Isopolymolybdate-Based Cobalt/Nickel Coordination Polymers Constructed by V-Type N-Donor Ligands

Four novel isopolymolybdate-based coordination polymers (CPs), constructed from 2,6-bis(1,2,4-triazol-1-yl)pyridine (btp), 1,3-bis(4H-1,2,4-triazol-4-yl) benzene (btb), and 3,5-bis(1-imidazolium)pyridine (bip), have been synthesized under a hydrothermal method: {[Co(btp)(H2O)(2)(beta-Mo8O26)(0.5)]center dot 3H(2)O}(n) (1), [Ni(btp)(H4Mo6O22)(0.5)](n) (2), [Co(btb)(H2O)(beta-Mo8O26)(0.5)](n) (3), and {[Co(Hbip)(2)(H2O)(2)(gamma-Mo8O26)]center dot 6H(2)O}(n) (4). Complex 1 exhibits one 3D framework with an unexpected 3-nodal 2,4,6-c net topology containing the 1D {beta-Mo8O26}(n) chains, 6-connected Co-II centers, and V-type coordinated btp ligands. The neighboring [Mo6O22](4-) anions of complex 2 are bridged by the Ni-II centers to build one 2D {Ni-2(Mo6O22)} network, which is arranged into the 3D framework through the weak pi center dot center dot center dot pi stacking interactions. In compound 3, one 3D framework is formed by the adjacent 1D {Co-2(btp)(2)}(n) chains connected by {beta-Mo8O26}(n) units, which demonstrates a rare 4,6-c fsc topology. In complex 4, one 2D {Co(Hbip)(2)(gamma-Mo8O26)} layer with a (4, 4) network is connected to one 3D hydrogen-bonding framework via N-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonds. Magnetic data indicate that complexes 1 and 4 exhibit antiferromagnetic behaviors, whereas complexes 2 and 3 reveal spin-canting magnetic behavior and metamagnetic behavior, respectively. In addition, the proton conductivity of complexes 3 and 4 was investigated, showing that compound 4 has good proton conductivity at 85 degrees C and a relative humidity of 98% RH.