A two-dimensional coordination polymer bearing an Evans-Showell-type polyoxometalate: Synthesis, structure and biological insight†

Abstract

An Evans-Showell-type polyoxometalate (POM) based coordination polymer (CP), [H2(Co2Mo10H4O38)2(Co3(L)3(HL)2(H2O)6)(HL)2]·14H2O (1), {L = 4,4′-bipyridine}, was synthesized under hydrothermal conditions and structurally characterized by infrared spectroscopy (IR), elemental analysis, powder X-ray diffraction (PXRD), diffuse reflectance spectroscopy (DRS) and single crystal X-ray diffraction methods. In 1, two [Co2Mo10H4O38]6− POMs are joined together via two Co-O interactions to form a dimer which is centrosymmetric. Here, the dimers act as repeating units and are expanded by another crystallographically independent Co ion in the structure. Binding of the cations to the O atoms of the POM and the N atoms of organic ligand resulted in the formation of a 2D CP structure. Compound 1 is the first example of an inorganic-organic polymer architecture constructed from Evans-Showell-type POM in which Co cations act as metal nodes. The topology of 1 can be rationalized as a 2D square lattice (sql) coordination network with point symbol {44.62} in which [Co2Mo10H4O38]6− and 4,4′-bipyridine units act as linkers and the Co cations as nodes. The cytotoxicity effects of the POM were evaluated on the cancer CT26 and normal L929 cell lines by an MTT assay from which an IC50 value of cancer CT26 cells of approximately 366 ppm was obtained, but normal L929 cells did not show significant toxicity.