An international team coordinated by researchers from the Jagiellonian University has discovered a simple coordination compound that can be switched using light. This breakthrough paves the way for the development of light-controlled nanomagnets operating at room temperature, with potential applications in smart materials.
When molecules with a specific electronic structure (often containing conjugated bonds or chromophores) absorb visible light, they undergo transformations that drive key photoactive processes such as photosynthesis, solar energy conversion, or photocatalysis. The excited state is usually extremely short-lived, yet in some systems it can be “frozen” for weeks or even months before returning to the ground state. Such materials are known as photoswitchable and have potential applications in solar energy harvesting, information storage, or even light-activated drug design.
Until now, most studied systems were organic molecules – however, they rarely exhibit changes in magnetic properties under light. In some inorganic compounds, so-called spin transitions have been observed, but these effects vanish at extremely low temperatures (around -200 °C), limiting their practical use. The latest research shows that harnessing the photochemical properties of cyanometallates may bring such effects closer to room temperature, opening the door to magnetic photoswitches with real-world applications.
Scientists from the Jagiellonian University, in collaboration with the University of Bordeaux, the European Synchrotron Radiation Facility (ESRF), as well as researchers from Spain and Germany, discovered a cyanometallate that can be reversibly switched by light through a reversible photodissociation reaction in a single crystal.
“No one expected this could actually work,” admits Dr. hab. Dawid Pinkowicz from the Faculty of Chemistry at the Jagiellonian University. “But a few years ago, when we carefully analyzed reports on photodissociation reactions in coordination compounds, we realized there might be a chance. In 2022, I received an ERC Consolidator Grant specifically to achieve visible-light-activated magnets at room temperature based on photodissociation reactions.”
Their latest study showed that crystals of potassium heptacyanomolybdate can reversibly and collectively break and restore the metal–cyanide bond: violet light breaks it, while red light restores it, without damaging the crystal structure. This unique, non-destructive phenomenon allows the magnetic moment of the metallic center to be switched at record-high temperatures, offering a real prospect for designing photomagnetic materials — that is, materials whose magnetic properties can be controlled by light.
The discovery opens new possibilities for molecule-based data storage and molecular magneto-optical sensors.
The findings of the international team have just been published in Nature Communications.
Source: naukawpolsce.pl / UJ
