Syntheses, Structures, and Magnetic Properties of a Series of Heterotri-, Tetra- and Pentanuclear LnIII⁻CoII Compounds.

Three types of Ln(III)⁻Co(II) heterometallic compounds, LnCo2(L1)7(bipy)2 (Ln = Pr-1, Eu-2, Sm-3, Gd-4, Tb-5, Dy-6) (L1 = 4-chlorobenzoate, bipy = 2,2'-bipyridine), Ln2Co2(L2)10(bipy)2 (Ln = Sm-7, Gd-8, Tb-9, Dy-10, Ho-11, Er-12, Yb-13), (L2 = 2,4-dichlorobenzoate, bipy = 2,2'-bipyridine, phen = 1,10-phenanthroline), and Ln2Co3(L1)12(bipy)2 (Ln = Ho-14, Er-15, Yb-16), were synthesized under hydrothermal conditions and characterized by single crystal X-ray diffraction, IR spectroscopy and magnetic measurements. Structural analyses revealed that 14⁻16 take on a unique linear pentanuclear structural motif. Interestingly, the Ho-containing compound 14 exhibits magnetic relaxation behavior.

Effect of toll-like receptor 3 agonist poly I:C on intestinal mucosa and epithelial barrier function in mouse models of acute colitis.

AIM: To investigate potential effects of poly I:C on mucosal injury and epithelial barrier disruption in dextran sulfate sodium (DSS)-induced acute colitis. METHODS: Thirty C57BL/6 mice were given either regular drinking water (control group) or 2% (w/v) DSS drinking water (model and poly I:C groups) ad libitum for 7 d. Poly I:C was administrated subcutaneously (20 µg/mouse) 2 h prior to DSS induction in mice of the poly I:C group. Severity of colitis was evaluated by disease activity index, body weight, colon length, histology and myeloperoxidase (MPO) activity, as well as the production of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin 17 (IL-17) and interferon-γ (IFN-γ). Intestinal permeability was analyzed by the fluorescein isothiocyanate labeled-dextran (FITC-D) method. Ultrastructural features of the colon tissue were observed under electron microscopy. Expressions of tight junction (TJ) proteins, including zo-1, occludin and claudin-1, were measured by immunohistochemistry/immunofluorescence, Western blot and real-time quantitative polymerase chain reaction (RT-qPCR). RESULTS: DSS caused significant damage to the colon tissue in the model group. Administration of poly I:C dramatically protected against DSS-induced colitis, as demonstrated by less body weight loss, lower disease activity index score, longer colon length, colonic MPO activity, and improved macroscopic and histological scores. It also ameliorated DSS-induced ultrastructural changes of the colon epithelium, as observed under scanning electron microscopy, as well as FITC-D permeability. The mRNA and protein expressions of TJ protein, zo-1, occludin and claudin-1 were also found to be significantly enhanced in the poly I:C group, as determined by immunohistochemistry/immunofluorescence, Western blot and RT-qPCR. By contrast, poly I:C pretreatment markedly reversed the DSS-induced up-regulated expressions of the inflammatory cytokines TNF-α, IL-17 and IFN-γ. CONCLUSION: Our study suggested that poly I:C may protect against DSS-induced colitis through maintaining integrity of the epithelial barrier and regulating innate immune responses, which may shed light on the therapeutic potential of poly I:C in human colitis.

Synthesis, structure, and magnetic properties of Dy2Co2L10(bipy)2 and Ln2Ni2L10(bipy)2, Ln = La, Gd, Tb, Dy, and Ho: slow magnetic relaxation in Dy2Co2L10(bipy)2 and Dy2Ni2L10(bipy)2.

The 3,5-dichlorobenzoate anion, L(-), serves as a bridging ligand and 2,2'-bipyridine, bipy, as a terminal bidentate ligand to yield, through hydrothermal syntheses, the tetranuclear clusters Dy2Co2L10(bipy)2, 1, and Ln2Ni2L10(bipy)2, where Ln is the trivalent La, 2, Gd, 3, Tb, 4, Dy, 5, or Ho, 6, ion. Single-crystal X-ray diffraction reveals that the six complexes are all isomorphous with the monoclinic P21/c space group and with lattice parameters that decrease with the lanthanide contraction. The two cobalt(II) or nickel(II) and two Ln(III) cations are linked by the 10 L(-) anions to generate Dy2Co2 or Ln2Ni2 3d-4f cationic heteronuclear clusters with a slightly bent Co···Dy···Dy···Co or Ni···Ln···Ln···Ni arrangement. Direct current magnetic susceptibility studies reveal that the complexes are essentially paramagnetic, with room-temperature χ(M)T values close to the expected values for two cobalt(II) or nickel(II) and two Ln(III) cations. The temperature dependence of χ(M)T for 1 and 5 is well reproduced by ab initio calculations with the inclusion of weak magnetic exchange between the cobalt(II) or nickel(II) and a dysprosium(III) and between two dysprosium(III) ions. The calculated magnetic exchange parameters are J(Dy-Co) = 0.2 cm(-1) and J(Dy-Dy) = 0.02 cm(-1) for 1 and J(Dy-Ni) = -0.2 cm(-1) and J(Dy-Dy) = 0.03 cm(-1) for 5. Alternating current magnetic susceptibility studies reveal that 1 and 5 exhibit slow magnetic relaxation with effective energy barriers, Ueff, for the reversal of the magnetization for 1 of 82(2) cm(-1) in a 0 Oe dc bias field and 79.4(5) cm(-1) in a 1000 Oe dc bias field and, for 5, 73(1) cm(-1) in a 0 dc bias field; the calculated energies of 66.1(1) and 61.0(1) cm(-1) for the first excited spin-orbit state of dysprosium(III) in 1 and 5 agree rather well with these effective energy barriers. The entire Arrhenius plots of the logarithm of τ, the relaxation rate of the magnetization in 1 and 5, have been fit with contributions from quantum tunneling, direct Raman scattering, and Orbach thermal processes. The observation of a low-temperature magnetization reversal mechanism in 5 but not in 1 may be understood through the calculated exchange energy spectrum in their ground state.

Two acentric mononuclear molecular complexes with unusual magnetic and ferroelectric properties.

Two acentric, i.e., noncentrosymmetric, mononuclear complexes, Co(5-ATZ)(4)Cl(2), 1, and Cu(5-ATZ)(4)Cl(2), 2, where 5-ATZ is the monodentate 5-amino-1-H-tetrazole ligand, have been prepared and characterized. Both complexes crystallize in the tetragonal system with the P4nc space group, a member of the polar noncentrosymmetric 4mm class, and thus both 1 and 2 can exhibit ferroelectric and nonlinear optical properties. Magnetic studies indicate that 1 is a paramagnetic high-spin cobalt(II) complex with a rather extensive spin-orbit coupling, modeled as a zero-field splitting parameter, D, of ±91(3) cm(-1) and with very weak long-range antiferromagnetic exchange interactions. Direct current (dc) and ac magnetic studies indicate that 2 is a paramagnetic copper(II) complex that exhibits weak ferromagnetic exchange interactions below 15 K. Both 1 and 2 exhibit ferroelectric hysteresis loops at room temperature with remanent polarizations of 0.015 µC/cm(2) and coercive electric fields of 5.5 and 5.7 kV/cm, respectively.

Unprecedented (3,4)-connected metal-organic frameworks (MOFs) with 3-fold interpenetration and considerable solvent-accessible void space.

Via solvothermal synthesis, the self-assembly of CuCl(2), 1,3,5-benzenetricarboxylic acid, and N,N'-bis(4-pyridylformamide)-1,4-benzene in DMF generated a novel coordination polymer containing an unprecedented (3,4)-connected network; 3-fold interpenetration and considerable solvent-accessible cavities occupied by reversible guest water molecules were also observed.

One-pot synthesis of Schiff-base-containing Ni8 clusters: solvothermal synthesis, structure, and magnetic properties.

Solvothermal in situ generation of a Schiff-base ligand (L) in the presence NiCl(2) and trimesic acid (H(3)BTC) in ethanol resulted in clusters, Ni(8)(L)(4)Cl(8).(H(2)O)(0.5), consisting of three different coordination geometries, four paramagnetic and four diamagnetic Ni(II), exhibiting both ferromagnetic and antiferromagnetic exchange interactions.

Synthesis, structure, and characterization of three series of 3d-4f metal-organic frameworks based on rod-shaped and (6,3)-sheet metal carboxylate substructures.

Three series of porous lanthanide metal-organic coordination polymers, namely [Cu(bpy)Ln(3)(ip)(5)(Hip)(H(2)O)] [Ln = Er (1a), Y (1b), Eu (1c); bpy = 2,2'-bipyridine, H(2)ip=isophthalic acid], [Cu(3)(bpy)(2)Ln(2)(ip)(6)(H(2)O)(5)] [Ln = Yb (2a), Gd (2b), Tb (2c)], and [Cu(3)Ln(2)(ip)(6)] [Ln = Eu (3a), Gd (3b)] have been synthesized hydrothermally by the reaction of the combination of 3d-4f metal centers and N-/O-donor ligands. X-ray diffraction analyses reveal that polymers 1a-c and 2a-c, as well as 3a, b are isomorphous in structure. Polymers 1a-c consist of 3D alpha-Po networks based on a inorganic rod-shaped secondary building units (SBUs) of {Er(6)Cu(2)(bipy)(2)(O(2)C)(11)} which are 27.03 A in length. Polymers 2a-c also contain 3D alpha-Po networks, constructed from shorter (14.79 A) but similarly rod-shaped SBUs of {Yb(2)Cu(3)(bpy)(2)(O(2)C)(12)}. The structure also contains hydrogen-bonded (H(2)O)(6) chains which can be reversibly dehydrated/rehydrated. Polymers 3a, b contain metal carboxylate substructures which have 2D (6,3) topologies; these layers are bridged by the ip(2-) ligands to give an overall 3D network which contains two sorts of cavities. This series of Ln-Cu coordination polymers are further characterized by antiferromagnetic behavior.

A unique cyanide-bridged three-dimensional (3-D) copper(II)-copper(I) mixed-valence polymer containing 1-D water tapes with cyclic pentamer units.

A unique cyano-bridged copper(II)-copper(I) mixed-valence polymer, {[Cu(3)(CN)(4)(H(2)O)(3)](H(2)O)(2)}(n) (1), has been prepared and structurally determined by X-ray diffraction. The cyanide anions with (mu(2),eta(2)) and (mu(3),eta(2)) bridging modes connect the copper centers into a complicated zeolite-like 3-D network. Of further interest, coordinated and lattice water molecules in this structure form 1-D hydrogen-bonded water tapes consisting of linked cyclic pentamer clusters.