Related Concept Videos
01:26Photochemical Electrocyclic Reactions: Stereochemistry
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
02:17Reduction of Alkenes: Asymmetric Catalytic Hydrogenation
Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:28Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
01:22Heterogeneous Catalysis
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...
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Updated: Jul 14, 2026
![[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59739.jpg&w=3840&q=75)
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[(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, Michigan 48824, 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.
![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=75)
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.