Heteroleptic Copper(I) Complexes with Pyridine-Benzothiazole Ligands as Photocatalysts for Free Radical Photopolymerization and 3D Printing

Copper(I) complexes have attracted considerable attention as efficient redox photocatalysts (PCs) in photopolymerization. In this study, two copper(I) complexes bearing a pyridine-benzothiazole ligand were thoroughly investigated as photocatalysts for the free radical photopolymerization of ethoxylated trimethylolpropane triacrylate under violet and green light irradiation. A three-component system comprising a copper complex, di-tert-butyl-diphenyl iodonium hexafluorophosphate, and ethyl dimethylaminobenzoate as additives was investigated under various conditions. The copper complexes exhibited remarkable photoinitiation capabilities, achieving high monomer conversion rates and highlighting significant structure-reactivity relationships. Based on free energy calculations and spectroscopic analyses, a mechanistic pathway was proposed. The optimal conditions were successfully applied in 3D printing, producing smooth and uniform 3D structures.