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 {GeNb 12 V IV 2 O 42 }·20H 2 O ( 1 ), {Cu(en) 2 } 3 K 2 Na 4 {GeNb 12 V IV 2 O 42 }·23H 2 O ( 2 ), {Cu(en) 2 } 6 {SiNb 12 V IV 2 O 42 }·18H 2 O ( 3 ), and {Cu(en) 2 } 3 K 2 Na 4 {SiNb 12 V IV 2 O 42 }·19H 2 O ( 4 ) (en = ethanediamine), composed of polyoxoanions [TNb 12 O 40 ] 16– (T = Si and Ge) and [Cu(en) 2 ] 2+ building blocks, were successfully synthesized under hydrothermal conditions by reaction of K 7 HNb 6 O 19 ·13H 2 O, Cu(Ac) 2 ·3H 2 O, Na 2 VO 3, Na 2 SiO 3, or GeO 2 and en molecules. Polyoxoanion [TNb 12 VIV 2 O 42 ] 12– (T = Si and Ge) can be best described as a α-Keggin core [TNb 12 O 40 ] 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 [TNb 12 V IV 2 O 42 ] 12– (T = Si, Ge) decorated by three metal–organic fragments [Cu(en) 2 ] 2+, forming a trisupporting polyoxoanion {[Cu(en) 2 ] 3 [TNb 12 O 42 V IV 2 ]} 6– . Antitumor, electrochemical 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.