Structural Investigation of Flexible 1,4-Bis(1,2,4-triazol-1-ylmethyl)benzene Ligand in Keggin-Based Polyoxometalate Frameworks

By introducing the flexible 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene (btx) ligand into the molybdate system under the hydrothermal conditions, seven novel Keggin-based frameworks were obtained: [Ag(btx)]4[SiMo12O40]·2H2O (1), [Cu(btx)]4[SiMo12O40] (2), [Cu(btx)2]2[SiMo12O40] (3), [Zn(btx)2]2[SiMo12O40]·0.5H2O (4) and [M2(H2O)4(btx)3][SiMo12O40]·4H2O (M = Mn, Ni and Co) (5−7). Compound 1 contains 0D (zero dimensional) Keggin-based fragment, 1D polymer chain and 0D+1D poly-pseudo-rotaxane motif. Compound 2 exhibits interesting 1D+2D poly-pseudo-rotaxane architecture. Compound 3 has a 3D 4-connected diamond-related polymeric framework, which entraps the Keggin polyoxoanions into the stellate channels. Compound 4 contains isolated Keggin polyoxoanions and zipperlike polymer fragments, which are constructed from pairs of crumpled nets. Isostructural compounds 5−7 exhibit 2D→2D interpenetrated network structure featuring both polyrotaxane and polycatenane characters.