Jian-Zhong Cui

Modulating single-molecule magnet behaviour of phenoxo-O bridged lanthanide(III) dinuclear complexes by using different β-diketonate coligands

Three dinuclear Dy(III) complexes, [Dy2(tfa)4L2] (1), [Dy2(TTA)4L2] (2) and [Dy2(dbm)4L2·2CH3CN·0.5H2O] (3) (tfa = trifluoroacetylacetonate, TTA = 2-thenoyltrifluoroacetone, dbm = dibenzoylmethane and HL = 2-[((4-bromophenyl)-imino)methyl]-8-hydroxyquinoline, have been synthesized, and structurally and magnetically characterized. The Dy(III) ions are eight-coordinated with two bidentate β-diketonate and two μ2-O bridging 8-hydroxyquinoline Schiff base ligands. Magnetic studies reveal that 1–3 exhibit different magnetic relaxation behaviors with the anisotropic barriers of 9.61 K (1), 54.81 K (2) and 30.98 K (3), respectively. The different magnetic relaxation behaviors of the three Dy2 complexes originate from the different chemical environments of the central Dy3+ ions with different β-diketonate coligands.

Auxiliary ligand-assisted structural diversities of three metal–organic frameworks with potassium 1H-1,2,3-triazole-4,5-dicarboxylic acid: syntheses, crystal structures and luminescence properties

Three metal–organic frameworks (MOFs) with d10 metal ions, namely, {[Zn3(TDA)2(bpy)3]·(bpy)·10.5H2O}n (1), {[Zn3(TDA)2(azopy)2.5(H2O)]·4H2O}n (2) and {[Cd2K3(TDA)(HTDA)2(H2O)4]}n (3) (KH2TDA = potassium 1H-1,2,3-triazole-4,5-dicarboxylic acid, bpy = 4,4′-bipridine, azopy = 4,4′-azobispridine), have been successfully synthesized from KH2TDA with the aid of three different length-controllable auxiliary ligands and characterized by infrared spectra, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. MOF 1 shows an interesting three-dimensional (3D) (3,4,4,4)-connected KAVGAQ framework with a Schlafli symbol of {63}2{64·102}{64·82}2, which can be extended by 2D layers and bpy pillars. MOFs 2 and 3 also display 3D framework structures, corresponding to a 6-connected {44·611} net and a (6,12)-connected {312·430·520·64}{36·48·5} net, respectively. Moreover, a novel coordination mode of H3TDA is observed in 3. The luminescence properties of 1–3 are investigated.

Syntheses, structures, and photoluminescence of lanthanide coordination polymers with pyridine-2,3,5,6-tetracarboxylic acid

Six lanthanide(III) coordination polymers with the formulae {[Ln(Hpdtc)(H2O)3]·H2O}n [Ln = La (1), Ce (2), Pr (3)], {[Ln(Hpdtc)(H2O)2]·2H2O}n [Ln = Eu (4), Tb (5)] and {SmK(pdtc)(H2O)4}n (6) (H4pdtc = pyridine-2,3,5,6-tetracarboxylic acid) have been synthesized by reacting the corresponding rare earth salts or oxides with H4pdtc under hydrothermal conditions. In the three kinds of structure, H4pdtc displays three different coordination modes. H4pdtc is an elegant ligand with rich coordination sites and low symmetry, but has seldom been used to synthesize complexes. 1–6 are the first examples from lanthanide ions and H4pdtc. Furthermore, the novel wave-like T3(2)4(2)6(2) water tape with (H2O)4 as the substructure is present in complex 6. The two complexes of Eu(III) and Tb(III) exhibit the corresponding characteristic luminescence.

Novel lanthanide coordination polymers based on bis-tridentate chelator pyrazine-2,3,5,6-tetracarboxylate with nano-channels and water clusters

Three novel lanthanide coordination polymers with large channels and water clusters, [Yb2(pztc)1.5(H2O)6]·7H2O (1), [Lu2(pztc)1.5(H2O)6]·7.5H2O (2) and [Er2(pztc)1.5(H2O)6]·7H2O (3), have been synthesized by the reactions of pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) and Ln(III) salts in aqueous solution at room temperature or under hydrothermal conditions, and characterized by X-ray crystallography, elemental analysis, IR, UV-vis and thermal gravimetric analysis (TGA). Single crystal X-ray diffraction determination indicates that the Ln(III) ions were coordinated by three tridentate cheated pztc4− ligands and bis-tridentate cheated pztc4− ligands bridged Ln(III) ions to form hexanuclear metal ring structures with nano-channels which were filled with (H2O)14clusters.

ds-Block metal ions catalyzed decarboxylation of pyrazine-2,3,5,6-tetracarboxylic acid and the complexes obtained from hydrothermal reactions and novel water clusters

The factors that influence the decarboxylation of pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) under hydrothermal conditions were investigated. Higher temperature and lower pH are very effective promoters for the decarboxylation of H4pztc in the presence of ds-block metal ions. Four novel complexes of H4pztc and four complexes from the decarboxylation of H4pztc, [Zn2(pz25dc)(phen)4](NO3)2·10H2O (1), [Zn2(pztc)(phen)4]·12H2O (2), {[Zn2(pztc)(bpy)2(H2O)2]·2H2O}n (3), [Cu2(pz25dc)(phen)4](NO3)2·10H2O (4), {[Cu2(pztc)(bpy)2 H2O]·4H2O}n (5), [Cu2(H2pztc)(bpy)2(H2O)2](NO3)2·2H2O (6), [Cd(pz26dc)(phen)(H2O)2] (7) and [Cd(pz26dc)(bpy)(H2O)2] (8) (pz25dc = pyrazine-2,5-dicarboxylate, pz26dc = pyrazine-2,6-dicarboxylate, phen = 1,10-phenanthroline, bpy = 2,2′-bipyridyl) have been synthesized and characterized by X-ray single crystal diffraction, elemental analysis, IR, thermal gravimetric analysis (TGA) and fluorescence measurement. 1, 2, 4 and 6 are dinuclear complexes bridged by pztc or pz25dc, 3 and 5 are 1D coordination polymers. In 6, the Cu(II) ions are bridged by bis-tridentate H2pztc2−. 7 and 8 are mononuclear Cd(II) complexes. The 2D or 3D supramolecular structures of 1–8 were built up by hydrogen bonds and π⋯π interactions. Notably, a novel T5(0)A0 water tape and a S-shaped (H2O)10cluster are observed in 2 and 5, respectively.

Syntheses and crystal structures of two new nickel(II) complexes with pyrazine-2,3,5,6-tetracarboxylate

Pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) reacted with Ni(ClO4)2·6H2O and 1,10-phenanthroline (phen) in aqueous solutions to form two different complexes, [Ni(H2pztc)(phen)H2O]·H2O (1), [Ni(phen)3](H2pztc)·10.5H2O (2), under hydrothermal conditions and at room temperature respectively. In 1, Ni(II) ion is coordinated by tridentate chelated H2pztc2−. The carboxyl and carboxylate groups of H2pztc2− are roughly coplanar with the pyrazine ring and form intramolecular hydrogen bonds. While in 2, H2pztc2− remains uncoordinated, the carboxyl and carboxylate groups of H2pztc2− are out of plane of the pyrazine ring and do not form intramolecular hydrogen bonds. H2pztc2− and water molecules form negatively-charged channels and the channels are filled with [Ni(phen)3]2+ in the 3D supramolecular structure of 2. In addition, a novel water tape is present in 2.

Spin canting and metamagnetism in 3D pillared-layer homospin cobalt(II) molecular magnetic materials constructed via a mixed ligands approach

Two new 3D pillared-layer cobalt(II) molecular magnetic materials, formulated as {[Co2(TDA)(TZ)(H2O)2]·H2O}n (1) and {[Co3(TDA)2(bpy)3]·6.75H2O}n (2) (H3TDA = 1H-1,2,3-triazole-4,5-dicarboxylic acid, HTZ = 1H-1,2,4-triazole and bpy = 4,4′-bipyridine), have been successfully assembled with H3TDA and auxiliary ligands, respectively. In 1, the neighboring Co(II) ions are connected via TDA3− to generate 2D layers, which are further bridged by TZ− to build a 3D 8-connected bcu net with a Schlafli symbol of (424·64), whereas in 2, the nearest Co(II) ions are connected via TDA3− to form a hexagonal [Co6(TDA)6]6− macrocycle composed of 24-membered atoms, which can be further linked to each other to generate 2D Kagome layers. The Kagome layers are connected by bpy pillars to display a 3D (3,4,4,4)-connected KAVGAQ net with a Schlafli symbol of {63}2{64·102}{64·82}2. Magnetic studies reveal that both of them show the spin canting and metamagnetic behaviors with critical temperatures of 3.5 K and 4 K, respectively.

Syntheses, structures, and properties of 3D lanthanide coordination polymers based on pyridine-2,3,5,6-tetracarboxylate

Three new 3D lanthanide(III) coordination polymers with the formulas {K[Ln(pdtc)(H2O)]·H2O}n(Ln = Nd(1), Dy(2), Er(3); K4pdtc = potassium pyridine-2,3,5,6-tetracarboxylate) have been synthesized via hydrothermal methods and structurally characterized by X-ray single crystal diffraction analysis, elemental analysis and thermal gravimetric analysis. In complexes 1–3, the pdtc4− ligands adopt new coordination modes and the three complexes have similar 3D network structures which consist of dinuclear building units and novel K–O chains inserted into the structure. Furthermore, complex 2 shows corresponding characteristic luminescence and complex 3 exhibits weak antiferromagnetic properties.

Trinuclear Cu(II) and Zn(II) complexes bridged by μ3-carbonato anion

The trinuclear Cu(II) and Zn(II) complexes [(CuTPA),(μ3-CO,)] (C104)4(1) and [(ZnTPA),(μ3-C03)](C104)4 (2) (TPA = tri(pyridylmethy1)amine) have been synthesized. X-ray structure analysis of the two complexes proves that CO3 2- anion has an unusual triply bridging ligand, bridging three CuTPA and ZnTPA units respectively, and assembles new trinuclear complexes. The CO3 2- comes from atmospheric CO2. The structure of each trinuclear unit consists of three copper or zinc atoms in a five-coordinate triangular hipyramidal environment. The [(CuTPA)3(μ3-C03) ](C104), compound shows a very weak antifemmagnetic coupling.

Near-infrared luminescence and SMM behaviors of a family of dinuclear lanthanide 8-quinolinolate complexes

A new family of lanthanide complexes, [Ln2(dbm)4(OQ)2(CH3OH)2] (Ln = Nd (1), Tb (2), Dy (3), Ho (4); dbm = dibenzoylmethanate, OQ = 8-quinolinolate), and [Er2(dbm)4(OQ)2(CH3OH)]·CH3COCH3 (5) were synthesized and characterized using single-crystal X-ray diffraction, elemental analysis (EA), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and UV-vis spectra. X-ray crystallographic analyses reveal that 1–5 are μ-phenol bridged dinuclear complexes. For complexes 1–4, each LnIII ion is eight-coordinated with two bidentate dbm and two μ-phenol bridging OQ ligands and one methanol molecule. Complex 1 in the solid-state displays the typical emissions of the NdIII ions in the NIR region. Magnetic measurements were carried out on complexes 1–5. Dynamic magnetic studies reveal single-molecule magnet (SMM) behavior for complex 3. Fitting the dynamic magnetic data to the Arrhenius law gives the energy barrier ΔE/kB = 109.5 K and pre-exponential factor τ0 = 4.23 × 10−9 s under 3000 Oe dc field.