High-Dimensional Assembly Depending on Polyoxoanion Templates, Metal Ion Coordination Geometries, and a Flexible Bis(imidazole) Ligand

By introducing the flexible 1,1‘-(1,4-butanediyl)bis(imidazole) (bbi) ligand into the polyoxovanadate system, five
novel polyoxoanion-templated architectures based on [As8V14O42]4- and [V16O38Cl]6- building blocks were
obtained:  [M(bbi)2]2[As8V14O42(H2O)] [M = Co (1), Ni (2), and Zn (3)], [Cu(bbi)]4[As8V14O42(H2O)] (4), and [Cu(bbi)]6[V16O38Cl] (5). Compounds 1−3 are isostructural, and they exhibit a binodal (4,6)-connected 2D structure
with Schläfli symbol (34·42)(34·44·54·63)2, in which the polyoxoanion induces a closed four-membered circuit of
M4(bbi)4. Compound 4 exhibits an interesting 3D framework constructed from tetradentate [As8V14O42]4- cluster
anions and cationic ladderlike double chains. There exists a bigger M8(bbi)6O2 circuit in 4. The 3D extended structure
of 5 is composed of heptadentate [V16O38Cl]6- anions and flexural cationic chains; the latter consists of six Cu(bbi)
segments arranged alternately. It presents the largest 24-membered circuit of M24(bbi)24 so far observed made of
bbi molecules and transition-metal cations. Investigation of their structural relations shows the important template
role of the polyoxoanions and the synergetic interactions among the polyoxoanions, transition-metal ions, and
flexible ligand in the assembly process. The magnetic properties of compounds 1−3 were also studied.