Visible-Light-Activated Ni(II) Complexes as Photocatalysts for Radical Photopolymerization under LED Irradiation

Resumo

Nickel(II) complexes have gained significant attention as efficient redox-active photocatalysts in photopolymerization processes. In this study, two Ni(II) complexes containing phenanthroline ligands were successfully synthesized and fully characterized using FTIR, UV-Vis and fluorescence spectroscopy, along with MALDI-TOF mass spectrometry. Their performance as photocatalysts was investigated in the free radical photopolymerization (FRP) of ethoxylated trimethylolpropane triacrylate (TMPETA) under violet and blue LED irradiation. A three-component photoinitiating system comprising a nickel complex, either di-tert-butyl-diphenyl iodonium hexafluorophosphate (Iod) or phenacyl bromide (Ph-Br), and ethyl dimethylaminobenzoate (EDB) was tested under LED irradiation. The nickel complexes demonstrated effective photoinitiation, leading to high monomer conversion rates and revealing clear structure–reactivity relationships. The Ni(II) complex with higher absorption and fluorescence properties exhibited superior catalytic performance under both Iod/EDB and Ph-Br/EDB conditions.