Organometallic complexes of Mn(II), Fe(II) and Ni(II) as CRP2 redox photocatalysts: new strategy for light curing with LEDs

Abstract

The use of redox photocatalysts as radical activators and cationic polymerizations has been an advance in polymer synthesis, especially in relation to the significant decrease in activator concentrations, currently required in industrial processes. In addition, the photocatalysts applied in CRP reactions allow photocontrol of polymerizations and also make them occur at low temperature, expanding the monomers that can be used in macromolecular engineering. The main idea of this project is to obtain Mn(II), Fe(II) and Ni(II) complexes not reported in the literature for application in macromolecular synthesis. Therefore, the synthesis of N-heterocyclic carbenes bidentate ligands is planned to obtain the metallic complexes of Mn(II), Fe(II) and Ni(II), in order to be evaluated as new redox photocatalysts together with a alkyl bromide and an amine (aromatic or aliphatic) constituting the photoinitiator system (PIS) of CRP2. The proposal extends into three stages, which are completely interconnected in the development process. Initially, attention will be directed to the synthesis of NHCs ligands and new Mn(II), Fe(II) and Ni(II) complexes, involving the entire characterization part through FTIR, UV-vis, EPR, NMR techniques 1H and 13C, elemental analysis and mass spectrometry. The second stage will be dedicated to the evaluation of the photochemical properties of the synthesized complexes and their interactions with phenacyl bromide and with the amine, considering the CRP2 photoinitiator systems. The third step will be dedicated to the evaluation of Mn(II), Fe(II) and Ni(II) complexes as CRP2 redox photocatalysts of methyl methacrylate (MMA) in the presence of phenacyl bromide and the amine EDB (or TEA) under LED irradiation. The copolymerization of selected monomers will also be evaluated using the most efficient photoinitiator systems in the photocontrol of homopolymerization. (AU)