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Three isomorphous metal-organic frameworks of formula [M(ppdc)(H2O)2]n [M = Mn(II), Fe(II), and Co(II)] were synthesized from sodium p-phenylenediacrylic (Na2ppdc). Crystallographic studies revealed that the compounds are layer-pillared 3D frameworks in which the square-grid M(II) layers with single carboxylate bridges are interlinked by long organic spacers with large interlayer separations of about 13 Å. Magnetic investigations indicated that they all display intralayer antiferromagnetic interactions through the carboxylate bridges in the unusual skew-skew coordination mode but the bulk behaviors are quite different. The Co(II) compound, like most compounds containing similar M-O-C-O-M layers, shows no 3D magnetic ordering down to 2 K, while the Mn(II) and Fe(II) compounds exhibit spin-canted ordering, behaving as a weak ferromagnet (TC = 3.8 K) and a metamagnet (TN = 3.8 K, Hc = 650 Oe), respectively. Spin-canted ordering is still a rarity in this series of materials. Magnetostructural comparisons with analogous compounds indicate that the occurrence of spin-canted ordering can be related to the uncommon skew-skew and anti-anti coordination modes of carboxylate bridges, which induce stronger antiferromagnetic interactions than the common syn-anti mode. [ABSTRACT FROM AUTHOR]

A 2-fold interpenetrated metal−organic framework displaying intense yellow fluorescence is constructed from [Zn4O(COO)6] clusters and a new dicarboxylate ligand bearing the fluorene chromophore fluorene-2,7-dicarboxylic acid. The [Zn4O(COO)6] secondary building unit exhibits unusual coordination features and leads to the rare 3D pillared kagomé net topology (324865). [ABSTRACT FROM AUTHOR]

Solvothermal reactions of Zn(II), Cd(II), Mn(II), Co(II), or Ni(II) salts and 2-pyrimidinecarbonitrile (pymCN) in the presence of NaN3in DMF yielded seven metal−organic coordination polymers formulated as [Zn(pymtz)2]n(1), [NaMII(pymtz)3]n·G (M = Zn 2, Cd 3, Mn 4, Co for 5, and Ni for 6; G = DMF and/or H2O) and [Cd(pymtz)2]n(7) [pymtz = 5-(2′-pyrimidyl)tetrazolato]. Compounds 2−6are isomorphous and all contain neutral honeycomb layers in which pymtz serves as a bis(chelating) bridge between M(II) (M = Zn for 2, Cd for 3, Mn for 4, Co for 5, and Ni for 6) and Na, and the ellipse stacking of the layers generates one-dimensional hexagonal channels. Compounds 1and 7exhibit different (4,4) square grid networks. In 1, the Zn ions are octahedrally coordinated and linked by pymtz ligands in the μ2tridentate bridging mode, while in 7, the Cd(II) ions are eight-coordinated with a square prismatic geometry and bridged by bis(chelating) pymtz ligands. Compounds 2and 3can transform into 1and 7, respectively, by immersing the sample in appropriate solvents. Interestingly, photoluminescence measurements on Zn(II) and Cd(II) compounds show that the emission bands can be correlated to the coordination modes of the pymtz ligands. [ABSTRACT FROM AUTHOR]

Hydrothermal reactions of Cu(II) salts and 2,2′,4,4′-biphenyltetracarboxylic acid (2,2′,4,4′-H4bptc) in the presence of pyridyl ligands yielded three isomorphous 3D metal–organic coordination polymers formulated as [Cu2(2,2′,4,4′-bptc)(L)x]·H2O [x= 2 for L = pyridine; x= 1 for L = bis(4-pyridyl)ethene and bis(4-pyridyl)ethane]. In the structure, the distorted paddlewheel [Cu2(COO)4] motif and the twisted Π-shaped 2,2′,4,4′-bptc serve as dissimilar 4-connected SBUs to generate a 3D [Cu2(2,2′,4,4′-bptc)] mother framework with the PtS topology, which selectively accommodates pyridine or bis(pyridyl) ligands of appropriate size. [ABSTRACT FROM AUTHOR]