Dynamic supramolecular cations in conductive and magnetic [Ni(dmit)2] crystals

Abstract

Supramolecular cation (SC) structures with high degrees of chemically designed freedoms are one of the most effective building blocks for controlling the dynamic and physical properties of molecular assemblies. Various SC structures, ranging from simple metal ions with different sizes, valences, and magnetic spins to organic ammoniums with diverse molecular structures, can be formed via complexation of crown ether derivatives with different ring sizes, which can be introduced into the π-planar Ni-coordination complexes using electrically conductive and magnetic [Ni(dmit)2] salts (dmit2− = 2-thioxo-1,3-dithiole-4,5-dithiolate). Various dynamics such as ion transport, molecular rotation, and molecular oscillation coexist in a single crystal of [Ni(dmit)2], affecting its electrical conductivity, magnetic behavior, dielectric response, and ferroelectricity. Unlike the physical properties exhibited by a static crystal lattice, the physical properties of a dynamic system depends on external factors such as temperature and the presence of an electric field. These properties are governed by factors such as the motional symmetry, amplitude, and frequency of the dynamic SC units in the crystal lattice. In particular, the dynamics of the polar structural units is particularly prominent in the dielectric response and ferroelectricity. The dipole rotator structure is an example of achieving macroscopic physical properties of ferroelectrics along with microscopic molecular dynamics. Structural and functional control of dynamic molecular assemblies using the SC approach is fundamental to the fabrication of next-generation molecular electronic and mechatronic devices.