Visible light-promoted nickel-NHC photocatalysts for free radical photopolymerization and 3D printing application

Author(s)

Pesqueira, Naralyne M. ; Morlet-Savary, Fabrice ; Schmitt, Michael ; Carvalho Jr, Valdemiro P. ; Goi, Beatriz E. ; Lalevee, Jacques

• Document type: Journal article
• Source: Polymer Chemistry; v. 16, n. 20, p. 13-pg., 2025-04-23.

Abstract

The evaluation of NiII complexes bearing bidentate N-heterocyclic carbene (NHC) ligands has shown their great potential as catalysts in various reactions. However, their luminescence properties and photocatalytic applications remain underexplored. Two novel nickel-based NHC complexes, [Ni(py-NHC)2](PF6)2 (NiC1) and [Ni(ph-NHC)2] (NiC2), were synthesized with ligands N-mesityl-N '-2-pyridylimidazolium tetrafluorophosphate and 1-mesityl-3-phenyl-1H-imidazol-3-ium tetrafluorophosphate, respectively. The complexes were thoroughly characterized using spectroscopy techniques, including FTIR, UV-Vis, 1H NMR, and fluorescence, along with elemental analysis, cyclic voltammetry, and mass spectrometry. NiC1 and NiC2 exhibited emission properties and lifetimes of 3.8 and 9.1 ns, respectively. The photocatalytic properties of NiC1 and NiC2 were investigated for initiating free radical photopolymerization of ethoxylated trimethylolpropane triacrylate under violet light. This process incorporated di-tert-butyl-diphenyl iodonium hexafluorophosphate and ethyl dimethylaminobenzoate as additives. NiC2 achieved the highest monomer conversion under air or in laminate and was effective in on-off LED irradiation. Proposed oxidative and reductive mechanisms were supported by photolysis, fluorescence quenching, and electron spin resonance data. The optimized system was applied in 3D printing, producing smooth-surfaced, high-resolution patterns. (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: 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: 22/16213-2 - Controlled radical photopolymerization (CRP2) and 3D printing using novel Ni(II) complexes
• Grantee: Naralyne Martins Pesqueira
• Support Opportunities: Scholarships abroad - Research Internship - 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