Development of Novel Functional Organic Crystals by Utilizing Proton- and π-Electron-Donating/Accepting Abilities

Crystalline materials that comprise pi-electron organic molecules exhibit various interesting physical properties and functionalities, related to electrical conductivity, magnetism, optical properties, etc. Conventionally, such properties and functionalities are determined or controlled by the intermolecular pi-electron interactions in the crystal. Recently, however, the switching or control of the electronic structure and physical properties based on hydrogen dynamics was realized in a series of purely organic conductors. In this account article, the structure, properties, and switching phenomenon of this new type of organic conductors developed by utilizing proton-and pi-electron-donating/accepting abilities are summarized. In addition, a highly polarized pi-electron donor-acceptor type semiconductor molecule obtained in connection with the above conductors is also described.