Dynamics of Organic Cations in Switchable Quinuclidinium Metal Chloride Dielectrics

The synthesis and structure of a series of quinuclidinium-based organic-inorganic hybrids of Q(2)CuCl(4), Q(2)CoCl(4), and Q(4)Pb(3)Cl(10) are reported (Q = quinuclidinium, C7H13NH+). The dynamic disorder observed in the structure of quinuclidinium metal chlorides was investigated using variable-temperature single-crystal X-ray diffraction, IR, Raman, NMR, and dielectric spectroscopy. The crystals undergo phase transitions (PTs) where an order-disorder process takes place. However, it is assumed that in the case of Q(2)CoCl(4) and Q(2)CuCl(4), the reorientation of Q cations is a major force driving PT, while in Q(4)Pb(3)Cl(10), the reorientation of inorganic ions (Pb-Cl moieties) is at least equally important. All three hybrid compounds exhibit switchable and tunable properties of the dielectric function between two stable ON/OFF states. The magnetic properties were also investigated over a wide temperature range by measuring the magnetic susceptibility and magnetization as a function of temperature and external magnetic field, which allowed us to demonstrate the competition between the paramagnetic and diamagnetic signals in these compounds. The dynamics probed by NMR has shown a nonequivalence of Q cations in all studied compounds.