Organic ferroelectrics

Abstract

Ferroelectricity results from one of the most representative phase transitions in solids, and is widely used for technical applications. However, observations of ferroelectricity in organic solids have until recently been limited to well-known polymer ferroelectrics and only a few low-molecular-mass compounds. Whereas the traditional use of dipolar molecules has hardly succeeded in producing ferroelectricity in general, here we review advances in the synthesis of new organic materials with promising ferroelectric properties near room temperature, using design principles in analogy to inorganic compounds. These materials are based on non-covalent molecules formed by two or more components, in which ferroelectricity arises either from molecular displacements or from the collective transfer of electrons or protons. The principle of using multi-component molecular compounds leads to a much broader design flexibility and may therefore facilitate the development of future functional organics.

Relaxor ferroelectricity induced by electron correlations in a molecular dimer Mott insulator

“…This discovery will enable a deeper understanding of organic Mott insulators beyond the successful dimer lattice model and the discovery of new functionality. The origin of this ferroelectricity is different from the recently discovered hydrogen-bonded organic ferroelectrics 12 and the Peierls instability-induced inversion symmetry breaking in one-dimensional systems 13 .…”

Rhodizonic Acid on Noble Metals: Surface Reactivity and Coordination Chemistry

“…Note that the lowering in energy of the RA 6 LUMO versus the RA 3 LUMO is also seen in the gasphase. On the surface, there is more charge transfer into the RA 6 LUMO than that of RA 3 ; the calculated Bader charges on the molecules are 0.57 e higher for RA 6 compared to RA 3 . The difference in charge is only 0.08 e for the same Cu/RA network when optimized in the gas phase and the charges in both systems (the surface-adsorbed and gas-phase networks) are generally consistent with Cu 1+ and C 6 O 6 2-oxidation states.…”

“…The energy of the analogous 6-fold coordination of the Cu network was found to be higher than the low coordination model. When the metal-organic framework shown in Figure 3b was optimized in the gas-phase (without the Cu slab), it was found to remain intact in the sense that each Cu atom effectively bridged two nearby carbonyl groups belonging to neighboring molecules, although a third carbonyl group lies at slightly longer distances (~0.15-0.30 Å longer) to form a three-coordinate Cu environment in the shape shown in Figure 3a; the molecules are labeled either RA 3 or RA 6 to show their symmetries with respect to these "CuO 3 " shapes, as depicted in the figure. An alternative arrangement was considered wherein the molecules were rotated slightly to alter the manner in which they coordinated to the neighboring Cu atoms, and although the relative energy of the optimized lattice (see the Supporting Information for details) was found to be ~0.2 eV/molecule higher in energy, the networks' electronic signatures were changed little (as will be discussed below).…”

Polarization Switching Ability Dependent on Multidomain Topology in a Uniaxial Organic Ferroelectric

“…In this work, we target an emergent supramolecular ferroelectric material with the hydrogen-bonded chain 19 …”