A Photoreactive Iron(II) Complex Luminophore

Area of Science:

• Photochemistry
• Inorganic Chemistry
• Materials Science

Background:

• Controlling excited states is key for light-to-energy conversion in molecular systems.
• Ruthenium complexes are common sensitizers, but alternatives are sought.

Purpose of the Study:

• To report a novel luminescent and photoreactive iron(II) complex.
• To investigate its excited state properties and potential applications in light-driven synthesis.

Main Methods:

• Synthesis of a double cyclometalated iron(II) complex with a phenylphenanthroline framework.
• Characterization of its photophysical properties, including luminescence decay and excited-state redox potential.
• Demonstration of its use in a radical cross-coupling reaction.

Main Results:

• The iron(II) complex populates a triplet metal-to-ligand charge transfer (³MLCT) state as the lowest energy excited state.
• Near-infrared luminescence was observed with lifetimes of 1-2.4 ns in different phases and 14 ns at 77 K.
• The complex exhibits a ³MLCT excited-state redox potential of -2 V vs Fc/Fc⁺.
• Successful application in the radical cross-coupling of 4-chlorobromobenzene and benzene.

Conclusions:

• The developed iron(II) complex is a performant sensitizer, analogous to ruthenium complexes.
• Its favorable excited-state properties, including NIR luminescence and redox potential, enable its use in light-driven synthesis.
• This work expands the scope of metal-based chromophores for sustainable chemical transformations.