New strategy unlocks magnetic switching with hydrogen bonding at molecular level

A research team from Kumamoto University has successfully developed a new approach to create switchable magnetic materials by using hydrogen bonding at the molecular level. This groundbreaking study shows how certain metal complexes, previously unresponsive to external stimuli, can now exhibit sharp and complete magnetic transitions by introducing chiral hydrogen bonds.

The research team, led by Associate Professor Yoshihiro Sekine from Priority Organization for Innovation and Excellence (POIE), focused on creating switchable molecular assemblies composed of cobalt (Co²⁺) and iron (Fe³⁺) ions, that originally do not typically respond to external stimuli. The team's innovation lies in incorporating hydrogen bonding via a chiral carboxylic acid, allowing the molecules to switch between magnetic states (paramagnetic and diamagnetic) with remarkable precision. These assemblies, termed "Molecular Prussian Blue analogs," show promise for controlled electron transfer between cobalt and iron ions—something that was unattainable in conventional materials.

The other key finding of the study is the role of molecular chirality in the performance of these assemblies. Enantiopure hydrogen-bond donor (HBD) molecules enabled sharp, complete magnetic transitions, while racemic mixtures led to disordered structures with broad, incomplete transitions. This highlights the importance of precise molecular arrangement in developing functional materials with predictable behavior."The chiral hydrogen-bonding units are crucial for achieving the cooperative and abrupt phase transitions that we observed," said Associate Professor Sekine. "This opens up new avenues for designing switchable materials at the molecular level."

These findings could lead to the development of advanced materials for magnetic storage devices, sensors, and other electronic applications. The study highlights how subtle changes in molecular structure can lead to dramatic differences in material behavior, providing a new pathway for the development of functional molecular machines and smart materials.