High-Temperature Ferroelectricity and Photoluminescence in a Hybrid Organic–Inorganic Compound: (3-Pyrrolinium)MnCl3

Switchable dielectric phase transition originating from disorder–order transformation and distortion in {[(C4H4N2)Co(H2O)4]SO4·2H2O}n

Disorder–order transition of the SO₄²⁻ and distortion of the [(C₄H₄N₂)Co(H₂O)₄]²⁺ chain induce the phase transition of {[(C₄H₄N₂)Co(H₂O)₄]SO₄·2H₂O}_n.

[C5H12N]CdCl3: an ABX3 perovskite-type semiconducting switchable dielectric phase transition material

We report a new lead-free ABX₃ perovskite-type hybrid, which displays high thermal stability, semiconducting and striking switchable dielectric properties.

Reversible structural phase transition, ferroelectric and switchable dielectric properties of an adduct molecule of hexamethylenetetramine ferrocene carboxylic acid

An unprecedented metallo-organic ferroelectric, the adduct of hexamethylenetetramine ferrocene carboxylic acid displays a reversible structural phase transition around 187 K.

(Diisopropylammonium)2MnBr4: a multifunctional ferroelectric with efficient green-emission and excellent gas sensing properties

A luminescent ferroelectric, (diisopropylammonium)₂MnBr₄, is prepared, which exhibits efficient green emission, a high T_C value and excellent alcohol vapor sensing properties.

A high-temperature organic–inorganic ferroelectric with outstanding switchable dielectric characteristics

A new molecular ferroelectric is discovered in an organic–inorganic hybrid compound, (C₆H₅NH₃)₂CdCl₄, which undergoes a reversible order–disorder ferroelectric phase transition at 369 K.

Anomalously rotary polarization discovered in homochiral organic ferroelectrics

Molecular ferroelectrics are currently an active research topic in the field of ferroelectric materials. As complements or alternatives of conventional inorganic ferroelectrics, they have been designed to realize various novel properties, ranging from multiferroicity and semiconductive ferroelectricity to ferroelectric photovoltaics and ferroelectric luminescence. The stabilizing of ferroelectricity in various systems is owing to the flexible tailorability of the organic components. Here we describe the construction of optically active molecular ferroelectrics by introducing homochiral molecules as polar groups. We find that the ferroelectricity in (R)-(-)-3-hydroxlyquinuclidinium halides is due to the alignment of the homochiral molecules. We observe that both the specific optical rotation and rotatory direction change upon paraelectric-ferroelectric phase transitions, due to the existence of two origins from the molecular chirality and spatial arrangement, whose contributions vary upon the transitions. The optical rotation switching effect may find applications in electro-optical elements.

New homodinuclear tris(3-alkylpyrazolyl)borate complexes of CoII and NiII with a tetraacetylethane dianion as a bridging ligand

Polynuclear complexes and coordination polymers of 3d metals have attracted significant interest evoked by a number of their unique properties. One of the most common approaches to the directed synthesis of coordination polymers is the linking of pre-prepared discrete coordination units by polydentate ligands. The formation of polynuclear complexes is usually a spontaneous process and precise prediction of the products of such reactions is virtually impossible in most cases. Tris(pyrazolyl)borates (Tp) act as tripodal `capping' ligands which form stable complexes with 3d metal ions. In such 1:1 compounds, three metal-ion coordination sites are occupied by N atoms from a Tp anion. This limits the number of remaining coordination sites, and thus the number of additional ligands which may coordinate, and opens an attractive approach for the directed design of desirable structures by exploiting ligands with appropriate composition and topology. In the present study, Tp anions with neopentyl [Tp<sup>Np</sup>, tris(3-neopentylpyrazolyl)borate] and cyclohexyl [Tp<sup>Cy</sup>, tris(3-cyclohexylpyrazolyl)borate] substituents were used as `capping' ligands and the dianion of tetraacetylethane (3,4-diacetylhexa-2,4-diene-2,5-diolate, tae^2-) was employed as a bridge. The dinuclear complexes (μ-3,4-diacetylhexa-2,4-diene-2,5-diolato-κ⁴O²,O³:O⁴,O⁵)bis{[tris(3-cyclohexyl-1H-pyrazol-1-yl-κN²)borato]cobalt(II)} acetonitrile disolvate, [Co₂(C₂₇H₄₀BN₆)₂(C₁₀H₁₂O₄)]·2CH₃CN, (I)·2CH₃CN, and (μ-3,4-diacetylhexa-2,4-diene-2,5-diolato-κ⁴O²,O³:O⁴,O⁵)bis{[tris(3-neopentyl-1H-pyrazol-1-yl-κN²)borato]nickel(II)}, [Ni₂(C₂₄H₄₀BN₆)₂(C₁₀H₁₂O₄)], (II), were synthesized by the reaction of the mononuclear complexes Tp^CyCoCl or Tp^NpNiCl with H₂tae (3,4-diacetylhexane-2,5-dione or tetraacetylethane) in the presence of NEt₃ as base. Compounds (I) and (II) were characterized by mass spectrometry, elemental analysis, and X-ray crystallography. They possess similar molecular structures, X-ray diffraction revealing them to be dinuclear in nature and composed of discrete Tp-M units in which two metal ions are linked by a tae^2- dianion. Each metal ion possesses a five-coordinate square-pyramidal environment. The interplanar angles between the acetylacetonate fragments are significantly smaller than the near-90° values commonly observed.

Molecular Dynamics of Flexible Polar Cations in a Variable Confined Space: Toward Exceptional Two-Step Nonlinear Optical Switches

The changeable molecular dynamics of flexible polar cations in the variable confined space between inorganic chains brings about a new type of two-step nonlinear optical (NLO) switch with genuine "off-on-off" second harmonic generation (SHG) conversion between one NLO-active state and two NLO-inactive states.

Dual-Mode Luminescence Modulation upon Visible-Light-Driven Photochromism with High Contrast for Inorganic Luminescence Ferroelectrics

A luminescence ferroelectric oxide, Na(0.5)Bi(2.5)Nb2O9 (NBN), system with bismuth layer structure introduced by lanthanide ion (Er(3+)) has been demonstrated to exhibit reversible, high-contrast luminescence modulation (95%) and excellent fatigue resistance based on visible-light-driven photochromism (407 nm or sunlight). The coloration and decoloration process can be effectively read out by dual modes, upconversion and downshifting, and reversibly converted between green and dark gray by alternating visible light or sunlight irradiation and thermal stimulus. The luminescence modulation degree upon photochromic reactions is strongly dependent upon irradiation light wavelength and irradiation time. After undergoing several cycles, there are no significant degradations, showing high reversibility. Considering its high-contrast photoswitchable luminescence feature and intrinsic ferroelectricity of NBN host, NBN-based multifunctional materials can be suggested as a promising candidate for new potentials in photonic storage and optoelectronic multifunctional devices.

Symmetry breaking in molecular ferroelectrics

Symmetry breaking occurs between the high-temperature, high-symmetry paraelectric phase and the low-temperature, low-symmetry ferroelectric phase along with a reduction in the number of symmetry elements, obeying the Curie symmetry principle and relating to the ferroelectricity.

Dielectric and ferroelectric behavior of an incipient ferroelectric Sr(1−3x/2)CexTiO3 novel solid solution

Phase formation, chemical structure, microwave (MW) dielectric properties, and relaxor-to-ferroelectric phase transition behavior of a novel Sr_(1−3x/2)CexTiO₃ solid solution ceramic sintered in nitrogen have been investigated.