New ferroelectrics based on divalent metal ion alum

Magnetoelectric effect generated through electron transfer from organic radical to metal ion

Magnetoelectric (ME) materials induced by electron transfer are extremely rare. Electron transfer in these materials invariably occurs between the metal ions. In contrast, ME properties induced by electron transfer from an organic radical to a metal ion have never been observed. Here, we report the ME coupling effect in a mononuclear molecule-based compound [(CH₃)₃NCH₂CH₂Br][Fe(Cl₂An)₂(H₂O)₂] (1) [Cl₂An = chloranilate, (CH₃)₃NCH₂CH₂Br⁺ = (2-bromoethyl)trimethylammonium]. Investigation of the mechanism revealed that the ME coupling effect is realized through electron transfer from the Cl₂An to the Fe ion. Measurement of the magnetodielectric (MD) coefficient of 1 indicated a positive MD of up to ∼12% at 10^3.0 Hz and 370 K, which is very different from that of ME materials with conventional electron transfer for which the MD is generally negative. Thus, the current work not only presents a novel ME coupling mechanism, but also opens a new route to the synthesis of ME coupling materials.

Physicochemical Properties of Organic Molecular Ferroelectric Diisopropylammonium Chloride Thin Films

We fabricated ferroelectric films of the organic molecular diisopropylammonium chloride (DIPAC) using the dip-coating technique and characterized their properties using various methods. Fourier-transform infrared, scanning electron microscopy, and X-ray diffraction analysis revealed the structural features of the films. We also performed ab-initio calculations to investigate the electronic and polar properties of the DIPAC crystal, which were found to be consistent with the experimental results. In particular, the optical band gap of the DIPAC crystal was estimated to be around 4.5 eV from the band structure total density-of-states obtained by HSE06 hybrid functional methods, in good agreement with the value derived from the Tauc plot analysis (4.05 ± 0.16 eV). The films displayed an island-like morphology on the surface and showed increasing electrical conductivity with temperature, with a calculated thermal activation energy of 2.24 ± 0.03 eV. Our findings suggest that DIPAC films could be a promising alternative to lead-based perovskites for various applications such as piezoelectric devices, optoelectronics, sensors, data storage, and microelectromechanical systems.

EXAFS Study on the Coordination Chemistry of the Solvated Copper(II) Ion in a Series of Oxygen Donor Solvents

The structures of the solvated copper(II) ion in water and nine organic oxygen donor solvents with similar electron-pair donor ability, but with different space-demanding properties at coordination, have been studied by EXAFS. N,N′-Dimethylpropyleneurea and N,N,N′,N′-tetramethylurea are sufficiently space demanding at coordination to make the axial positions not accessible, resulting in square-planar copper(II) solvate complexes with an intense green color. The mean Cu–O bond distances in these two solvate complexes are 1.939(3) and 1.935(3) Å, respectively. The best fits of the remaining solvates, which are light blue in different hues, are obtained with a Jahn–Teller distorted-octahedral model consisting of four strongly bound solvent molecules in the equatorial positions at 1.96(2) Å and two in the axial positions but with different Cu–O_ax bond distances: ca. 2.15 and 2.32 Å. This is in agreement with observations in solid-state structures of compounds containing hexaaquacopper(II) complexes crystallizing in noncentrosymmetric space groups and all reported crystal structures containing a [Cu(H₂O)₅(O-ligand)] complex with Jahn–Teller distortion. Such a structure is in agreement with previous EPR and EXAFS studies proving the hydrated copper(II) ion to be a noncentrosymmetric complex in aqueous solution. The refinements of the EXAFS data of the solids [Cu(H₂O)₆](ClO₄)₂, [Cu(H₂O)₆](BrO₃)₂, [Cu(H₂O)₆]SiF₆, Cu(NO₃)₂·2.5H₂O, and CuSO₄·5H₂O gave Cu–O bond distances significantly different from those reported in the crystallographic studies but similar to the configuration and bond distances in the hydrated copper(II) ion in aqueous solution. This may depend on whether the orientation of the axial positions is random in one or three dimensions, giving a mean structure of the solid with symmetry higher than that of the individual complexes. This study presents the very first experimental data from the new X-ray absorption spectroscopy beamline Balder at the MAX IV synchrotron radiation facility in Lund, Sweden, as well as the utilized properties of the beamline.

The coordination chemistry of the solvated copper(II) ion has been studied in 10 solvents, including water. The copper(II) ion has a noncentrosymmetric Jahn−Teller distorted-octahedral geometry with the axial Cu−O bond distances differing by ca. 0.2 Å.

Systematic Parametrization of Divalent Metal Ions for the OPC3, OPC, TIP3P-FB, and TIP4P-FB Water Models

Divalent metal ions play important roles in biological and materials systems. Molecular dynamics simulation is an efficient tool to investigate these systems at the microscopic level. Recently, four new water models (OPC3, OPC, TIP3P-FB, and TIP4P-FB) have been developed and better represent the physical properties of water than previous models. Metal ion parameters are dependent on the water model employed, making it necessary to develop metal ion parameters for select new water models. In the present work, we performed parameter scanning for the 12-6 Lennard-Jones nonbonded model of divalent metal ions in conjunction with the four new water models as well as four previous water models (TIP3P, SPC/E, TIP4P, and TIP4P-Ew). We found that these new three-point and four-point water models provide comparable or significantly improved performance for the simulation of divalent metal ions when compared to previous water models in the same category. Among all eight water models, the OPC3 water model yields the best performance for the simulation of divalent metal ions in the aqueous phase when using the 12-6 model. On the basis of the scanning results, we independently parametrized the 12-6 model for 24 divalent metal ions with each of the four new water models. As noted previously, the 12-6 model still fails to simultaneously reproduce the experimental hydration free energy (HFE) and ion-oxygen distance (IOD) values even with these new water models. To solve this problem, we parametrized the 12-6-4 model for the 16 divalent metal ions for which we have both experimental HFE and IOD values for each of the four new water models. The final parameters are able to reproduce both the experimental HFE and IOD values accurately. To validate the transferability of our parameters, we carried out benchmark calculations to predict the energies and geometries of ion-water clusters as well as the ion diffusivity coefficient of Mg²⁺. By comparison to quantum chemical calculations and experimental data, these results show that our parameters are well designed and have excellent transferability. The metal ion parameters for the 12-6 and 12-6-4 models reported herein can be employed in simulations of various biological and materials systems when using the OPC3, OPC, TIP3P-FB, or TIP4P-FB water model.

New Series of Polar and Nonpolar Platinum Iodates A2Pt(IO3)6 (A = H3O, Na, K, Rb, Cs)

A new series of platinum iodates, namely, α-(H3O)2Pt(IO3)6, β-(H3O)2Pt(IO3)6, and A2Pt(IO3)6 (A = Na, K, Rb, Cs), have been synthesized. Interestingly, among these six stoichiometrically identical compounds, α-(H3O)2Pt(IO3)6 is polar, whereas other compounds are nonpolar and centrosymmetric. They all consist of zero-dimensional [Pt(IO3)6](2-) molecular units separated by H3O(+) or A(+) cations. All of the lone electron pairs of the IO3(-) groups are aligned and almost point to one direction for α-(H3O)2Pt(IO3)6, whereas IO3(-) groups are located trans to each other in other compounds. The material, α-(H3O)2Pt(IO3)6, exhibits very strong second harmonic generation (SHG) effects, approximately 1.2 × KTiOPO4 (KTP), and is phase-matchable. Thermogravimetric analysis, elemental analysis, infrared spectra, UV-vis spectra, nonlinear optical properties, and theoretical calculations are also reported.

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.

Controlling the self-assembly of homochiral coordination architectures of CuII by substitution in amino acid based ligands: synthesis, crystal structures and physicochemical properties

In this paper we report six chiral ligands based on l-tyrosine, l-serine and l-phenylalanine and their homochiral Cu^II complexes to study the effect of various substitutions in the ligands on the formation of diverse coordination architectures.

A homochiral luminescent compound with four-fold symmetry as a potential chemosensor for nitroanilines

Crystal structure of the first homochiral luminescent compound of a dansylated amino acid (tyrosine) of Cu(ii), [Cu₂(HTyr-N-Dan)₄(H₂O)₂]·2H₂O (1) (H₂Tyr-N-Dan = N-dansyltyrosine), and selective sensing of nitroanilines by both the ligand and 1 are reported.

Diimidazolium phthalate monohydrate

In the title compound, 2C₃H₅N₂⁺·C₈H₄O₄²⁻·H₂O, the cations, anion and water mol­ecule are connected by N—H⋯O and O—H⋯O hydrogen bonds, forming a three-dimensional network.

Benzene-1,2-dicarb-oxy-lic acid-pyridinium-2-olate (1/1)

The asymmetric unit of the title compound, C(5)H(5)NO·C(8)H(6)O(4), contains one o-phthalate acid mol-ecule and one pyridin-2-ol mol-ecule, which exists in a zwitterionic form. In the o-phthalate acid mol-ecule, the carboxyl-ate groups are twisted from the benzene ring by dihedral angles of 13.6 (1)° and 73.1 (1)°; the hy-droxy H atom in the latter group is disordered over two positons in a 1:1 ratio. In the crystal, O-H⋯O and N-H⋯O hydrogen bonds link the mol-ecules into zigzag chains in [-101].

Bis(2-trifluoro-methyl-1H-benzimidazol-3-ium) tetra-chloridomercurate dihydrate

In the title compound, (C₈H₆F₃N₂)₂[HgCl₄]·2H₂O, the Hg^II cation is coordinated by four Cl⁻ anions in a distorted tetra­hedral geometry. In the crystal, the 2-trifluoro­methyl-1H-benzimidazolium cations link to the [HgCl₄]²⁻ complex anions and lattice water mol­ecules via N—H⋯Cl and N—H⋯O hydrogen bonds, and the lattice water mol­ecules further link to the Hg complex anion and the organic cations via O—H⋯Cl and O—H⋯F hydrogen bonding. One of the trifluoro­methyl groups is disordered over two orientations in a 0.59 (4):0.41 (4) ratio.

Propanaminium p-toluene-sulfonate

In the crystal structure of the title salt, C₃H₁₀N⁺·C₇H₇O₃S⁻, N—H⋯O hydrogen bonds involving the ammonium groups of the cations and the sulfonate O atoms result in the formation of a three-dimensional network.

2-Hy-droxy-pyridinium p-toluene-sulfonate

In the title molecular salt, C(5)H(6)NO(+)·C(7)H(7)O(3)S(-), the cations and anions are connected by N-H⋯O and O-H⋯O hydrogen bonds, forming [100] chains.

Bis(3-methyl-anilinium) naphthalene-1,5-disulfonate

In the crystal of the title mol­ecular salt, 2C₇H₁₀N⁺·C₁₀H₆O₆S₂²⁻, the naphthalene-1,5-disulfonate anion is located on an inversion center and accepts N—H⋯O hydrogen bonds from the 3-methyl­anilinium cations, forming supra­molecular layers parallel to the ac plane.

5-Nitro-2-trifluoromethyl-1H-benzimidazole monohydrate

In the crystal structure of the title compound, C₈H₄F₃N₃O₂·H₂O, the main mol­ecule and the water mol­ecule are linked by an N—H⋯O hydrogen bond. O—H⋯N, O—H⋯O and C—H⋯O hydrogen bonds further link the mol­ecules into sheets.

1-Acetyloxymethyl-1,3,5,7-tetraazaadamantan-1-ium hexafluorophosphate

In the crystal structure of the title salt, C₉H₁₇N₄O₂⁺·PF₆⁻, the cations and anions are linked by weak C—H⋯F inter­actions while C—H⋯O inter­actions also occur between the cations.

Bis(1H-imidazol-3-ium) naphthalene-1,5-disulfonate

The asymmetric unit of the title organic salt, 2C₃H₅N₂⁺·C₁₀H₆O₆S₂²⁻, consists of an imidazolium cation and half a naphthalene-1,5-disulfonate dianion, completed to the full dianion through an inversion center. N—H⋯S and N—H⋯O hydrogen bonds link cations and anions in the crystal, forming a chain propagating along [101].

(1-Hy-droxy-ethyl-idene)(meth-yl)aza-nium bromide-N-methyl-acetamide (1/1)

The asymmetric unit of the organic hybrid salt, C(3)H(8)NO(+)·Br(-)·C(3)H(7)NO, comprises an N-methyl-acetamide cation, a N-methyl-acetamide mol-ecule and a bromide anion. The amide species are linked head-to-head through a short O⋯H⋯O hydrogen bond, giving a monocation, which is extended by N-H⋯Br hydrogen bonds into chains along the b-axis direction.

1-Cyano-methyl-1,4-diazo-niabicyclo-[2.2.2]octane tetra-chloridocadmate(II)

In the title salt, (C(8)H(15)N(3))[CdCl(4)], four Cl atoms coordinate the Cd(II) atom in a slightly distorted tetra-hedral geometry. In the crystal, each [CdCl(4)](2-) anion is connected to the 1-cyano-methyl-1,4-diazo-niabicyclo-[2.2.2]octane dications by N-H⋯Cl hydrogen bonds, forming chains parallel to [001]. C-H⋯Cl inter-actions also occur.