Organic–Inorganic Hybrids Based on Monovacant Keggin-type Silicotungstates and 3d-4f Heterometals

A series of organic–inorganic hybrid lacunary
Keggin silicotungstate
3d-4f heterometallic derivatives, {[Cu (en)2]1.5Ln­[(α-SiW11O39)2]}220– [Ln = GdIII for 1,
TbIII for 2, DyIII for 3, ErIII for 4, LuIII for 5], {[Cu­(en)2]1.5Ln­[(α-SiW11O39)]}2– [Ln = LaIII for 6, CeIII, for 7] and {[Cu­(en)2(H2O)]­[Cu­(en)2]nLn­[(α-SiW11O39)2]}m− [(Ln, n, m) = (PrIII, 2, 7) for 8, (SmIII, 3, 5) for 9] (en = ethylenediamine) have
been successfully synthesized under hydrothermal conditions and further
characterized by elemental analyses, inductively coupled plasma atomic
emission spectrometry (ICP-AES) analyses, X-ray powder diffraction
(XRPD), IR spectra, thermogravimetric (TG) analyses, and single-crystal
X-ray diffraction. The common features of 1–5 and 8–9 are that they all
consist of a sandwich-type [Ln­(α-SiW11O39)2]13– polyoxoanion, whereas both 6 and 7 consist of the unusual 1:1 [Ln­(α-SiW11O39)]5– units and [Cu­(en)2]2+ coordination cations. 1–5 show dimeric structures, and 6–9 display unprecedented three-dimensional (3D) frameworks,
representing the first 3D 3d-4f heterometallic silicotungstates. The
features of 6 and 7 are that the components
are closely packed along the 21 screw axis to generate
scarce 5-connected network structures with the Schläfli symbol
of (48·62), while 8 and 9 exhibit the 4-connected (66) topology and 6-connected
(48·54·63) topology
structures, respectively. Furthermore, 2, 3, and 9 manifest apparent fluorescence signals, which
can be assigned to the characteristic emissions of TbIII, DyIII, and SmIII cations, respectively.