Researchers at Johannes Gutenberg University Mainz have created a new manganese-based metal complex that promises to transform light-driven chemical reactions. This breakthrough replaces scarce noble metals with abundant manganese, offering simple synthesis and exceptional efficiency. The complex's long excited-state lifetime could enable sustainable applications like hydrogen production.
Chemical reactions traditionally depend on heat, but photochemistry uses light for precise control. However, many light-driven processes have relied on rare and expensive elements like ruthenium, osmium, and iridium, which pose environmental challenges due to mining.
A team led by Professor Katja Heinze at Johannes Gutenberg University Mainz (JGU) has developed a manganese complex that addresses these issues. Manganese is over 100,000 times more abundant on Earth than ruthenium, making it a practical alternative. "This metal complex sets a new standard in photochemistry: it combines a record-breaking excited-state lifetime with simple synthesis," Heinze said. "It thus offers a powerful and sustainable alternative to the noble metal complexes that have long dominated light-driven chemistry."
The complex is synthesized in a single step from commercially available ingredients, overcoming previous hurdles of nine- or ten-step processes and short excited-state durations in manganese systems. Dr. Nathan East, who performed the initial synthesis, noted, "The newly developed manganese complex overcomes both challenges." Combining manganese with a specially designed ligand yields an intense purple solution, indicating unique formation.
The complex excels in light absorption, capturing photons with high efficiency. Its excited-state lifetime reaches 190 nanoseconds—two orders of magnitude longer than prior common-metal complexes like those with iron or manganese. Dr. Robert Naumann, who analyzed it via luminescence spectroscopy, explained, "The lifetime of the complex of 190 nanoseconds is also remarkable." This duration allows sufficient time for the excited catalyst to transfer electrons through diffusion.
The researchers confirmed functionality by detecting the photoreaction's initial product. "We were able to detect the initial product of the photoreaction—the electron transfer that occurred—and thus prove that the complex reacts as desired," Heinze added. Published in Nature Communications (2025, volume 16, issue 1), this work paves the way for scalable photochemical technologies, potentially advancing sustainable hydrogen production.