Is Iron the New Ruthenium?

Area of Science:

• Photophysics and photochemistry
• Coordination chemistry
• Materials science

Background:

• Ruthenium polypyridine complexes are widely used in photophysics and photochemistry due to their long-lived, luminescent metal-to-ligand charge-transfer (MLCT) excited states.
• Iron is a desirable alternative to ruthenium due to its abundance and lower cost, but achieving similar photophysical properties in iron complexes has been challenging.
• Iron(II) complexes typically suffer from rapid deactivation of MLCT states, preventing luminescence and limiting applications.

Purpose of the Study:

• To review the challenges and strategies for developing photoactive iron complexes.
• To highlight recent advances in extending the lifetimes of MLCT states in iron complexes.
• To discuss the potential paradigm shift introduced by luminescent iron(III) complexes.

Main Methods:

• Review of fundamental challenges in iron complex photophysics.
• Discussion of key strategies employed to enhance photophysical and photochemical properties.
• Highlighting recent conceptual breakthroughs in the field.

Main Results:

• Significant progress has been made in extending MLCT state lifetimes in iron complexes.
• The first examples of luminescent iron complexes have been reported.
• These luminescent complexes are iron(III) species with distinct electronic structures.

Conclusions:

• Recent advances in iron(III) complexes offer a new direction for photoactive earth-abundant metal complexes.
• These findings could lead to a paradigm shift, moving away from traditional iron(II) targets.
• Further research into these iron complexes holds potential for applications in lighting, sensing, solar cells, and catalysis.