A 3D porous cobalt-organic framework exhibiting spin-canted antiferromagnetism and field-induced spin-flop transition

Two 3D cobalt-organic frameworks formulated as [Co3(2,4-pydc)2(micro3-OH)2]n.5nH2O (1) and [Co3(2,4-pydc)2(micro3-OH)2(H2O)]n.7nH2O (2) (2,4-pydc=pyridine-2,4-dicarboxylate) have been hydrothermally synthesized and characterized. Both compounds 1 and 2 exhibit the 3D porous frameworks with hydroxyl-bridged metal Delta-chains. However, in comparison with only two crystallographically independent CoII ions in a unit of 2, three crystallographically independent CoII ions are found in an asymmetric unit of 1, where their Delta-chains are constructed by two types of vertexes sharing quadrangles formed via edge-sharing triangles. Magnetic studies show that 1 exhibits spin-canted antiferomagnetism and a field-induced spin-flop transition while 2 behaves as a normal antiferromagnet. The magnetic properties are largely retained by the porous frameworks of dehydrated 1 and 2 compounds. Gas adsorption measurements indicate that both the dehydrated compounds absorb H2 into their pores.     

Order-disorder antiferroelectric phase transition in a hybrid inorganic-organic framework with the perovskite architecture

[(CH3)2NH2]Zn(HCOO)3, 1, adopts a structure that is analogous to that of a traditional perovskite, ABX3, with A = [(CH3)2NH2], B = Zn, and X = HCOO. The hydrogen atoms of the dimethyl ammonium cation, which hydrogen bond to oxygen atoms of the formate framework, are disordered at room temperature. X-ray powder diffraction, dielectric constant, and specific heat data show that 1 undergoes an order-disorder phase transition on cooling below 156 K. We present evidence that this is a classical paraelectric to antiferroelectric phase transition that is driven by ordering of the hydrogen atoms. This sort of electrical ordering associated with order-disorder phase transition is unprecedented in hybrid frameworks and opens up an exciting new direction in rational synthetic strategies to create extended hybrid networks for applications in ferroic-related fields.     

Novel 3-D PtS-like tetrazolate-bridged manganese(II) complex exhibiting spin-canted antiferromagnetism and field-induced spin-flop transition

Two novel manganese(II) tetrazolate coordination polymers, Mn 3(Hbta) 4(mu 2 -OH) 2(H 2O).2H 2O ( 1) and Mn(bta)(H 2O) ( 2), were obtained by the hydrothermal reaction of MnCl 2.4H 2O with N, N-bis[1(2) H-tetrazol-5-yl]amine (H 2bta) in different pH values. Compound 1 exhibits a 2-D (4,4) layer structure, which is built from binuclear Mn 2(mu 2-OH) 2 subunits and mu 3-bridging Hbta (-) linkers. Compound 2 is a helical framework, and its 3-D PtS-like net is constructed by Mn 2(bta) 2 dimers and mu 5-bridging bta (2-) linkers. Magnetic measurements reveal that compound 1 displays an antiferromagnetic ordering, while compound 2 exhibits the coexistence of a spin-canted antiferromagnetic coupling and a field-induced spin-flop transition.     

A homochiral metal-organic framework membrane for enantioselective separation

For the first time, a homochiral metal-organic framework membrane was prepared for the enantioselective separation of important chiral compounds, especially chiral drug intermediates, which will allow for the potential development of a new, sustainable and highly efficient chiral separation technique.     

A 3D chiral nanoporous coordination framework consisting of homochiral nanotubes assembled from octuple helices

A 3D chiral nanoporous coordination framework consisting of homochiral nanotubes assembled from octuple helices with a 19.4 A by 22.4 A aperture is formed by the parallel alignment of eight infinite helical chains.     

A homochiral 3D covalent framework assembled from vertical chiral layers with achiral bridging ligands

A novel metal-organic coordination polymer, [Cd(HPT)₂(4,4′-bpy)]_n (PT=phthalate), has been hydrothermally synthesized and characterized by elemental analysis, IR, TG and single crystal X-ray diffraction. Colorless crystals crystallized in the tetragonal system, space group I4₁22, a=8.294(5), b=8.294(5), c=33.7535(17) Å, V=2321.8(18) Å³, Z=4 and R=0.0207. The structure of the compound exhibiting a homochiral 3D covalent framework based on achiral bridging ligands has been constructed by an alternating assembly of vertical chiral layers consisting of homochiral helices.     

Enantioselective sorption of alcohols in a homochiral metal-organic framework

Single-crystal X-ray diffraction study reveals the host-guest interactions between a homochiral metal-organic framework and two enantiomers of a chiral alcohol providing the key driving force for the enantioselective sorption of alcohols in the framework.     

Evidence for magnetic anisotropy of [Nb(IV)(CN)8]4- in a pillared-layered Mn2Nb framework showing spin-flop transition

The first example of the [Nb(CN)(8)]-based pillared-layered-type framework system {[Mn(II)(2)(bpdo)(H(2)O)(4)][Nb(IV)(CN)(8)]·6H(2)O}(n) (bpdo = 4,4'-bipyridyl-N,N'-dioxide) has been obtained and characterized structurally and magnetically. The presented results provide the first evidence for substantial magnetic anisotropy of [Nb(IV)(CN)(8)].     

Spontaneously resolved homochiral 3D lanthanide-silver heterometallic coordination framework with extended helical Ln-O-Ag subunits

Two novel homochiral lanthanide-silver heterometallic coordination polymers LnAg(OAc)(IN)3 [Ln = Nd (1), Eu (2), HIN = isonicotinic acid, HOAc = acetic acid] have been prepared under hydrothermal conditions, which were characterized by elemental analysis, infrared, thermogravimetric analysis, and single-crystal X-ray diffraction. Both complexes are isostructural and crystallize in a hexagonal system, chiral space group P6(1)22. Both polymers are constructed from infinite right-handed homochiral helical chains with Ln-O-Ag connectivity, representing the first examples of homochiral lanthanide-transition metal heterometallic coordination polymers with a 3D coordination framework based on spontaneous resolution. Furthermore, the luminescent properties of 2 were studied.     

A porous metal-organic framework with helical chain building units exhibiting facile transition from micro- to meso-porosity

A metal-organic framework (MOF) with helical channels has been constructed by bridging helical chain secondary building units with 2,6-di-p-carboxyphenyl-4,4'-bipyridine ligands. The activated MOF shows permanent porosity and gas adsorption selectivity. Remarkably, the MOF exhibits a facile transition from micro- to meso-porosity.     

The first semiquinone-bridged bisdithiazolyl radical conductor: a canted antiferromagnet displaying a spin-flop transition

The alternating ABABAB π-stacked bis-1,2,3-dithiazolyl radical 2a (2, R(2)=Ph) has a conductivity σ of 3×10(-5) S cm(-1) at 300 K, and orders as a spin-canted antiferromagnet (T(N)=4.5 K) which undergoes a spin-flop transition to a field-induced ferromagnetic state saturating (at 2 K) at H ～20 kOe.     

A homochiral porous metal-organic framework for highly enantioselective heterogeneous asymmetric catalysis

A homochiral porous noninterpenetrating metal-organic framework (MOF), 1, was constructed by linking infinite 1D [Cd(mu-Cl)2]n zigzag chains with axially chiral bipyridine bridging ligands containing orthogonal secondary functional groups. The secondary chiral dihydroxy groups accessible via the large open channels in 1 were utilized to generate a heterogeneous asymmetric catalyst for the addition of diethyzinc to aromatic aldehydes to afford chiral secondary alcohols at up to 93% enantiomeric excess (ee). Control experiments with dendritic aromatic aldehydes of different sizes indicate that the heterogeneous asymmetric catalyst derived from 1 is both highly active and enantioselective as a result of the creation of readily accessible, uniform active catalyst sites inside the porous MOF.     

A new enantiopure unsaturated dicarboxylate as a 4-connected unit in a flexible homochiral PtS-type framework

Metal cation mediated chiral ligand transformation of (S)-camphanic acid leads to a new enantiopure unsaturated dicarboxylate that links tetrahedral Zn(2+) sites into 3-D homochiral 4-connected PtS-type framework structures, Zn(tced) (1, H(2)tced=1,2,2-trimethyl-3-cyclopentene-1,3-dicarboxylic acid) and Zn(4)(tced)(4)(4,4'-bipy) (2, 4,4'-bipy=4,4'-bipyridine).     

Flexible 3D porous metal-organic framework exhibiting selective adsorption for H2O over organic solvents

A new flexible 3D porous metal-organic framework (MOF) with 1D open nanotube,[Co2(μ5-CTAI)(dpe)(H2O)2]n·6n(H2O)(1) (CTA=cyclohexane-1,2,4,5-tetracarboxylic acid,dpe=1,2-di(4-pyridyl) ethylene) has been prepared and structurally characterized.Meanwhile,each 1D nanotubes filled with 1D water chain with dimension of 13.711 × 12.275 2.Compound 1 represents a new example that collapse/deform upon dehydration/hydration and shows adsorb H 2 O selectively over organic solvents.     

1D and 2D homochiral metal-organic frameworks built from a new chiral elongated binaphthalene-derived bipyridine

Six homochiral coordination polymers 1-6 based on a new enantiopure elongated (S)-2,2'-diethoxy-1,1'-binaphthyl-6,6'-bis(4-vinylpyridine) ligand (L) and divalent metal (Zn, Cd, and Ni) connecting points were synthesized and characterized by single-crystal X-ray diffraction studies. These new homochiral coordination polymers adopt two distinct framework structures: a one-dimensional infinite chain structure with bridging L ligands occupying the axial positions of the metal centers and a two-dimensional rhombic grid structure formed by linking octahedrally coordinated metal centers with four pyridyl groups of bridging L ligands in the equatorial positions. The structures of these coordination polymers are sensitive to the nature of the anions as well as the solvents from which the coordination polymer crystals were grown. Powder X-ray diffraction studies showed that the two-dimensional chiral rhombic grids exhibited porosity, which could potentially find applications in enantioselective separations and catalysis.     

Chiral azide-bridged two-dimensional Cu(II) compounds showing a field-induced spin-flop transition

Two azide-bridged chiral Cu(II) compounds, [Cu(R,R-dacy)(N3)2]n (R,R-dacy = trans-(1R,2R)-diaminocyclohexane) and [Cu(S,S-dacy)(N3)2]n (S,S-dacy = trans-(1S,2S)-diaminocyclohexane), with two-dimensional layer structures exhibiting end-to-end and end-on azide bridging patterns, were prepared and among them was examined to show a field-induced spin-flop transition.     

Divalent-metal-stabilized aluminophosphates exhibiting a new zeolite framework topology

Two divalent-metal-containing aluminophosphates, (C(5)H(14)N(2))[Co(2)Al(4)P(6)O(24)] and (C(5)H(14)N(2))[Zn(2)Al(4)P(6)O(24)] (denoted as MAPO-CJ62; M = Co, Zn), have been hydrothermally synthesized by using N-methylpiperazine as the structure directing agent. Their structures are determined by single crystal X-ray diffraction and further characterized by powder X-ray diffraction, inductively coupled plasma, and thermogravimetric and diffuse reflectance spectroscopy analyses. Both of these two compounds exhibit a new zeolite framework topology. This new zeolite framework contains 1-dimensional 8-ring channels running along the [010] direction. All the metal and P atoms are tetrahedrally coordinated and alternately connected to each other through bridging O atoms. Inductively coupled plasma analysis shows that the molar ratio of M:Al in MAPO-CJ62 is 1:2. The M(2+) ions in MAPO-CJ62 selectively occupy two of the three possible crystallographically distinct positions. A pure aluminophosphate analogue of MAPO-CJ62 without M(2+)-incorporation, denoted as AlPO-CJ62, has not been obtained in our experiment so far. The necessity of introducing M(2+) ions and their ordered distribution in MAPO-CJ62 has been elucidated by analyzing the distortions of Al-centered tetrahedra in the hypothetical framework of AlPO-CJ62.     

A 3D porous lanthanide-fumarate framework with water hexamer occupied cavities, exhibiting a reversible dehydration and rehydration procedure

[Sm2(fumarate)3(H2O)4] x 3 H2O, a new porous pillared layer framework with 0D cavities for the accommodation of chair-like hexameric water clusters, possesses three kinds of fumarate ligand with their two COO ends adopting different coordination modes and shows reversible de- and re-hydration behavior.     

A homochiral nanotubular crystalline framework of metallomacrocycles for enantioselective recognition and separation

A highly ordered homochiral nanotubular crystalline framework was assembled from a hexameric Zn6L6metallaycle that was built from metallosalen ZnL units (H2L = (R,R)-(-)-N,N'-Bis(3-tert-butyl-5-(4- pyridyl) salicylidene)-1,2-diaminocyclohexane) by the complementary coordination of the pyridyl groups to the metal centers. Chiral channels and hydrophobic functionality presented by this structure make it an excellent host to recognize and separate racemic alcohols with high enantioselectivity (up to 99.5%). The crystalline solid can be easily recycled and reused five times without loss of crystallinity and enantioselectivity.