Photo-induced organo-manganese-mediated radical polymerization of acrylates under LED irradiation

Author(s)

Pesqueira, Naralyne M. ; Lira, Kathia H. ; Bignardi, Camila ; da Silva, Milene K. C. ; Silva, Thiago F. ; Machado, Antonio E. H. ; Nascimento, Otaciro R. ; Carvalho-Jr, Valdemiro P. ; Goi, Beatriz E.

• Document type: Journal article
• Source: APPLIED ORGANOMETALLIC CHEMISTRY; v. 38, n. 7, p. 14-pg., 2024-04-28.

Abstract

The role of manganese in photo-induced organometallic-mediated radical polymerization (photo-OMRP) under LED (light-emitting diode) irradiation has not been previously explored. In this study, four manganese (II) complexes, namely [Mn(6-tert-butyl-N,N '-propanebis [salicylimine])] (Mn-Bu), [Mn(6,3-di-tert-butyl-N,N '-propanebis [salicylimine])] (Mn-Bu-2), [Mn(6-ethoxy-N,N '-propanebis [salicylimine])] (Mn-Ethoxy), and [Mn(6,3-di-ethoxy-N,N '-propanebis [salicylimine])] (Mn-Ethoxy(2)), were synthesized using both symmetrical and non-symmetrical tetradentate N2O2 Schiff base ligands. The Schiff base ligands were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), and nuclear magnetic resonance spectroscopy (NMR). The Mn (II) complexes were characterized by FTIR, UV-Vis, elemental analysis, molar conductivity, cyclic voltammetry, MALDI-TOF mass spectrometry, electron paramagnetic resonance, and rationalized with density functional theory (DFT) studies. All complexes were evaluated as photo-OMRP mediators under LED irradiation at 390 nm and in the 400-800 nm range. The photopolymerization utilized methyl acrylate (MA) and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) in varying molar ratios of [MA]/[Mn-II]/[TPO] (900/1/1, 600/1/1, and 600/1/0.5). The photo-OMRP of MA mediated by Mn-Bu-2 showed the best control over molecular weight (M-n matching M-n,M-th) and dispersity (& ETH; < 1.30) at a [MA]/[Mn-II]/[TPO] = 600/1/0.5 M ratio. The polymerization system demonstrated a living character, as evidenced by reversible "on/off" light source switching. Furthermore, a block copolymer of poly (methyl acrylate)-b-poly (butyl acrylate) was successfully synthesized employing a sequential visible-light-induced process, with the Mn-Bu-2 system showing the best results. (AU)

• FAPESP's process: 21/13128-1 - Development of new polymeric materials via coupling of mechanistically incompatible reactions using Ru/Pd and Ru/Ni heterobimetallic catalysts
• Grantee: Valdemiro Pereira de Carvalho Júnior
• Support Opportunities: Regular Research Grants
• FAPESP's process: 22/16571-6 - Organometallic complexes of Mn (II), Fe (II) and Co (II) as CRP2 redox photocatalysts.
• Grantee: Camila Bignardi
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 21/11741-8 - Ni(II) complexes for controlled radical photopolymerization reactions (photo-OMRP and CRP2) and application in 3D printing
• Grantee: Naralyne Martins Pesqueira
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 21/11873-1 - Organometallic complexes of Mn(II), Fe(II) and Ni(II) as CRP2 redox photocatalysts: new strategy for light curing with LEDs
• Grantee: Beatriz Eleutério Goi Carvalho
• Support Opportunities: Regular Research Grants