A paraelectric-ferroelectric phase transition of an organically templated zinc oxalate coordination polymer

Crystal engineering and structural diversity of 2-aminopyridinium hypodiphosphates obtained by crystallization and dehydration

Organic-inorganic salts and ionic co-crystals of hypodiphosphoric acid (H4P2O6) with 2-aminopyridne (2ap) have been synthesized and characterized by X-ray crystallography, thermogravimetry, element analysis and Fourier-transform infared spectroscopy. (2apH)4(H3P2O6)2(H2P2O6)∙2H2O (1), (2apH)2(H2P2O6)∙2H2O...

Room temperature ferroelectric copper(ii) coordination polymers based on amino acid hydrazide ligands

This work brings into focus the superior coordination properties and facile applicability of amino acid hydrazide ligands for the design of molecular magnets and molecular ferroelectrics.

Single-Crystal-to-Single-Crystal Transformation and Catalytic Properties of New Hybrid Perhalidometallates

Two new organic–inorganic salts of perhalidometallates with protonated organic amine cations have been synthesized and characterized by X-ray diffraction and thermal analysis. (CHBMAH2)ZnBr4·3/2H2O 1 and (CHBMAH2)ZnCl4 4 [(CHBMAH2)2+: 1,3-cyclohexanebis(methylammonium)] were obtained in single-crystal form. The crystal packing in all of the obtained compounds is governed by the formation of various non-covalent intermolecular forces between tetrahalidometallate anions and organic cations, assisted by water molecules in the hydrates. Hirshfeld surface analysis denotes that the most important contributions to the crystal packing are X···H/H···X (X: Cl, Br, I) and H···H interactions. Interestingly, the compound 1,3-cyclohexanebis(methylammonium)tetrachloridozincate (II) dihydrate, (CHBMAH2)ZnCl4·2H2O 2, undergoes thermally-triggered single-crystal-to-single-crystal (SCSC) transformation upon dehydration to produce a supramolecular solid compound, 1,3-cyclohexanebis(methylammonium) tetrachloridozincate (II), (CHBMAH2)ZnCl4 4. The SCSC transformation causes changes in the lattice parameters and a structural rearrangement. Furthermore, the catalytic properties of (CHBMAH2)ZnCl4·2H2O 2 and (CHBMAH2)CdI4·2H2O 3 have been explored in the acetalization process using various uncommon alcohols, beyond methanol or ethanol, for the first time in the literature, with outstanding results, and opening the door to the formation of alternative acetals.

An unusual high-frequency ferroelectric obtained via the post-synthetic modification of a metal-organic framework

Ferroelectrics as crucial functional materials have attracted much interest since ferroelectricity was discovered in 1920. Herein, an unusual high-frequency ferroelectric, (CH3)2NH·HCl@Cd-MOF, was successfully obtained through a dual-step synthetic methodology. A chiral porous Cd-MOF with a channel size of 6.8 × 6.8 Å was synthesized via self-assembly of chiral Schiff-base ligands and Cd2+ ions. Subsequently, polarizable (CH3)2NH·HCl was introduced into the channels of the Cd-MOF and hence the host-guest system (CH3)2NH·HCl@Cd-MOF was formed. The as-synthesized (CH3)2NH·HCl@Cd-MOF displays obvious ferroelectricity at a high frequency of 1 kHz. Such a high-frequency ferroelectric is extremely rare among MOF-based ferroelectric materials, and the high-frequency ferroelectricity means that (CH3)2NH·HCl@Cd-MOF has potential for use in ferroelectric memories. The results again demonstrate that post-synthetic modification is a promising approach for achieving rational and precise design of ferroelectric materials.

Two 1D homochiral heterometallic chains: crystal structures, spectra, ferroelectricity and ferromagnetic properties

Two new homo chiral Cu–Ln (Ln = Gd and Ho) compounds bearing a chiral Schiff base ligand (1R,3S)-N′,N′′-bis[3-methoxysalicylidene]-1,3-diamino-1,2,2-trimethylcyclopentane (H₂L) have been synthesized and characterized by elemental analysis, IR spectroscopic and single-crystal X-ray diffraction techniques. The compounds were found to exhibit 1D zig-zag skeletons with double μ-1,5 bridging dicyanamide anions. Circular dichroism (CD) spectra have been used to verify their chiroptical activities. Magnetic studies suggest that 1 and 2 hold the same magnetic behavior with the dinuclear compounds presenting ferromagnetic interaction. Furthermore, both compounds show ferroelectricity with the remnant polarization (P_r) value of 0.23 and 0.18 μC cm⁻² at room temperature, respectively.

Two homochiral 1D heterometallic chains are potential multifunctional molecules coexisting optical activity, ferromagnetic and ferroelectric properties.

Role of the B′-site metal ion in the framework structures and dielectric transitions in host–guest type cyanometalates (HIm)2[B′Co(CN)6] (HIm = imidazolium cation)

The B′-site alkali metal ion in (HIm)₂[B′Co(CN)₆] plays a key role in the change of the framework structures and the dynamic behaviours of the guest.

The dehydration process in the DL-phenylglycinium trifluoromethanesulfonate monohydrate crystal revealed by XRD, vibrational and DSC studies

Thermal analysis, X-ray diffraction and temperature-dependent IR spectroscopy were used to study the dehydration process of crystalline DL-phenylglycinium trifluoromethanesulfonate monohydrate (PGTFH), C₈H₁₀NO₂⁺·CF₃SO₃^-·H₂O. PGTFH dehydrates in one step centred at 353 K and crystallizes in the monoclinic space group C2/c, whereas the anhydrous compound (PGTF) crystallizes in the triclinic space group P-1. The dehydration process in PGTFH is preceded by a weakening of both the noncovalent aromatic-aromatic interactions and the packing contacts. This process is accompanied by the breakage of medium-strength O-H...O hydrogen bonds between ions inside layers and a reorganization of the ions within the layers. This reorganization results in the formation of two different ion pairs (DL-phenylglycinium trifluoromethanesulfonate) and the formation of a new hydrogen-bond network. The dehydration process does not destroy the nature of the crystal structure. Both crystals, i.e. hydrated and anhydrous, have a layered structure, although the layers of each crystal are arranged somewhat differently.

Isostructural phase transition, quasielastic neutron scattering and magnetic resonance studies of a bistable dielectric ion-pair crystal [(CH3)2NH2]2KCr(CN)6

We have synthesised and characterised a novel organic-inorganic hybrid crystal, [(CH3)2NH2]2KCr(CN)6. The thermal DSC, TMA, DTG and DTA analyses indicate two solid-to-solid structural phase transitions (PTs). According to the X-ray diffraction experiments, the first PT at 220 K is isostructural, since it does not involve a change of the space group. This transition occurs between the states, where the (CH3)2NH2+ cations are orientationally disordered and ordered (frozen). The other reversible PT at 481 K leads to a melt-like phase similar to the one observed in plastic crystals or polar liquids. Dielectric spectroscopy has been used to characterise the switching properties of the dipole moments in the vicinity of the PTs. Continuous-wave electron paramagnetic resonance spectroscopy was employed to investigate the effect of ordering on the local environment of the Cr3+ ions. We have also applied the quasielastic neutron scattering (QENS) technique as well as 1H NMR spectroscopy to measure the dynamics of the (CH3)2NH2+ cations residing in the inorganic framework.

Ultrahigh phase transition temperature in a metal–halide perovskite-type material containing unprecedented hydrogen bonding interactions

An ABX₃ perovskite-type compound (N,N-dimethylethanolammonium)CdCl₃ with hydrogen bonding interactions between organic ammonium cations undergoes a phase transition at super-high temperatures.

Chemical exchange at the ferroelectric phase transition of lead germanate revealed by solid state 207Pb nuclear magnetic resonance

Multi-dimensional NMR is used to quantitatively identify a mixed order–disorder and displacive mechanism for the ferroelectric phase transition of lead germanate.