Dynamics of Organic Cations in Switchable Quinuclidinium Metal Chloride Dielectrics

Abstract

The synthesis and structure of a series of quinuclidinium-based organic–inorganic hybrids of Q2CuCl4, Q2CoCl4, and Q4Pb3Cl10 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 Q2CoCl4 and Q2CuCl4, the reorientation of Q cations is a major force driving PT, while in Q4Pb3Cl10, 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.