pH-Dependent assembly of two octamolybdate hybrid materials: A self-threading CdSO4-type framework and a 3D 4-connected framework

Two octamolybdate hybrid materials, namely, [Co-2(HL)(2)(L)(H2Mo8O28)] (1) and [Co (L)(2.5)(Mo8O26)(0.5)]center dot H2O(2) (L = 1,1'-(1,4-butanediyl)bis(imidazole)) have been successfully synthesized at different pH values under hydrothermal conditions. Compound 1 displays a 3D (6(5).8) CdSO4-type framework. The most peculiar feature of 1 is that each window constructed by four Co(II) ions and two [H2Mo8O28](6)(-) anions is threaded by two dangling HL+ ligands belonging to the framework itself. Compound 1 represents the first example of self-threading CdSO4-type framework. Compound 2 is a 3D 4-connected framework with the (6(4).8(2))(6(2).8(4)) topology. The structural diversities of 1 and 2 reveal that the pH value of the reaction system plays a crucial role in the assembly of octamolybdate hybrid materials. In addition, the optical band gap and magnetic property of 1 have also been investigated.