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)](1.5)Ln[(alpha-SiW11O39)(2)]}(2)(20-) [Ln = Gd-III for 1, Tb-III for 2, Dy-III for 3, Er-III for 4, Lu-III for 5], {[Cu(en)(2)](1.5)Ln[(alpha-SiW11O39)]}(2-) [Ln = La-III for 6, Ce-III, for 7] and {[Cu(en)(2)(H2O)][Cu(en)(2)](n)Ln-[(alpha- SiW11O39)(2)]}(m-) [(Ln, n, m) = (Pr-III, 2, 7) for 8, (Sm-III, 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(alpha-SiW11O39)(2)](13-) polyoxoanion, whereas both 6 and 7 consist of the unusual 1:1 [Ln(alpha-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 2(1) screw axis to generate scarce 5-connected network structures with the Schlafli symbol of (4(8).6(2)), while 8 and 9 exhibit the 4-connected (6(6)) topology and 6-connected (4(8).5(4).6(3)) topology structures, respectively. Furthermore, 2, 3, and 9 manifest apparent fluorescence signals, which can be assigned to the characteristic emissions of Tb-III, Dy-III, and Sim(III) cations, respectively.