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

Abstract

Two octamolybdate hybrid materials, namely, [Co₂(HL)₂(L)(H₂Mo₈O₂₈)] (1) and [Co(L)_2.5(Mo₈O₂₆)_0.5]·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 (6⁵·8) 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 (6⁴·8²)(6²·8⁴) 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.