By virtue of the stereochemical effect of the lone-electron pair located on the
trigonal-pyramidal-AsO3 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-AsO3 inducing nanosized
poly(polyoxotungstate) aggregates
[H2N(CH3)2]6
Na24H16{[Ln10W16(H2O)30O50](B-α-AsW9O33)8}·97H2O
[Ln = EuIII (1),
SmIII (2), GdIII (3),
TbIII (4), DyIII (5),
HoIII (6), ErIII (7),
TmIII (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
{[Ln10W16(H2O)30O50](B-α-AsW9O33)8}46−
is constructed from eight trivacant Keggin
[B-α-AsW9O33]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.