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Controlling how oxygen reacts is important for improving technologies such as batteries, fuel cells and environmentally sustainable chemical processes. A research team led by professor Seung Jun Hwang from KAIST's Department of Chemistry has developed a molecular system capable of directing oxygen activation along a selected electron-transfer pathway.
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By combining germanium with a molecular framework that can store and transfer electrons, the team established a design principle for selectively switching oxygen activation between two- and four-electron pathways. The results were published in Chem.
Germanium takes on a harder role
Catalysts for controlling oxygen reactions have traditionally been developed around transition-metal centers such as iron, cobalt and nickel. Germanium, by contrast, is a main-group element in the same group of the periodic table as silicon and has generally been considered less suitable for reactions requiring the coordinated transfer of several electrons.
To overcome this limitation, the research team combined germanium with a redox-active ligand, a molecular framework capable of storing, accepting and transferring electrons. The ligand serves as an electron reservoir and cooperates with the germanium center, allowing the entire molecular structure to participate in multielectron reactions.
Switching between oxygen pathways
When oxygen reacts, the products and reaction outcomes depend on whether two or four electrons are transferred. In general, two-electron oxygen reduction produces hydrogen peroxide, while four-electron reduction produces water. Selectively controlling these pathways is therefore an important challenge in the development of batteries, fuel cells and greener chemical catalysts.
The study presents a rare example of a main-group molecular system in which two- and four-electron reactivity can be selectively accessed within the same underlying molecular framework. This approach broadens the range of elements that may be considered in catalyst design and provides an alternative strategy to relying exclusively on transition metals.
A stable clue to reactivity
The team also succeeded in isolating and analyzing a germanium compound representing the two-electron stage of the reaction, which they stabilized by attaching a methyl group to the germanium complex. Remarkably, the germanium atom in this compound could both donate and accept electrons, providing an important clue to how the system controls different reaction pathways.
The team also confirmed the practical potential of the new system. Under mild, light-free conditions, the germanium complex removed halogen atoms such as bromine and chlorine from organic compounds and regenerated alkenes (organic compounds containing a carbon-carbon double bond), which are widely used as raw materials for pharmaceuticals, plastics and other chemical products.
Simpler routes to feedstocks
These results suggest that useful chemical feedstocks could be produced through simpler and potentially more energy-efficient processes.
"We expect these findings to inform the development of next-generation catalysts for energy conversion and to contribute to more selective and efficient chemical processes," Hwang said.
The study was conducted by Sung Gyu Kim and Jinrok Oh, currently postdoctoral researchers in the KAIST Department of Chemistry, and Dae Eui Choi, a student in the combined master's and doctoral program in the Department of Chemistry at POSTECH.
More information: Sung Gyu Kim et al, Germanium ligand redox cooperativity: A key to ambiphilicity and switchable two- and four-electron transfer, Chem (2026). DOI: 10.1016/j.chempr.2026.103127
Provided by The Korea Advanced Institute of Science and Technology (KAIST)
This story was originally published on Phys.org.
