Molecular Design of a Metal-Nitrosyl Ferroelectric with Reversible Photoisomerization

Abstract

The development of photo-responsive ferroelectrics whose polarization may be remotely controlled by optical means is of fundamental importance for basic research and technological applications. Herein, we report the design and synthesis of a new metal-nitrosyl ferroelectric crystal (DMA)­(PIP)­[Fe­(CN)5(NO)] (1) (DMA = dimethylammonium, PIP = piperidinium) with potential phototunable polarization via a dual-organic-cation molecular design strategy. Compared to the parent non-ferroelectric (MA)2[Fe­(CN)5(NO)] (MA = methylammonium) material with a phase transition at 207 K, the introduction of larger dual organic cations both lowers the crystal symmetry affording robust ferroelectricity and increases the energy barrier of molecular motions, endowing 1 with a large polarization of up to 7.6 μC cm–2 and a high Curie temperature (T c) of 316 K. Infrared spectroscopy shows that the reversible photoisomerization of the nitrosyl ligand is accomplished by light irradiation. Specifically, the ground state with the N-bound nitrosyl ligand conformation can be reversibly switched to both the metastable state I (MSI) with isonitrosyl conformation and the metastable state II (MSII) with side-on nitrosyl conformation. Quantum chemistry calculations suggest that the photoisomerization significantly changes the dipole moment of the [Fe­(CN)5(NO)]2– anion, thus leading to three ferroelectric states with different values of macroscopic polarization. Such optical accessibility and controllability of different ferroelectric states via photoinduced nitrosyl linkage isomerization open up a new and attractive route to optically controllable macroscopic polarization.

Field-Induced Antiferroelectric–Ferroelectric Transformation in Organometallic Perovskite Displaying Giant Negative Electrocaloric Effect

“…Since the dielectric permittivity comes from the reorientation transformation of structural components, − the real part ( ε′ ) of the complex dielectric constant displays two obvious anomalies around T 1 and T 2 (Figure S10), which is in line with two successive structural phase transition. In addition, the pretty small imaginary part ( ε′′ ) of the complex dielectric constant (dielectric loss <0.03) indicates the low intrinsic heating dissipation in 1 (Figure S11), which is conducive to its working stability. , It is worth noting that the imaginary part exhibits more obvious frequency dispersion compared to the real part, which is the typical features of the dielectric relaxation .…”

A Sn-Based Hybrid Ferroelastic Semiconductor with High-Temperature Dielectric Switching

“…In recent years, organic–inorganic hybrids (OIHs) have been extensively investigated and applied in the field of optoelectronics, which profit from their excellent properties such as high photoelectrical efficiency, long carrier lifetimes, low energy consumption, and light weight. − It should be noted that some studies have attributed the excellent photoelectric properties of hybrid ferroelastic materials to their ferroelasticity and further proved this inference by experiments. For example, the fascinating photovoltaic properties of [CH 3 NH 3 ]­PbI 3 might be associated with the synergistic effect of ferroelasticity and superior semiconductor performance. − However, with the world's increasing attention to environment problems, the design of novel lead-free, nontoxic, and pollution-free OIHs has become a matter urgent to settle . Thus, lessening the usage of Pb by replacing them with other elements in OIHs but keeping their favorable properties is a better strategy .…”

A muconic acid derivative isomeric organic–inorganic metal halide with high-temperature phase transition

“…1–6 In addition to these diverse physical properties, OIMHs have also received increasing interest for their phase transitions. The physical properties of phase transition materials can be switched between different phases under external stimuli, accompanied by changes in crystal structures, 7–11 which makes them increasingly widely applied in memory, signal processing, sensing, and other information technology fields. 12–15 Structurally, OIMHs contain inorganic metal halide anionic frameworks and organic cations, where the organic cations are located in the space between metal halide anionic frameworks with weak intermolecular interactions such as hydrogen bonding interactions between the inorganic and organic components.…”