Hydrothermal Syntheses and Structural Characterization of Two 3-D Supramolecular Networks Constructed from Tetra-Co~(II) Sandwiched Polyoxometalates

摘要

Two Co_4-substituted sandwich-type polyoxometalates (H_2en)_9[Co_4(H_2O)_2 (PW_9O_(34))_2]{[Co(H_2O)_4][Co_4(H_2O)_2(PW_9O_(34))_2]}?18H_2O (1) and (H_2en)_5[Co_4(H_2O)_2 (H_3GeW_9O_(34))_2]{[Co(H_2O)_4]_2[Co_4(H_2O)_2(H_2GeW_9O_(34))_2]}?16H_2O (2) (en = ethylenediamine) have been hydrothermally synthesized and characterized by IR spectra, elemental analyses, thermogravimetric analyses, powder X-ray diffraction and singlecrystal X-ray diffraction. Single-crystal structure analysis reveals that the molecules of 1 and 2 contain two Co_4-substituted sandwich-type polyoxoanions. This type of a molecular unit containing double polyoxoanions is very rare. From the viewpoint of supramolecular chemistry, the sandwich-type polyoxoanions in 1 and 2 can be further extended to 3-D frameworks via extensive hydrogen-bonding interactions.