Xiu-Mei Zhang

Four metal–organic frameworks based on the 5-(1H-tetrazol-5-yl)isophthalic acid ligand: luminescence and magnetic properties

Four transition metal coordination polymers with 5-(1H-tetrazol-5-yl)isophthalic acid ligand (H3TZI) were synthesized and structurally characterized. They are formulated as [Zn(TZI)]·(CH3)2NH2+·H2O (1), [Cd2(OH)(TZI)(H2O)2]·DMF·0.5H2O (2), [MnNa(TZI)]·2H2O (3), and [Mn3(TZI)2(12H2O)]·4H2O (4). Compound 1 displays a 3D (4,4)-connected framework with a Schlafli symbol of 426282. 2 exhibits 3D frameworks in which strip-shaped chains with Cd3(μ3-OH) triangles are linked by TZI ligands, presenting a rare (3,4,5,6)-connected 4-nodal net topology with the point symbol (43)(4462)(4664)(4768). 3 features 2D 2p–3d heterometallic layers in which 1D chains with mixed bridges linking alternating Mn(II) ions and Na(I) ions are interlinked by TZI spacers. The layers are further stabilized and associated into 3D architectures through intra- and interchain hydrogen bonds and/or π–π stacking. 4 consists of 1D double chains, and the 1D chains are assembled through hydrogen bonds to give a 3D supramolecular architecture. Intriguingly, Mn(II) ions from different double chains are linked through hydrogen bonding bridges to give unprecedented hydrogen bonded chains with alternating single O–H⋯O bridges and double (O–H⋯O)2 bridges. Compounds 1 and 2 display intense photoluminescence properties in the solid state at room temperature, while 4 exhibits an antiferromagnetic interaction between Mn(II) ions.

Four coordination polymers based on dinuclear and trinuclear units with a new multifunctional pyridyl-dicarboxylate ligand: luminescence and magnetic properties

Four coordination polymers of different transition metal ions with a new pyridyl-dicarboxylate ligand, 4-(3,5-dicarboxylphenyl)-2-methylpyridine (H2L), were synthesized under solvothermal conditions and their structures and properties were characterized. They are formulated as [Zn(L)(H2O)]·H2O (1), [Mn3(L)2Cl2(H2O)2]·2H2O (2), [Co3(L)2(NO3)2(H2O)2] (3) and [Ni3(L)2(NO3)2(H2O)2]] (4). Compound 1 exhibits a 2D network with a (3,6)-connected kgd topology based on the dinuclear [Zn2O2] units. In compound 2, the linear trinuclear [Mn3(μ-Ocarboxylate)2(COO)2Cl2] units with mixed carboxylate and μ-Cl triple bridges are cross-linked by the L ligands into a 3D framework with a (3,6)-connected rtl topology. Compounds 3 and 4 are isostructural and both show 2D networks in which the linear trinuclear [M3(μ-Ocarboxylate)2(COO)2(μ-ONO3)2] units (M = Co (3) and Ni (4)) are cross-linked by the L ligands. Compound 1 shows strong blue emissions in the solid state at room temperature. Magnetic studies indicate that the mixed triple [(μ-Ocarboxylate)(COO)Cl] bridges transmit antiferromagnetic interactions between Mn(II) ions in 2, while the mixed triple (μ-Ocarboxylate)(COO)(μ-ONO3) bridges in 3 and 4 transmit ferromagnetic interactions. Further magnetic studies demonstrated that the Co(II) compound shows no long-range magnetic ordering at 2 K.

Spin-canting magnetization in 3D metal organic frameworks based on strip-shaped Δ-chains

Three isostructural coordination polymers, M2(TZI)(OH)(H2O)2·xH2O (x = 3, M = Cu(II) 1, x = 4, M = Co(II) 2 and Ni(II) 3) (H3TZI = 5-(1H-tetrazol-5-yl)isophthalic acid), have been synthesized under hydrothermal conditions. The compounds consist of 3D frameworks, in which the magnetic Δ-chain motifs based on corner-sharing M3(μ3-OH) isosceles triangle are linked by the TZI ligands, and they represent the rare (3,4,5,6)-connected 4-nodal net topology with the point symbol (43)(4462)(4664)(4768). Magnetic analyses indicate that compound 1 shows the coexistence of spin canting, metamagnetism and antiferromagnetic ordering, whereas compounds 2 and 3 exhibit canted antiferromagnetic coupling without magnetic ordering down to 2 K. Such magnetic behaviors above 2 K are still rare in Cu(II), Co(II) and Ni(II) compounds with similar chains.

Four 3D coordination polymers based on layers with single syn–anti carboxylate bridges: synthesis, structures, and magnetic properties

Four novel coordination polymers (CPs) based on a new 4-(3,5-dicarboxylphenyl) picolinic acid ligands (H3L), [M3(L)2(H2O)6]·4H2O (M3 = Mn3, 1; Co3, 2; Ni3, 3, Co1.01Ni1.99, 4), have been hydrothermally synthesized, and structurally and magnetically characterized. In these isomorphous CPs, octahedrally coordinated metal ions are linked by the single syn–anti carboxylate bridge (μ-COO) to give linear trinuclear motifs. The motifs are connected through the other single syn–anti carboxylate bridge (μ-COO) to give a 2D (4,4) layer, and the layers are interlinked by the L ligands into 3D frameworks. Magnetic measurement indicates that antiferromagnetic interactions between metal ions are mediated through the single syn–anti carboxylate bridges in 1 and 2, while the same carboxylate bridges in 3 transmit ferromagnetic couplings. The bimetallic CP 4 shows interesting complicated magnetic behaviors due to the competition effect of Co(II) and Ni(II) ions.