Topologically novel copper molybdate phases based on 3,4'-dipyridylketone: Hydrothermal synthesis, structural characterization, and magnetic properties

Hydrothermal treatment of CuCl2.2H2O, MoO3, and 3,4'-dipyridylketone (3,4'-dpk) in 1:1:2 mole ratio afforded the new mixed metal oxide phases [Cu2(MoO4)2(3,4'-dpk)(H2O)] (1) or [Cu4(3,4'-dpk)4(Mo8O26)] (2), depending on the pH of the initial reaction mixture. Compound 1 possesses unique one-dimensional (1-D) [Cu2(MoO4)2(H2O)]n ribbons constructed from the linkage of {CuII4O6} tetrameric units through isolated [MoO4]2- tetrahedra. These ribbons in turn are connected into a two-dimensional (2-D) coordination polymer structure by tethering 3,4'-dpk ligands. Compound 2, containing monovalent copper ions, manifests an unprecedented 'X-rail' 1-D extended structure with (628)4(66) topology formed from the bracketing of discrete [β-Mo8O26]4- anions by four [CuI(3,4'-dpk)]nn+ chains. The variable temperature magnetic susceptibility behavior of 1 was fit to a linear tetramer model, with g=2.03(3), J1=25.8(7) cm-1 and J2=-46(1) cm-1. Antiferromagnetic inter-tetramer interactions (zJ'=-0.21(3) cm-1) were also evident. Crystallographic data: 1 monoclinic, P21/c, a=10.3911(11) A, b=6.9502(6) A, c=22.958(2) A, β=100.658(7)o, V=1629.5(3) A3, R1=0.1256, and wR2=0.2038; 2 triclinic, P1-bar,a=10.9000(3) A, b=11.7912(4) A, c=13.5584(4) A, α=102.482(2)o, β=102.482(2)o, γ=117.481(2)o, V=1450.98(8) A3, R1=0.0428, and wR2=0.0630. - Graphical abstract: [Cu2(MoO4)2(3,4'-dpk)(H2O)] (1, 3,4'-dpk=3,4'-dipyridylketone) and [Cu4(3,4'-dpk)4(Mo8O26)] (2) have been prepared by hydrothermal methods. 1 possesses 1-D [Cu2(MoO4)2(H2O)]n ribbons containing magnetically interacting {Cu4O6} tetramers. The ribbons are connected into 2-D by 3,4'-dpk ligands. The reduced phase 2 manifests an unprecedented 1-D 'X-rail' chain motif