A Two-Fold Interpenetrating Porous Metal–Organic Framework with a Large Solvent-Accessible Volume: Gas Sorption and Luminescent Properties

A luminescent porous metal–organic framework based on π-electron-rich tricarboxylate has been solvothermally prepared and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analyses, and single-crystal X-ray diffraction analysis. This compound is a 2-fold interpenetrating framework with a large solvent-accessible volume and exhibits gas sorption behaviors for N₂, H₂, and CO₂ gases and relatively strong interactions between CO₂ and the framework. Furthermore, it also shows interesting guest-responsive luminescent changes toward different solvent molecules

Temperature-Dependent Crystal Self-Assembly, Disassembly, and Reassembly Among Three Cadmium(II) Carboxylate-Phosphinates

A metastable three-dimensional cadmium­(II) coordination polymer with (2-carboxyethyl)­(phenyl)­phosphinate (L^2–) and 4,4′-bipyridine (bipy) as ligands, namely, [Cd­(L)­(bipy)­(H₂O)₂] (<b>1</b>), can be converted to two new two-dimensional/three-dimensional varieties under hydrothermal treatments at different temperatures, that is, [Cd­(L)­(bipy)] (<b>2</b>) and [Cd­(L)­(bipy)_0.5]·0.5H₂O (<b>3</b>). Their syntheses, crystal structures, structural transformations, and luminescent properties are presented. In addition, <b>1</b> shows a second harmonic generation response that is ∼0.3 times that of KDP (KH₂PO₄)

Temperature-Dependent Crystal Self-Assembly, Disassembly, and Reassembly Among Three Cadmium(II) Carboxylate-Phosphinates

A metastable three-dimensional cadmium­(II) coordination polymer with (2-carboxyethyl)­(phenyl)­phosphinate (L^2–) and 4,4′-bipyridine (bipy) as ligands, namely, [Cd­(L)­(bipy)­(H₂O)₂] (<b>1</b>), can be converted to two new two-dimensional/three-dimensional varieties under hydrothermal treatments at different temperatures, that is, [Cd­(L)­(bipy)] (<b>2</b>) and [Cd­(L)­(bipy)_0.5]·0.5H₂O (<b>3</b>). Their syntheses, crystal structures, structural transformations, and luminescent properties are presented. In addition, <b>1</b> shows a second harmonic generation response that is ∼0.3 times that of KDP (KH₂PO₄)

Matching of Host–Guest Symmetry/Orientation and Molecular Dynamics in Two Double Perovskite-Like Azido Coordination Polymers

Two new double perovskite-like azido coordination polymers with trimethylammonium as the guest cation, namely, (Me₃NH)₂[CrNa­(N₃)₆] and (Me₃NH)₂[CrK­(N₃)₆], have been prepared. The molecular dynamics for both compounds are investigated and are clearly uncovered by the first-principles molecular dynamics simulation and the significant dielectric relaxation. Structural analyses of these compounds in combination with their analogue (Me₃NH)­[Mn­(N₃)₃] reveal that the guest trimethylammonium has flexible structural adaptability, especially with a variety of disordered distributions, to match the different symmetries of varied metal-azido frameworks. Interestingly, the replacement of the divalent metal ion by mixed monovalent/trivalent metal ions can change the symmetry, shape, and charge distribution of the host cage unit; thus it may influence and regulate the arrangement of the guest inclusion and its molecular dynamics as well as the structural phase transition

Crystalline Supramolecular Gyroscope with a Water Molecule as an Ultrasmall Polar Rotator Modulated by Charge-Assisted Hydrogen Bonds

A new strategy for the construction of crystalline molecular rotors is presented. The combination of a conformation-modifiable macrocyclic host and two cooperative guests affords one supramolecular gyroscope-like compound, (<i>t</i>-BuNH₃)­(18-crown-6)­[ZnCl₃(H₂O)], in which the coordinated water molecule functions as an ultrasmall polar rotator, revealed by its significant dielectric relaxation and the molecular dynamics simulations. In addition, such a compound can reversibly undergo a polar-to-polar phase transition triggered by the changed conformation of the 18-crown-6 host, leading to a switchable on/off rotation of water molecule, well controlled by strength and direction of charge-assisted hydrogen bonds

Crystalline Supramolecular Gyroscope with a Water Molecule as an Ultrasmall Polar Rotator Modulated by Charge-Assisted Hydrogen Bonds

A new strategy for the construction of crystalline molecular rotors is presented. The combination of a conformation-modifiable macrocyclic host and two cooperative guests affords one supramolecular gyroscope-like compound, (<i>t</i>-BuNH₃)­(18-crown-6)­[ZnCl₃(H₂O)], in which the coordinated water molecule functions as an ultrasmall polar rotator, revealed by its significant dielectric relaxation and the molecular dynamics simulations. In addition, such a compound can reversibly undergo a polar-to-polar phase transition triggered by the changed conformation of the 18-crown-6 host, leading to a switchable on/off rotation of water molecule, well controlled by strength and direction of charge-assisted hydrogen bonds

Anion Effects on Lanthanide(III) Tetrazole-1-acetate Dinuclear Complexes Showing Slow Magnetic Relaxation and Photofluorescent Emission

Three types of lanthanide complexes based on the tetrazole-1-acetic acid ligand and the 2,2′-bipyridine coligand were prepared and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analyses; the formulas of these complexes are [Ln₂(1-tza)₄(NO₃)₂(2,2′-bipy)₂] (Ln = Sm (<b>1</b>), Eu (<b>2</b>), Gd (<b>3</b>), Tb (<b>4</b>), Dy (<b>5</b>)), [Dy₂(1-tza)₄Cl₂(2,2′-bipy)₂] (<b>6</b>), and [Yb₂(1-tza)₄(NO₃)₂(2,2′-bipy)₂] (<b>7</b>) (1-tza = tetrazole-1-acetate and 2,2′-bipy = 2,2′-bipyridine). They are dinuclear complexes possessing similar structures but different lanthanide­(III) ion coordination geometries because of the distinction of peripheral anions (such as NO₃^– and Cl^–) and the effect of lanthanide contraction. The variable-temperature magnetic susceptibilities of <b>1</b>–<b>6</b> were measured. Both Dy^III complexes (<b>5</b> and <b>6</b>) display field-induced single-molecule magnet behaviors. Ab initio calculations revealed that the Dy^III complex <b>6</b> possesses a more anisotropic Dy^III ion in comparison to that in <b>5</b>. The room-temperature photoluminescence spectra of Sm^III (<b>1</b>), Eu^III (<b>2</b>), Tb^III (<b>4</b>), and Dy^III (<b>5</b> and <b>6</b>) complexes exhibit strong characteristic emissions in the visible region, whereas the Yb^III (<b>7</b>) complex shows near-infrared (NIR) luminescence

Crystalline Supramolecular Gyroscope with a Water Molecule as an Ultrasmall Polar Rotator Modulated by Charge-Assisted Hydrogen Bonds

A new strategy for the construction of crystalline molecular rotors is presented. The combination of a conformation-modifiable macrocyclic host and two cooperative guests affords one supramolecular gyroscope-like compound, (<i>t</i>-BuNH₃)­(18-crown-6)­[ZnCl₃(H₂O)], in which the coordinated water molecule functions as an ultrasmall polar rotator, revealed by its significant dielectric relaxation and the molecular dynamics simulations. In addition, such a compound can reversibly undergo a polar-to-polar phase transition triggered by the changed conformation of the 18-crown-6 host, leading to a switchable on/off rotation of water molecule, well controlled by strength and direction of charge-assisted hydrogen bonds

Structural Transition in the Perovskite-like Bimetallic Azido Coordination Polymers: (NMe₄)₂[B′·B″(N₃)₆] (B′ = Cr³⁺, Fe³⁺; B″ = Na⁺, K⁺)

Through in situ variable-temperature single-crystal X-ray diffraction analysis, a solid–solid structural phase transition induced by the successive displacements of the [NMe₄]⁺ guest and a subsequent abrupt order–disorder transform for both the cationic guest and the cage-like framework was tracked in four perovskite-like bimetallic azido coordination polymers: (NMe₄)₂­[B′·B″(N₃)₆] (B′ = Cr³⁺, Fe³⁺; B″ = Na⁺, K⁺). Such structural transition was also confirmed by differential scanning calorimeter measurement, variable-temperature powder X-ray diffraction analysis, and variable-temperature dielectric permittivity measurement, as well as molecular dynamics simulation. Conclusively, these compounds provide a good host–guest model for understanding and modulating the thermal motion behavior of the [NMe₄]⁺ guest in various confined spaces constructed by the perovskite-like azido frameworks

Plastic Crystals with Polar Halochromate Anion: Thermosensitive Dielectrics Based upon Plastic Transition and Dipole Rotation

Plastic crystals functioning with rotatable components offer new opportunities in areas such as modern optoelectronic materials. Here, by taking advantage of controllable rotation of the polar component within the ion-pair plastic-crystal system, we present two such crystals, namely, (Et₄N)­(CrO₃X) (X = Cl or Br), which are unusual examples exhibiting two-staged thermosensitive dielectric responses above room temperature. The frequency-dependent response in the first stage is due to the structural phase transitions, whereas that in the second stage is induced by dynamic rotation of the polar halochromate anions in their NaCl-type plastic-crystal phases. The intrinsic mechanisms were also explicated by molecular dynamics simulations, providing a direct insight into the dynamic characteristics of these two compounds. These studies show that ionic plastic crystals functioning with polar groups are an attractive candidate as sensitive thermoresponsive dielectric materials