Two three-dimensional {V16Ge4}-based open frameworks stabilized by diverse types of CoII-amine bridges and magnetic properties

Abstract

Two novel three-dimensional (3D) extended vanadogermanate-based frameworks, [Co(pdn)₂]₃[Co₂(pdn)₄][V₁₆Ge₄O₄₄(OH)₂(H₂O)]·5H₂O (1), [Co₂(en)₃][Co(en)₂]₂[Co(en)₂(H₂O)][V₁₆Ge₄O₄₄(OH)₂(H₂O)]·10.5H₂O (2), (pdn = 1,2-propanediamine, en = ethylenediamine) have been synthesized under hydrothermal conditions via changing the organic amine. X-ray crystal structure analyses reveal that both frameworks are built of [V₁₆Ge₄O₄₄(OH)₂(H₂O)]¹⁰⁻ anions and different Co-amine cations. They represent the first example of incorporating elemental Co into the extended vanadogermanate frameworks. Compound 1 shows a 3D framework with NaCl topology based on {V₁₆Ge₄} clusters as nodes, while compound 2 exhibits a 3D (4,6)-connected network with a Schläfli symbol of (4⁶·6⁷·8²)₂(4²·6⁴), which is found for the first time in polyoxovanadate chemistry. The diverse types of metal–organoamine subunits play critical roles in the formation on the final structures. Furthermore, variable temperature susceptibility measurements on compounds 1 and 2 demonstrate the presence of anticipated rare ferrimagnetic behavior.