Four Polyoxonibate-Based Inorganic–Organic
Hybrids Assembly from Bicapped Heteropolyoxonibate with Effective
Antitumor Activity
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Abstract
Four
novel heteropolyoxonibate-based inorganic–organic hybrids
{Cu(en)<sub>2</sub>}<sub>6</sub>{GeNb<sub>12</sub>V<sup>IV</sup><sub>2</sub>O<sub>42</sub>}·20H<sub>2</sub>O (<b>1</b>), {Cu(en)<sub>2</sub>}<sub>3</sub>K<sub>2</sub>Na<sub>4</sub>{GeNb<sub>12</sub>V<sup>IV</sup><sub>2</sub>O<sub>42</sub>}·23H<sub>2</sub>O (<b>2</b>), {Cu(en)<sub>2</sub>}<sub>6</sub>{SiNb<sub>12</sub>V<sup>IV</sup><sub>2</sub>O<sub>42</sub>}·18H<sub>2</sub>O (<b>3</b>), and {Cu(en)<sub>2</sub>}<sub>3</sub>K<sub>2</sub>Na<sub>4</sub>{SiNb<sub>12</sub>V<sup>IV</sup><sub>2</sub>O<sub>42</sub>}·19H<sub>2</sub>O (<b>4</b>) (en = ethanediamine), composed
of polyoxoanions [TNb<sub>12</sub>O<sub>40</sub>]<sup>16–</sup> (T = Si and Ge) and [Cu(en)<sub>2</sub>]<sup>2+</sup> building blocks,
were successfully synthesized under hydrothermal conditions by reaction
of K<sub>7</sub>HNb<sub>6</sub>O<sub>19</sub>·13H<sub>2</sub>O, Cu(Ac)<sub>2</sub>·3H<sub>2</sub>O, Na<sub>2</sub>VO<sub>3</sub>, Na<sub>2</sub>SiO<sub>3</sub>, or GeO<sub>2</sub> and en
molecules. Polyoxoanion [TNb<sub>12</sub>VIV<sub>2</sub>O<sub>42</sub>]<sup>12–</sup> (T = Si and Ge) can be best described as a
α-Keggin core [TNb<sub>12</sub>O<sub>40</sub>] with two [VO]
units capping on its two “opened windows”. Compounds <b>1</b> and <b>3</b> are both composed of the bicapped heteropolyoxonibate
core surrounded by a shell consisting of twelve [Cu(en)<sub>2</sub>]<sup>2+</sup> groups, which represent a promising structural model
toward core–shell nanostructures. Compounds <b>2</b> and <b>4</b> are also composed of a bicapped polyoxoanion [TNb<sub>12</sub>V<sup>IV</sup><sub>2</sub>O<sub>42</sub>]<sup>12–</sup> (T
= Si, Ge) decorated by three metal–organic fragments [Cu(en)<sub>2</sub>]<sup>2+</sup>, forming a trisupporting polyoxoanion {[Cu(en)<sub>2</sub>]<sub>3</sub>[TNb<sub>12</sub>O<sub>42</sub>V<sup>IV</sup><sub>2</sub>]}<sup>6–</sup>. Antitumor, electrochemical study,
and UV–vis spectra indicate that compounds <b>1</b>–<b>4</b> exhibit effective antitumor activity against SGC7901 cells
and HepG2 cells and could keep the structural integrity in this process
