Dynamics of Organic Cations in Switchable Quinuclidinium Metal Chloride Dielectrics

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.