Lanthanide-Connecting and Lone-Electron-Pair Active Trigonal-Pyramidal-AsO(3) Inducing Nanosized Poly(polyoxotungstate) Aggregates and Their Anticancer Activities

By virtue of the stereochemical effect of the lone-electron pair located on the trigonal-pyramidal-AsO(3) groups and the one-pot self-assembly strategy in the conventional aqueous solution, a series of novel lanthanide-bridging and lone-electron-pair active trigonal-pyramidal-AsO(3) inducing nanosized poly(polyoxotungstate) aggregates [H(2)N(CH(3))(2)](6) Na(24)H(16){[Ln(10)W(16)(H(2)O)(30)O(50)](B-α-AsW(9)O(33))(8)}·97H(2)O [Ln = Eu(III) (1), Sm(III) (2), Gd(III) (3), Tb(III) (4), Dy(III) (5), Ho(III) (6), Er(III) (7), Tm(III) (8)] were prepared and further characterized by elemental analyses, IR spectra, UV spectra, thermogravimetric (TG) analyses and single-crystal X-ray diffraction. The most remarkable structural feature is that the polyanionic skeleton of {[Ln(10)W(16)(H(2)O)(30)O(50)](B-α-AsW(9)O(33))(8)}(46−) is constructed from eight trivacant Keggin [B-α-AsW(9)O(33)](9−) fragments through ten Ln centers and sixteen bridging W atoms in the participation of fifty extraneous oxygen atoms. Notably, 4 and 8 can be stable in the aqueous solution not only for eight days but also in the range of pH = 3.9–7.5. Moreover, the cytotoxicity tests of 4 and 8 toward human cervical cancer (HeLa) cells, human breast cancer (MCF–7) cells and mouse fibroblast (L929) cells were performed by the 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and the cell apoptosis processes were characterized by calcein AM/PI staining experiments, annexin V-FITC/PI staining experiments and morphological changes.