Xiao-Ming Ren

Larger Spontaneous Polarization Ferroelectric Inorganic―Organic Hybrids: [PbI3]∞ Chains Directed Organic Cations Aggregation to Kagomé-Shaped Tubular Architecture

Four isostructural inorganic-organic hybrid ferroelectric compounds, assembled from achiral 3-R-benzylidene-1-aminopyridiniums (R = NO(2), Br, Cl, or F for 1-4, respectively) and [PbI(3)](-) anions with the chiral Kagomé-shaped tubular aggregating architecture, show larger spontaneous polarizations.

Complicated magnetic behavior in one-dimensional nickel(III) chain complex [1-(4′-cyanobenzyl)pyridinium][Ni(mnt)2](mnt2−=maleonitriledithiolate)

Abstract A new ion-pair complex [1-(4′-cyanobenzyl)pyridinium] [Ni(mnt)2] (1), in which mnt2−=maleonitriledithiolate, have been fabricated and its X-ray single crystal structural analyses at 293, 180 and 140 K shown that the [Ni(mnt)2]− anions and [CNBzPy]+ cations form a well-separated stacking column along c-axis direction, within which [Ni(mnt)2]− anions are uniformly spaced to give a one-dimensional (1-D) chain structure. Bulk magnetic properties of this complex have been investigated in the temperature range of 2–400 K and shown there exists spin kink at ∼190 K. In low temperature region, weak ferromagnetic behavior occurs in 1.

Construction of hybrid d10 metal–organic frameworks by flexible aromatic dicarboxylate and N-donor ligands : syntheses, structures and physical properties

Six novel metal coordination polymers with flexible aromatic dicarboxylate ligands and N-donor ligands, Zn2(DPA)2(mbix)(H2O) (1), Cd2(DPA)2(mbix) (2), ZnCd(DPA)2(bix) (3), Cd(SDBA)(mbix)(H2O)2 (4), Cd(SDBA)(bimb) (5) and [Cd(SDBA)(4,4′-bipy)0.5(H2O)]·H2O (6) (H2DPA = diphenic acid, H2SDBA = 4,4′-dicarboxybiphenyl sulfone, mbix = 1,3-bis(imidazol-1-ylmethyl)benzene, bix = 1,4-bis(imidazol-1-ylmethyl)benzene, bimb = 4,4′-bis(imidazol-1-ylmethyl) biphenyl and 4,4′-bipy = 4,4′-bipyridine), have been synthesized and structurally characterized by elemental analysis, IR, TGA and X-ray single crystal diffraction. Complex 1 has a two-dimensional (2D) (3,4)-connected layer network with a novel (62.8)(4.62.83)(4.6.8) topology, whereas complex 2 crystallizes in the chiral space groupP61 and has a guest-free three-dimensional (3D) chiral framework structure with one-dimensional (1D) homochiral chains. Complex 3 shows a complicated 2D framework consisting of a heteroquadrinuclear cluster which comprises a centrosymmetric linear array of two Zn atoms and two Cd atoms which are bridged by carboxylate groups of DPA ligands. Complex 4 presents a puckered chiral layer structure with rare heterostranded double helices. Complex 5 exhibits a 2D chiral structure with an open channel by incorporating the auxiliary bimb ligand, while complex 6 features an uncommon self-penetrating 2D network containing double-stranded helices. The results indicate that the dicarboxylate DPA2− and SDBA2− ligand can adopt varied coordination modes in the formation of the complexes and the configuration and flexibility of the ligands play a key role in directing the related properties of the complexes. The photoluminescence properties of 1–6 were studied in the solid state at room temperature. The nonlinear optical measurements showed that 2 and 5 displayed a second-harmonic-generation (SHG) response of 0.7 and 0.8 times that for urea, respectively. Moreover, the ferroelectric properties of 5 have also been investigated.

Zn(II) and Cu(II) coordination polymers assembled from V-shaped tetracarboxylate ligands and N-donor ancillary ligands: syntheses, structures and properties

Six novel zinc(II) and cupric(II) metal coordination polymers with V-shaped ligands and N-donor ligands, [Zn2(SA)(phen)2]·2H2O (1), Zn2(FA)(phen)2(H2O)·H2O (2), Cu3(H2FA)3(phen)3·H2O (3), Cu(H2FA)(2,2′-bipy)·1.54(H2O) (4), [Cu2(SA)(4,4′-bipy)1.5]·2.7(H2O) (5) and [Zn2(SA)(4,4′-bipy)2]·8H2O (6) (H4SA = 3,3′,4′,4′-diphenyl-sulfonetetracarboxylate acid, H4FA = 4,4′-(hexafluoroisopropylidene)diphthalic acid, phen = 1,10-phenanthroline, 2,2′-bipy = 2,2′-bipyridine and 4,4′-bipy = 4,4′-bipyridine), have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Complex 1 has a two-dimensional (2D) layer network, whereas complex 2 exhibits a 1D helical chain structure because of the introduction of a H4FA ligand. Complex 3 shows a complicated 2D framework. Complex 4 has a 1D chiral structure with an open channel by incorporating the auxiliary ligand 2,2′-bipy, while complexes 5 and 6 have a complicated 3D framework which is of particular interest because it adopts interesting and rare framework topologies. The results indicate that the multicarboxylate H4SA and H4FA ligand can adopt varied coordination modes in the formation of the complexes and the configuration and flexibility of the ligands play a key role in directing the related properties of the complexes. The photoluminescence properties of H4SA and H4FA, 1, 2, 6 were studied in the solid state at room temperature. Moreover, nonlinear optical measurements showed that 4, 5 displayed a second-harmonic-generation (SHG) response of 0.8 and 0.7 times that for urea, respectively.

Two zinc(II) supramolecular isomers of square grid networks formed by two flexible ligands: syntheses, structures and nonlinear optical properties

Assemblies of 4,4′-dicarboxybiphenyl sulfone (H2sdba), 1,2-bis(1-imidazolyl- methyl)benzene (bimb) and Zn(NO3)2·6H2O afford two supramolecular isomers [Zn(sdba)(bimb)]n of square grid networks depending on the assembly conditions. Single-crystal X-ray diffraction showed that complex 1 entangled into 2-fold parallel interpenetrated sheets containing undulated (4,4) layers, which, furthermore, are polycatenated to generate an unique 3D array. While 2 also possesses [Zn(sdba)(bimb)]n 2D layer motifs, parallel sets of layer motifs aggregate into 2D + 2D → 3D mutually inclined interpenetrated systems.

Temperature-induced assembly of MOF polymorphs: Syntheses, structures and physical properties

Four new coordination polymers, namely, [Co(BIPA)(titmb)]·H2O (1), [Co3(BIPA)3(titmb)2]·0.73H2O (2), [Ni(SDBA)(bix)]·2H2O (3) and [Ni(SDBA)(bix)(H2O)]·0.38H2O (4) (H2BIPA = 5-bromoisophthalic acid, H2SDBA = 4,4′-dicarboxybiphenyl sulfone, titmb = 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-tri-methylbenzene, bix = 1,4-bis(imidazol-1-ylmethyl)benzene), were obtained under hydrothermal conditions. Four complexes were characterized by elemental analyses, IR spectra, thermogravimetric analyses and single-crystal X-ray diffraction. Complexes 1 and 2 are polymorphs formed from Co(II) cations, BIPA2− anions, titmb ligands and water molecules, showing a three-dimensional (3,5)-connected network with the topology of (63)(69.8) for 1 and a three-dimensional (3,4)-connected coordination framework with the topology of (4.6.8)(4.62.83)(6.85)(62.83.10)(83) for 2. Complexes 3 and 4 are also two polymorphs constructed from Ni(II) cations, SDBA2− anions, bix ligands and water molecules. Complex 3 exhibits a two-dimensional lamella structure with (4,4) topology, whereas complex 4 displays a two-dimensional 2-fold interpenetrating (6,3) network. It is shown that the reaction temperature plays a crucial role in the formation of the final products. Moreover, the nonlinear optical and ferroelectric properties of 1 have also been investigated.

A rhombus channel metal–organic framework comprised of Sr2+ and thiophene-2, 5-dicarboxylic acid exhibiting novel dielectric bistability

A metal–organic framework (MOF) compound, comprised of Sr2+ and thiophene-2,5-dicarboxylic acid (H2TDA) with a formula of Sr(TDA)(DMF), was prepared via the solvothermal method, this MOF compound crystallizes in the monoclinic space group P21/c with unit cell parameters a = 6.0078(4) A, b = 16.9401(12) A, c = 13.0061(8) A, β = 116.158(3)° and V = 1188.10(14) A3. The spaces of rhombus channels in the MOF crystal are occupied by the disordered DMF molecules. The striking structural feature is that the connectivity between inorganic hendecahedron units of SrO7 and TDA2− ligands gives rise to the uncommon I1O2 type 3-D framework of 1. The dielectric relaxation and novel dielectric bistability behaviors were observed for this MOF compound in the lower frequency regime (f 160 °C), which originated from the orientation motion of the disordered polar DMF molecules under an ac electric field. This study suggested the possibility of dielectric bistability in the designed MOFs with pores or channels.

Observation of magnetic bistability in polymorphs of the [Ni(dmit)(2)](-) complexes.

Four ion-pair complexes of [Ni(dmit)(2)](-) with [NO(2)bzql](+) have been obtained, which belong to two kinds of polymorph forms, [NO(2)bzql][Ni(dmit)(2)] (1alpha and 1beta) and [NO(2)bzql][Ni(dmit)(2)].CH(3)COCH(3) (2alpha and 2beta) (where dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate and [NO(2)bzql](+) = 1-(4-nitrobenzyl)quinolinium). Though 1alpha, 2alpha, and 2beta all show anionic dimerization structures at room temperature, they have different anionic and cationic arrangement fashions, which give rise to different magnetic behaviors for these polymorphs or pseudo-polymorphs. Compounds 1alpha, 1beta, and 2alpha exhibit magnetic bistabilities. In particular, 1alpha has a hysteretic loop at approximately 55 K, while 2beta does not display a spin transition in the 2-300 K range. On the basis of the crystal structure data of 2alpha in high- and low-temperature phases, the magnetic coupling feature within the [Ni(dmit)(2)](-) spin dimer was explored with the broken-symmetry approach at the UBPW91/LANL2DZ level; combined with the experimental data and theoretical analyses, the relationship between the magnetic coupling nature and the stacking pattern of [Ni(dmit)(2)](-) anions as well as the origin of the phase interconversion are discussed.

Structural, morphological, and magnetic study of nanocrystalline cobalt-nickel-copper particles

Nanocrystalline Co(x)Ni(y)Cu(100-x-y) particles were synthesized by the reduction of metal acetates in a mixture of polyol and Tween 80. Inductively coupled plasma (ICP) analysis revealed that the actual wt% of Co, Ni, and Cu in these nanoparticles was nearly the same as in the starting solutions. The structures of the particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) spectroscopy, and vibrating sample magnetometry (VSM). The results of XRD and VSM confirmed that there was no metastable alloying in the particles. The particles were composites, consisting of nanoscale crystallites of face-centered cubic (fcc) Cu, face-centered cubic (fcc) Ni, and face-centered cubic (fcc) Co. During preparation the nucleation of Cu occurred first; then small Cu nuclei acted as cores for the precipitation of Co and Ni. The particles showed an increase in saturation magnetization (M(s)) as the concentration of Co or Ni in the particles was increased. The changes of both M(s) and coercivity of the particles with increasing annealing temperatures were studied. The coercivity of the particles was very high; it could reach as high as 489 Oe for Co34.3Ni31.2Cu34.5) .

Inorganic–organic hybrid compounds based on face-sharing octahedral [PbI3]∞ chains: self-assemblies, crystal structures, and ferroelectric, photoluminescence properties

Eight inorganic-organic hybrid compounds with a formula of [R-Bz-1-APy][PbI(3)] (R-Bz-1-APy(+) = mono-substituted benzylidene-1-aminopyridinium Schiff base derivative; R = m-CN (1), m-CH(3) (2), H (3), p-F (4), p-Cl (5), p-Br (6), o-Cl (7), o-Br (8)) have been synthesized and characterized structurally. The common characteristic of the crystal structures of 1-8 is that the inorganic components form straight and face-sharing octahedral [PbI(3)](∞) chains and the Schiff base cations surround the [PbI(3)](∞) chains to form molecular stacks. The substituent (R) on the phenyl ring of the Schiff base cation clearly influences the packing structures of 1-8, and the hybrid compound crystallizes in the space group P6(3) when R = CN (1) in the meta-position of the phenyl ring, and in a central symmetric space group when R is in the ortho- or para-position of the phenyl ring. The conformation of the Schiff base cation is related to the R position, and the dihedral angle between the phenyl and pyridyl rings increases in the order of para- < meta- < ortho-position substitution of the phenyl ring. The long molecular axis of the Schiff base cation adopts a manner approximately parallel to the straight inorganic [PbI(3)](∞) chain in the para-substituted hybrid compounds, and perpendicular to the straight inorganic [PbI(3)](∞) chain in the ortho-substituted hybrid compounds. 1 is second harmonic generation (SHG) active with a comparable response as that of urea and also exhibits ferroelectricity with larger P(s) and P(r) values; 1-8 emit multi-band luminescence in the 300-650 nm regions under the excitation of ultraviolet light.