A Ferroelectric Iron(II) Spin Crossover Material

A dual‐function material in which ferroelectricity and spin crossover coexist in the same temperature range has been obtained. Our synthetic strategy allows the construction of acentric crystal structures in a predictable way and is based on the high directionality of hydrogen bonds. The well‐known iron(II) spin crossover complex [Fe(bpp)₂]²⁺ (bpp=2,6‐bis(pyrazol‐3‐yl)pyridine), a four‐fold noncentrosymmetric H‐bond donor, was combined with a disymmetric H‐bond acceptor such as the isonicotinate (isonic) anion to afford [Fe(bpp)₂](isonic)₂⋅2 H₂O. This low‐spin iron(II) compound crystallizes in the acentric nonpolar I space group and shows piezoelectricity and SHG properties. Upon dehydration, it undergoes a single‐crystal to single‐crystal structural rearrangement to a monoclinic polar Pc phase that is ferroelectric and exhibits spin crossover.     

Ferroelectric Behavior of a Hexamethylenetetramine‐Based Molecular Perovskite Structure

We report the development of a molecular ferroelectric material inspired by the hexamethylenetetramine (hmta) non‐centrosymmetric molecular rotator. The bromide salt of diprotonated hmta (hmtaH₂) crystalized as (hmtaH₂)(NH₄)Br₃ in a metal‐free ABX₃ perovskite‐type structure, in which the A and B sites are occupied by hmtaH₂²⁺ and ammonium cations, respectively. The compound crystallized in the Pma2 polar space group. A distorted polar perovskite structure formed owing to the distortion of {(NH₄)Br₆} octahedrons that are stabilized through the formation of NH???Br hydrogen bonds and the orientational ordering of positive charges on the non‐centrosymmetric hmtaH₂ molecules. This spontaneous polarization exhibited ferroelectric behavior with a nominally high Curie temperature (>400 K), in which the electrical switching of polarization originates from the rotation of the hmtaH₂ unit.     

A Metamagnetic Two-Dimensional Molecular Material with Nickel(II) and Azide

Bridging azido ligands transmit both ferro- and antiferromagnetic interactions. The sheetlike structured complex [Ni(μ-N(3))(2)(N,N-Et(2)-N'-Me-en)](n) (see picture) exhibits a range of magnetic behaviors at low temperature. Short-range ferromagnetic and three-dimensional antiferromagnetic ordering compete, giving metamagnetic behaviors. N,N-Et(2)-N'-Me-en=N,N-diethyl-N'-methylethylenediamine.     

Tailored Engineering of an Unusual (C4H9NH3)2(CH3NH3)2Pb3Br10 Two‐Dimensional Multilayered Perovskite Ferroelectric for a High‐Performance Photodetector

Two‐dimensional (2D) layered hybrid perovskites have shown great potential in optoelectronics, owing to their unique physical attributes. However, 2D hybrid perovskite ferroelectrics remain rare. The first hybrid ferroelectric with unusual 2D multilayered perovskite framework, (C₄H₉NH₃)₂(CH₃NH₃)₂Pb₃Br₁₀ ( 1 ), has been constructed by tailored alloying of the mixed organic cations into 3D prototype of CH₃NH₃PbBr₃. Ferroelectricity is created through molecular reorientation and synergic ordering of organic moieties, which are unprecedented for the known 2D multilayered hybrid perovskites. Single‐crystal photodetectors of 1 exhibit fascinating performances, including extremely low dark currents (ca. 10⁻¹² A), large on/off current ratios (ca. 2.5×10³), and very fast response rate (ca. 150 μs). These merits are superior to integrated detectors of other 2D perovskites, and compete with the most active CH₃NH₃PbI₃.     

Nickel(II) aminoalkoxides

Summary Nickel alkoxides react with mono-, di- and tri-ethanolamines in different stoichiometric ratios and novel products have been isolated and characterized by elemental analyses, i.r. and electronic reflectance spectra. Insertions across the Ni-O bond in aminoalkoxides have been studied for the first time.     

Molecular Organization in Layers of Nickel(II) Dimethylglyoximate and Hydroxylaminooximate

Layers of Ni(DMG)₂ and Ni(HAO)₂ 0.5-1 m thick were obtained by vacuum deposition. It was established by X-ray diffraction analysis (DRON-3M, DRON-SEIFERT-RM4, R = 192 mm, CuK radiation) that the layers are oriented polycrystalline films irrespective of the type of support used. Structural organization of the films and molecular orientations relative to the support surface were analyzed based on crystal data.     

Neutral Nickel(II) and Copper(II) Tetraazamacrocyclic Complexes as Molecular Rods Attached to Gold Electrodes

New dithiolated derivatives of neutral Cu^II and Ni^II tetraazamacrocyclic complexes have been synthesized and characterized by spectroscopic and diffractional methods. These rod‐shaped molecules were assembled in monocomponent and mixed monolayers on gold electrodes. In the mixed monolayers, the active molecules were embedded in a hexanethiol matrix. The dithiolated complexes are oriented perpendicularly to the electrode, and reveal faster kinetics of electron transfer than those assembled in a single‐component monolayer. They appear as protrusions, which are easily addressed by using the STM method. In the presence of a suitable electron acceptor in the solution, the donor properties of the anchored Cu complex were weakened, which revealed donor–acceptor interactions with the monolayer. The peak position in the voltammogram indicates a stronger interaction of the solution‐based acceptor with the reduced Cu^II form than with the Cu^III complex. This suggests the possibility of switching the association on or off by applying an appropriate potential.     

A Dicubane-Like Tetrameric Nickel(II) Azido Complex

A combination of azido and dipyridylketone (dpk) ligands led to the isolation of the tetranuclear Ni(II) complex 1 (dpkOH and dpkOCH(3) result from solvolysis of dpk). The complex exhibits ferromagnetic behavior, and its structure can be described as a dicubane unit with two missing vertices (see picture).     

Cadmium(II) and Nickel(II) 1-Oxypyridyl-2-Selenolates: Synthesis and Molecular and Crystal Structures

Russian Journal of Coordination Chemistry - Cadmium (C20H16Cd2N4O4Se4) (I) and nickel (C10H8N2NiO2Se2) (II) selenolates are synthesized by the exchange reactions of sodium 1-oxypyridyl-2-selenolate...     

Synthesis and Crystal and Molecular Structures of Nickel(II) and Copper(II) 1,5-Napthalenedisulfonate Complexes with Nicotinamide

Russian Journal of Coordination Chemistry - Coordination compounds of nickel(II) and copper(II) 1,5-naphthalenedisulfonates with nicotinamides, [Ni(L)2(H2O)4](Nds) · 3H2O (I) and...     

钙钛矿铁电纳米片诱导的P (VDF-TrFE)取向生长

Ferroelectric polymers are particularly attractive for applications in flexible electronic devices, and controlling its crystalline phase growth is crucial for obtaining optimized ferroelectric properties. Herein we report that a very low introduction (0.2% (w)) of single-domain ferroelectric PbTiO₃ nanoplates can effectively mediate the nucleation and subsequent growth of a crystalline phase within P (VDF-TrFE) (denoted by PVTF), forming highly oriented films and significantly improving the ferroelectric properties due to an alignment of the polarization directions of the polymer and the nanoplates.     

Highly Proton-Conductive Zinc Metal-Organic Framework Based On Nickel(II) Porphyrinylphosphonate

The design of new solid-state proton-conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate-based MOF ( IPCE-1Ni ), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE-1Ni exhibits one of the highest value of the proton conductivity among reported proton-conducting MOF materials based on porphyrins (1.55×10⁻³ S cm⁻¹ at 75 °C and 80 % relative humidity).