Four Polyoxonibate-Based Inorganic-Organic Hybrids Assembly from Bicapped Heteropolyoxonibate with Effective Antitumor Activity

Four novel heteropolyoxonibate-based inorganic-organic hybrids {Cu(en)(2)}(6){(GeNb12V2O42)-O-IV}center dot 20H(2)O (1), {Cu (en)(2)}(3)K2Na4{(GeNb12V2O42)-O-IV}center dot 23H(2)O (2), {Cu(en)(2)}(6){(SiNb12V2O42)-O-IV} center dot 18H(2)O (3), and {Cu(en)(2)}(3)K2Na4{(SiNb12V2O42)-O-IV}center dot 19H(2)O (4) (en = ethanediamine), composed of polyoxoanions [TNb12O4](16-) (T = Si and Ge) and [Cu(en)(2)](2+) building blocks, were successfully synthesized under hydrothermal conditions by reaction of K7HNb6O19 center dot 13H(2)O, Cu(Ac)(2)center dot 3H(2)O, Na2VO3, Na2SiO3, or GeO2 and en molecules. Polyoxoanion [TNb12VIV2O42](12-) (T = Si and Ge) can be best described as a alpha-Keggin core [TNb12O40] with two [VO] units capping on its two "opened windows". Compounds 1 and 3 are both composed of the bicapped heteropolyoxonibate core surrounded by a shell consisting of twelve [Cu(en)(2)](2+) groups, which represent a promising structural model toward core-shell nanostructures. Compounds 2 and 4 are also composed of a bicapped polyoxoanion [(TNb12V2O42)-O-IV](12-) (T = Si, Ge) decorated by three metal-organic fragments [Cu(en)(2)](2+), forming a trisupporting polyoxoanion {[Cu(en)(2)](3)[TNb12O42V2IV]}(6-). Antitumor, electro-chemical study, and UV-vis spectra indicate that compounds 1-4 exhibit effective antitumor activity against SGC7901 cells and HepG2 cells and could keep the structural integrity in this process.