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Updated: Jul 14, 2026
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09:12
[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst
Published on: May 21, 2019
Metal-Centered Photoredox Catalysis using d6 Transition Metal-based Chromophores
Micheal M Alowakennu1, Bekah E Bowers1, Björn Pfund1
1Department of Chemistry, Michigan State University, 578 South Shaw Lane, East Lansing, Michigan48824, United States.
Accounts of Chemical Research
|July 13, 2026
Summary
Earth-abundant iron and cobalt complexes, utilizing metal-centered (MC) excited states, offer a distinct platform for photoredox catalysis. These MC states enable selective and productive electron-transfer pathways, challenging previous assumptions about their utility.
Area of Science:
- Photochemistry
- Catalysis
- Inorganic Chemistry
Background:
- Transition metal chromophores are crucial for light-driven chemistry, including solar energy and photoredox catalysis.
- Ruthenium (Ru) and Iridium (Ir) complexes dominate due to long-lived charge-transfer (CT) states.
- Elemental scarcity and selectivity issues motivate exploring alternatives like earth-abundant metals.
Purpose of the Study:
- To challenge the paradigm that metal-centered (MC) excited states in Fe(II) and Co(III) complexes are unsuitable for photochemistry.
- To establish MC excited states as distinct and mechanistically powerful platforms for productive photochemistry.
- To outline design principles for tuning reactivity in first-row transition metal complexes.
Main Methods:
- Summarizing recent work on Fe(II) and Co(III) complexes.
- Identifying the nature and spin-state character of reactive MC excited states.
- Analyzing potential energy landscapes and competing reaction pathways.
Main Results:
- Fe(II) 5T2 excited states are unreactive in photoredox processes due to high reorganization energy.
- Fe(II) and Co(III) 3T1 excited states enable productive electron-transfer pathways by minimizing spin and structural reorganization.
- MC excited states offer enhanced selectivity compared to traditional CT-based systems.
Conclusions:
- MC excited states in earth-abundant Fe(II) and Co(III) complexes are a viable and advantageous platform for photoredox catalysis.
- Controlling spin state, ligand field strength, and structural reorganization are key design rules.
- This work opens new opportunities in photoredox catalysis using earth-abundant metals.
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