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{GeNb12VIV2O42}·20H2O (1), {Cu­(en)2}3K2Na4{GeNb12VIV2O42}·23H2O (2), {Cu­(en)2}6{SiNb12VIV2O42}·18H2O (3), and {Cu­(en)2}3K2Na4{SiNb12VIV2O42}·19H2O (4) (en = ethanediamine), composed
of polyoxoanions [TNb12O40]16– (T = Si and Ge) and [Cu­(en)2]2+ building blocks,
were successfully synthesized under hydrothermal conditions by reaction
of K7HNb6O19·13H2O, Cu­(Ac)2·3H2O, Na2VO3, Na2SiO3, or GeO2 and en
molecules. Polyoxoanion [TNb12VIV2O42]12– (T = Si and Ge) can be best described as a
α-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 [TNb12VIV2O42]12– (T
= Si, Ge) decorated by three metal–organic fragments [Cu­(en)2]2+, forming a trisupporting polyoxoanion {[Cu­(en)2]3[TNb12O42VIV2]}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.

四种基于杂多铌氧酸盐（heteropolyoxonibate）的新型无机-有机杂化物，即{Cu(en)₂}₆{GeNb₁₂Vᴵᵛ₂O₄₂}·20H₂O（1）、{Cu(en)₂}₃K₂Na₄{GeNb₁₂Vᴵᵛ₂O₄₂}·23H₂O（2）、{Cu(en)₂}₆{SiNb₁₂Vᴵᵛ₂O₄₂}·18H₂O（3）以及{Cu(en)₂}₃K₂Na₄{SiNb₁₂Vᴵᵛ₂O₄₂}·19H₂O（4）（其中en为乙二胺（ethanediamine)），其构筑基元为多氧阴离子（polyoxoanions）[TNb₁₂O₄₀]¹⁶⁻（T=Si、Ge）与[Cu(en)₂]²⁺。该系列杂化物以K₇HNb₆O₁₉·13H₂O、Cu(Ac)₂·3H₂O、Na₂VO₃、Na₂SiO₃或GeO₂与en分子为反应物，通过水热法成功合成。

多氧阴离子[TNb₁₂Vᴵᵛ₂O₄₂]¹²⁻（T=Si、Ge）可被最优描述为：以α-Keggin型核心[TNb₁₂O₄₀]为主体，在其两个“开放窗口”处各封端一个[VO]单元。化合物1与3均由双封端杂多铌氧酸盐核心与由十二个[Cu(en)₂]²⁺基团构成的外壳组装而成，该结构代表了一种面向核壳纳米结构（core–shell nanostructures）的极具应用潜力的结构模型。化合物2与4则同样以[TNb₁₂Vᴵᵛ₂O₄₂]¹²⁻（T=Si、Ge）双封端多氧阴离子为主体，通过三个金属有机片段[Cu(en)₂]²⁺进行修饰，形成了三支撑多氧阴离子{[Cu(en)₂]₃[TNb₁₂O₄₂Vᴵᵛ₂]}⁶⁻。

抗肿瘤活性测试、电化学研究以及紫外-可见光谱（UV–vis spectra）结果表明，化合物1~4对人胃癌SGC7901细胞与人肝癌HepG2细胞均表现出显著的抗肿瘤活性，且在该测试过程中可保持结构完整性。