Well-defined non-symmetric NHC-iron(III) catalyst for photoinduced atom-transfer radical polymerization of methyl methacrylate

Author(s)

Figueiredo, Maria L. B. ; Bignardi, Camila ; Pesqueira, Naralyne M. ; Machado, Antonio E. H. ; Carvalho-Jr, Valdemiro P. ; Nascimento, Otaciro R. ; Goi, Beatriz E.

• Document type: Journal article
• Source: JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY; v. 452, p. 8-pg., 2024-03-08.

Abstract

Photoinduced atom transfer radical polymerization (photo-ATRP) has emerged as a prominent technique in contemporary polymer chemistry, offering a potent means to create precisely structured materials. Well-defined catalysts are essential for controlling the growth of polymers with reproducible results; however, most photoATRP catalytic systems involve mixing the metal salt with the ligand. Herein we present a well-defined iron (III) based photo-ATRP catalyst bearing bidentate NHC ligand, 3-Methyl-1-phenyl-1H-3,1-benzimidazol-3-ium iodide (Pmb). The [FeBr(Pmb)2] was successfully synthesized and fully characterized by FTIR, UV-Vis, and EPR spectroscopic studies, elemental analysis, MALDI-TOF mass spectrometry, and computational studies. [FeBr (Pmb)2] was employed as the catalyst for photo-ATRP of methyl methacrylate (MMA) under ultraviolet light irradiation (365 nm). The catalytic activity of [FeBr(Pmb)2] in the photo-ATRP of MMA was evaluated under different conditions using EBPA as the initiator. The polymerizations showed robust activity, yelding in polymers with controlled molecular weights and a narrow molecular weight distribution (MWD). Remarkably, this was achieved with low catalysts loading (102.6 ppm), mainly at the molar ratio [MMA]/[EBPA]/[Fe] = 200/1/0.04. Well-defined polyMMA was synthesized and temporal control over photo-ATRP was successfully demonstrated through "on/off" experiments. For example, photo-ATRP of MMA with a molar ratio of [200/1/0.04] after 12 h at T = 25 C in bulk resulted in PMMA with a polydispersity () of 1.15 at 50 % monomer conversion. (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: 21/11873-1 - 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