Qing-Lun Wang

A Niccolite Structural Multiferroic Metal–Organic Framework Possessing Four Different Types of Bistability in Response to Dielectric and Magnetic Modulation

Multiple switchable physical properties have been demonstrated in one single niccolite structural metal-organic framework, [(CH3 CH2 )2 NH2 ][FeIII FeII (HCOO)6 ] (1), including (i) a reversible ferroelastic phase transition triggered by freezing the disordered (CH3 CH2 )2 NH2+ cations, (ii) a thermally switchable dielectric constant transition accompanied by phase transition, and (iii) thermal and positive magnetic field driven magnetic poles reversal at low temperatures, attributed to different responses of the magnetization of FeII and FeIII sublattices to external stimuli. More interestingly, the exchange anisotropy between the two sublattices can also give rise to tunable positive and negative exchange bias fields. Straightforwardly, such diverse demonstrations of bistability in one single material (depending on the specific tuning way) will provide extra freedom and flexibility for the design of switcher devices.

A family of lanthanide–nitronyl nitroxide complexes: syntheses, crystal structures and magnetic properties

Seven Ln(III) complexes based on a novel nitronyl nitroxide radical have been synthesized and characterized structurally and magnetically: [Ln(hfac)3(NITNapOMe)2] (Ln = Pr(1), Gd(2), Tb(3), Dy(4), Ho(5), Er(6), Tm(7); hfac = hexafluoroacetylacetonate; NITNapOMe = 2-6′-methoxy-2′-naphthyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide). The single-crystal analyses show that these complexes have similar mononuclear tri-spin structures, in which central Ln(III) ions are eight coordinated by three hfac molecules and two NITNapOMe radicals. The variable-temperature magnetic susceptibility studies reveal the ferromagnetic interactions between Ln(III) ion and radicals in complexes 3, 4, and 7 and antiferromagnetic interactions in complexes 1, 2, 5, and 6.

Syntheses, structures and magnetic properties of 1-D complex {[Ni(μ1,5-dca)(pn)2](ClO4)}n, 2-D complex [Mn(μ1,5-dca)2(phen)]n and 3-D complex [Mn(μ1,5-dca)2L]n (dca = dicyanamide, N(CN)2-; pn = 1,3-propane diamine; phen = phenanthroline; L = 4,4'-ditriazole methane)

Abstract Three novel dicyanamide complexes {[Ni(μ1,5-dca)(pn)](ClO4)}n (I), [Mn(μ1,5-dca)2(phen)]n (II) and [Mn(μ1,5-dca)2L]n (III) have been synthesized and structurally characterized. Complex I forms 1-D chain and II forms 2-D layer structure, which are both bridged via μ1,5-dca ligands. Whereas complex III contains 3-D networks bridging via μ1,5-dca and 4,4′-ditriazole methane ligands. The magnetic measurements indicate that all these complexes exhibit weak antiferromagnetic interaction through the five-atom [NCNCN]− bridging ligands, with J=−6.3, −1.3 and −1.1 cm−1 for complex I, II and III, respectively.

Two novel three-dimensional coordination polymers with [Ag(CN)2]− as bridging ligands: synthesis and structural characterization of {KMn[Ag(CN)2]3(H2O) }n and {Mn[Ag(CN)2]2(bpy)2}n (bpy=4,4′-bipyridine)

Abstract Two novel three-dimensional coordination polymers {KMn[Ag(CN)2]3(H2O)}n 1 and {Mn[Ag(CN)2(bpy)]2}n 2 have been prepared and structurally as well as magnetically characterized. In both compounds, the three-dimensional networks are constructed entirely by coordinative linkages with all the CN− anions of [Ag(CN)2]−, bpy and water ligands involved in bridging and the novel 3-D structure of 1 is unprecedented.

Linear chain and mononuclear tri-spin compounds based on the lanthanide-nitronyl nitroxide radicals: structural design and magnetic properties

Four Ln(III) complexes based on two nitronyl nitroxide radicals with different steric hindrance have been synthesized, characterized structurally and magnetically: [Ln(hfac)3(NITPhOEt)]n (Ce (1), Pr (2); hfac = hexafluoroacetylacetonate; and NITPhOEt = 4′-ethoxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide); [Ln(hfac)3(NITPhOCH2Ph)2] (Ce (3), Pr (4); NITPhOCH2Ph = 4′-benzyloxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide). The X-ray crystal structure analyses show that small steric hindrance of the radical makes complexes 1 and 2 show similar linear chain structures composed of Ln(hfac)3 units bridged by NITPhOEt radicals through their N–O groups. While the larger steric hindrance of the radical induces complexes 3 and 4 to be mononuclear tri-spin compounds, in which central Ln(III) ions are coordinated by three hfac and two NITPhOCH2Ph radicals. The variable-temperature magnetic susceptibility studies reveal that there are antiferromagnetic interactions between the paramagenetic ions (Ln(III) and radical) in all four complexes.

A new D2d-symmetry DyIII mononuclear single-molecule magnet containing a monodentate N-heterocyclic donor ligand

Three new lanthanide complexes [Ln(hfac)3(pz)2] (Ln = Dy (1), Tb (2), Ho (3); hfac = hexafluoroacetylacetonate; pz = pyrazole) based on pyrazole have been prepared and characterized structurally. X-ray crystallographic analysis reveals that all three complexes are isomorphous. The crystal structures of these complexes consist of a mononuclear molecule unit in which the center LnIII ion is surrounded with a slightly distorted D2d-dodecahedron LnO6N2 coordination sphere from three hfac anions and two pyrazole ligands. Both static and dynamic magnetic properties were studied for complex 1, which is proved to be a rarely reported D2d-symmetry DyIII mononuclear single-molecule magnet containing a monodentate N-heterocyclic donor ligand, and the luminescence characterization of complexes 1–3 in both visible and NIR regions is also studied.

Hydrolytic synthesis and structural characterization of five hexanuclear oxo-hydroxo lanthanide clusters

Five hexanuclear oxo-hydroxo lanthanide clusters are synthesized by hydrolysis of the lanthanide ions together with 4-amido-3,5-dimethyl-1,2,4-triazole (L). They all have a [Ln6(µ6–O)(µ3–OH)8]8+ core structure and the triazole groups stabilize the core structure in different fashions. The oxo group functions as an anion template to induce the self-assembly of lanthanide ions.

Three lanthanide-radical complexes: Synthesis, structure and magnetic properties

National Natural Science Foundation of China [21101096, 90922032, 21071085, 20971072]; NSF of Tianjin [09JCYBJC05500]; Research Fund for the Doctoral Program of Higher Education [20100031120013]; National Innovation Projects for the Undergraduates of China [101005533]

Two [Au(CN)2]−-bridged heterometallic coordination polymers directed by different 2,2′-bipyridyl-like ligands

Two new cyanide-bridged heterobimetallic coordination polymers constructed by using the [Au(CN)2]− building block, {Cd(bipy)[Au(CN)2]2}n (1) and {{Cd(phen)[Au(CN)2]2(H2O)}·iPrOH}n (2) (bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized and characterized. Complex 1 with chiral P3112 space group exhibits a novel three-fold interpenetrating quartz-like 3-D network, which is completely unsupported by aurophilic interactions, while complex 2 with the replacement of bipy by phen shows C2/c space group and features the 1-D zigzag chain structure and an extended supramolecular 2-D array in which aurophilic interactions may play an important role in sustaining the supramolecular solid-state architectures. 1 and 2 feature various networks most likely due to the different steric hindrances of the bipy and phen ligands. In addition, the solid state photoluminescence spectrum of complex 2 exhibits a strong green emission band (λmax = 524 nm) at room temperature.

Ionic liquid-assisted solvothermal synthesis of oriented self-assembled Fe3O4 nanoparticles into monodisperse nanoflakes

Self-assembled Fe3O4 nanoflakes have been synthesized via an ionic liquid-assisted solvothermal method. The obtained Fe3O4 nanoflakes are composed of well-aligned nanoparticles with an average diameter of about 15 nm. More importantly, the ionic liquid [C16mim]Cl (1-hexadecyl-3-methylimidazolium chloride) plays a critical role for the self-assembly of nanoparticles into nanoflakes by adsorbing onto the surfaces of the primary Fe3O4 nanoparticles.