Tailoring Cobalt(II) Schiff Base Photocatalysts for Enhanced LED-Induced Free Radical Polymerization

Area of Science:

• Materials Science
• Polymer Chemistry
• Photochemistry

Background:

• Cobalt(II) complexes are cost-effective alternatives to noble-metal photocatalysts.
• Their application in free radical photopolymerization (FRP) remains underexplored.
• Schiff base ligands can modulate the properties of cobalt complexes.

Purpose of the Study:

• To synthesize and characterize novel Cobalt(II) Schiff base complexes.
• To evaluate their photocatalytic activity in free radical photopolymerization (FRP).
• To investigate the influence of structural and electronic properties on photocatalytic performance.

Main Methods:

• Synthesis and characterization of Cobalt(II) complexes using FTIR, UV-vis, fluorescence spectroscopy, MALDI-TOF, and cyclic voltammetry.
• Density Functional Theory (DFT/TD-DFT) calculations for electronic structure analysis.
• Photopolymerization experiments using three-component photoinitiating systems under UV, violet, and blue LED irradiation.

Main Results:

• Synthesized and characterized five Cobalt(II) Schiff base complexes (Co-Ph, Co-EtO, Co-Cl, Co-Me, Co-tBu).
• Demonstrated efficient FRP of trimethylolpropane ethoxylate triacrylate (TMPETA) under UV irradiation without inhibition.
• Co-EtO complex showed superior photocatalytic efficiency across tested wavelengths.
• Mechanism involving oxidative and reductive pathways was proposed and supported by experiments and calculations.

Conclusions:

• Cobalt(II) Schiff base complexes are effective photocatalysts for FRP.
• The Co-EtO complex offers enhanced performance due to its unique properties.
• These findings highlight the potential of cobalt complexes as sustainable alternatives in photopolymerization.