Guan-Cheng Xu

Coexistence of magnetic and electric orderings in the metal-formate frameworks of [NH4][M(HCOO)3].

A family of three-dimensional chiral metal-formate frameworks of [NH(4)][M(HCOO)(3)] (M = Mn, Fe, Co, Ni, and Zn) displays paraelectric to ferroelectric phase transitions between 191 and 254 K, triggered by disorder-order transitions of NH(4)(+) cations and their displacement within the framework channels, combined with spin-canted antiferromagnetic ordering within 8-30 K for the magnetic members, providing a new class of metal-organic frameworks showing the coexistence of magnetic and electric orderings.

Disorder―Order Ferroelectric Transition in the Metal Formate Framework of [NH4][Zn(HCOO)3]

A three-dimensional chiral metal formate framework compound, [NH(4)][Zn(HCOO)(3)], undergoes a paraelectric-ferroelectric phase transition at 191 K triggered by the disorder-order transition of NH(4)(+) cations within the structure.

Phase Transitions, Prominent Dielectric Anomalies, and Negative Thermal Expansion in Three High Thermally Stable Ammonium Magnesium–Formate Frameworks

We present three Mg-formate frameworks, incorporating three different ammoniums: [NH4][Mg(HCOO)3] (1), [CH3CH2NH3][Mg(HCOO)3] (2) and [NH3(CH2)4NH3][Mg2(HCOO)6] (3). They display structural phase transitions accompanied by prominent dielectric anomalies and anisotropic and negative thermal expansion. The temperature-dependent structures, covering the whole temperature region in which the phase transitions occur, reveal detailed structural changes, and structure-property relationships are established. Compound 1 is a chiral Mg-formate framework with the NH4(+) cations located in the channels. Above 255 K, the NH4(+) cation vibrates quickly between two positions of shallow energy minima. Below 255 K, the cations undergo two steps of freezing of their vibrations, caused by the different inner profiles of the channels, producing non-compensated antipolarization. These lead to significant negative thermal expansion and a relaxor-like dielectric response. In perovskite 2, the orthorhombic phase below 374 K possesses ordered CH3CH2NH3(+) cations in the cubic cavities of the Mg-formate framework. Above 374 K, the structure becomes trigonal, with trigonally disordered cations, and above 426 K, another phase transition occurs and the cation changes to a two-fold disordered state. The two transitions are accompanied by prominent dielectric anomalies and negative and positive thermal expansion, contributing to the large regulation of the framework coupled the order-disorder transition of CH3CH2NH3(+). For niccolite 3, the gradually enhanced flipping movement of the middle ethylene of [NH3(CH2)4NH3](2+) in the elongated framework cavity finally leads to the phase transition with a critical temperature of 412 K, and the trigonally disordered cations and relevant framework change, providing the basis for the very strong dielectric dispersion, high dielectric constant (comparable to inorganic oxides), and large negative thermal expansion. The spontaneous polarizations for the low-temperature polar phases are 1.15, 3.43 and 1.51 μC cm(-2) for 1, 2 and 3, respectively, as estimated by the shifts of the cations related to the anionic frameworks. Thermal and variable-temperature powder X-ray diffraction studies confirm the phase transitions, and the materials are all found to be thermally stable up to 470 K.

Single-Molecule-Magnet Behavior in a Fe12Sm4 Cluster

Through the combination of Sm(III) spin carriers with a Fe(III) system, the largest Fe-Ln cluster so far has been synthesized. To our knowledge, the new complex, Fe(12)Sm(4), is the first Sm(III) single-molecule magnet. Furthermore, Fe(12)La(4) and Fe(12)Gd(4) have also been synthesized to help understand the magnetic exchange interactions and origin of magnetic anisotropy in Fe(12)Sm(4).

Abrupt spin transition around room temperature and light induced properties in FeII complexes with N4O2 coordination sphere

Mononuclear spin-crossover complex Fe(II)(L)(2) x CH(3)OH (1 x CH(3)OH) and its desolvated product 1 exhibit abrupt spin transitions around room temperature. 1 also shows a light induced excited spin state trapping (LIESST) effect and a light induced thermal hysteresis (LITH) phenomenon at low temperature.

A novel tricyanoruthenium(III) building block for the construction of bimetallic coordination polymers

Reaction of excess cyanide with a ruthenium(VI) nitrido complex bearing a tridentate Schiff base ligand produces a novel tricyanoruthenium(III) complex in which nucleophilic substitution of an imine hydrogen of the Schiff base by cyanide has occurred, this complex is a useful building block for the construction of 3d-Ru(III) magnetic materials.

Syntheses, crystal structures and luminescent properties of four Zn(II) coordination polymers with pyrazolone derivatives and 4,4′-bipyridine

Four new Zn(II) coordination polymers, {[Zn(L1)(4,4′-bipy)]·0.52CH3OH}n (1), {[Zn(L2)(4,4′-bipy)]·CH3OH}n (2), {[Zn3(L3)3(4,4′-bipy)0.5]·3CH3OH}n (3), {[Zn(L4)(4,4′-bipy)]·2CH3OH}n (4) (H2L1 = N-(1,3-diphenyl-4-propylene-5-pyrazolone) p-nitrobenzoylhydrazide, H2L2 = N-(1-phenyl-3-benzyl-4-propylene-5-pyrazolone) p-nitrobenzoylhydrazide, H2L3 = N-(1,3-diphenyl-4-propylene-5-pyrazolone) isoniazid, H2L4 = N-(1-phenyl-3-benzyl-4-propylene-5-pyrazolone) isoniazid, 4,4′-bipy = 4,4′-bipyridine) have been synthesized by the reactions of zinc acetate with the corresponding 4-acyl pyrazolone derivatives and 4,4′-bipyridine. The X-ray diffraction analyses revealed that complexes 1 and 2 exhibit 1D zigzag chain structures. The ligands (H2L1 and H2L2) serve as divalent tridentate chelating agents to coordinate with Zn(II) atoms. Complex 3 displays a complicated pillared-layer 3D framework and the ligands H2L3 adopt two different kinds of coordination modes. In the case of complex 4, the octahedral Zn(II) atoms are connected by the tetradentate ligands to form a 1D chain, then the 4,4′-bipyridine molecules further connect the 1D chains along the axial direction to generate a 2D network structure. The effect of the coordination groups and substituents at the 3-position of the ligands on the structure of the complexes have been discussed. Additionally, the luminescent properties of the complexes have been investigated in the solid state.

Study of fluorescence properties of several 4-acyl pyrazolone derivatives and their Zn (II) complexes.

Fluorescence properties of four 4-acyl pyrazolone derivatives (H(2)L(1)=N-(1,3-diphenyl-4-propylene-5-pyrazolone)-salicylidene hydrazone (1), H(2)L(2)=N-(1,3-diphenyl-4-ethylene-5-pyrazolone)-salicylidene hydrazone (2), H(2)L(3)=N-(1,3-diphenyl-4-benzylidene-5-pyrazolone)-salicylidene hydrazone (3), H(2)L(4)=N-(1,3-diphenyl-4-phenylethylene-5-pyrazolone)-salicylidene hydrazone (4), and their Zn (II) complexes: (Zn(H(2)L(1))(2) (5), Zn(H(2)L(2))(2).3CH(3)OH (6), Zn(H(2)L(3))(2).2CH(3)OH (7), and Zn(4)(H(2)L(4))(4) (8)) were studied at room temperature. It was revealed that these compounds show different fluorescence properties both in the solid state and in solution. Density functional theory (DFT) calculations on ligands 1-4 were also performed to further understand their emission properties. The calculation results indicate that the energy gaps between the highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) of these ligands are in the following order 1>2>3, which is consistent with the redshift of the emission spectra.

A novel pyrazolone-based derivative induces apoptosis in human esophageal cells via reactive oxygen species (ROS) generation and caspase-dependent mitochondria-mediated pathway

Pyrazolone complexes have strong bio-activity but the anti-tumor mechanism of pyrazolone-based metal complexes is not fully understood. In this study, the inhibitory effect and possible mechanism of a novel pyrazolone-based derivative compound (Cd-PMPP-SAL) on human esophageal cancer cells were investigated. We found that Cd-PMPP-SAL inhibited the proliferation of Eca-109 cells in a dose-dependent manner and induced the apoptosis in the cells. Interestingly, Cd-PMPP-SAL promoted the production of ROS, loss of mitochondrial membrane potential, PARP cleavage and activation of caspase-3/9. These results suggest Cd-PMPP-SAL-induced apoptosis might be mediated by the increased production of ROS and caspase-dependent mitochondria-mediated pathway. These results suggest that Cd-PMPP-SAL is a potential candidate for the treatment of esophageal cancer.

Preparation and exceptional adsorption performance of porous MgO derived from a metal–organic framework

Porous MgO materials have unique and highly attractive properties. In this paper, porous MgO microstructures with hexagonal and double hexagonal pyramid architectures (MgO-hex and MgO-dhp) were prepared simply by annealing Mg-based metal–organic framework [NH4][Mg(HCOO)3]. The monodisperse porous MgO-hex and MgO-dhp products inherit the morphologies of the [NH4][Mg(HCOO)3] precursors and have large surface areas. The adsorption performance of porous MgO-hex and MgO-dhp were systematically tested towards Congo red (CR) as a model pollutant. The adsorption capacities are 1380 mg g−1 for MgO-hex and 1413 mg g−1 for MgO-dhp toward CR after 150 minutes at the initial concentration of 1000 mg L−1. The prepared MgO materials exhibit potential applications in wastewater treatment. The experimental data were fitted by two isotherm models, and the adsorption isotherm obeys the Langmuir model. Moreover, the kinetic studies indicate that the kinetic data followed a pseudo-second-order model.