Role of Coordination Complexes’ Structure in Achieving Maximum Polymerization Efficiency

Objectives: To evaluate the effect of the size of pyridyl-imine ligands in the synthesis of iron-based coordination complexes and their wavelength absorption range as dental photoinitiators.
Methods: Three structurally distinct pyridyl-imine ligands (2, 3, or 5 carbons) were used in the synthesis of Fe(II) coordination complexes, then characterized using 1H-NMR, FT-IR, and UV-vis spectroscopy. Maximum polymerization efficiency on a 1:1 bisphenol A glycerolate dimethacrylate and triethyleneglycol dimethacrylate blend was tested using the different wavelength emissions determined by the maximum absorption peak of each complex synthesized. Light exposures were standardized using 1000mw/cm2 radiant emittance and radiant exposure of 20J/cm2.
Results: Fe(II) complexes synthesized with distinct pyridyl-imine ligands exhibited similar absorption spectra range but distinct absorption peaks. The size of the pyridyl-imine ligands seems to have a direct correlation with their absorption peak shift. All complexes demonstrated maximum polymerization efficiency within their absorption peaks.
Conclusions: Changes in coordination complexes’ structure can play a role in maximizing polymerization efficiency within a specific spectral peak.