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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]

A series of transition metal coordination polymers with azide and flexible zwitterionic dicarboxylate ligands was synthesized and structurally and magnetically characterized. These compounds are formulated as [M2(L¹)(N3)4] (L¹ = 4,4'-trimethylenedipyridinio-N,N'-diacetate and M = Mn, 1; Co, 2; and Ni, 3) and [ML²(N3)6(H2O)2] (L² = 4,4'-dipyridinio-N,N'-diacetate and M = Mn, 4; Co, 5). The isomorphous compounds 1-3 consist of two-dimensional coordination layers in which the anionic chains with mixed triple bridges (two end-on (EO) azides and a syn-syn carboxylate) are cross-linked by the flexible cationin 4,4'-trimethylenedipyridinium spacers, while the isomorphous compounds 4 and 5 consist of alternating chains with triple (two EO azides plus a carboxylate) and double (two end-to-end azides) bridges, the 4,4'-dipyridinium spacers serving as side bridges along the chain. Magnetic studies demonstrated that the triple bridge transmits antiferromagnetic coupling in the Mn(II) compounds (1 and 4) but ferromagnetic coupling in the Co(II) and Ni(II) species (2, 3, and 5). The differences have been discussed in terms of the collaboration or competition between the carboxylate and azide pathways. Compound 4 exhibits alternating antiferromagnetic interactions, while alternating ferromagnetic-ferromagnetic-antiferromagnetic interactions with spin canting are suggested for 5. [ABSTRACT FROM AUTHOR]