Tuning Slow Magnetic Relaxation in a Two-Dimensional Dysprosium Layer Compound through Guest Molecules.

A novel two-dimensional dysprosium(III) complex, [Dy(L)(CH3COO)]·0.5DMF·H2O·2CH3OH (1), has been successfully synthesized from a new pyridine-N-oxide (PNO)-containing ligand, namely, N'-(2-hydroxy-3-methoxybenzylidene)pyridine-N-oxidecarbohydrazide (H2L). Single-crystal X-ray diffraction studies reveal that complex 1 is composed of a dinuclear dysprosium subunit, which is further extended by the PNO part of the ligand to form a two-dimensional layer. Magnetic studies indicate that complex 1 shows well-defined temperature- and frequency-dependent signals under a zero direct-current (dc) field, typical of slow magnetic relaxation with an effective energy barrier Ueff of 33.6 K under a zero dc field. Interestingly, powder X-ray diffraction and thermogravimetric analysis reveal that compound 1 undergoes a reversible phase transition that is induced by the desorption and absorption of methanol and water molecules. Moreover, the desolvated sample [Dy(L)(CH3COO)]·0.5DMF (1a) also exhibits slow magnetic relaxation but with a higher anisotropic barrier of 42.0 K, indicating the tuning effect of solvent molecules on slow magnetic relaxation.

A robust microfluidic device for the synthesis and crystal growth of organometallic polymers with highly organized structures.

A simple and robust microfluidic device was developed to synthesize organometallic polymers with highly organized structures. The device is compatible with organic solvents. Reactants are loaded into pairs of reservoirs connected by a 15 cm long microchannel prefilled with solvents, thus allowing long-term counter diffusion for self-assembly of organometallic polymers. The process can be monitored, and the resulting crystalline polymers are harvested without damage. The device was used to synthesize three insoluble silver acetylides as single crystals of X-ray diffraction quality. Importantly, for the first time, the single-crystal structure of silver phenylacetylide was determined. The reported approach may have wide applications, such as crystallization of membrane proteins, synthesis and crystal growth of organic, inorganic, and polymeric coordination compounds, whose single crystals cannot be obtained using traditional methods.

Cytochalasans from the Endophytic Fungus Aspergillus sp. LE2: Their Structures, Antibacterial and NO Production Inhibitory Activities.

Six new cytochalasans-namely, aspergicytochalasins A-F (1-6)-together with five known analogs were isolated and characterized from the endophytic fungus Aspergillus sp. from the medicinal plant Lonicera japonica. The structures of the new compounds were established by NMR and MS methods as well as single crystal X-ray diffractions. Compounds 3 and 4 showed weak antibacterial activities to Staphylococcus aureus, with MIC values of 128 and 64 µg/mL, respectively. Compounds 1, 3, 5 and 6 showed inhibitory activities on NO production, with IC50 values less than 40 µM.

Structural investigation of a fucoidan containing a fucose-free core from the brown seaweed, Hizikia fusiforme.

A fucoidan, obtained from the hot-water extract of the brown seaweed, Hizikia fusiforme, was separated into five fractions by DEAE Sepharose CL-6B and Sepharose CL-6B column chromatography. All five fractions contained predominantly fucose, mannose and galactose and also contained sulfate groups and uronic acid. The fucoidans had MWs from 25 to 950 kDa. The structure of fraction F32 was investigated by desulfation, carboxyl-group reduction, partial hydrolysis, methylation analysis and NMR spectroscopy. The results showed that the sugar composition of F32 was mainly fucose, galactose, mannose, xylose and glucuronic acid; sulfate was 21.8%, and the MW was 92.7 kDa. The core of F32 was mainly composed of alternating units of -->2)-alpha-D-Man(1--> and -->4)-beta-D-GlcA(1-->, with a minor portion of -->4)-beta-D-Gal(1--> units. The branch points were at C-3 of -->2)-Man-(1-->, C-2 of -->4)-Gal-(1--> and C-2 of -->6)-Gal-(1-->. About two-thirds of the fucose units were at the nonreducing ends, and the remainder were (1-->4)-, (1-->3)- and (1-->2)-linked. About two-thirds of xylose units were at the nonreducing ends, and the remainder were (1-->4)-linked. Most of the mannose units were (1-->2)-linked, and two-thirds of them had a branch at C-3. Galactose was mainly (1-->6)-linked. The absolute configurations of the sugar residues were alpha-D-Manp, alpha-L-Fucp, alpha-D-Xylp, beta-D-Galp and beta-D-GlcpA. Sulfate groups in F32 were at C-6 of -->2,3)-Man-(1-->, C-4 and C-6 of -->2)-Man-(1-->, C-3 of -->6)-Gal-(1-->, C-2, C-3 or C-4 of fucose, while some fucose had two sulfate groups. There were no sulfate groups in either the GlcA or xylose residues.

Thermostability and photoluminescence of Dy(iii) single-molecule magnets under a magnetic field.

A series of compounds [ADyL4]·[solvent] composed of a dysprosium(iii) ion coordinated by four chelated naphthyridine-like ligands (L = 4-hydroxy-8-methyl-1,5-naphthyridine-3-carbonitrile) and an alkali metal ion (A = Na, K, Rb, Cs) were synthesized and characterized. They behave as single-molecule magnets under a zero dc field with an effective energy barrier of around 95 cm-1. Meanwhile, the main part, [ADyL4], of these SMMs is thermostable and sublimable. The geometric structures of three sublimed compounds are identical to the original ones without solvents, which is confirmed by X-ray diffraction using single crystal and powder samples. The static and dynamic magnetic properties remain unchanged before and after sublimation. Luminescence measurements at 5-77 K were performed to verify the energy gap between low-lying states and to understand the pathway of the thermal relaxation process of magnetization, as well as to inspect the tiny variation in magnetic sublevels for the ground term of Dy(iii). The photoluminescence spectra under a magnetic field (0-36 T) for the Dy-SMMs are investigated for the first time. The energy splitting of the two lowest sublevels of the ground term 6H15/2 of Dy(iii) are analyzed using the Zeeman formula.

Facile synthesis of magnetic homochiral metal-organic frameworks for "enantioselective fishing".

Magnetic functionalized homochiral metal-organic frameworks (MOFs) were prepared and applied to efficient enantioselective fishing of chiral drug intermediates. Under optimized conditions, the enantiomeric excess (ee) value as high as 85.2% was achieved for methyl phenyl sulfoxide (MPS) within 3 min.

Metal-organic frameworks built from achiral 3-(5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)benzoic acid: syntheses and structures of metal(II) complexes.

Using a novel flexible achiral ligand, 3-(5-(pyridin-4-yl)-4H-1,2,4-triazol-3-yl)benzoic acid (HL), four metal(II)-complexes formulated as ZnL2·2H2O (1), CdL2(H2O)2·8H2O (2) and ML2(H2O)·H2O (M = Co 3 and Ni 4) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1, 3 and 4 all feature a uninodal 2D layer with a 4(4)-sql topology, and two such (4,4) nets interpenetrate in a parallel manner. Complex 2 exhibits a similar 4(4)-sql topology, but no interpenetration is observed in complex 2. Among the four complexes, only complex 1 is a homochiral network, which is evidenced by the CD spectrum. In complex 1, packing of the 2D layers generates a 41 screw axis along the c direction, and two-fold axes along the a and b directions, respectively. In complex 2, the Zn(II) center lies about an inversion center, giving rise to the centrosymmetric structure of complex 2. In complexes 3 and 4, packing of the 2D units generates a 21 screw axis along the c direction in the two complexes, and an inversion center is found between two neighboring 2-fold interpenetrated layers. The work indicates that the chirality of the space group for the homochiral complex 1 comes from the supramolecular packing of the 2D layers.

Two novel Co(II) coordination polymers based on 1,4-bis(3-pyridylaminomethyl)benzene as electrocatalysts for oxygen evolution from water.

Based on the L (1,4-bis(3-pyridylaminomethyl)benzene) ligand, two MOFs formulated as Co(L)0.5(adip) (H2adip = adipic acid) (1) and Co2(L)2(5-bdc)2(H2O)2·H2O (2) (5-H2bdc = 5-nitroisophthalic acid) (2) were synthesized and structurally characterized by single-crystal X-ray diffraction. Complex 1 features a uninodal 4-connected non-interpenetrated sql/Shubnikov tetragonal plane net with {4(4).6(2)} topology. In complex 2, two L link two Co(II) centers into a quadrangular cage, and different cages are further connected by two strands of 5-bdc(2-) into a 1D chain. The two complexes both exhibit electrocatalytic activities toward generating O2 from water with lowered overpotentials and enhanced currents, and they show different UV-vis absorption spectra and thermal stabilities.

Metal(II) complexes based on 1,4-bis(3-pyridylaminomethyl)benzene: structures, photoluminescence and photocatalytic properties.

Using a novel ditopic N-donor ligand, 1,4-bis(3-pyridylaminomethyl)benzene (L), four metal(II)-complexes formulated as CdL(SO4)(H2O)2 (1), CdL(1,3-bdc) (1,3-H2bdc = 1,3-benzene dicarboxylic acid) (2), PbL(1,3-bdc) (3) and ZnL(1/2)(2,5-tdc) (2,5-H2tdc = 2,5-thiophene dicarboxylic acid) (4) have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 3 feature uninodal 4-connected non-interpenetrated sql/Shubnikov tetragonal plane nets with {4(4).6(2)} topology. Complex 2 exhibits a 2-nodal (3,4)-connected 2D V2O5-type net with (4(2).6(3).8) (4(2).6) topology. Complex 4 exhibits a uninodal 6-connected hxl/Shubnikov plane net (3,6) with {3(6).4(6).5(3)} topology. The hemi-rigid L ligand possesses similar conformation in complexes 1, 3 and 4: the two pyridine rings of L are parallel, and the phenyl moiety is almost perpendicular to the two terminal pyridine rings. Complexes 1-4 show different thermal stabilities, UV-vis absorption, emission spectra, photoluminescence lifetimes and they are photocatalytically active for the decomposition of methyl orange under UV light irradiation.