"Development of molecular conductors, magnetic materials, and dielectrics including supramolecular rotor structures"

Organic molecular assembly behaved as magnets, storage devices and so on... Normally, when some molecules assemble, they have not often shown enough function of molecules in order to have the closest packed structure. 

In our laboratory, we have created a molecular assembly with an ideal molecular sequence to bring out the function of a substance by using the method of "supramolecular chemistry". Among them, the polarization of the entire crystal was reversed by the axial rotation of the molecule, and we succeeded in producing a crystal with "ferroelectricity", which is one of the memory characteristics. This has attracted attention from all over the world as a "flip-flop supramolecular rotor-type ferroelectric materials" that imitates the movement of molecular motors found in biomolecular systems.

Furthermore, we have advanced the method of "supramolecular chemistry" to synthesize "multifunctional molecular assemblies" in which various functions such as magnetic characteristics and strong dielectric properties are combined into a single crystal. We are conducting research with the aim of developing an "artificial molecular motor" that rotates in only one direction like a biomolecule, designing a new molecular rotor structure, and developing its functions.

As an electronic device that is becoming thinner, building a device with "molecular size" is one of the major goals. We are focusing on polyoxometallates (POMs) as a substance that pioneers molecular-sized electronics. POMs are clusters of metal oxides formed by dehydration condensation of molybdic acid, tungstic acid, etc., and the structure can be designed by the same method as organic synthesis, and can be combined with organic cations. Another feature is that the structure is accurately determined on a nanoscale.

The transition metal ions that make up POMs exist in a mixed valence state, and electrons and spins move around in the cluster like bulk metal oxides. In addition, since one cluster contains many transition metal ions, it is also of interest as a multi-stage electron storage material (battery) capable of storing many electrons.

Targeting such synthetic clusters, we are searching for new substances by combining them with magnetic metal ions and organic molecules.

Protons (H +) play an important role in controlling the movement of living organisms, such as material transmission and energy generation. The movement of protons plays an important role not only in living organisms but also in the function of matter. By controlling the movement of protons inside a solid substance, it is possible to realize proton conduction, which is the operating principle of fuel cells. Ferroelectricity, which is one of the memory functions, can be also developed by motion of protons.

We are developing a new electronic system by introducing hydrogen-bonding units into the molecular assembly. We have created a dielectric phase transition system that utilizes the proton transfer phenomenon due to the temperature change of protons along the hydrogen bond chain in the crystal. Due to deuterium substitution, the phase transition temperature changes significantly.

Based on a series of research, we aim to develop a new electron-proton interlocking system.