A series of aliphatic organoimido derivatives of hexamolybdate based on amantadine, namely (nBu4 N)2 [Mo6 O18 (NC10 H15 )] (1), (nBu4 N)2 {cis-[Mo6 O17 (NC10 H15 )2 ]} (2), (nBu4 N)2 {trans-[Mo6 O17 (NC10 H15 )2 ]} (3), and (nBu4 N)2 [Mo6 O16 (NC10 H15 )3 ] (4), was synthesized in reasonable yield by dehydration with N,N'-dicyclohexylcarbodiimide (DCC). They were characterized by IR and UV/Vis spectroscopy, elemental analysis, ESI mass spectrometry, and single-crystal X-ray structure analysis. The spectral and structural similarities and differences between monosubstituted, cis-disubstituted, and trans-disubstituted organoimido derivatives were elucidated and may provide guidance for related work on organoimido-functionalized Lindqvist-type polyoxometalates. In addition, trans-disubstituted and polysubstituted derivatives containing aliphatic organoimido ligands have not yet been reported, and the crystal structure of the trans isomer may lead us to a deeper understanding of disubstituted derivatives. Furthermore, proliferation and morphology of MCF-7 cells were studied with compound 1. The present results show that the DCC-dehydrating protocol could be an efficient approach to covalently graft bioactive ligands such as amantadine onto POMs and enhance their application in clinical cancer treatment.

High efficacy and low toxicity are critical for cancer treatment. Polyoxometalates (POMs) have been reported as potential candidates for cancer therapy. On accounts of the slow clearance of POMs, leading to long-term toxicity, the clinical application of POMs in cancer treatment is restricted. To address this problem, a degradable organoimido derivative of hexamolybdate is developed by modifying it with a cleavable organic group, leading to its degradation. Of note, this derivative exhibits favourable pharmacodynamics towards human malignant glioma cell (U251), the ability to penetrate across blood brain barrier and low toxicity towards rat pheochromocytoma cell (PC12). This line of research develops an effective POM-based agent for glioblastoma inhibition and will pave a new way to construct degradable anticancer agents for clinical cancer therapy.

Polyoxometalate-based organic-inorganic hybrids were synthesized by direct modification of the parent Anderson cluster with both the traditional tripodal ligand, CH3C(CH2OH)3, and a novel one containing a carboxyl group, CH3C(CH2OH)2(COOH), which was inaccessible from the traditional self-assembly protocol.