Supramolecular Ni(dmit)2 salts with halopyridinium cations -development of multifunctional molecular conductors with the use of competing supramolecular interactions

Halopyridinium cations with multiple halogen and hydrogen bonding donor sites have been used as the counter ions for the Ni(dmit)2 anion (dmit = 1,3-dithiole-2-thione-4,5-dithiolate). Because of the competing supramolecular interactions, such as halogen and hydrogen bondings, some of the Ni(dmit)2 salts showed complicated structures with multiple functionality that originates from the intriguing molecular arrangements. In these multifunctional salts, Ni(dmit)2 molecules play two roles, conducting and magnetic, depending on the molecular arrangement in the layers that they belong to. The physical properties of these salts have been examined by conductivity measurements, with or without hydrostatic/uniaxial pressure, as well as magnetic susceptibility and band calculations. By analysing the low temperature conductivity, it can be concluded that the itinerant electrons in the conducting layer have magnetic coupling with the localized spins in the magnetic layers to result in a Kondo singlet formation.