporção com uma concentração intermediária de complexo de ferro(III) (200/1/0.04) observou-se a maior conversão (49.3%) e um controle adequado da polimerização, com um índice de polidispersidade de 1,10. Assim como verificou-se que o sistema possui controle temporal, em que na ausência de luz não há a continuidade da polimerização. Sendo assim, o sistema desenvolvido utiliza um complexo inédito de Fe(III) para polimerização do MMA, com um significativo controle temporal e seletividade (foto-induzido).
There has been a great increase in the interest of development of new controlled radical polymerization (CRP) systems in recent years. Based on this, this work presents a synthesis of a new Fe(III) complex with carbene N-heterocyclic ligands (NHC). The precursors, ligand and complex were characterized by absorption spectroscopy in the UV-Vis region, vibrational spectroscopy in the infrared region (FTIR), cyclic voltammetry and nuclear magnetic resonance (NMR 1H). The [Fe(Pmb)2Br] complex was used as a photo-redox mediator in photo-ATRP (Atom Transfer Radical Polymerization) reaction of methyl methacrylate (MMA) in different molar ratios [MMA]/[EBPA]/[FeIII]. The kinetic study of the polymerization system presented a pseudo-first order profile. In the proportion with an intermediate concentration of iron(III) complex (200/1/0.04), the highest conversion (49.3%) and good polymerization control were observed, with a polydispersity index of 1.10. As it was found that the system has temporal control, in which in the absence of light there is no continuity of polymerization. Therefore, the developed system uses an unprecedented Fe(III) complex for MMA polymerization, with a significant temporal control and selectivity (photo-induced)
There has been a great increase in the interest of development of new controlled radical polymerization (CRP) systems in recent years. Based on this, this work presents a synthesis of a new Fe(III) complex with carbene N-heterocyclic ligands (NHC). The precursors, ligand and complex were characterized by absorption spectroscopy in the UV-Vis region, vibrational spectroscopy in the infrared region (FTIR), cyclic voltammetry and nuclear magnetic resonance (NMR 1H). The [Fe(Pmb)2Br] complex was used as a photo-redox mediator in photo-ATRP (Atom Transfer Radical Polymerization) reaction of methyl methacrylate (MMA) in different molar ratios [MMA]/[EBPA]/[FeIII]. The kinetic study of the polymerization system presented a pseudo-first order profile. In the proportion with an intermediate concentration of iron(III) complex (200/1/0.04), the highest conversion (49.3%) and good polymerization control were observed, with a polydispersity index of 1.10. As it was found that the system has temporal control, in which in the absence of light there is no continuity of polymerization. Therefore, the developed system uses an unprecedented Fe(III) complex for MMA polymerization, with a significant temporal control and selectivity (photo-induced)
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Palavras-chave
photo-ATRP, Iron(III) complex, Complexo de Fe(III), Carbenos N-Heterocíclicos, N-Heterocyclic Carbenes