The syntheses and structural and physical properties for molecular functional materials such as molecular (super)conductors, magnets, and dielectrics have been studied. The attractive points of molecular materials are 1) that there is a variety of materials since around 50 million kinds of molecules have been synthesized so far, 2) that molecules and intermolecular interactions are designable and controllable, 3) that large response of external pressure and electron-phonon coupling are observed due to softness of molecules, and 4) that large Coulomb interactions (electron correlation) reflect the magnetism as well as conductivity in molecular conductors. Our group has investigated the curious molecular functional materials based upon charge, lattice, spin, and molecular degree of freedom by changing physical parameters with designed molecules. Recently, we found new organic superconductors, in which the superconducting state is competitive to the charge ordered state owing to the electron correlation and the bending and stretching of designed molecules. (See the figures)
Organic superconductor [κ-ET2Cu(NCS)2] prepared by the electrocrystallization method
Electrical resistivities under pressures for new organic superconductor, β-(meso-DMBEDT-TTF)2PF6. The metal-insulator transition occurs at 90 K at ambient pressure with accompanying checkerboard-type charge ordering. By applying pressure, the transition was suppressed, and the superconductivity was found at 4.3 K under 4.0 kbar.