Tailoring microstructures of isopolymolybdates: regular tuning of the ligand spacer length and metal coordination preferences

Four new isopolymolybdate compounds based on two kinds of isomers, [Cu(2)(I)bte][a-Mo3O10] (1), [Cu(2)(I)btp][b-Mo3O10]center dot H2O (2), [Cu-II(bte)(1.5)(H2O)][gamma-Mo8O26](0.5) (3) and [Cu-II(btp)(2)(H2O)][b-Mo8O26](0.5)center dot 2H(2)O (4) [bte = 1,2-bis(1,2,4-triazol-1-yl)ethane, btp = 1,3-bis(1,2,4-triazol-1-yl) propane], were obtained under hydrothermal conditions, indicating that isopolymolybdate clusters can be tailored by regular tuning of the spacer length of the flexible ligands and the metal coordination preferences. In compound 1, wave-like a-[Mo3O10](2-) chains intersect with [Cu(2)(I)bte](2+) chains by sharing Cu-I cations, forming a 3D framework. Compound 2, with a similar 3D structure but different ligand (btp) to 1, is based on linear b-[Mo3O10](2-) chains. In compound 3, gamma-[Mo8O26](4-) chains insert into the rectangular windows of parallel [Cu(2)(II)bte](4+) sheets and connect them via four Cu-II-O bonds, leading to a 3D framework. Compound 4 is an unusual 2D -> 3D polycatenated array of a [CuII(btp)(2)(H2O)][b-Mo8O26] pillar-layered framework. The thermal stability and luminescent properties of compounds 1-4 were investigated in the solid state.