Biphenyl Bis [(π-cyclopentadienyl) iron] Dication as an Efficient Cationic Photoinitiator for Epoxy Polymerization

Ferrocenium monocations as photoinitiators for cationic photopolymerization suffer from a limitation of low absorption and low reactivity under high-pressure Hg lamp. Here, a ferrocenium dication salt, biphenyl bis [(π-cyclopentadienyl)iron] hexafluorophosphate ([bis(Cp-Fe)-biphenyl] (PF6)2 was synthesized by the ligand exchange reaction between ferrocene and biphenyl. The chemical structure was characterized with FTIR and 1HNMR. The separation of ferrocenium monocation cyclopentadien-iron-biphenyl hexafluorophosphate ([Cp-Fe-biphenyl] PF6) and dication [bis(Cp-Fe)-biphenyl] (PF6)2 was carried out by column chromatography. The photoactivity of initiating photopolymerization of epoxide ERl4221 was studied as a cationic photoinitiator. [Bis(Cp-Fe)-biphenyl] (PF6)2 can efficiently absorb radiation above 300nm and its photoactivity is higher than that of its monocation.